Malaria vectors and transmission dynamics in coastal south-western Cameroon

Diversity, abundance of anopheline species, and malaria transmission dynamics in high-altitude areas of western Cameroon

Background

Assessing vector bionomics is crucial to improving vector control strategies. Several entomological studies have been conducted to describe malaria transmission in different eco-epidemiological settings in Cameroon; knowledge gaps persist, particularly in highland areas. This study aimed to characterize malaria vectors in three localities along an altitudinal gradient in the western region: Santchou (700 m), Dschang (1400 m), and Penka Michel (1500 m).

Methods

Human landing catches were conducted from May to June 2023 from 6:00 pm to 9:00 am. Mosquitoes were sorted into genera, and all Anopheles species were identified using morphological taxonomic keys and species-specific Polymerase Chain reaction (PCR). Entomological indicators were assessed including species composition and abundance, biting behavior, infection rate, and entomological inoculation rate (EIR). Genomic DNA from the head and thoraces were tested for Plasmodiuminfection by real-time PCR.

Results

2,835 Anopheles mosquitoes were identified, including An. gambiae, An. coluzzii, An. funestus, An. leesoni, An. nili, and An. ziemanni, with An. gambiae being the most prevalent at all sites. The human-biting rate of An. gambiae s.l. was significantly higher (p-value < 0.001) in Penka Michel compared to Santchou and Dschang (45.25 b/h/n vs 3.1 b/h/n and 0.41 b/h/n), and appears to be the most infected vector, and infectious vector distribution is highly focal, with entomological inoculation rates 13-fold higher in Penka Michel compared to Santchou (1.11 vs 0.08ibites/human/night). P. falciparum was the dominant malaria parasite (67% at Santchou, 62% at Penka Michel), but P. malariae (30%) and P. ovale (1.21%) infections were also detected.

Conclusion

The study highlights a difference in mosquito composition and host-seeking behavior with altitude and the need for continued surveillance to monitor vector populations and prevent potential malaria outbreaks in these highland areas.

Immunoglobulin G (IgG) specific responses to recombinant Qβ displayed MSP3 and UB05 in plasma of asymptomatic Plasmodium falciparum-infected children living in two different agro-ecological settings of Cameroon

Introduction

in areas with intense perennial malaria transmission, limited data is available on the impact of environmental conditions especially rainfall on naturally acquired immunity against promising malaria vaccine candidates. For this reason, we have compared IgG antibody responses specific to Plasmodium spp. derived MSP3 and UB05 vaccine candidates, in plasma of children living in two areas of Cameroon differing in rainfall conditions.

Methods

data about children less than 5 years old was collected during the years 2017 and 2018. Next malaria asymptomatic P. falciparum (Pf) infected children were selected following malaria test confirmation. MSP3 and UB05 specific IgG antibody responses were measured in participant´s plasma using enzyme-linked immunosorbent assay (ELISA).

Results

interestingly, IgG antibody responses specific to UB05 were significantly higher (p<0.0001) in Pf-negative children when compared to their asymptomatic Pf-infected counterparts living in monomodal rainfall areas. In contrast, a significantly higher (p<0.0001) IgG response to MSP3 was observed instead in asymptomatic Pf-infected children in the same population. In addition, IgG responses specific to UB05 remained significantly higher in bimodal when compared to monomodal rainfall areas irrespective of children´s Pf infection status (p<0.0055 for Pf-positive and p<0.0001 for negative children). On the contrary, IgG antibody responses specific to MSP3 were significantly higher in bimodal relative to monomodal rainfall areas (P<0.0001) just for Pf-negative children.

Conclusion

thus IgG antibody responses specific to UBO5 are a better correlate of naturally acquired immunity against malaria in Pf-negative Cameroonian children especially in monomodal rainfall areas.

Contribution of Anopheles gambiae sensu lato mosquitoes to malaria transmission during the dry season in Djoumouna and Ntoula villages in the Republic of the Congo

BACKGROUND

Mosquitoes belonging to the Anopheles gambiae sensu lato complex play a major role in malaria transmission across Africa. This study assessed the relative importance of members of An. gambiae s.l. in malaria transmission in two rural villages in the Republic of the Congo.

METHODS

Adult mosquitoes were collected using electric aspirators from June to September 2022 in Djoumouna and Ntoula villages and were sorted by taxa based on their morphological features. Anopheles gambiae s.l. females were also molecularly identified. A TaqMan-based assay and a nested polymerase chain reaction (PCR) were performed to determine Plasmodium spp. in the mosquitoes. Entomological indexes were estimated, including man-biting rate, entomological inoculation rate (EIR), and diversity index.

RESULTS

Among 176 mosquitoes collected, An. gambiae s.l. was predominant (85.8%), followed by Culex spp. (13.6%) and Aedes spp. (0.6%). Three members of the An. gambiae s.l. complex were collected in both villages, namely An. gambiae sensu stricto (74.3%), Anopheles coluzzii (22.9%) and Anopheles arabiensis (2.8%). Three Plasmodium species were detected in An. gambiae s.s. and An. coluzzii (Plasmodium falciparum, P. malariae and P. ovale), while only P. falciparum and P. malariae were found in An. arabiensis. In general, the Plasmodium infection rate was 35.1% (53/151) using the TaqMan-based assay, and nested PCR confirmed 77.4% (41/53) of those infections. The nightly EIR of An. gambiae s.l. was 0.125 infectious bites per person per night (ib/p/n) in Djoumouna and 0.08 ib/p/n in Ntoula. The EIR of An. gambiae s.s. in Djoumouna (0.11 ib/p/n) and Ntoula (0.04 ib/p/n) was higher than that of An. coluzzii (0.01 and 0.03 ib/p/n) and An. arabiensis (0.005 and 0.0 ib/p/n).

CONCLUSIONS

This study provides baseline information on the dominant vectors and dynamics of malaria transmission in the rural areas of the Republic of the Congo during the dry season. In the two sampled villages, An. gambiae s.s. appears to play a predominant role in Plasmodium spp.

TRANSMISSION

Molecular speciation of Plasmodium and multiplicity of P. falciparum infection in the Central region of Ghana

Malaria is endemic in the Central region of Ghana, however, the ecological and the seasonal variations of Plasmodium population structure and the intensity of malaria transmission in multiple sites in the region have not been explored. In this cross-sectional study, five districts in the region were involved. The districts were Agona Swedru, Assin Central and Gomoa East (representing the forest zone) and Abura-Asebu-Kwamankese and Cape Coast representing the coastal zone. Systematically, blood samples were collected from patients with malaria. The malaria status was screened with a rapid diagnostic test (RDT) kit (CareStart manufactured by Access Bio in Somerset, USA) and the positive ones confirmed microscopically. Approximately, 200 μL of blood was used to prepare four dried blood spots of 50μL from each microscopy positive sample. The Plasmodium genome was sequenced at the Malaria Genome Laboratory (MGL) of Wellcome Sanger Institute (WSI), Hinxton, UK. The single nucleotide polymorphisms (SNPs) in the parasite mitochondria (PfMIT:270) core genome aided the species identification of Plasmodium. Subsequently, the complexity of infection (COI) was determined using the complexity of infection likelihood (COIL) computational analysis. In all, 566 microscopy positive samples were sequenced. Of this number, Plasmodium genome was detected in 522 (92.2%). However, whole genome sequencing was successful in 409/522 (72.3%) samples. In total, 516/522 (98.8%) of the samples contained P. falciparum mono-infection while the rest (1.2%) were either P. falciparum/P. ovale (Pf/Po) (n = 4, 0.8%) or P. falciparum/P. malariae/P. vivax (Pf/Pm/Pv) mixed-infection (n = 2, 0.4%). All the four Pf/Po infections were identified in samples from the Assin Central municipality whilst the two Pf/Pm/Pv triple infections were identified in Abura-Asebu-Kwamankese district and Cape Coast metropolis. Analysis of the 409 successfully sequenced genome yielded between 1-6 P. falciparum clones per individual infection. The overall mean COI was 1.78±0.92 (95% CI: 1.55-2.00). Among the study districts, the differences in the mean COI between ecological zones (p = 0.0681) and seasons (p = 0.8034) were not significant. However, regression analysis indicated that the transmission of malaria was more than twice among study participants aged 15-19 years (OR = 2.16, p = 0.017) and almost twice among participants aged over 60 years (OR = 1.91, p = 0.021) compared to participants between 20-59 years. Between genders, mean COI was similar except in Gomoa East where females recorded higher values. In conclusion, the study reported, for the first time, P. vivax in Ghana. Additionally, intense malaria transmission was found to be higher in the 15-19 and > 60 years, compared to other age groups. Therefore, active surveillance for P. vivax in Ghana and enhanced malaria control measures in the 15-19 year group years and those over 60 years are recommended.

Entomological indicators of Plasmodium species transmission in Goma Tsé-Tsé and Madibou districts, in the Republic of Congo

BACKGROUND

Malaria remains a major public health problem in the Republic of Congo, with Plasmodium falciparum being the deadliest species of Plasmodium in humans. Vector transmission of malaria is poorly studied in the country and no previous report compared rural and urban data. This study aimed to determine the Anopheles fauna and the entomological indices of malaria transmission in the rural and urban areas in the south of Brazzaville, and beyond.

METHODS

Indoor household mosquitoes capture using electric aspirator was performed in rural and urban areas during raining and dry seasons in 2021. The identification of Anopheles species was done using binocular magnifier and nested-PCR. TaqMan and nested-PCR were used to detect the Plasmodium species in the head/thorax and abdomens of Anopheles. Some entomological indices including the sporozoite infection rate, the entomological inoculation rate and the man biting rate were estimated.

RESULTS

A total of 699 Anopheles mosquitoes were collected: Anopheles gambiae sensu lato (s.l.) (90.7%), Anopheles funestus s.l. (6.9%), and Anopheles moucheti (2.4%). Three species of An. gambiae s.l. were identified including Anopheles gambiae sensu stricto (78.9%), Anopheles coluzzii (15.4%) and Anopheles arabiensis (5.7%). The overall sporozoite infection rate was 22.3% with a predominance of Plasmodium falciparum, followed by Plasmodium malariae and Plasmodium ovale. Anopheles aggressiveness rate was higher in households from rural area (1.1 bites/night) compared to that from urban area (0.8 ib/p/n). The overall entomological inoculation rate was 0.13 ib/p/n. This index was 0.17 ib/p/n and 0.092 ib/p/n in rural and in urban area, respectively, and was similar during the dry (0.18 ib/p/n) and rainy (0.14 ib/p/n) seasons.

CONCLUSION

These findings highlight that malaria transmission remains high in rural and urban area in the south of Republic of Congo despite the ongoing control efforts, thereby indicating the need for more robust interventions.

Entomological longitudinal surveys in two contrasted eco-climatic settings in Cameroon reveal a high malaria transmission from Anopheles funestus associated with GSTe2 metabolic resistance

BACKGROUND

The impact of metabolic resistance to insecticides on malaria transmission remains poorly characterised notably through application of entomological parameters. The lack of resistance markers has been one of the limiting factors preventing a robust assessment of such impact. To this end, the present study sought to investigate how the L119F-Gste2 metabolic gene influences entomological parameters underpinning mosquitos' propensity to transmit Plasmodium spp.

METHODS

Longitudinal studies were carried out in Mibellon and Elende, two different eco-climatic settings in Cameroon and mosquitoes were collected using Human Landing Catch (HLC), Centre for Disease Control Light Trap (CDC-LT) and Pyrethrum Spray Catch (PSC) technics. Plasmodium sporozoite parasites were detected by TaqMan and Nested PCR, and blood meal origin by ELISA. The allele-specific PCR (AS-PCR) method was used to genotype the L119F-GSTe2 marker and association with malaria transmission was established by comparing key transmission parameters such as the Entomological Inoculation Rate (EIR) between individuals with different L119F-GSTe2 genotypes.

RESULTS

An. funestus s.l was the predominant malaria vector collected during the entomological survey in both sites (86.6% and 96.4% in Elende and Mibellon, respectively) followed by An. gambiae s.l (7.5% and 2.4%, respectively). Sporozoite infection rates were very high in both collection sites (8.7% and 11% in Elende and Mibellon, respectively). An. funestus s.s exhibited a very high entomological inoculation rate (EIR) (66 ib/h/month and 792 ib/h/year) and was responsible for 98.6% of all malaria transmission events occurring in both sites. The Human Blood Index was also high in both locations (HBI = 94%). An. funestus s.s. mosquitoes with both 119 F/F (RR) and L119F (RS) genotypes had a significantly higher transmission intensity than their susceptible L/L119 (SS) counterparts (IRR = 2.2, 95%CI (1.1-5.2), p = 0.03; IRR = 2.5, 95% CI (1.2-5.8), p = 0.01 respectively).

CONCLUSION

This study highlights the major role that An. funestus s.s plays in malaria transmission in Cameroon with an aggravation from GSTe2-based metabolic resistance.

Seasonal and environmental dynamics of intra-urban freshwater habitats and their influence on the abundance of Bulinus snail host of Schistosoma haematobium in the Tiko endemic focus, Mount Cameroon region

Urogenital schistosomiasis (UGS) caused by Schistosoma haematobium is endemic in the South West Region of Cameroon. An understanding of the abundance and distribution of the Bulinus snail, intermediate host can inform strategic snail control programmes at a local scale. This study investigated seasonal dynamics and environmental factors influencing occurrence and abundance of freshwater snail intermediate hosts in Tiko, a semi-urban endemic focus in the Mount Cameroon area. A longitudinal malacological field survey was conducted between December 2019 and December 2020 in the Tiko municipality. Snails were collected for one year monthly at 12 different human water contact sites along a stretch of the Ndongo stream using a standardized sampling technique. Freshwater snails were identified using shell morphological features. In addition, water temperature, pH, electrical conductivity, total dissolved solutes, salinity, water depth, width and flow velocity were measured, and vegetation cover as well as substrate type were determined. Bayesian regression models were used to identify the main environmental factors affecting the occurrence and abundance of Bulinus intermediate host. In total, 2129 fresh water snails were collected during the study period. Physa (51.4%) was the most abundant genus followed by Melanoides (28.6%) then, Bulinus (15.5%), Lymnaea (4.2%), Indoplanorbis (0.2%) and Potadoma (0.1%). Seasonality in abundance was significant in Bulinus sp as well as other genera, with greater numbers in the dry season (peaks between December and February). Water temperature, a rocky or sandy substrate type associated positively with Bulinus sp, meanwhile a higher water flow rate and medium vegetation negatively influenced the snail intermediate host population. These findings underscore the importance of timing behavioural and snail control interventions against schistosomiasis as well as increase vigilance of other trematode diseases in the study area. The continuous spread of planorbid snail hosts is a major concern.

Status of the Multidrug Resistance-1 Gene of Plasmodium falciparum in Four Malaria Epidemiological Strata, Two Decades after the Abolition of Chloroquine as First-Line Treatment for Uncomplicated Malaria in Cameroon

Drug-resistant malaria parasites pose a threat to global malaria control efforts, and it is important to know the extent of these drug-resistant mutations in each region to determine appropriate control measures. Chloroquine (CQ) was widely used in Cameroon for decades, but its declining clinical efficacy due to resistance prompted health authorities in 2004 to resort to artemisinin-based combination therapy (ACT) as the first-line treatment for uncomplicated malaria. Despite numerous efforts to control malaria, it persists, and the emergence and spread of resistance to ACTs make the development of new drugs or the possible reintroduction of discontinued drugs increasingly urgent. Malaria-positive blood samples were collected from 798 patients on Whatman filter paper to determine the status of resistance to CQ. DNA was extracted by boiling in Chelex and analysis of Plasmodium species. Four hundred P. falciparum monoinfected samples, 100 per study area, were amplified by nested PCR, and allele-specific restriction analysis of Pfmdr1 gene molecular markers was performed. Fragments were analyzed using a 3% ethidium bromide-stained agarose gel. P. falciparum was the most abundant Plasmodium species, accounting for 87.21% of P. falciparum monoinfections only. No infection with P. vivax was detected. The majority of samples contained the wild type for all 3 SNPs evaluated on the Pfmdr1 gene with N86, Y184, and D1246 accounting for 45.50%, 40.00%, and 70.00%, respectively. The most abundant haplotype observed was the Y184D1246 double wild type at 43.70%. The results suggest that P. falciparum is the major infecting species and that P. falciparum species with the susceptible genotype are gradually recapturing the parasite population.

Burden of mosquito-borne diseases across rural versus urban areas in Cameroon between 2002 and 2021: prospective for community-oriented vector management approaches

BACKGROUND

Over the past two decades, Cameroon has recorded one of the highest rates of urban population growth in sub-Saharan Africa. It is estimated that more than 67% of Cameroon's urban population lives in slums, and the situation is far from improving as these neighbourhoods are growing at an annual rate of 5.5%. However, it is not known how this rapid and uncontrolled urbanization affects vector populations and disease transmission in urban versus rural areas. In this study, we analyse data from studies conducted on mosquito-borne diseases in Cameroon between 2002 and 2021 to determine the distribution of mosquito species and the prevalence of diseases they transmit with regards to urban areas versus rural areas.

METHODS

A search of various online databases, such as PubMed, Hinari, Google and Google Scholar, was conducted for relevant articles. A total of 85 publications/reports were identified and reviewed for entomological and epidemiological data from the ten regions of Cameroon.

RESULTS

Analysis of the findings from the reviewed articles revealed 10 diseases transmitted by mosquitoes to humans across the study regions. Most of these diseases were recorded in the Northwest Region, followed by the North, Far North and Eastern Regions. Data were collected from 37 urban and 28 rural sites. In the urban areas, dengue prevalence increased from 14.55% (95% confidence interval [CI] 5.2-23.9%) in 2002-2011 to 29.84% (95% CI 21-38.7%) in 2012-2021. In rural areas, diseases such as Lymphatic filariasis and Rift valley fever, which were not present in 2002-2011, appeared in 2012-2021, with a prevalence of 0.4% (95% CI 0.0- 2.4%) and 10% (95% CI 0.6-19.4%), respectively. Malaria prevalence remained the same in urban areas (67%; 95% CI 55.6-78.4%) between the two periods, while it significantly decreased in rural areas from 45.87% (95% CI 31.1-60.6%) in 2002-2011 to 39% (95% CI 23.7-54.3%) in the 2012-2021 period (*P = 0.04). Seventeen species of mosquitoes were identified as involved in the transmission of these diseases, of which 11 were involved in the transmission of malaria, five in the transmission of arboviruses and one in the transmission of malaria and lymphatic filariasis. The diversity of mosquito species was greater in rural areas than in urban areas during both periods. Of the articles reviewed for the 2012-2021 period, 56% reported the presence of Anopheles gambiae sensu lato in urban areas compared to 42% reported in 2002-2011. The presence of Aedes aegypti increased in urban areas in 2012-2021 but this species was absent in rural areas. Ownership of long-lasting insecticidal nets varied greatly from one setting to another.

CONCLUSIONS

The current findings suggest that, in addition to malaria control strategies, vector-borne disease control approaches in Cameroon should include strategies against lymphatic filariasis and Rift Valley fever in rural areas, and against dengue and Zika viruses in urban areas.

High vector diversity and malaria transmission dynamics in five sentinel sites in Cameroon

BACKGROUND

Malaria remains one of the main causes of morbidity and mortality in Cameroon. To inform vector control intervention decision making, malaria vector surveillance was conducted monthly from October 2018 to September 2020 in five selected sentinel sites (Gounougou and Simatou in the North, and Bonabéri, Mangoum and Nyabessang in the South).

METHODS

Human landing catches (HLCs), U.S. Centers for Disease Control and Prevention (CDC) light traps, and pyrethrum spray catches (PSCs) were used to assess vector density, species composition, human biting rate (HBR), endophagic index, indoor resting density (IRD), parity, sporozoite infection rates, entomological inoculation rate (EIR), and Anopheles vectorial capacity.

RESULTS

A total of 139,322 Anopheles mosquitoes from 18 species (or 21 including identified sub-species) were collected across all sites. Out of the 18 species, 12 were malaria vectors including Anopheles gambiae sensu lato (s.l.), Anopheles funestus s.l.., Anopheles nili, Anopheles moucheti, Anopheles paludis, Anopheles demeilloni, Anopheles. pharoensis, Anopheles ziemanni, Anopheles multicinctus, Anopheles tenebrosus, Anopheles rufipes, and Anopheles marshallii. Anopheles gambiae s.l. remains the major malaria vector (71% of the total Anopheles) collected, though An. moucheti and An. paludis had the highest sporozoite rates in Nyabessang. The mean indoor HBR of Anopheles ranged from 11.0 bites/human/night (b/h/n) in Bonabéri to 104.0 b/h/n in Simatou, while outdoors, it varied from 24.2 b/h/n in Mangoum to 98.7 b/h/n in Simatou. Anopheles gambiae s.l. and An. moucheti were actively biting until at least 8:00 a.m. The mean Anopheles IRD was 17.1 females/room, and the parity rate was 68.9%. The mean EIRs for each site were 55.4 infective bites/human/month (ib/h/m) in Gounougou, 99.0 ib/h/m in Simatou, 51.2 ib/h/m in Mangoum, 24.4 ib/h/m in Nyabessang, and 18.1 ib/h/m in Bonabéri. Anopheles gambiae s.l. was confirmed as the main malaria vector with the highest vectorial capacity in all sites based on sporozoite rate, except in Nyabessang.

CONCLUSION

These findings highlight the high malaria transmission occurring in Cameroon and will support the National Malaria Control Program to design evidence-based malaria vector control strategies, and deployment of effective and integrated vector control interventions to reduce malaria transmission and burden in Cameroon, where several Anopheles species could potentially maintain year-round transmission.

Malaria transmission pattern across the Sahelian, humid savanna, highland and forest eco-epidemiological settings in Cameroon

BACKGROUND

Malaria remains a major public health concern in Cameroon. Understanding vector distribution and malaria transmission dynamics is of paramount importance for evaluating the performance of control strategies. This study assesses patterns of malaria transmission in four eco-epidemiological settings in Cameroon.

METHODS

Adult mosquitoes were collected using Human Landing Catches (HLC) once every 4 months from August 2019 to November 2021 in Kaélé, Tibati, Santchou and Bertoua. Mosquitoes were sorted by genus and Anopheles gambiae sensu lato (s.l.) species complex were identified using PCR. The presence of Plasmodium falciparum circumsporozoite protein (CSP) was measured by ELISA; the entomological inoculation rates (EIR) was estimated in each locality.

RESULTS

A total of 23,536 mosquitoes were collected. Anopheles gambiae and/or Anopheles coluzzii were the main malaria vectors in all sites. Anopheles arabiensis was recorded in low frequency in Kaélé and Tibati. Other species collected included Anopheles funestus, Anopheles pharoensis and Anopheles ziemmani. High anopheline biting rates were recorded outdoor in all sites except in Kaélé. Important differences in species biting dynamics were observed between sites. The sporozoite infection rate varied from 0.36 to 4%. The daily EIR was found to vary from 0.07 in Santchou to 0.26 infected bites/man/night (ib/m/n) in Kaélé).

CONCLUSION

The study suggests heterogeneous patterns of malaria transmission in different ecoepidemiological settings across the country. The findings stress the need to improve malaria vector control strategies.

Current status of 4-aminoquinoline resistance markers 18 years after cessation of chloroquine use for the treatment of uncomplicated falciparum malaria in the littoral coastline region of Cameroon

The onset and rapid spread of chloroquine resistance and the introduction of amodiaquine for the treatment of uncomplicated malaria in Cameroon have influenced the proportion of Plasmodium falciparum sensitive and resistant alleles related to 4-aminoquinoline drugs. This study was undertaken to determine the prevalence of resistance markers to antimalarial 4-aminoquinolines in Douala in the Littoral Region, and Buea in the South West Region in June 2020. Dry blood spots were prepared from malaria microscopy positive cases and used for parasite DNA extraction by chelex-100 method. Plasmodium species identification was carried out by PCR amplification/agarose gel electrophoresis of 18srRNA. The Pfcrt and Pfmdr1 genes were amplified by PCR followed by restriction digestion. The prevalence of single nucleotide polymorphisms (SNPs) was compared between study sites and with previous studies carried out between 2003-2005 and 2009-2011 using the Chi square test. The results showed that Plasmodium falciparum was the dominant species occurring as mono-infections (84.6%). The wild type K76 allele of the Pfcrt gene was found in 74.9% of isolates while the wild N86, Y184 and D1246 alleles of the Pfmdr1 gene were found respectively in 87.2%, 89.6% and 100% of field isolates. The results showed a significant reduction in the mutant alleles compared to results obtained in 2003-2005 and 2009-2013. The KNYD haplotype was observed to be the most prevalent. The results indicated that there is a gradual erosion of the mutant Pfcrt and Pfmdr1 genotype and a gradual return to the sensitive P. falciparum genotype in Cameroon.

Diversity and behavioral activity of Anopheles mosquitoes on the slopes of Mount Cameroon

BACKGROUND

Malaria remains endemic in Cameroon, with heterogeneous transmission related to eco-climatic variations, vector diversity and spatial distribution. The intensification of malaria prevention and control through the free distribution of insecticide-treated nets in recent years may have altered the composition, geographic distribution and natural infection rate of Anopheles species, with implications for malaria transmission dynamics. The present study seeks to assess the vectorial diversity, dynamics and infectivity across different seasons and altitudes in relationship to parasite prevalence around the slopes of Mount Cameroon, southwestern region.

METHOD

Mosquitoes were sampled (indoors and outdoors) in 11 eco-epidemiological settings at low (18-197 m), intermediate (371-584 m) and high (740-1067 m) altitude by nightly human landing catches. The mosquitoes were identified morphologically and Anopheles gambiae sibling species identified by PCR. Parity status was ascertained by examining the ovaries and the entomological inoculation rates (EIR) determined by Plasmodium falciparum circumsporozoite antigen ELISA of the head-thorax. The prevalence of Plasmodium infection across target communities was assessed using rapid diagnostic tests.

RESULTS

A total of 7327 (18.0 mosquitoes/trap/night) mosquitoes were trapped, mainly during the rainy season (5678, 77.5%) and at low altitude (3669, 50.1%). Anopheles spp. (5079, 69.3%) was the most abundant genera and An. gambiae complex (2691, 36.7%) the major vector, varying with altitude (χ² = 183.87, df = 8, P < 0.001) and season (χ² = 28.14, df = 4, P < 0.001). Only An. gambiae (s.s.) was identified following molecular analysis of An. gambiae complex siblings. The overall biting peak for An. gambiae complex was 2-3 a.m. Anopheles cinctus was the most abundant secondary vector in the area. The average EIR in the area was 2.08 infective bites per person per night (ib/p/n), higher at low (2.45 ib/p/n) than at intermediate altitude (1.39 ib/p/n) and during the rainy (1.76 ib/p/n) compared to the dry season (0.34 ib/p/n). Anopheles funestus was most infectious overall (28.1%, 16/57) while An. gambiae had the highest inoculation rates averaging 1.33 ib/p/n. Most Anopheles species across all altitudes and seasons were parous, highest in communities with the highest proportion of malaria parasite infections.

CONCLUSION

Anopheles gambiae (s.s.) remains the major malaria vector in the area and An. cinctus possibly a secondary vector of the disease in the slopes of Mt. Cameroon. The seasonal and altitudinal effects on the distribution of these mosquitoes may have implications for the transmission of malaria and its control strategies in the area. Regular monitoring of the bionomics of local Anopheles vector species and targeted control interventions in the 'hotspots' is necessary to curb the prevalence of the infection and incidence of disease.

Seasonal variation of microbiota composition in Anopheles gambiae and Anopheles coluzzii in two different eco-geographical localities in Cameroon

Understanding the environmental factors affecting the microbiota in malaria vectors may help in the development of novel vector control interventions, similar to paratransgenesis. This study evaluated seasonal and geographical variations in the microbial community of the two major malaria vectors. Adult Anopheles mosquitoes were collected across two different eco-geographical settings in Cameroon, during the dry and wet seasons. DNA was extracted from the whole individual mosquitoes from each group and processed for microbial analysis using Illumina Miseq sequencing of the V3-V4 region of the 16S rRNA gene. Data analysis was performed using QIIME2 and R software programs. A total of 1985 mosquitoes were collected and among them, 120 were selected randomly corresponding to 30 mosquitoes per season and locality. Overall, 97 bacterial taxa were detected across all mosquito samples, with 86 of these shared between dry and wet seasons in both localities and species. There were significant differences in bacterial composition between both seasons, with a clear separation observed between the dry and wet seasons (PERMANOVA comparisons of beta diversity, Pseudo-F = 10.45; q-value = 0.01). This study highlights the influence of seasonal variation on microbial communities and this variation's impact on mosquito biology and vectorial capacity should be further investigated.

Inference and dynamic simulation of malaria using a simple climate-driven entomological model of malaria transmission

Given the crucial role of climate in malaria transmission, many mechanistic models of malaria represent vector biology and the parasite lifecycle as functions of climate variables in order to accurately capture malaria transmission dynamics. Lower dimension mechanistic models that utilize implicit vector dynamics have relied on indirect climate modulation of transmission processes, which compromises investigation of the ecological role played by climate in malaria transmission. In this study, we develop an implicit process-based malaria model with direct climate-mediated modulation of transmission pressure borne through the Entomological Inoculation Rate (EIR). The EIR, a measure of the number of infectious bites per person per unit time, includes the effects of vector dynamics, resulting from mosquito development, survivorship, feeding activity and parasite development, all of which are moderated by climate. We combine this EIR-model framework, which is driven by rainfall and temperature, with Bayesian inference methods, and evaluate the model’s ability to simulate local transmission across 42 regions in Rwanda over four years. Our findings indicate that the biologically-motivated, EIR-model framework is capable of accurately simulating seasonal malaria dynamics and capturing of some of the inter-annual variation in malaria incidence. However, the model unsurprisingly failed to reproduce large declines in malaria transmission during 2018 and 2019 due to elevated anti-malaria measures, which were not accounted for in the model structure. The climate-driven transmission model also captured regional variation in malaria incidence across Rwanda’s diverse climate, while identifying key entomological and epidemiological parameters important to seasonal malaria dynamics. In general, this new model construct advances the capabilities of implicitly-forced lower dimension dynamical malaria models by leveraging climate drivers of malaria ecology and transmission.

Climate plays a fundamental and complex role in malaria transmission, by acting on multiple aspects of mosquito ecology and parasite transmissibility. However, to express malaria transmission pressure, malaria models with implicit vector dynamics have relied on indirect predictors of vector ecology, such as temporal seasonality or interpolations of rainfall/temperature, instead of entomological processes directly informed by ambient conditions. This approach obscures the specific influence of environmental conditions on relevant vector and parasite ecology, as well as meaningful interpretation of climate variability within these models. Here, we demonstrate that both interpretability and ecological effect from climate can be instantiated in lower dimension dynamical models through representation of transmission pressures via a climate-driven Entomological Inoculation Rate (EIR). This process-based model framework is driven by local rainfall and temperature, which regulate multiple aspects of the EIR, namely mosquito density, host-seeking activity, and parasite infectivity. Our results indicate that the climate-driven model construct is able to reproduce regional and local malaria transmission at seasonal and inter-annual time scales, while enabling identification of key entomological determinants of transmission.

Ecological and seasonal variations and other factors associated with clinical malaria in the Central Region of Ghana: A cross-sectional study

BACKGROUND

This study investigated malaria transmission under various contrasting settings in the Central Region, a malaria endemic region in Ghana.

METHODS

This cross-sectional study was carried out in five randomly selected districts in the Central Region of Ghana. Three of the districts were forested, while the rest was coastal. Study participants were selected to coincide with either the regular rainy or dry season. From each study site, hospital attendees were randomly selected with prior consent. Consciously, study participants were selected in both rainy (September and October, 2020) and dry (November and December, 2020) seasons. Clinical data for each patient was checked for clinical malaria suspicion and microscopic confirmation of malaria. Using SPSS Version 24 (Chicago, IL, USA), bivariate analysis was done to determine the association of independent variables (ecological and seasonal variations) with malaria status. When the overall analysis did not yield significant association, further statistical analysis was performed after stratification of variables (into age and gender) to determine whether any or both of them would significantly associate with the dependent variable.

RESULTS

Of the 3993 study participants, 62.5% were suspected of malaria whereas 38.2% were confirmed to have clinical falciparum malaria. Data analysis revealed that in both rainy and dry seasons, malaria cases were significantly higher in forested districts ) than coastal districts (x2 = 217.9 vs x2 = 50.9; p < 0.001). Taken together, the risk of malaria was significantly higher in the dry season (COR = 1.471, p < 0.001) and lower in coastal zones (COR = 0.826, p = 0.007). There was significant reduced risk of participants aged over 39 years of malaria (COR=0.657, p < 0.001). Whereas, in general patients between 10 and 19 years were insignificantly less likely to have malaria (COR = 0.911, p = 0.518) compared to participants aged less than< 10 years, the reverse was observed in coastal districts where patients less than 10 years of age in coastal districts were less likely to have malaria (COR=2.440, p = 0.003). In general, gender did not associate with malaria, but when stratified by study district, the risk of female gender to malaria was significantly higher in Agona Swedru (COR = 5.605, p < 0.001), Assin central (COR = 2.172, p < 0.001), Awutu Senya (COR = 2.410, p < 0.001) and Cape Coast (COR = 3.939, p < 0.001) compared to Abura-Asebu-Kwamankese.

CONCLUSION

This study demonstrated that the predictors of malaria differ from one endemic area to another. Therefore, malaria control interventions such as distribution of long-lasting insecticide treated bed nets, residual spraying with insecticide and mass distribution of antimalaria prophylaxis must be intensified in forested districts in all seasons with particular attention on females.

The effect of climatic factors on the number of malaria cases in an inland and a coastal setting from 2011 to 2017 in the equatorial rain forest of Cameroon

BACKGROUND

Weather fluctuation affects the incidence of malaria through a network of causuative pathays. Globally, human activities have ultered weather conditions over time, and consequently the number of malaria cases. This study aimed at determining the influence of humidity, temperature and rainfall on malaria incidence in an inland (Muyuka) and a coastal (Tiko) settings for a period of seven years (2011-2017) as well as predict the number of malaria cases two years after (2018 and 2019).

METHODS

Malaria data for Muyuka Health District (MHD) and Tiko Health District (THD) were obtained from the Regional Delegation of Public Health and Tiko District Health service respectively. Climate data for MHD was obtained from the Regional Delegation of Transport while that of THD was gotten from Cameroon Development Coorporation. Spearman rank correlation was used to investigate the relationship between number of malaria cases and the weather variables and the simple seasonal model was used to forecast the number of malaria cases for 2018 and 2019.

RESULTS

The mean monthly rainfall, temperature and relative humidity for MHD were 200.38 mm, 27.050C, 82.35% and THD were 207.36 mm, 27.57 °C and 84.32% respectively, with a total number of malaria cases of 56,745 and 40,160. In MHD, mean yearly humidity strongly correlated negatively with number of malaria cases (r = - 0.811, p = 0.027) but in THD, a moderate negative yearly correlation was observed (r = - 0.595, p = 0.159). In THD, the mean seasonal temperature moderately correlated (r = 0.599, p = 0.024) positively with the number of malaria cases, whereas MHD had a very weak negative correlation (r = - 0.174, p = 0.551). Likewise mean seasonal rainfall in THD moderately correlated (r = - 0.559, p = 0.038) negatively with malaria cases, contrary to MHD which showed a very weak positive correlation (r = 0.425, p = 0.130). The simple seasonal model predicted 6,842 malaria cases in Muyuka, for 2018 and same number for 2019, while 3167 cases were observed in 2018 and 2848 in 2019. Also 6,738 cases of malaria were predicted for MHD in 2018 likewise 2019, but 7327 cases were observed in 2018 and 21,735 cases in 2019.

CONCLUSION

Humidity is the principal climatic variable that negatively influences malaria cases in MHD, while higher seasonal temperatures and lower seasonal rain fall significantly increase malaria cases in THD.

Intermittent preventive treatment with Sulphadoxine-Pyrimethamine (IPTp-SP) is associated with protection against sub-microscopic P. falciparum infection in pregnant women during the low transmission dry season in southwestern Cameroon: A Semi - longitudinal study

The current guidelines for malaria prevention and control during pregnancy in Africa is predicated on the prevention of infection and/or disease through intermittent preventive treatment in pregnancy (IPTp), insecticide-treated nets (ITNs) and effective malaria case diagnosis and management. Concerns that increasing SP resistance in some areas of SSA may have compromised IPTp-SP efficacy prompted this contemporaneous study, designed to assess the prevalence and risk factors of sub-microscopic infection in parturient women during the low transmission season in Mutengene, a rapidly growing semi-urban area in Southwest Region, Cameroon. Pregnant women originally reporting for the establishment of antenatal clinic care during the dry season were followed-up to term and their pregnancy outcomes recorded. About 2 ml of venous blood was collected for malaria diagnosis using PfHRP2/pLDH malaria rapid diagnostic kit and light microscopy. DNA was extracted from dried blood spots by the Chelex-100 method and the Plasmodium falciparum status detected by nested PCR amplification of the 18SrRNA gene using specific predesigned primers. Of the 300 women enrolled, the proportion of malaria parasite infected as determined by microscopy, RDT and PCR was 12.9%, 16.4% and 29.4% respectively, with 39.9% overall infected with P. falciparum by microscopy and/or RDT and/or PCR and a very low-density infection, averaging 271 parasites per microliter of blood. About 25.0% (68/272) of women who were negative by microscopy were positive by PCR (submicroscopic P. falciparum infection), with primigravidae and IPTp-SP non usage identified as independent risk factors for submicroscopic P. falciparum parasitaemia while fever history (aOR = 4.83, 95% CI = 1.28-18.22, p = 0.020) was associated with risk of malaria parasite infection overall. IPTp-SP use (p = 0.007) and dosage (p = 0.005) significantly influenced whether or not the participant will be malaria parasite negative or carry submicroscopic or microscopic infection. Although Infant birthweight and APGAR score were independent of the mother's P. falciparum infection and submicroscopic status, infant's birthweight varied with the gravidity status (p = 0.001) of the mother, with significantly lower birthweight neonates born to primigravidae compared to secundigravidae (p = 0.001) and multigravidae (p = 0.003). Even in holo-endemic dry season, there exists a large proportion of pregnant women with very low density parasitaemia. IPTp-SP seems to be relevant in controlling submicroscopic P. falciparum infections, which remains common in pregnant women, and are hard to diagnose, with potentially deleterious consequences for maternal and fetal health. Future studies should be carried out in hyperendemic malaria foci where the parasitemia levels are substantially higher in order to confirm the efficacy of IPTp-SP.

An update on the mosquito fauna and mosquito-borne diseases distribution in Cameroon

The expansion of mosquito-borne diseases such as dengue, yellow fever, and chikungunya in the past 15 years has ignited the need for active surveillance of common and neglected mosquito-borne infectious diseases. The surveillance should be designed to detect diseases and to provide relevant field-based data for developing and implementing effective control measures to prevent outbreaks before significant public health consequences can occur. Mosquitoes are important vectors of human and animal pathogens, and knowledge on their biodiversity and distribution in the Afrotropical region is needed for the development of evidence-based vector control strategies. Following a comprehensive literature search, an inventory of the diversity and distribution of mosquitoes as well as the different mosquito-borne diseases found in Cameroon was made. A total of 290 publications/reports and the mosquito catalogue website were consulted for the review. To date, about 307 species, four subspecies and one putative new species of Culicidae, comprising 60 species and one putative new species of Anopheles, 67 species and two subspecies of Culex, 77 species and one subspecies of Aedes, 31 species and one subspecies of Eretmapodites, two Mansonia, eight Coquillettidia, and 62 species with unknown medical and veterinary importance (Toxorhynchites, Uranotaenia, Mimomyia, Malaya, Hodgesia, Ficalbia, Orthopodomyia, Aedeomyia, and Culiseta and Lutzia) have been collected in Cameroon. Multiple mosquito species implicated in the transmission of pathogens within Anopheles, Culex, Aedes, Eretmapodites, Mansonia, and Coquillettidia have been reported in Cameroon. Furthermore, the presence of 26 human and zoonotic arboviral diseases, one helminthic disease, and two protozoal diseases has been reported. Information on the bionomics, taxonomy, and distribution of mosquito species will be useful for the development of integrated vector management programmes for the surveillance and elimination of mosquito-borne diseases in Cameroon.

Seasonal prevalence of Plasmodium falciparum infection and use of insecticide-treated nets among children in three agroecosystems in Aboisso, Côte d'Ivoire

Agroecosystems have been associated with risk of malaria. The aim of this study was to determine the relationship between three agroecosystems: (i) rubber plantation (RP); (ii) oil palm plantation (OPP); (iii) no cash crop plantation (NCCP) and the prevalence of Plasmodium falciparum infection among children living in the Aboisso region. In the three villages within (Ehania-V5) or close (N'zikro) or far from (Ayébo) to each agroecosystem (RP, OPP, and NCCP), two cross-sectional parasitological surveys were carried out during the dry and the peak of the long wet seasons. A total of 586 children aged 1-14 years were recruited in the three villages to determine the prevalence of malaria using conventional microscopy. Plasmodium falciparum was the dominant species with an overall infection prevalence of 40.8%. There was a significant difference in prevalence between agroecosystems, during both the dry (p = 0.002) and wet seasons (p < 0.001), which was higher in agricultural settings compared with the NCCP environment, whatever the season. The prevalence of P. falciparum infection increased from the dry to the wet season in agricultural settings (RP and OPP), whereas no difference was noted for NCCP. Less than 18% of children use insecticide-treated nets (ITNs) in the three villages, ranging from 6 (in RP) to 30% (in OPP). Multivariate analysis indicated that age (1-4; 5-9; and 10-14 years) was not associated with malaria risk, but the season and living in agricultural villages were associated with a greater risk of malaria infection. Risk of malaria exposure was fourfold higher in children from agricultural villages than their counterpart from the non-agricultural area. Our findings highlight significant variations in the prevalence of P. falciparum according to agroecosystem and season. The findings will be useful in designing and implementing malaria control interventions by the National Malaria Control Program.

Comparison of conventional and non-invasive diagnostic tools for detecting Plasmodium falciparum infection in southwestern Cameroon: a cross-sectional study

Background

Malaria remains a significant health challenge in sub-Saharan Africa, with early diagnosis critical to reducing its morbidity and mortality. Despite the increasing Plasmodium spp. diagnostic capabilities, access to testing is limited in some cases by the almost absolute requirement for blood from potentially infected subjects as the only sample source for all conventional methods. A rapid test on non-invasive specimen with comparable performance to microscopy for the screening or diagnosis of all participants is invaluable. This study sought to compare conventional and non-invasive diagnostic tools for detecting Plasmodium falciparum.

Methods

This was a cross-sectional study, carried out between March and August 2019 to evaluate and compare the diagnostic performance of a PfHRP2/pLDH-based malaria rapid diagnostic test (mRDT) on patients’ blood, saliva and urine relative to conventional light microscopy and nested PCR at outpatient clinics in the Buea and Tiko health districts of Southwestern Cameroon. The significance of differences in proportions was explored using the Pearson’s χ² test whereas differences in group means were assessed using analyses of variance.

Results

A total of 359 individuals of both sexes, aged 1–92 years, were enrolled into the study. Of the 301 individuals tested by light microscopy and mRDTs on blood, saliva and urine, 84 (27.9%), 81 (26.9%), 87 (28.9%) and 107 (35.5%) respectively were positive. However, only 34.3%, 90.5%, 91.4%, 83.9% and 65.4% febrile, light microscopy and mRDT positives on blood, saliva and urine respectively had P. falciparum infection as confirmed by PCR. The sensitivity and specificity of presumptive diagnosis, light microscopy and mRDT on blood, saliva and urine were 86.9% and 19.7%, 77.8% and 96.1%, 75.8% and 96.6%, 74.5% and 93.1%, and 70.7% and 81.8%, respectively. The agreement between mRDT on saliva (k = 0.696) and microscopy (k = 0.766) compared to PCR was good.

Conclusion

The study highlighted the low performance of presumptive diagnosis, reinforcing the need for parasitological tests prior to antimalarial therapy. The higher PfHRP2/pLDH mRDT parasite detection rates and sensitivity in saliva compared to urine suggests that the former is a practical adjunct to or alternative worth optimising for the routine diagnosis of malaria.

Graphic Abstract

Flow chart for diagnosis of P. falciparum infection by light microscopy, rapid diagnostic tests and nested PCR.

Epidemiological and entomological studies of malaria transmission in Tibati, Adamawa region of Cameroon 6 years following the introduction of long-lasting insecticide nets

BACKGROUND

Malaria remains a serious public health problem in Cameroon. Implementation of control interventions requires prior knowledge of the local epidemiological situation. Here we report the results of epidemiological and entomological surveys carried out in Tibati, Adamawa Region, Cameroon, an area where malaria transmission is seasonal, 6 years after the introduction of long-lasting insecticidal bed nets.

METHODS

Cross-sectional studies were carried out in July 2015 and 2017 in Tibati. Thick blood smears and dried blood spots were collected from asymptomatic and symptomatic individuals in the community and at health centers, respectively, and used for the molecular diagnosis of Plasmodium species. Adult mosquitoes were collected by indoor residual spraying and identified morphologically and molecularly. The infection status of Plasmodium spp. was determined by quantitative PCR, and positivity of PCR-positive samples was confirmed by Sanger sequencing.

RESULTS

Overall malaria prevalence in our study population was 55.0% (752/1367) and Plasmodium falciparum was the most prevalent parasite species (94.3%), followed by P. malariae (17.7%) and P. ovale (0.8%); 92 (12.7%) infections were mixed infections. Infection parameters varied according to clinical status (symptomatic/asymptomatic) and age of the sampled population and the collection sites. Infection prevalence was higher in asymptomatic carriers (60.8%), but asexual and sexual parasite densities were lower. Prevalence and intensity of infection decreased with age in both the symptomatic and asymptomatic groups. Heterogeneity in infections was observed at the neighborhood level, revealing hotspots of transmission. Among the 592 Anopheles mosquitoes collected, 212 (35.8%) were An. gambiae, 172 (29.1%) were An. coluzzii and 208 (35.1%) were An. funestus (s.s.). A total of 26 (4.39%) mosquito specimens were infected by Plasmodium sp. and the three Anopheles mosquitoes transmitted Plasmodium at equal efficiency. Surprisingly, we found an An. coluzzii specimen infected by Plasmodium vivax, which confirms circulation of this species in Cameroon. The positivity of all 26 PCR-positive Plasmodium-infected mosquitoes was successively confirmed by sequencing analysis.

CONCLUSION

Our study presents the baseline malaria parasite burden in Tibati, Adamawa Region, Cameroon. Our results highlight the high malaria endemicity in the area, and hotspots of disease transmission are identified. Parasitological indices suggest low bednet usage and that implementation of control interventions in the area is needed to reduce malaria burden. We also report for the first time a mosquito vector with naturally acquired P. vivax infection in Cameroon.

Insights into factors sustaining persistence of high malaria transmission in forested areas of sub-Saharan Africa: the case of Mvoua, South Cameroon

BACKGROUND

In Mvoua, a village situated in a forested area of Cameroon, recent studies have reported high prevalence of Plasmodium falciparum infection among the population. In order to understand factors that can sustain such a high malaria transmission, we investigated the biology of Anopheles vectors and its susceptibility to insecticides, as well as long-lasting insecticidal net (LLIN) coverage, use and bio-efficacy.

METHODS

A longitudinal entomological survey was conducted from July 2018 to April 2019. Adult mosquitoes were collected using the human landing catch (HLC) method and identified using morphological and molecular techniques. Anopheles gambiae (s.l.) larvae were sampled from several stagnant water pools throughout the village and reared to generate F1 adults. The presence of P. falciparum circumsporozoite antigen was detected in the heads and thoraces of mosquitoes collected as adults using an enzyme-linked immunosorbent assay. The insecticide susceptibility status of the local An. gambiae (s.l.) F1 population to the pyrethroid insecticides deltamethrin 0.5% and permethrin 0.75% was determined using World Health Organization-tube bioassays, while the frequency of the knockdown resistance (kdr) mutation was determined by PCR. Coverage, use and physical integrity of LLINs were assessed in households, then cone assays were used to test for their bio-efficacy on both the reference insecticide-susceptible Kisumu strain and on field F1 An. gambiae (s.l.) RESULTS: In total, 110 Anopheles mosquitoes were collected, of which 59.1% were identified as Anopheles funestus (s.l.), 38.18% as An. gambiae (s.l.) and 2.72% as An. ziemanii. Anopheles funestus was the most abundant species except in the long rainy season, when An. gambiae (s.l.) predominated (65.8%). In the dry seasons, vectors were principally endophagous (76% of those collected indoors) while they tended to be exophagous (66% of those collected outdoors) in rainy seasons. High Plasmodium infection was observed in An. gambiae (s.l.) and An. funestus, with a circumsporozoitic rate of 14.29 and 10.77%, respectively. Anopheles gambiae (s.l.) was highly resistant to pyrethroid insecticides (mortality rates: 32% for permethrin and 5% for deltamethrin) and harbored the kdr-L1014F mutation at a high frequency (89.74%). Of the 80 households surveyed, only 47.69% had achieved universal coverage with LLNs. Around 70% of the LLINs sampled were in poor physical condition, with a proportionate hole index > 300. Of the ten LLNs tested, eight were effective against the An. gambiae reference insecticide-susceptible Kisumu strain, showing mortality rate of > 80%, while none of these LLINs were efficient against local An. gamabie (s.l.) populations (mortality rates < 11.5%).

CONCLUSION

A combination of elevated P. falciparum infection in Anopheles vector populations, insufficient coverage and loss of effectiveness of LLINs due to physical degradation, as well as high resistance to pyrethroid insecticides is responsible for the persistence of high malaria transmission in forested rural area of Mvoua, Cameroon.

Influence of a Major Mountainous Landscape Barrier (Mount Cameroon) on the Spread of Metabolic (GSTe2) and Target-Site (Rdl) Resistance Alleles in the African Malaria Vector Anopheles funestus

Increased levels of insecticide resistance in major malaria vectors such as Anopheles funestus threaten the effectiveness of insecticide-based control programmes. Understanding the landscape features impacting the spread of resistance makers is necessary to design suitable resistance management strategies. Here, we examined the influence of the highest mountain in West Africa (Mount Cameroon; 4095 m elevation) on the spread of metabolic and target-site resistance alleles in An. funestus populations. Vector composition varied across the four localities surveyed along the altitudinal cline with major vectors exhibiting high parity rate (80.5%). Plasmodium infection rates ranged from 0.79% (An. melas) to 4.67% (An. funestus). High frequencies of GSTe2^R (67–81%) and Rdl^R (49–90%) resistance alleles were observed in An. funestus throughout the study area, with GSTe2^R frequency increasing with altitude, whereas the opposite is observed for Rdl^R. Patterns of genetic diversity and population structure analyses revealed high levels of polymorphisms with 12 and 16 haplotypes respectively for GSTe2 and Rdl. However, the reduced diversity patterns of resistance allele carriers revealed signatures of positive selection on the two genes across the study area irrespective of the altitude. Despite slight variations associated with the altitude, the spread of resistance alleles suggest that control strategies could be implemented against malaria vectors across mountainous landscapes.

Role of Anopheles gambiae s.s. and Anopheles coluzzii (Diptera: Culicidae) in Human Malaria Transmission in Rural Areas of Bouaké, in Côte d'Ivoire

Studies done in Bouaké (Côte d'Ivoire) about 20-yr ago reported that Anopheles gambiae s.l. Giles was the major malaria vector. The present study aimed to update these data and to identify the main vectors. Mosquitoes were collected in Allokokro and Petessou villages between June 2014 and December 2015 using the human landing catching method. Potential breeding sites of An. gambiae s.l. were identified in August and October 2014 and mapped using GPS. Anopheles species were morphologically and molecularly [polymerase chain reaction (PCR)] identified. Ovaries of female were dissected to determine the parity and infection with Plasmodium was detected in head and thorax by quantitative PCR. In Allokokro, the biting rate of An. gambiae s.s was significantly greater than Anopheles coluzzii, whereas, in Petessou, biting rates of both species were comparable. Plasmodium falciparum (Haemosporida: Plasmodiidae), Plasmodium malariae (Haemosporida: Plasmodiidae), and Plasmodium ovale (Haemosporida: Plasmodiidae) identified in both villages. The infection rates of An. gambiae s.s. and An. coluzzii were not significantly different. The entomological inoculation rate (EIR) of An. gambiae s.s. for P. falciparum was 9-fold greater than that of An. coluzzii in Allokokro; however, in Petessou, the EIRs of both species were comparable. In both village, An. gambiae s.s was responsible for P. falciparum and P. ovale transmission whereas An. coluzzii transmitted all three Plasmodium species.

Vector dynamics predicts transmission dynamics: a simple, realistic and sensible approach for measuring malaria endemicity

Entomological indicators such as vector density, distribution, biology and bionomics and their vectorial attributes are important parameters for measuring the pattern and intensity of malaria transmission. Although published articles provide evidence for the existence of associations between entomological indices and malaria transmission dynamics, none of them is able to establish a strong correlation. In order to address this issue, the present study aims to assess how malaria transmission is influenced and can be predicted by local major vector dynamics. We carried out an entomological assessment of major Anopheline vector abundance, habit/habitat, resting and feeding behavior, infectivity rates, and other entomological parameters. Results suggest that malaria transmission was correlated with a vector control intervention and non-intervention scenario in a high endemic region of Kalahandi district of Odisha, India. Amongst all indices, infective anthropophagic vectors established a strong positive correlation with malaria morbidity in comparison to infective or anthropophagic vector species during both the study periods. Though other entomological parameters influenced the transmission intensity, little quantifiable association was detected among study sites. This study provides strong baseline evidence of an association between entomological indices and malaria transmission dynamics, which could be used as an early warning system for outbreak prediction.

The effect of improved housing on indoor mosquito density and exposure to malaria in the rural community of Minkoameyos, Centre Region of Cameroon

BACKGROUND

This study evaluated the effectiveness of improved housing on indoor residual mosquito density and exposure to infected Anophelines in Minkoameyos, a rural community in southern forested Cameroon.

METHODS

Following the identification of housing factors affecting malaria prevalence in 2013, 218 houses were improved by screening the doors and windows, installing plywood ceilings on open eaves and closing holes on walls and doors. Monthly entomological surveys were conducted in a sample of 21 improved and 21 non-improved houses from November 2014 to October 2015. Mosquitoes sampled from night collections on human volunteers were identified morphologically and their parity status determined. Mosquito infectivity was verified through Plasmodium falciparum CSP ELISA and the average entomological inoculation rates determined. A Reduction Factor (RF), defined as the ratio of the values for mosquitoes collected outdoor to those collected indoor was calculated in improved houses (RFI) and non-improved houses (RFN). An Intervention Effect (IE = RFI/RFN) measured the true effect of the intervention. Chi square test was used to determine variable significance. The threshold for statistical significance was set at P < 0.05.

RESULTS

A total of 1113 mosquitoes were collected comprising Anopheles sp (58.6%), Culex sp (36.4%), Aedes sp (2.5%), Mansonia sp (2.4%) and Coquillettidia sp (0.2%). Amongst the Anophelines were Anopheles gambiae sensu lato (s.l.) (95.2%), Anopheles funestus (2.9%), Anopheles ziemanni (0.2%), Anopheles brohieri (1.2%) and Anopheles paludis (0.5%). Anopheles gambiae sensu stricto (s.s.) was the only An. gambiae sibling species found. The intervention reduced the indoor Anopheles density by 1.8-fold (RFI = 3.99; RFN = 2.21; P = 0.001). The indoor density of parous Anopheles was reduced by 1.7-fold (RFI = 3.99; RFN = 2.21; P = 0.04) and that of infected Anopheles by 1.8-fold (RFI = 3.26; RFN = 1.78; P = 0.04). Indoor peak biting rates were observed between 02 a.m. to 04 a.m. in non-improved houses and from 02 a.m. to 06 a.m. in improved houses.

CONCLUSION

Housing improvement contributed to reducing indoor residual anopheline density and malaria transmission. This highlights the need for policy specialists to further evaluate and promote aspects of house design as a complementary control tool that could reduce indoor human-vector contact and malaria transmission in similar epidemiological settings.

Monthly Entomological Inoculation Rate Data for Studying the Seasonality of Malaria Transmission in Africa

A comprehensive literature review was conducted to create a new database of 197 field surveys of monthly malaria Entomological Inoculation Rates (EIR), a metric of malaria transmission intensity. All field studies provide data at a monthly temporal resolution and have a duration of at least one year in order to study the seasonality of the disease. For inclusion, data collection methodologies adhered to a specific standard and the location and timing of the measurements were documented. Auxiliary information on the population and hydrological setting were also included. The database includes measurements that cover West and Central Africa and the period from 1945 to 2011, and hence facilitates analysis of interannual transmission variability over broad regions.

Video Recording Can Conveniently Assay Mosquito Locomotor Activity

Anopheles gambiae and Aedes aegypti are perhaps the best studied mosquito species and important carriers of human malaria and arbovirus, respectively. Mosquitoes have daily rhythms in behaviors and show a wide range of activity patterns. Although Anopheles is known to be principally nocturnal and Aedes principally diurnal, details of mosquito activity are not easily assayed in the laboratory. We recently described FlyBox, a simple tracking system for assaying Drosophila locomotor activity rhythms and thought that it might also be applicable to monitoring mosquito activity. Indeed, we show here that FlyBox can easily, conveniently, affordably and accurately measure the activity of Anopheles as well as Aedes over several days. The resulting profiles under light-dark as well as constant darkness conditions are compatible with results in the literature, indicating that this or similar systems will be useful in the future for more detailed studies on a range of insect species and under more diverse laboratory conditions.

Modelled and observed mean and seasonal relationships between climate, population density and malaria indicators in Cameroon

Background

A major health burden in Cameroon is malaria, a disease that is sensitive to climate, environment and socio-economic conditions, but whose precise relationship with these drivers is still uncertain. An improved understanding of the relationship between the disease and its drivers, and the ability to represent these relationships in dynamic disease models, would allow such models to contribute to health mitigation and adaptation planning. This work collects surveys of malaria parasite ratio and entomological inoculation rate and examines their relationship with temperature, rainfall, population density in Cameroon and uses this analysis to evaluate a climate sensitive mathematical model of malaria transmission.

Methods

Co-located, climate and population data is compared to the results of 103 surveys of parasite ratio (PR) covering 18,011 people in Cameroon. A limited set of campaigns which collected year-long field-surveys of the entomological inoculation rate (EIR) are examined to determine the seasonality of disease transmission, three of the study locations are close to the Sanaga and Mefou rivers while others are not close to any permanent water feature. Climate-driven simulations of the VECTRI malaria model are evaluated with this analysis.

Results

The analysis of the model results shows the PR peaking at temperatures of approximately 22 °C to 26 °C, in line with recent work that has suggested a cooler peak temperature relative to the established literature, and at precipitation rates at 7 mm day⁻¹, somewhat higher than earlier estimates. The malaria model is able to reproduce this broad behaviour, although the peak occurs at slightly higher temperatures than observed, while the PR peaks at a much lower rainfall rate of 2 mm day⁻¹. Transmission tends to be high in rural and peri-urban relative to urban centres in both model and observations, although the model is oversensitive to population which could be due to the neglect of population movements, and differences in hydrological conditions, housing quality and access to healthcare. The EIR follows the seasonal rainfall with a lag of 1 to 2 months, and is well reproduced by the model, while in three locations near permanent rivers the annual cycle of malaria transmission is out of phase with rainfall and the model fails.

Conclusion

Malaria prevalence is maximum at temperatures of 24 to 26 °C in Cameroon and rainfall rates of approximately 4 to 6 mm day⁻¹. The broad relationships are reproduced in a malaria model although prevalence is highest at a lower rainfall maximum of 2 mm day⁻¹. In locations far from water bodies malaria transmission seasonality closely follows that of rainfall with a lag of 1 to 2 months, also reproduced by the model, but in locations close to a seasonal river the seasonality of malaria transmission is reversed due to pooling in the transmission to the dry season, which the model fails to capture.

Review of malaria situation in Cameroon: technical viewpoint on challenges and prospects for disease elimination

Malaria still has a devastating impact on public health and welfare in Cameroon. Despite the increasing number of studies conducted on disease prevalence, transmission patterns or treatment, there are to date, not enough studies summarising findings from previous works in order to identify gaps in knowledge and areas of interest where further evidence is needed to drive malaria elimination efforts. The present study seeks to address these gaps by providing a review of studies conducted so far on malaria in Cameroon since the 1940s to date. Over 250 scientific publications were consulted for this purpose. Although there has been increased scale-up of vector control interventions which significantly reduced the morbidity and mortality to malaria across the country from a prevalence of 41% of the population reporting at least one malaria case episode in 2000 to a prevalence of 24% in 2017, the situation is not yet under control. There is a high variability in disease endemicity between epidemiological settings with prevalence of Plasmodium parasitaemia varying from 7 to 85% in children aged 6 months to 15 years after long-lasting insecticidal nets (LLINs) scale-up. Four species of Plasmodium have been recorded across the country: Plasmodium falciparum, P. malariae, P. ovale and P. vivax. Several primate-infecting Plasmodium spp. are also circulating in Cameroon. A decline of artemisinin-based combinations therapeutic efficacy from 97% in 2006 to 90% in 2016 have been reported. Several mutations in the P. falciparum chloroquine resistance (Pfcrt) and P. falciparum multidrug resistance 1 (Pfmdr1) genes conferring resistance to either 4-amino-quinoleine, mefloquine, halofanthrine and quinine have been documented. Mutations in the Pfdhfr and Pfdhps genes involved in sulfadoxine-pyrimethamine are also on the rise. No mutation associated with artemisinin resistance has been recorded. Sixteen anopheline species contribute to malaria parasite transmission with six recognized as major vectors: An. gambiae, An. coluzzii, An. arabiensis, An. funestus, An. nili and An. moucheti. Studies conducted so far, indicated rapid expansion of DDT, pyrethroid and carbamate resistance in An. gambiae, An. coluzzii, An. arabiensis and An. funestus threatening the performance of LLINs. This review highlights the complex situation of malaria in Cameroon and the need to urgently implement and reinforce integrated control strategies in different epidemiological settings, as part of the substantial efforts to consolidate gains and advance towards malaria elimination in the country.

Coverage and usage of insecticide treated nets (ITNs) within households: associated factors and effect on the prevalance of malaria parasitemia in the Mount Cameroon area

Background

Insecticide-treated nets (ITNs) are a widely used tool that has been proven to be effective in the prevention and control of malaria in malaria endemic countries. However, usage varies among households and can greatly affect the benefits of ITNs as a control tool for malaria transmission. This study determined the coverage and usage of ITNS as well as associated factors and the effect of coverage and usage on the prevalence of malaria parasitemia within households in the Mount Cameroon area.

Methods

A cross-sectional survey was conducted between August and September 2014 in six communities within the Mount Cameroon area. Households within the communities were enrolled through multistage sampling and household survey was done using a structured questionnaire. Capillary blood was collected for malaria parasite determination. Data was analysed using SPSS version 20 for windows. Differences in proportions were assessed using the Chi-square test while factors affecting ITNs usage were assessed in multivariate logistic regression at a statistical significance of P ≤ 0.05.

Results

A total of 504 households were surveyed, 1564 bed spaces reported while 915(58.5, 95% CI: 56.1–60.9) of the bed spaces had nets and 391(77.6, 95% CI, 74.0–80.2) of the households had at least one bed net. The odds of using ITNs was 2 folds higher (OR = 2.41; 95% CI 1.58–3.69 p = 0.001) and 3 folds higher (OR = 3.149, 95% CI 1.53–6.47 p = 0.002) among houses with 5 to 9 occupants and above 10 occupants respectively when compared to houses with less than 5 occupants. In addition, Individuals living in cement block houses were less likely to use ITNs.

Compared to those living in wooden houses (OR = 0.488, 95% CI: 0.269–0.885; p = 0 .018). Rural communities had lower ITN coverage compared to semi-urban communities (p = 0.0001). Increase in ITNs coverage significantly reduces malaria prevalence (correlation − 0.899, p = 0.015).

Conclusion

Despite the efforts made to scale up ITN distribution so that universal coverage can be attained, coverage remains low. Increasing coverage and putting in place a mechanism to replace torn nets will go a long way reduce the prevalence of malaria parasitemia.

Electronic supplementary material

The online version of this article (10.1186/s12889-019-7555-x) contains supplementary material, which is available to authorized users.

Malaria Perceptions among Medicine Vendors in Buea Community: An Assessment of Knowledge of Malaria and Conditions of Antimalarial Drug Dispensing

Background:

Lack of knowledge of rational use of antimalarial drugs among medicine vendors is a serious problem, notably in areas of intense transmission. These misunderstandings increase the risks of resistance and adverse drug reactions. This study aimed to assess knowledge of malaria and environments wherein medicine vendors dispense antimalarials in the Buea community.

Methods:

Administration of a community-based cross-sectional survey of a random sample of 140 medicine vendors living within the Buea community occurred between March and June 2017. The survey sought to obtain information from medicine vendors on their general knowledge of malaria as well as their dispensing practices. Statistically significant findings were associated with p ≤ .05.

Results:

The majority of participants were aware that use of insecticide – treated bed nets (ITNs) and maintenance of a clean environment equate to effective malaria prevention efforts. Alternatively, only one-third of participants correctly attributed the causative organism of malaria to being protozoan. Participants employed within drugstore settings had less knowledge of malaria than their hospital/community counterparts did. A directly proportional relationship existed between the amount of experience that participants had in their respective disciplines with an increased knowledge of malaria overall.

Conclusion:

These findings reveal fluctuating knowledge of malaria among study participants. Reported antimalarial dispensing practices also warrants room for improvement. Routine monitoring and evaluation to prevent emergence of resistant strains to current efficacious antimalarials remains paramount.

Influence of infant feeding practices on the occurrence of malnutrition, malaria and anaemia in children ≤5 years in the Mount Cameroon area: A cross sectional study

BACKGROUND

The objective of this study was to evaluate the influence of different infant feeding habits on the occurrence of malnutrition, Plasmodium falciparum parasitaemia and anaemia in children ≤5 years in the Mount Cameroon area.

METHODOLOGY

A total of 1227 children ≤5 years of age were recruited in a descriptive cross-sectional study. Socio demographic data and information on the different infant feeding habits was obtained by the use of semi-structured questionnaire. Nutritional status was assessed by the use of anthropometric measurements. Plasmodium was detected by light microscopy and haemoglobin was measured by use of an auto-haematology analyser. Anaemia as well as its severity was classified based on WHO standards. The associations between variables were assessed using logistic regression analysis.

RESULTS

The prevalence of exclusive breast feeding (EBF) was 22.6%, mixed feeding (MF) was 60.1% and those not breastfed (NBF) at all was 17.3%. The prevalence of malnutrition, P. falciparum parasitaemia and anaemia was 32.6%, 30.4% and 77.3% respectively. Children who had EBF had significantly lower (P <0.001) prevalence of malaria parasite (16.2%) than those NBF at all (61.3%). The prevalence of anaemia was significantly higher (P <0.001) in children who had MF (80.5%) while, severe and moderate anaemia was highest in those NBF at all (6.6%, 67.1% respectively; P = 0.029) than their counterparts. The significant predictors of anaemia were age group (P <0.001), marital status (P <0.001) and educational level of parent (P <0.001), that for malaria parasitaemia was infant feeding habit (MF: P< 0.001 and NBF: P <0.001) and malnutrition was age group (≤2 years: P <0.008 and 2.1-4.0 years: P = 0.028).

CONCLUSION

The infant feeding habit significantly influenced the occurrence of malaria parasite infection and not malnutrition and anaemia, hence EBF should be encouraged in malaria endemic zones.

Patterns of anopheline feeding/resting behaviour and Plasmodium infections in North Cameroon, 2011-2014: implications for malaria control

Background

Effective malaria control relies on evidence-based interventions. Anopheline behaviour and Plasmodium infections were investigated in North Cameroon, following long-lasting insecticidal net (LLIN) distribution in 2010.

Methods

During four consecutive years from 2011 to 2014, adult mosquitoes were collected indoors, outdoors and in exit traps across 38 locations in the Garoua, Pitoa and Mayo-Oulo health districts. Anophelines were morphologically and molecularly identified, then analysed for blood meal origins and Plasmodium falciparum circumsporozoite protein (Pf-CSP). Blood from children under 5 years-old using LLINs was examined for Plasmodium infections.

Results

Overall, 9376 anophelines belonging to 14 species/sibling species were recorded. Anopheles gambiae (s.l.) [An. arabiensis (73.3%), An. coluzzii (17.6%) and An. gambiae (s.s.) (9.1%)] was predominant (72%), followed by An. funestus (s.l.) (20.5%) and An. rufipes (6.5%). The recorded blood meals were mainly from humans (28%), cattle (15.6%) and sheep (11.6%) or mixed (45%). Pf-CSP rates were higher indoors (3.2–5.4%) versus outdoors (0.8–2.0%), and increased yearly (χ² < 18, df = 10, P < 0.03). Malaria prevalence in children under 5 years-old, in households using LLINs was 30% (924/3088).

Conclusions

The present study revealed the variability of malaria vector resting and feeding behaviour, and the persistence of Plasmodium infections regardless the use of LLINs. Supplementary interventions to LLINs are therefore needed to sustain malaria prevention in North Cameroon.

Involvement of Anopheles nili in Plasmodium falciparum transmission in North Benin

BACKGROUND

Several studies carried out in Benin have shown the involvement of Anopheles gambiae sensu lato (s.l.), the Anopheles funestus group in malaria transmission, but none of them reported the contribution of the Anopheles nili group to the transmission of this disease. The current study investigated the question through an entomological cross-sectional survey performed in Northern Benin.

METHODS

Mosquito samplings were performed in September and October 2017 in 4 villages located in two districts: Bambaba and Wodara (Kérou district) and, Péhunco 2 and Béké (Péhunco district). The collections were carried out indoors and outdoors using human landing catches (HLC) to assess the human biting rate (HBR) and pyrethrum spray catches (PSC) to evaluate the blood feeding rate and the blood meal origin using the ELISA test. All collected mosquitoes were morphologically identified and, the polymerase chain reaction (PCR) technique was used for molecular identification of sibling species of An. gambiae s.l., An. funestus group and An. nili group sporozoite index (SI) was also assessed by the ELISA test.

RESULTS

Overall, An. gambiae s.l., An. funestus group and An. nili group were the three vectors found in the study area. A significantly higher human biting rate (HBR) was recorded in An. nili group (5 bites/human/night) compared to An. funestus group (0.656 bites/human/night) in the Kérou district (p < 0.0001). Anopheles gambiae s.l. displayed the highest HBR (26.19 bites/human/night) in the same district. The entomological inoculation rate (EIR) was 1.875 infected bites/human/month in An. nili group against 13.05 infected bites/human/month in An. gambiae s.l. and 0.938 infected bites/human/month in An. funestus group in Kérou. In Péhunco, the EIR was 1.02 infected bites/human/month in An. gambiae s.l. PCR results showed that An. nili sensu stricto (s.s.) and An. funestus s.s. were the only species of the An. nili and An. funestus groups, respectively. The anthropophagic character of An. gambiae s.l. was also highlighted.

CONCLUSION

This study provides useful information on the contribution of An. nili group as secondary vector to malaria transmission in northern Benin. Broader studies must also be carried out in a larger study area to assess the involvement of other Anopheles species to malaria transmission. This will aid to better plan malaria vector control interventions.

Comparison of the Accuracy of Four Malaria Diagnostic Methods in a High Transmission Setting in Coastal Cameroon

Background

Despite recommendation from the World Health Organization that all malaria suspected patients undergo a parasitological confirmation using rapid diagnostic test or light microscopy prior to treatment, health facilities in remote malaria endemic settings sometimes resort to presumptive diagnosis of malaria for clinical management for various reasons. Following observation of this practice, we undertook a cross-sectional study aimed at comparing presumptive diagnosis based on axillary temperature, SD Bioline™ rapid test, and light microscopy as strategies for malaria diagnosis in the coastal region of Mutengene in the South West of Cameroon with the overall goal of supporting improved malaria diagnosis at local levels.

Methodology

Venous blood from 320 participants was used to detect the presence of malaria parasite using SD Bioline™ mRDT and Giemsa stained microscopy or spotted on filter paper for PCR amplification of the 18s rRNA gene of Plasmodium sp following standard procedures. The axillary temperature of each participant was also measured. The sensitivity, specificity, and predictive values and their confidence intervals were determined for each of the methods with PCR as the reference. The area under the curve was used to estimate accuracy of diagnostic method and compared between test method using the X² test with P<0.05 considered significant.

Results

The overall diagnostic sensitivities of presumptive diagnosis using axillary temperature, light microscopy, and SD Bioline™ were observed to be 74.30% (95%CI: 67.90-80.01), 94.86% (95%CI: 90.99-97.41), and 95.33% (95%CI: 91.57-97.74), respectively, and their respective diagnostic specificities were 53.77% (95%CI: 43.82-63.51), 94.34% (95%CI: 88.09-97.87), and 94.34%(95%CI: 88.09-97.89). SD Bioline™ had a diagnostic sensitivity of 91.80% [95%CI: 81.90-97.28] at a parasitaemia of less than 500 parasites/μl of blood but a sensitivity of 100% for parasite counts above 500 parasites/μl of blood. The predictive values of the positive test were highly comparable between light microscopy (90.09%, [95%CI: 83.61-94.18]) and SD Bioline™ mRDT (90.91%, [95%CI: 84.50-94.83]), P=0.98 with kappa values of 0.898 but lower for presumptive diagnosis (50.89%, [95%CI: 43.72-58.03]), P<0.0001, and kappa value of 0.277. Perfect agreement was observed between SD Bioline™ mRDT and light microscopy (Cohen kappa= 0.924).

Conclusions

The study showed that SD Bioline™ was as good as light microscopy in the diagnosis of malaria in remote areas of perennial transmission in South West Cameroon. This study equally revealed the limitations of presumptive diagnosis of malaria (as opposed to the use of RDTs or microscopy). Efforts should be made in such areas to promote parasitological confirmation of malaria using quality assured rapid tests or light microscopy for case management of malaria. The presence of nonnegligible levels of Plasmodium ovale in this study area indicate that treatment guidelines may require revision if same trend is proven in several other areas of same ecology.

Bionomics and vectorial role of anophelines in wetlands along the volcanic chain of Cameroon

BACKGROUND

The epidemiological profiles of vector-borne diseases, such as malaria, are strongly associated with landscape components. The reduction of malaria burden in endemic and epidemic regions mainly depends on knowledge of the malaria-transmitting mosquito species, populations and behavioural characteristics, as well as malaria exposure risks. This work aimed at carrying out a holistic study in order to characterise Anopheles species in relation to human malaria in seven wetlands along the lower section of the volcanic chain of Cameroon.

RESULTS

Eight malaria vectors: Anopheles arabiensis, An. coluzzii, An. funestus (s.s.), An. gambiae, An. hancocki, An. melas, An. nili and An. ziemanni, were found biting humans. Anopheles gambiae was widespread; however, it played a secondary role in the Ndop plain where An. ziemmani was the primary vector species (79.2%). Anophelines were more exophagic (73.6%) than endophagic (26.4%), showing a marked nocturnal activity (22:00-4:00 h) for An. coluzzii and An. gambiae while An. funestus (s.s.) was mostly caught between 1:00 and 6:00 h and An. ziemanni having an early evening biting behaviour (18:00-00:00 h). Female Anopheles were mostly observed to have relative high parity rates (≥ 70%), with the exception of the Meanja site where species parity varies from 46 to 55%. Overall, the transmission level was low with entomological inoculation rates estimated to 0.7 infected bites per person per month (ib/p/mth) in Tiko and Ndop, 1.4 ib/p/mth in Mamfe and 2.24 ib/p/mth in Santchou.

CONCLUSIONS

The present study represents detailed Anopheles vector characterisation from an understudied area along the volcanic chain of Cameroon with endemic malaria transmission. The significant differences in bionomics and Anopheles species distribution within the studied wetlands, highlights the importance of providing baseline data and an opportunity to assess the outcome of ongoing malaria control interventions in the country.

Insecticide susceptibility status of Anopheles gambiae (s.l.) in South-West Cameroon four years after long-lasting insecticidal net mass distribution

BACKGROUND

Members of the Anopheles gambiae (s.l.) complex are one of the major vectors of malaria in Africa. LLINs and IRS are the most effective tools used in vector control of malaria. However, their effectiveness may be hampered by the development and spread of insecticide resistance in the target vectors species. The objective of this study was to assess the susceptibility of Anopheles gambiae (s.l.) mosquitoes from South-West Cameroon to deltamethrin, permethrin and to malathion, four years after the mass deployment of LLINs.

METHODS

Anopheles larvae were collected from Limbe, Tiko and Buea, three cities of the Fako division and reared until adult emergence. Adult mosquitoes from field larvae were identified as belonging to the Anopheles gambiae (s.l.) complex using standard identification keys. Susceptibility of mosquito samples to deltamethrin, permethrin and malathion was assessed using WHO susceptibility tests protocol for adult mosquitoes. Molecular identification of tested samples was performed using the PCR SINE200 protocol and by PCR-RFLP. The kdr alleles were genotyped using the hot ligation oligonucleotide assay (HOLA).

RESULTS

Two species of the An. gambiae (s.l.) complex, An. coluzzii and An. gambiae (s.s.) were identified in all three study locations with high proportions of An. coluzzii in Limbe (84.06%) and Tiko (92.2%), while in Buea, An. coluzzii (55.6%) and An. gambiae (s.s.) (44.4%) occurred almost in the same proportions. Tested samples were found resistant to pyrethroids (deltamethrin and permethrin) in all locations (< 90% mortality), with > 3-fold increase of KDT₅₀ values compared with the Kisumu susceptible reference strain of An. gambiae (s.s.). However, the mosquito populations from Limbe and Buea were fully susceptible to malathion. The L1014F kdr was found in both An. coluzzii and An. gambiae (s.s.) with the highest frequencies found in An. gambiae (s.l.) populations from Tiko (94%) and Buea (90%) compared with the Limbe population (66%) (P = 0.00063, df = 2). No kdr L1014S was observed in analyzed samples.

CONCLUSIONS

These findings reemphasize the ongoing development of An. gambiae (s.l.) resistance to pyrethroids used in impregnating LLINs and suggest the use of malathion as an alternative insecticide for IRS in complementarity with LLINs.

Effects of Drug Policy Changes on Evolution of Molecular Markers of Plasmodium falciparum Resistance to Chloroquine, Amodiaquine, and Sulphadoxine-Pyrimethamine in the South West Region of Cameroon

BACKGROUND

As a result of the spread of parasites resistant to antimalarial drugs, Malaria treatment guidelines in Cameroon evolved from nonartemisinin monotherapy to artemisinin-based combination therapy. The aim of this study was to assess the effect of these therapy changes on the prevalence of molecular markers of resistance from 2003 to 2013 in Mutengene, Cameroon.

METHODOLOGY

Dry blood samples (collected in 2003-2005 and 2009-2013) were used for parasite DNA extraction. Drug resistance genes were amplified by PCR and hybridized with oligonucleotide probes or subjected to restriction digestion. The prevalence of individual marker polymorphisms and haplotypes was compared in these two study periods using the Chi square test.

RESULTS

Alleles conferring resistance to 4-aminoquinolines in the Pfcrt 76T and Pfmdr1 86Y, 184F, and 1246Y genotypes showed a significant reduction of 97.0% to 66.9%, 83.6% to 45.2%, 97.3% to 56.0%, and 3.1% to 0.0%, respectively (P < 0.05). No difference was observed in SNPs associated with antifolate drugs resistance 51I, 59R, 108N, or 540E (P > 0.05). Haplotype analysis in the Pfmdr1 gene showed a reduction in the YFD from 75.90% to 42.2%, P < 0.0001, and an increase in the NYD (2.9% to 30.1%;  P < 0.0001).

CONCLUSIONS

The results indicated a gradual return of the 4-aminoquinoline sensitive genotype while the antifolate resistant genotypes increased to saturation.

Challenges of DHS and MIS to capture the entire pattern of malaria parasite risk and intervention effects in countries with different ecological zones: the case of Cameroon

BACKGROUND

In 2011, the demographic and health survey (DHS) in Cameroon was combined with the multiple indicator cluster survey. Malaria parasitological data were collected, but the survey period did not overlap with the high malaria transmission season. A malaria indicator survey (MIS) was also conducted during the same year, within the malaria peak transmission season. This study compares estimates of the geographical distribution of malaria parasite risk and of the effects of interventions obtained from the DHS and MIS survey data.

METHODS

Bayesian geostatistical models were applied on DHS and MIS data to obtain georeferenced estimates of the malaria parasite prevalence and to assess the effects of interventions. Climatic predictors were retrieved from satellite sources. Geostatistical variable selection was used to identify the most important climatic predictors and indicators of malaria interventions.

RESULTS

The overall observed malaria parasite risk among children was 33 and 30% in the DHS and MIS data, respectively. Both datasets identified the Normalized Difference Vegetation Index and the altitude as important predictors of the geographical distribution of the disease. However, MIS selected additional climatic factors as important disease predictors. The magnitude of the estimated malaria parasite risk at national level was similar in both surveys. Nevertheless, DHS estimates lower risk in the North and Coastal areas. MIS did not find any important intervention effects, although DHS revealed that the proportion of population with an insecticide-treated nets access in their household was statistically important. An important negative relationship between malaria parasitaemia and socioeconomic factors, such as the level of mother's education, place of residence and the household welfare were captured by both surveys.

CONCLUSION

Timing of the malaria survey influences estimates of the geographical distribution of disease risk, especially in settings with seasonal transmission. In countries with different ecological zones and thus different seasonal patterns, a single survey may not be able to identify all high risk areas. A continuous MIS or a combination of MIS, health information system data and data from sentinel sites may be able to capture the disease risk distribution in space across different seasons.

Comparative evaluation of a rapid diagnostic test, an antibody ELISA, and a pLDH ELISA in detecting asymptomatic malaria parasitaemia in blood donors in Buea, Cameroon

BACKGROUND

In malaria endemic areas, infected blood donors serve as a source of infection to blood recipients, which may adversely affect their prognosis. This necessitates the proper screening of blood to be used for transfusion in these areas. The purpose of this study was to determine the prevalence of malaria parasitaemia in blood donors in Buea, Cameroon, and to evaluate the performance of a rapid diagnostic test (RDT), a malaria antibody enzyme-linked immunosorbent assay (ELISA), and a Plasmodium lactate dehydrogenase (pLDH) ELISA in the detection of asymptomatic malaria parasitaemia in the target population.

METHODS

In a prospective study conducted between September 2015 and June 2016, 1 240 potential blood donors were enrolled. The donors were screened for malaria parasites using Giemsa microscopy (GM) and a RDT. A sub-sample of 184 samples, comprising 88 positive and 96 negative samples, were selected for the evaluation of the pLDH ELISA and the antibody ELISA. The chi-square test and correlation analysis were performed as part of the statistical analyses. The statistical significance cut-off was set at P < 0.05.

RESULTS

The prevalence of malaria parasitaemia in this study was found to be 8.1% (95% CI: 6.6 - 9.7). The prevalence was not observed to be dependent on the age or sex of the participants. The RDT had a sensitivity (88.0%), specificity (99.1%), and negative predictive value (99.0%) higher than the ELISAs. The performance of the pLDH ELISA, which demonstrated the highest positive predictive value (91.6%), was generally comparable to the RDT. The sensitivity was lowest with the antibody ELISA (69.9%), which also demonstrated the highest false positive and false negative rates. The detection threshold for the pLDH (three parasites/μl) was lower compared to the RDT (50 - 60 parasites/μl). Non-significant positive correlations were observed between the parasite density and the pLDH titers and malaria antibody titers.

CONCLUSIONS

Overall, the RDT and the pLDH ELISA demonstrated a perfectly correlated agreement with GM, meanwhile the antibody ELISA demonstrated a substantially correlated agreement with GM. The pLDH is therefore recommended for mass screening of blood (to detect malaria parasitaemia) for transfusions in the study area. However, where this is not feasible, an RDT will suffice.

Identification of the Plasmodium species in clinical samples from children residing in five epidemiological strata of malaria in Cameroon

Background

Malaria in Cameroon was previously known to be caused solely by Plasmodium falciparum but today, evidence points to other Plasmodium species including P. vivax, P. ovale and P. malariae. The purpose of this study was to identify the Plasmodium species in clinical samples from children residing in five epidemiological strata of malaria in Cameroon, so as to advise control policies.

Methods

One thousand six hundred nine febrile children (≤15 years) were recruited from five epidemiological strata of malaria including the Sudano-sahelian (SS) strata, the High inland plateau (HIP) strata, the South Cameroonian Equatorial forest (SCEF) strata, the High western plateau (HWP) strata and the Coastal (C) strata. Malaria parasites were detected by Giemsa microscopy (GM) while a multiplex polymerase chain reaction (PCR) was used to identify the Plasmodium species. Statistical analysis performed included the Pearson chi-square test, and statistical significance was set at p < 0.05.

Results

The PCR-adjusted prevalence of malaria was 17.6%. The detection rate of PCR was higher than GM (p = 0.05). However, GM demonstrated a high sensitivity (85.5%) and specificity (100%) and, overall, a perfectly correlated agreement with PCR (97.5%). The prevalence of malaria was significantly higher in children between 60 and 119 months (p < 0.001) and in Limbe (in the Coastal strata) (p < 0.001). Contrariwise, the prevalence of malaria was not associated with gender (p = 0.239). P. falciparum was identified in all (100%) the cases of malaria; P. ovale, P. vivax, P. malariae and P. knowlesi were all absent. No case of mixed infection was identified.

Conclusions

P. falciparum was the only species causing clinical malaria in the target population, which is contrary to studies that have reported P. vivax, P. malariae and P. ovale as causing clinical malaria in Cameroon.

Ethnobotanical survey of medicinal plants used as insects repellents in six malaria endemic localities of Cameroon

BACKGROUND

The combined efforts to combat outdoor/indoor transmission of malaria parasites are hampered by the emerging vector resistance in a wide variety of malaria-endemic settings of Africa and the rest of the world, stressing the need for alternative control measures. This study aimed at documenting insect's repellent plant species used by indigenous populations of 6 localities of East, South, West and Centre regions of Cameroon.

METHODS

Information was gathered through face-to-face interviews guided by a semi-structured questionnaire on the knowledge of medicinal plants with insect repellent properties.

RESULTS

A total of 182 informants aged from 25 to 75 years were recruited by convenience from May to June 2015. The informants had general knowledge about insects' repellent plants (78.6%). A total of 16 plant species were recorded as insects' repellents with 50% being trees. The most cited plants were Canarium schweinfurthii (Burseraceae) (in four localities, 58/182), Elaeis guineensis (Arecaceae) (in three localities, 38/182), Chromolaena odorata (Compositae) (16/182) and Citrus limon (Rutaceae) (11/182) in two localities each. Among the repellent plant species recorded, 50% were reported to be burnt to produce in-house smokes, 31.2% were mashed and applied on the body, and 18.8% were hung in the houses. The leaf was the most commonly used plant part (52.9%), followed by the bark (17.6%).

CONCLUSIONS

This study has shown that rural populations of the 6 targeted localities possess indigenous knowledge on repellent plants that are otherwise cost-effective and better choice for repelling insects including malaria-transmitting mosquitoes. Meanwhile, such practices should be validated experimentally and promoted as sustainable malaria transmission control tools in the remotely located communities.

Malaria over-diagnosis in Cameroon: diagnostic accuracy of Fluorescence and Staining Technologies (FAST) Malaria Stain and LED microscopy versus Giemsa and bright field microscopy validated by polymerase chain reaction

Background

Malaria is a major world health issue and its continued burden is due, in part, to difficulties in the diagnosis of the illness. The World Health Organization recommends confirmatory testing using microscopy-based techniques or rapid diagnostic tests (RDT) for all cases of suspected malaria. In regions where Plasmodium species are indigenous, there are multiple etiologies of fever leading to misdiagnoses, especially in populations where HIV is prevalent and children. To determine the frequency of malaria infection in febrile patients over an 8-month period at the Regional Hospital in Bamenda, Cameroon, we evaluated the clinical efficacy of the Flourescence and Staining Technology (FAST) Malaria stain and ParaLens Advance^TM microscopy system (FM) and compared it with conventional bright field microscopy and Giemsa stain (GS).

Methods

Peripheral blood samples from 522 patients with a clinical diagnosis of “suspected malaria” were evaluated using GS and FM methods. A nested PCR assay was the gold standard to compare the two methods. PCR positivity, sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) were determined.

Results

Four hundred ninety nine samples were included in the final analysis. Of these, 30 were positive via PCR (6.01%) with a mean PPV of 19.62% and 27.99% for GS and FM, respectively. The mean NPV was 95.01% and 95.28% for GS and FM, respectively. Sensitivity was 26.67% in both groups and specificity was 92.78% and 96.21% for GS and FM, respectively. An increased level of diagnostic discrepancy was observed between technicians based upon skill level using GS, which was not seen with FM.

Conclusions

The frequency of malarial infections confirmed via PCR among patients presenting with fever and other symptoms of malaria was dramatically lower than that anticipated based upon physicians’ clinical suspicions. A correlation between technician skill and accuracy of malaria diagnosis using GS was observed that was less pronounced using FM. Additionally, FM increased the specificity and improved the PPV, suggesting this relatively low cost approach could be useful in resource-limited environments. Anecdotally, physicians were reluctant to not treat all patients symptomatically before results were known and in spite of a negative microscopic diagnosis, highlighting the need for further physician education to avoid this practice of overtreatment. A larger study in an area with a known high prevalence is being planned to compare the two microscopy methods against available RDTs.

Electronic supplementary material

The online version of this article (doi:10.1186/s40249-017-0251-0) contains supplementary material, which is available to authorized users.

Role of Anopheles (Cellia) rufipes (Gough, 1910) and other local anophelines in human malaria transmission in the northern savannah of Cameroon: a cross-sectional survey

BACKGROUND

As part of a study to determine the impact of insecticide resistance on the effectiveness of long-lasting insecticide treated nets (LLINs) in the north of Cameroon, the unexpectedly high density and anthropophilic behaviour of Anopheles rufipes lead us to investigate this species bionomics and role in human malaria parasite transmission.

METHODS

For four consecutive years (2011-2014), annual cross-sectional sampling of adult mosquitoes was conducted during the peak malaria season (September-October) in three health districts in northern Cameroon. Mosquitoes sampled by human landing catch and pyrethrum spray catch methods were morphologically identified, their ovaries dissected for parity determination and Anopheles gambiae siblings were identified by molecular assay. Infection with P. falciparum and blood meal source in residual fauna of indoor resting anopheline mosquitoes were determined by enzyme-linked-immunosorbent assays.

RESULTS

Anopheles gambiae (sensu lato) (s.l.) comprised 18.4% of mosquitoes collected with An. arabiensis representing 66.27% of the sibling species. The proportion of An. rufipes (2.7%) collected was high with a human-biting rate ranging between 0.441 and 11.083 bites/person/night (b/p/n) and an anthropophagic rate of 15.36%. Although overall the members of An. gambiae complex were responsible for most of the transmission with entomological inoculation rates (EIR) reaching 1.221 infective bites/person/night (ib/p/n), An. arabiensis and An. coluzzii were the most implicated. The roles of An. funestus, An. pharoensis and An. paludis were minor. Plasmodium falciparum circumsporozoite protein rate in Anopheles rufipes varied from 0.6 to 5.7% with EIR values between 0.010 and 0.481 ib/p/n.

CONCLUSIONS

The study highlights the epidemiological role of An. rufipes alongside the members of the An. gambiae complex, and several other sympatric species in human malaria transmission during the wet season in northern Cameroon. For the first time in Cameroon, An. rufipes has been shown to be an important local malaria vector, emphasising the need to review the malaria entomological profile across the country as pre-requisite to effective vector management strategies.

Hepatitis B, HIV, and Syphilis Seroprevalence in Pregnant Women and Blood Donors in Cameroon

Objectives. We estimated seroprevalence and correlates of selected infections in pregnant women and blood donors in a resource-limited setting. Methods. We performed a cross-sectional analysis of laboratory seroprevalence data from pregnant women and voluntary blood donors from facilities in Cameroon in 2014. Rapid tests were performed to detect hepatitis B surface antigen, syphilis treponemal antibodies, and HIV-1/2 antibodies. Blood donations were also tested for hepatitis C and malaria. Results. The seroprevalence rates and ranges among 7069 pregnant women were hepatitis B 4.4% (1.1–9.6%), HIV 6% (3.0–10.2%), and syphilis 1.7% (1.3–3.8%) with significant variability among the sites. Correlates of infection in pregnancy in adjusted regression models included urban residence for hepatitis B (aOR 2.9, CI 1.6–5.4) and HIV (aOR 3.5, CI 1.9–6.7). Blood donor seroprevalence rates and ranges were hepatitis B 6.8% (5.0–8.8%), HIV 2.2% (1.4–2.8%), syphilis 4% (3.3–4.5%), malaria 1.9%, and hepatitis C 1.7% (0.5–2.5%). Conclusions. Hepatitis B, HIV, and syphilis infections are common among pregnant women and blood donors in Cameroon with higher rates in urban areas. Future interventions to reduce vertical transmission should include universal screening for these infections early in pregnancy and provision of effective prevention tools including the birth dose of univalent hepatitis B vaccine.

The Effect of Intestinal Parasitic Infection on the Clinical Outcome of Malaria in Coinfected Children in Cameroon

Background

The interaction between intestinal parasites and malaria is still not clear. Data in published literature are conflicting. We studied the effect of intestinal parasitic infection (IPI) on the clinical outcome of malaria in coinfected children.

Methods

In a cross sectional study performed between October 2014 and September 2015, children infected with malaria, as demonstrated by the presence of asexual parasites in Giemsa stained blood films, were enrolled. Stool samples were obtained from participants and subjected to the formol-ether concentration technique for the detection of intestinal parasites. The Complete blood count was performed using an automated haematology analyser (Mindray, BC-2800). The risk ratio, Pearson’s chi-square and the student T test were all performed as part of the statistical analyses. Statistical significance was set at p < 0.05.

Results

In all, 405 children successfully took part in the study. The children were between 1 week and 120 months of age (mean ± SD = 41.5 ± 33.5). Coinfection with intestinal parasites was observed in 11.6%. The rate of severe malaria (SM) attack in this study was 10.9%. SM was not observed to be associated with age (p = 0.377) or gender (p = 0.387), meanwhile coinfection with intestinal parasites was associated with age (p = 0.003). Among SM cases, IPI prevalence was higher in children with mild (WHO group 3) severe malaria (p = 0.027). Overall, IPI was not observed to be associated with SM (p = 0.656) or malaria parasite density (p = 0.185) or haemoglobin concentration (p = 0.205). The main clinical features of SM observed were hyperpyrexia (68.2%), severe malarial anaemia (61.4%), and multiple convulsion (52.3%).

Conclusion

IPI was not observed to be associated with the severity of malaria, the malaria parasite density, and the haemoglobin concentration in coinfected children in Cameroon. The clinical outcome of malaria in children coinfected with intestinal parasites may depend on the geographical setting after all.

Coinfection with malaria and intestinal parasites are common in Sub-Saharan Africa, particularly in impoverished and poor sanitary settings. The interaction between intestinal parasites and malaria in coinfected children is still not clear. Some published papers suggest intestinal parasites, especially Ascaris lumbricoides, may attenuate the severity of malaria in the presence of coinfection. In this cross-sectional study, we evaluated the effect of intestinal parasitic infection on the severity of malaria, malaria parasite density and the haemoglobin concentration in children coinfected with malaria and intestinal parasites in Cameroon. We did not observe any significant association between intestinal parasitic infection and severe malaria or malaria parasite density or haemoglobin concentration. Stratification of severe malaria according to the degree of severity revealed a significant association with intestinal parasitic infection, in which prevalence of intestinal parasites was higher in children with mild severe malaria. Analyzing the different species of intestinal parasite did not yield any significant association either. These findings are contrary to many research publication on the subject. Several factors could have contributed to our observation, including the regular deworming campaign organized by the Cameroon Ministry of Public health, accounting for the lower prevalence of intestinal parasitic infection, and also the geographical setting.

Increase in cases of malaria in Mozambique, 2014: epidemic or new endemic pattern?

OBJECTIVE

To describe the increase in cases of malaria in Mozambique.

METHODS

Cross-sectional study conducted in 2014, in Mozambique with national weekly epidemiological bulletin data. I analyzed the number of recorded cases in the 2009-2013 period, which led to the creation of an endemic channel using the quartile and C-Sum methods. Monthly incidence rates were calculated for the first half of 2014, making it possible to determine the pattern of endemicity. Months in which the incidence rates exceeded the third quartile or line C-sum were declared as epidemic months.

RESULTS

The provinces of Nampula, Zambezia, Sofala, and Inhambane accounted for 52.7% of all cases in the first half of 2014. Also during this period, the provinces of Nampula, Sofala and Tete were responsible for 54.9% of the deaths from malaria. The incidence rates of malaria in children, and in all ages, have showed patterns in the epidemic zone. For all ages, the incidence rate has peaked in April (2,573 cases/100,000 inhabitants).

CONCLUSIONS

The results suggest the occurrence of an epidemic pattern of malaria in the first half of 2014 in Mozambique. It is strategic to have a more accurate surveillance at all levels (central, provincial and district) to target prevention and control interventions in a timely manner.

Malaria, helminths, co-infection and anaemia in a cohort of children from Mutengene, south western Cameroon

Background

Malaria and helminthiases frequently co-infect the same individuals in endemic zones. Plasmodium falciparum and helminth infections have long been recognized as major contributors to anaemia in endemic countries. Several studies have explored the influence of helminth infections on the course of malaria in humans but how these parasites interact within co-infected individuals remains controversial.

Methods

In a community-based longitudinal study from March 2011 to February 2012, the clinical and malaria parasitaemia status of a cohort of 357 children aged 6 months to 10 years living in Mutengene, south-western region of Cameroon, was monitored. Following the determination of baseline malaria/helminths status and haemoglobin levels, the incidence of malaria and anaemia status was determined in a 12 months longitudinal study by both active and passive case detection.

Results

Among all the children who completed the study, 32.5 % (116/357) of them had at least one malaria episode. The mean (±SEM) number of malaria attacks per year was 1.44 ± 0.062 (range: 1–4 episodes) with the highest incidence of episodes occuring during the rainy season months of March–October. Children <5 years old were exposed to more malaria attacks [OR = 2.34, 95 % CI (1.15–4.75), p = 0.019] and were also more susceptible to anaemia [OR = 2.24, 95 % CI (1.85–4.23), p = 0.013] compared to older children (5–10 years old). Likewise children with malaria episodes [OR = 4.45, 95 % CI (1.66–11.94), p = 0.003] as well as those with asymptomatic parasitaemia [OR = 2.41, 95 % CI (1.58–3.69) p < 0.001] were susceptible to anaemia compared to their malaria parasitaemia negative counterparts. Considering children infected with Plasmodium alone as the reference, children infected with helminths alone were associated with protection from anaemia [OR = 0.357, 95 % CI (0.141–0.901), p = 0.029]. The mean haemoglobin level (g/dl) of participants co-infected with Plasmodium and helminths was higher (p = 0.006) compared to participants infected with Plasmodium or helminths alone.

Conclusion

Children below 5 years of age were more susceptible to malaria and anaemia. The high prevalence of anaemia in this community was largely due to malaria parasitaemia. Malaria and helminths co-infection was protective against anaemia.

Electronic supplementary material

The online version of this article (doi:10.1186/s12936-016-1111-2) contains supplementary material, which is available to authorized users.