A possible role for Phlebotomus (Anaphlebotomus) rodhaini (Parrot, 1930) in transmission of Leishmania donovani

Sex-structured disease transmission model and control mechanisms for visceral leishmaniasis (VL)

BACKGROUND

Leishmaniasis are a group of diseases caused by more than 20 species of the protozoan that are transmitted through the bite of female sand fly. The disease is endemic to 98 countries of the world. It affects most commonly the poorest of the poor and mainly males. Several research has been conducted to propose disease control strategies. Effective medical care, vector control, environmental hygiene, and personal protection are the mainstays of the current preventative and control methods. The mathematical models for the transmission dynamics of the disease studied so far did not consider the sex-biased burden of the disease into consideration.

METHODOLOGY

Unlike the previous VL works, this study introduces a new deterministic sex-structured model for understanding the transmission dynamics of visceral leishmaniasis. Basic properties of the model including basic reproduction number ([Formula: see text]), and conditions for the existence of backward bifurcation of the model are explored. Baseline parameter values were estimated after the model was fitted to Ethiopia's VL data. Sensitivity analysis of the model was performed to identify the parameters that significantly impact the disease threshold. Numerical simulations were performed using baseline parameter values, and scenario analysis is performed by changing some of these parameters as appropriate.

CONCLUSION

The analysis of the model shows that there is a possibility for a backward bifurcation for [Formula: see text], which means bringing [Formula: see text] to less than unity may not be enough to eradicate the disease. Our numerical result shows that the implementation of disease-preventive strategies, as well as effectively treating the affected ones can significantly reduce the disease prevalence if applied for more proportion of the male population. Furthermore, the implementation of vector management strategies also can considerably reduce the total prevalence of the disease. However, it is demonstrated that putting more effort in treating affected reservoir animals may not have any significant effect on the overall prevalence of the disease as compared to other possible mechanisms. The numerical simulation infers that a maximum of 60% of extra preventative measures targeted to only male population considerably reduces the total prevalence of VL by 80%. It is also possible to decrease the total prevalence of VL by 69.51% when up to 50% additional infected males receive treatment with full efficacy. Moreover, applying a maximum of 15% additional effort to reduce the number of vectors, decreases the total VL prevalence by 57.71%. Therefore, in order to reduce the disease burden of visceral leishmaniasis, public health officials and concerned stakeholders need to give more emphasis to the proportion of male humans in their intervention strategies.

Detection of Leishmania DNA in Phlebotomine Sand Flies in Tsatee, a Community in the Volta Region, Ghana

Leishmania parasites, which are spread by infected female sand flies, are the cause of the disease leishmaniasis. Although cutaneous leishmaniasis has been found to occur in the Volta Region, there is limited data on vector species and reservoirs. This study focused on the Tsatee community, in the South Dayi District of the Volta Region, and is aimed at identifying the sand fly fauna and detecting the presence of Leishmania DNA by the use of primers that target the conserved region of Leishmania spp. minicircle DNA of the parasite kinetoplast. The miniature light traps and hand aspirators provided by the Centers for Disease Control and Prevention (CDC) were used to collect outdoor and indoor sand flies for five months in a guinea woodland and semideciduous forest area. From the collections, 4,580 phlebotomine sand flies were obtained and identified, and females were examined for Leishmania DNA using PCR. The male flies were 1,202 (26.24%), non-blood-fed females were 3,321 (72.51%), and 57 (1.25%) were blood-fed females. It was observed that Sergentomyia species constituted 99.91% of the total collected sand flies with S. africana (76.77%) as the predominant species. Phlebotomus rodhaini (0.09%) was the only Phlebotomus species identified from the study area. From 283 non-blood-fed sand fly pools and 57 individual blood-fed species screened, Leishmania DNA was detected in 12 (4.24%) pools and 8 (14.04%) individuals, respectively. It was observed that Leishmania DNA was detected in all the sand fly species identified except S. collarti. This study reports the first detection of Leishmania DNA in P. rodhaini in Ghana, with an infection rate of 33.33% (95% CI, 1.23-88.32). The findings suggest that the role of Phlebotomus in disease transmission in the study area cannot be discounted. Future studies should include continuous surveillance, blood meal preferences, and vector competence of the various infected phlebotomine sand flies to create effective control measures.

Sero-prevalence of visceral leishmaniasis and its associated factors among asymptomatic individuals visiting Denan health center, southeastern Ethiopia

BACKGROUND

In the Somali region of Ethiopia, visceral leishmaniasis (VL) is a public health concern. However, VL epidemiology and sand fly vectors have not been well studied in various areas of the regional state, including Denan district. Therefore, this study was conducted to determine the sero-prevalence, associated factors, and distribution of sand fly vectors of VL in Denan district, south-eastern Ethiopia.

METHODS

A facility-based cross-sectional study was conducted from April to September 2021 among VL patients with classic signs and symptoms visiting Denan Health Center in south-eastern Ethiopia. Using a convenience sampling method, 187 blood samples were collected from individuals who visited Denan Health Center during the study period. Blood samples were subjected to Direct Agglutination Test for the detection of antibodies to VL. A pre-tested structured questionnaire was also used to gather information on risk factors and other characteristics of knowledge and attitude assessment. Sand flies were also collected from indoor, peri-domestic, mixed forest, and termite mounds using light and sticky traps to determine the fauna and abundance.

RESULTS

The overall sero-prevalence rate was 9.63% (18/187). The sero-prevalence was significantly associated with outdoor sleeping (OR = 2.82), the presence of damp floors (OR = 7.76), and sleeping outdoor near animals (OR = 3.22). Around 53.48% of the study participants had previously heard about VL. Study participants practiced different VL control methods, including bed nets (42%), insecticide spraying (32%), smoking plant parts (14%), and environmental cleaning (8%). In total, 823 sand fly specimens, comprising 12 species in two genera (Phlebotomus and Sergentomyia), were trapped and identified. The most abundant species was Sergentomyia clydei (50.18%), followed by Phlebotomus orientalis (11.42%). Also, a higher proportion of P. orientalis was found in termite mounds (65.43%), followed by mixed forest (37.8%) and peri-domestic (20.83%) habitats.

CONCLUSION

The study demonstrated a 9.63% sero-positivity of VL and a remarkable gap in knowledge, attitude, and practices towards VL. P. orientalis was also detected, which could be a probable vector in this area. Thus, public education should be prioritized to improve the community's awareness of VL and its public health impact. In addition, detailed epidemiological and entomological studies are recommended.

Phlebotomine sandflies (Diptera: Psychodidae) of Ethiopia

Phlebotomine sandflies have a long history of association with humans, which makes them the only proven natural vectors of Leishmania species, the parasitic protozoans that cause leishmaniases in humans and animals. In Ethiopia, the three forms of leishmaniases, viz., visceral, dermal and mucocutaneous are endemic in different parts of the country. Since the first report of phlebotomine sandflies in Ethiopia in 1936, the distribution of different species and their role in the transmission of leishmaniases have been extensively studied. The objective of this review was to summarize the patchy information and give an updated list of phlebotomine sandfly species in Ethiopia and their known geographical distribution in the country. Peer-reviewed literature search was conducted using online databases. All articles published which focus on distribution and medical importance of Phlebotomus and Sergentomyia species of Ethiopia starting from 1936 up to 2022 were reviewed. Until July 2022, 65 phlebotomine sandfly species have been reported, belonging to the genus Phlebotomus and Sergentomyia. The genus Phlebotomus in Ethiopia is represented by six subgenera such as Adlerius, Anaphlebotomus, Larroussius, Paraphlebotomus Phlebotomus and Synphlebotomus, whereas the genus Sergentomyia is represented by six subgenera, namely Grassomyia, Parrotomyia, Parvidens, Rondanomyia, Sergentomyia, and Sintonius.

Clinical and laboratory profiles of visceral leishmaniasis among adult patients admitted to Felege Hiwot Hospital, Bahir Dar, Ethiopia

Background:

Visceral leishmaniasis is a vector-borne disease caused by Leishmania donovani transmitted by sand fly species. It is the third most common vector-borne disease globally. Visceral leishmaniasis is endemic in Ethiopia with an estimated annual incidence ranging from 3700 to 7400 cases. This research aimed to assess the clinical presentations and laboratory profiles of visceral leishmaniasis for early diagnosis and timely initiation of management.

Objective:

To describe the clinical and laboratory manifestation and diagnostic modalities of visceral leishmaniasis among adult patients admitted to Felege Hiwot Hospital, from 1 September 2016 to 30 August 2019.

Method:

Institution-based retrospective cross-sectional study was conducted among 141 patients admitted to Felege Hiwot Hospital from 1 September 2016 to 30 August 2019. Descriptive statistics were used to describe the clinical presentation and laboratory profiles of patients with visceral leishmaniasis.

Results:

Among a total of 141 enrolled patients in the study, males were affected 13-fold. Most of them were travelers to endemic areas during the winter season for labor work. The mean duration of illness was 48 days. Common symptoms were fever (96.5%), weightless (82.5%), jaundice (18.4%), vomiting/diarrhea (13.5%), and bleeding episodes (11.3%). Splenomegaly was seen in 98.6%, ascites in 35.5%, and lymphadenopathy in 9.9%. Lymphadenopathy was seen significantly in HIV patients (40%). Anemia was seen in 95%, thrombocytopenia in 90.2%, leukopenia in 86.4%, and pancytopenia in 79.4%. Half of the patients had coinfection. Neutropenic sepsis was seen in 21.3%. The diagnosis was made by tissue aspiration in 65% of patients.

Conclusion:

The majority of patients who were diagnosed to have visceral leishmaniasis were young male adults who traveled to the endemic areas seasonally. Fever and splenomegaly were seen as the commonest clinical presentation. Lymphadenopathy occurred in high frequency among HIV co-infected patients. Anemia was the commonest hematologic finding.

Studies of host preferences of wild-caught Phlebotomus orientalis and Ph. papatasi vectors of leishmaniasis in Sudan

Introduction

Understanding the feeding behavior and host choice of sand flies provides valuable information on vector-host relationships and elucidates the epidemiological patterns of leishmaniasis transmission. Blood meal analysis studies are essential for estimating the efficiency of pathogen transmission, assessing the relative human disease risk, and assist in identifying the other potential hosts of leishmaniasis. In Sudan and most of East Africa, there are large remaining gaps in knowledge regarding the feeding habits of phlebotomine vectors. The study aimed to identify the blood meal sources and, therefore, the host preferences of the principal vectors Phlebotomus orientalis and Ph. papatasi in leishmaniasis endemic areas of eastern and central Sudan.

Materials and methods

Sand flies were collected from two endemic villages in eastern and central Sudan using CDC light traps and sticky traps. The phlebotomine sand flies were morphologically and then molecularly identified. The source of blood meal of the engorged females was determined using a multiplex PCR methodology and specific primers of cytochrome b gene of mitochondrial DNA for human, goat, cow, and dog. The detection of the Leishmania parasite was done using PCR.

Results

The total number of collected female phlebotomine sand flies was 180. Morphological identification revealed the abundance of Ph. orientalis 103 (57.2%), Ph. papatasi 42 (23.3%), Ph. bergeroti 31 (17.2%), Ph. rodhaini 2 (1.1%) and Ph. duboscqi 2 (1.1%) in the study sites. Out of the 180 collected, 31 (17%) were blood-fed flies. Three species were blood-fed and molecularly identified: Ph. papatasi (N = 7, 22.6%), Ph. bergeroti (N = 9, 26%), and Ph. orientalis (N = 15, 48.4%). Blood meal analysis revealed human DNA in two Ph. orientalis (6.4%), hence, the anthropophilic index was 13.3%.

Conclusions

Multiplex PCR protocol described here allowed the identification of blood meal sources of many vertebrate species simultaneously. The results indicate that wild-caught Ph. orientalis are anthropophilic in the study areas. Further studies on larger blood-fed sample size are required to validate the potential applications of this technique in designing, monitoring and evaluating control programs, particularly in investigating the potential non-human hosts of leishmaniasis.

Visceral Leishmaniasis in West Africa: Clinical Characteristics, Vectors, and Reservoirs

Visceral leishmaniasis (VL) is the most serious form of human leishmaniasis. VL is understudied in West Africa. The increasing number of patients at-risk, including persons living with HIV and other chronic immunosuppressive diseases, and likely underreporting of VL related to diagnostic challenges advocate for review of existing data to understand VL regional epidemiology. Our review aims to describe the clinical characteristics and epidemiology of Human VL (HVL) in West Africa. We conducted a literature search to identify peer-reviewed articles and grey literature sources using the search terms “Visceral leishmaniasis West Africa”, “Leishmania donovani West Africa”; and “Leishmania infantum West Africa”. Thirty published articles report HVL from seven countries, including The Gambia, Niger, Nigeria, Ivory Coast, Togo, Burkina Faso, and Guinea Bissau. Three countries report cases of Canine Visceral Leishmaniasis (CVL), including The Gambia, Senegal, and Burkina Faso. Niger, Nigeria, and Ivory Coast report the greatest number of HVL cases. As VL is present in West Africa, active surveillance, increased diagnostic capacity, and studies of vectors and reservoirs are essential to better understand VL epidemiology in the region.

Epidemiology of visceral leishmaniasis in Shebelle Zone of Somali Region, eastern Ethiopia

Background

Visceral leishmaniasis (VL), a vector-borne disease caused by species of the L.donovani complex, has (re)-emerged in Ethiopia during the last two decades and is currently of increasing public health concern. However, very little is known about VL epidemiology in the Somali Region of Ethiopia. The aim of this study was to provide detailed epidemiological information on seroprevalence, associated factors and incriminated vectors of VL in Shebelle Zone and Ethiopian Somali Region in general.

Methods

A cross-sectional epidemiological study was conducted between March and May 2016 in Gode and Adadle districts of Shebelle Zone, Ethiopian Somali Region. Two-stage semi-random sampling was applied for selecting study participants for the field survey. The study included structured questionnaire interviews, serological assays (rK39-immunochromatographic test), ELISA and entomological surveys.

Results

From a total of 361 participants, 57 (15.8%) were seropositive for VL including 46 (12.7%) rK39 positive and 11 (3.0%) positive by both rK39 and ELISA. VL seroprevalence was higher (P < 0.001) in Adadle (31.1%) compared to Gode (12.7%) district. The VL seroprevalence rate was higher in females than in males [rK39 (17.2 vs 14.0%) and ELISA (3.4 vs 2.5%)]. Children under the 15 years of age were the most highly affected group [rK39 (20.4%) and ELISA (4.4%)]. Increased VL risk was associated with presence of termite hills, study district, outdoor sleeping, Acacia trees and domestic animals [odds ratio (95% confidence interval): 12.58 (5.911–26.763), 5.40 (2.90–10.07), 5.31 (2.283–12.364), 2.37 (1.1190–4.728) and 0.199 (0.097–0.410), respectively]. The entomological survey identified 74 Phlebotomus [P. (Larroussius) orientalis (52/74), P. (Anaphlebotomus) rodhaini (14/74), P. (Paraphlebotomus) sergenti (8/74)] and 11 Sergentomyia sand flies. The average frequency of P. orientalis (3.06 ± 0.66) collected by all traps per night was higher than that of other species. The average frequency of total and specific (P. orientalis) female sand flies was higher in Adadle (1.89 ± 0.423 vs 1.11 ± 0.309) than in Gode (0.62 ± 0.324 vs 0.38 ± 0.183) district. The highest mean numbers of total (8 ± 1.5) and P. orientalis (6 ± 0.913) sand flies were collected in termite hills.

Conclusions

The present findings revealed potential new VL-transmission foci in the study districts. Therefore, the need for parasitological and molecular characterization of the parasite in humans and vector sand flies is of paramount importance to confirm transmission.

Electronic supplementary material

The online version of this article (10.1186/s13071-019-3452-5) contains supplementary material, which is available to authorized users.

Leishmaniasis in Eurasia and Africa: geographical distribution of vector species and pathogens

Leishmaniasis is a vector-borne disease with a broad global occurrence and an increasing number of recorded cases; however, it is still one of the world's most neglected diseases. We here provide climatic suitability maps generated by means of an ecological niche modelling approach for 32 Phlebotomus vector species with proven or suspected vector competence for five Leishmania pathogens occurring in Eurasia and Africa. A GIS-based spatial overlay analysis was then used to compare the distributional patterns of vectors and pathogens to help evaluate the vector species-pathogen relationship currently found in the literature. Based on this single factor of vector incrimination, that is, co-occurrence of both vector and pathogen, most of the pathogens occurred with at least one of the associated vector species. In the case of L. donovani, only a not yet confirmed vector species, P. rodhaini, could explain the occurrence of the pathogen in regions of Africa. Phlebotomus alexandri and P. longiductus on the other hand, proven vector species of L. donovani, do not seem to qualify as vectors for the pathogen. Their distribution is restricted to northern latitudes and does not match the pathogen's distribution, which lies in southern latitudes. Other more locally confined mismatches were discussed for each pathogen species. The comparative geographical GIS-overlay of vector species and pathogens functions as a first indication that testing and re-evaluation of some pathogen-vector relationships might be worthwhile to improve risk assessments of leishmaniasis.

Malaria-visceral leishmaniasis co-infection and associated factors among migrant laborers in West Armachiho district, North West Ethiopia: community based cross-sectional study

Background

Malaria and leishmaniasis are the two largest parasitic killers in the world. Due togeographical overlap of these diseases, malaria-visceral leishmaniasis co-infections occur in large populations and exist in different areas even if they have been poorly investigated. The aim of this study was to determine malaria-visceral leishmaniasis co-infection and their associated factors among migrant laborers.

Methods

Community based cross-sectional study was conducted from October–December 2016 on migrant laborers who are residents of rural agricultural camp in West Armachiho district and involved in sesame and sorghum harvesting. Standardized questionnaire was used to collect socio-demographic data and risk factors. Capillary blood was collected for giemsa stained blood film examination to detect and identify Plasmodium parasites. Recombinant kinensin (rk39) antigen test was performed to detect anti-leishmania donovani antibody. Data was coded, entered, checked for completeness and analyzed using SPSS version-20 statistical software. Chi-square test was applied to show a significant association between variables. P-value < 0.05 was considered as statistically significant.

Results

A total of 178 migrant laborers were included in this study. Of these, 74.2% belong to the age group 15–29; 61.2% come from lowland areas and 51.6% visit the area more than four times. Seroprevalence of visceral leishmaniasis was 9.6% (17/178); and 22.4% (40/178) of tested migrant laborers were found malaria infected. The overall prevalence of malaria-visceral leishmaniasis co-infection was 2.8%. Of the total migrant laborer, 47.8% used bed nets, of them 1.2% were malaria-visceral leishmaniasis co-infected; 72.5% used outdoor sites as usual sleeping site, among them 3.1% were malaria-visceral leishmaniasis co-infected; 60.1% were migrants, of which 2.8% were malaria-visceral leishmaniasis co-infected. All variables were not significantly associated with malaria-visceral leishmaniasis co-infection (P > 0.05).

Conclusions

Prevalence of malaria-visceral leishmaniasis co-infection was low and it is not significantly associated with residence, number of visits, bed net utilization and outdoor sleeping habit even if both diseases are prevalent in the study area.

Dynamic spatiotemporal modeling of the infected rate of visceral leishmaniasis in human in an endemic area of Amhara regional state, Ethiopia

Visceral Leishmaniasis is a very dangerous form of leishmaniasis and, shorn of appropriate diagnosis and handling, it leads to death and physical disability. Depicting the spatiotemporal pattern of disease is important for disease regulator and deterrence strategies. Spatiotemporal modeling has distended broad veneration in recent years. Spatial and spatiotemporal disease modeling is extensively used for the analysis of registry data and usually articulated in a hierarchical Bayesian framework. In this study, we have developed the hierarchical spatiotemporal Bayesian modeling of the infected rate of Visceral leishmaniasis in Human (VLH). We applied the Stochastics Partial Differential Equation (SPDE) approach for a spatiotemporal hierarchical model for Visceral leishmaniasis in human (VLH) that involves a GF and a state process is associated with an autoregressive order one temporal dynamics and the spatially correlated error term, along with the effect of land shield, metrological, demographic, socio-demographic and geographical covariates in an endemic area of Amhara regional state, Ethiopia. The model encompasses a Gaussian Field (GF), affected by an error term, and a state process described by a first-order autoregressive dynamic model and spatially correlated innovations. A hierarchical model including spatially and temporally correlated errors was fit to the infected rate of Visceral leishmaniasis in human (VLH) weekly data from January 2015 to December 2017 using the R package R-INLA, which allows for Bayesian modeling using the stochastic partial differential equation (SPDE) approach. We found that the mean weekly temperature had a significant positive association with infected rate of VLH. Moreover, net migration rate, clean water coverage, average number of households, population density per square kilometer, average number of persons per household unit, education coverage, health facility coverage, mortality rate, and sex ratio had a significant association with the infected rate of visceral leishmaniasis (VLH) in the region. In this study, we investigated the dynamic spatiotemporal modeling of Visceral leishmaniasis in Human (VLH) through a stochastic partial differential equation approach (SPDE) using integrated nested Laplace approximation (INLA). Our study had confirmed both metrological, demographic, sociodemographic and geographic covariates had a significant association with the infected rate of visceral leishmaniasis (VLH) in the region.

Kala-azar in Darfur: Evidence for indigenous transmission in Al-Malha Locality, North Darfur, western Sudan

BACKGROUND

Recent reports showed high numbers of visceral leishmaniasis cases in North Darfur, western Sudan. Due to a lack of previous studies, no information is available on local transmission of the disease in these areas. Therefore, a pilot entomological and epidemiological study was conducted in Al-Malha Locality during the year 2013, to investigate possibility of local transmission and places and times of the year where and when people contract the infection.

METHODS

Kala-azar incidence data were obtained from records of Ministry of Health, North Darfur; Al-Malha rural hospital; and the Federal Ministry of Health, Division of Communicable and Non-communicable Diseases. Sand flies were collected using sticky paper and rodent burrow traps from five different microhabitats during three different phases of the year. Species identification was undertaken using appropriate taxonomic keys. Data were statistically analyzed to determine the distribution of kala-azar among different age groups and between sexes, and to compare the species richness and distribution of different sandfly species between the different microhabitats.

RESULTS

The most affected age groups with kala-azar during the period 2013-2016 were children between one and five years old and those under one year. Females were found to be more affected than males. A total of 918 sand fly specimens were collected using sticky paper and rodent burrow traps from five microhabitats. Identified specimens belong to 13 species; 5 Phlebotomus and 8 Sergentomyia. Phlebotomus orientalis, the principal vector of visceral leishmaniasis (VL) in Sudan and other East African countries, was found for the first time in the area. No other known vector of VL was found in the collection. The highest number of sand flies was recorded during the summer season (63%), with S. antennata (48%) and S. schwetzi (24.1%) being the most abundant species. Among Phlebotomus species, P. orientalis showed relatively high density (8.6%). A dry seasonal water course (called "Khor") seems to be the most preferred habitat for most of the sand fly species since most of the collections (41.2%) were made from this site, followed by the rodent burrows.

CONCLUSIONS

The presence of P. orientalis and the high prevalence of VL in infants in the Al-Malha area provide the first evidence for local transmission of the parasite causing kala-azar in Darfur. Transmission is probably occurring during summer near the woodland where a high density of the vector was recorded. As a pre-requisite for designing effective control of VL in North Darfur, large scale entomological and epidemiological studies are recommended.

Diversity and altitudinal distribution of phlebotomine sand flies (Diptera: Psychodidae) in visceral leishmaniasis endemic areas of northwest Ethiopia

BACKGROUND

The Leishmaniases are caused by the protozoan parasites of the genus Leishmania and are transmitted to humans by the bite of infected female phlebotomine sand flies. Both visceral and cutaneous leishmaniases are widely distributed in different parts of Ethiopia. The aim of this study was to determine the diversity and altitudinal distribution of phlebotomine sand flies from Kafta Humera to Gondar town in northwest Ethiopia.

METHODS

Seven localities were selected with distinct altitudinal variations between 550m above sea level (m a.s.l) and 2300m a.s.l. In each locality, sand flies were collected using standard CDC light traps and sticky traps during the active sand fly season from December 2012 to May 2013. Shannon-Weiner species diversity index and Jaccard's coefficient were used to estimate species diversity and similarity between altitudes and localities, respectively.

RESULTS

A total of 89,044 sand flies (41,798 males and 47, 246 females) were collected from the seven localities/towns throughout the study period. Twenty-two species belonging to 11 species in the genus Phlebotomus and 11 species in the genus Sergentomyia were documented. Of these, Sergentomyia clydei (25.87%), S. schwetzi (25.21%), S. africana (24.65%), S. bedfordi (8.89%), Phlebotomus orientalis (6.43%), and S. antennata (4.8%) were the most prevalent species. The remaining 10 Phlebotomus species and six Sergentomyia were less frequent catches. In CDC light trap and sticky trap, higher species diversity and richness for both male and female sand flies was observed at low altitude ranging from 550 to 699m a.s.l in Adebay village in Kafta Humera district whereas low species richness and high evenness of both sexes were also observed in an altitude 1950-2300m a.s.l.

CONCLUSION

The results revealed that the presence of leishmaniasis vectors such as P. orientalis, P. longipes, P. papatasi, and P. duboscqi in different altitudes in northwest Ethiopia. P. orientalis a vector of L. donovani, occurred between altitude 500-1100m a.s.l, the area could be at high risk of VL. P. longipes a vector of L. aethiopica, was recorded in the highland area in Tikil-Dingay and Gondar town, implicating the possibility of CL transmission. Hence, further investigation into vector competence in relation to leishmaniasis (VL and CL) in the region is very vital.

Phlebotomine sandflies of Botswana: a taxonomic review and a faunistic update with the first record of genus Phlebotomus

The first records of phlebotomine sandflies from Botswana have been published only recently, comprising of four species of genus Sergentomyia. This update presents the first record of genus Phlebotomus, namely Ph. (Anaphlebotomus) rodhaini Parrot, which is also the first detection of a putative vector of leishmaniasis in Botswana. In addition, records of the Sergentomyia "bedfordi (Newstead) group" are reviewed, and the molecular taxonomy of all taxa known from Botswana is analysed based on three mitochondrial gene fragments (mtDNA). The presence of Se. congolensis (Bequaert and Walrveus) and Se. salisburiensis (Abonnenc) is confirmed, whereas the previously mentioned Se. caliginosa Davidson and unassigned specimens of the "bedfordi group" are proposed to belong to the tentatively named Se. bedfordi "Maun" form. The mtDNA analyses confirmed the species delimitations. For the first time, portions of the ND5 gene were used for the purpose of sandfly molecular taxonomy. This gene revealed a high inter-specific variability and may thus be applied as an alternative molecular marker for future studies.

Transmission of Leishmania infantum in the Canine Leishmaniasis Focus of Mont-Rolland, Senegal: Ecological, Parasitological and Molecular Evidence for a Possible Role of Sergentomyia Sand Flies

Leishmania (L.) infantum is the causative agent in an endemic focus of canine leishmaniasis in the Mont-Rolland district (Thiès, Senegal). In this area, the transmission cycle is well established and more than 30% of dogs and 20% of humans are seropositive for L. infantum. However, the sand fly species involved in L. infantum transmission cycle are still unknown. Between 2007 and 2010, 3654 sand flies were collected from different environments (indoor, peridomestic, farming and sylvatic areas) to identify the main L. infantum vector(s). Nine sand fly species were identified. The Phlebotomus genus (n = 54 specimens; Phlebotomus (Ph) duboscqi and Phlebotomus (Ph). rodhaini) was markedly under-represented in comparison to the Sergentomyia genus (n = 3600 specimens; Sergentomyia (Se) adleri, Se. clydei, Se. antennata, Se. buxtoni, Se. dubia, Se. schwetzi and Se. magna). Se. dubia and Se. schwetzi were the dominant species indoor and in peridomestic environments, near humans and dogs. Blood-meal analysis indicated their anthropophilic behavior. Some Se. schwetzi specimens fed also on dogs. The dissection of females in the field allowed isolating L. infantum from sand flies of the Sergentomyia genus (0.4% of Se. dubia and 0.79% of Se. schwetzi females). It is worth noting that one Se. dubia female not engorged and not gravid revealed highly motile metacyclic of L. infantum in the anterior part of the midgut. PCR-based diagnosis and sequencing targeting Leishmania kinetoplast DNA (kDNA) highlighted a high rate of L. infantum-positive females (5.38% of Se. dubia, 4.19% of Se. schwetzi and 3.64% of Se. magna). More than 2% of these positive females were unfed, suggesting the parasite survival after blood-meal digestion or egg laying. L. infantum prevalence in Se. schwetzi was associated with its seroprevalence in dogs and humans and L. infantum prevalence in Se. dubia was associated with its seroprevalence in humans. These evidences altogether strongly suggest that species of the Sergentomyia genus are probably the vectors of canine leishmaniasis in the Mont-Rolland area and challenge one more time the dogma that in the Old World, leishmaniasis is exclusively transmitted by species of the Phlebotomus genus.

Leishmaniases, neglected tropical vector-borne diseases, remain today a problem of public health. Classically, the sand flies involved in Leishmania transmission belong either to the Phlebotomus genus (Old World) or to the Lutzomyia genus (New World). In the rural community of Mont-Rolland (Senegal, West Africa), Leishmania infantum is the causative agent in an endemic focus of canine leishmaniasis. Recent surveys revealed more than 30% of dogs and 20% of humans with a positive serological test for Leishmania in this community. However, the sand fly species involved in L. infantum transmission were still unknown. Between 2007 and 2010, we carried out a study in this community to identify the sand fly species responsible for L. infantum transmission. We collected nine species belonging mainly to Sergentomyia genus and in low proportion to Phlebotomus genus. The abundance around dogs and humans, the detection of live and mature parasites in anterior midgut, the high rate of L. infantum-positive females using molecular analyses and the identification of dog and human blood in the fed females incriminates Se. schwetzi and Se. dubia as possible vectors of L. infantum. This hypothesis is strongly supported by statistical analyses performed to compare the prevalence of infected sand flies with the seroprevalence data in humans and dogs.

A review of visceral leishmaniasis during the conflict in South Sudan and the consequences for East African countries

Background

Visceral leishmaniasis (VL), caused predominantly by Leishmania donovani and transmitted by both Phlebotomus orientalis and Phlebotomus martini, is highly endemic in East Africa where approximately 30 thousands VL cases are reported annually. The largest numbers of cases are found in Sudan - where Phlebotomus orientalis proliferate in Acacia forests especially on Sudan’s eastern border with Ethiopia, followed by South Sudan, Ethiopia, Somalia, Kenya and Uganda. Long-standing civil war and unrest is a dominant determinant of VL in East African countries. Here we attempt to identify the correlation between VL epidemics and civil unrest.

Objective and methodology

In this review, literature published between 1955 and 2016 have been gathered from MSF, UNICEF, OCHA, UNHCR, PubMed and Google Scholar to analyse the correlation between conflict and human suffering from VL, which is especially apparent in South Sudan.

Findings

Waves of forced migration as a consequence of civil wars between 1983 and 2005 have resulted in massive and lethal epidemics in southern Sudan. Following a comprehensive peace agreement, but especially with increased allocation of resources for disease treatment and prevention in 2011, cases of VL declined reaching the lowest levels after South Sudan declared independence. However, in the latest epidemic that began in 2014 after the onset of a civil war in South Sudan, more than 1.5 million displaced refugees have migrated internally to states highly endemic for VL, while 800,000 have fled to neighboring countries.

Conclusion

We find a strong relationship between civil unrest and VL epidemics which tend to occur among immunologically naïve migrants entering VL-endemic areas and when Leishmania-infected individuals migrate to new areas and establish additional foci of disease. Further complicating factors in East Africa’s VL epidemics include severe lack of access to diagnosis and treatment, HIV/AIDS co-infection, food insecurity and malnutrition. Moreover, cases of post-kala-azar dermal leishmaniasis (PKDL) can serve as important reservoirs of anthroponotic Leishmania parasites.

Visceral Leishmaniasis in Benishangul-Gumuz Regional State, Western Ethiopia: Reemerging or Emerging?

Kala-azar is a growing public health problem in Ethiopia. Benishangul-Gumuz regional state was previously not known to be endemic for the disease. In response to a case report from the region, we conducted a rapid assessment survey. A pretested questionnaire was used to capture sociodemographic and clinical histories pertinent to kala-azar. Study participants with complaints of fever and headache for 2 weeks or more were tested for kala-azar and malaria. All participants were screened with the leishmanin skin test and the direct agglutination test for exposure to Leishmania, defined as a positive result with either or both tests. Of 275 participants, 20 were exposed giving an overall leishmaniasis seroprevalence rate of 7.3%. Among the 20 positive individuals, 19 were farmers and nine of them reported no travel history outside their district. It appears that kala-azar is emerging in Dangur and Guba districts of Benishangul-Gumuz regional state, probably in connection with human encroachment into one or several previously out-of-reach zoonotic foci. We recommend integrated epidemiological surveys for confirmation and early containment of disease transmission in the area.

Physiological Age Structure and Leishmania spp. Detection in Phlebotomus (Larroussius) orientalis (Parrot, 1936) (Diptera: Psychodidae) at an Endemic Focus of Visceral Leishmaniasis in Northern Ethiopia

Visceral leishmaniasis (VL) caused by Leishmania donovani is endemic in northern Ethiopia, where P. orientalis is the most important presumed vector. This study was designed to determine the physiological age structure and the occurrence of Leishmania infection in the vector of VL in Tahtay Adiyabo district, northern Ethiopia. Sand flies were collected using CDC light traps from peridomestic and agricultural fields between May 2011 and April 2012 and P. orientalis females were dissected for age determination and detection of Leishmania promastigotes. Sand flies were also analyzed for L. donovani detection using molecular methods. Of 1,282 P. orientalis examined for abdominal stages and age characterization, 66.2%, 28.2%, 4.1%, and 1.6% were unfed, freshly fed, half-gravid, and gravid. Parous rate in unfed females was 34.1% and 35.4% in peridomestic and agricultural fields, respectively. Out of 921 P. orientalis females dissected, one specimen (0.1%) was found naturally infected with promastigotes. Five pools (25 females) of unfed P. orientalis were also found with DNA of Leishmania spp. In particular, a single P. orientalis was positive for L. donovani (0.5%). Based on this and other evidences (abundance, human blood feeding, and xenodiagnostic studies), P. orientalis is the principal vector of VL in this endemic focus.

Eco-epidemiology of visceral leishmaniasis in Ethiopia

Visceral leishmaniasis (VL, Kala-azar) is one of the growing public health challenges in Ethiopia with over 3.2 million people at risk and estimated up to 4000 new cases per year. Historically, VL was known as the diseases of the lowlanders; in the lower and upper Kola agro-ecological zones of Ethiopia. The 2005–07 out breaks in highlands of Libo Kemkem and Fogera, in the Woina Degas, that affected thousands and claimed the life of hundreds misdiagnosed as drug resistance malaria marked that VL is no more the problem of the lowlanders. The Kola (lower and upper) and the Woina Dega are the most productive agroecological zones, supporting both the ongoing and planned expansions of large or small scale agriculture and/or agriculture based industries. Thus, the (re)emergence of VL is not only a public health and social problem but also have a direct implication on the country’s economy and further development. Thus is high time for its control and/or elimination. Yet, the available data seem incomplete to plan for a cost-effective and efficient VL control strategy: there is a need to update data on vector behaviour in specific ecosystems and the roles of domestic animals need to be ascertained. The effectiveness and social acceptability of available vector control tools need be evaluated. There is a need for identifying animal reservoir(s), or establish the absence of zoonosis in Ethiopia. The planning of prevention of (re)emergence and spread of VL to areas adjacent to endemic foci need be supported with information from spatio-temporal mapping. In affected communities, available data showed that their knowledge about VL is generally very low. Thus, well designed studies to identify risk factors, as well as better tools for social mobilization with the understanding of their knowledge, aptitude and practice towards VL are necessary.

Species composition of phlebotomine sand flies and bionomics of Phlebotomus orientalis (Diptera: Psychodidae) in an endemic focus of visceral leishmaniasis in Tahtay Adiyabo district, Northern Ethiopia

Background

Visceral leishmaniasis (VL) is a neglected tropical disease, which is strongly associated with poverty. VL caused by Leishmania donovani and transmitted by Phlebotomus orientalis is endemic in various remote areas of north and north-west Ethiopia. The present study was designed to determine the sand fly fauna and bionomics of P. orientalis in the VL endemic focus of Tahtay Adiyabo district.

Methods

Sand flies were collected using CDC light traps (n = 602), sticky traps (n = 9,350) and indoor pyrethrum spray catches (n = 578 house visits) from indoor, peri-domestic and agricultural field habitats between May 2011 to April 2012. All sand fly specimens collected were identified to species level and counted.

Results

In total, 100,772 sand fly specimens, belonging to 25 sand fly species (nine Phlebotomus and sixteen Sergentomyia) were collected and identified. S. africana and P. orientalis made up 59.1% and 23.5% of the collected sand flies, respectively. As it could be determined from the proportion of collections from outdoor (peri-domestic and agricultural fields) and indoor locations, P. orientalis appears to exhibit increased exophilic behavior. The outdoor to indoor index was 79:1 on m² of sticky traps. Mean density of P. orientalis caught was significantly higher on horizontally placed sticky traps (mean = 60 ± 14.56/m²/night) than vertically deployed sticky traps (12 ± 3.57/m²/night). The highest abundance of P. orientalis occurred between March and April. Through July to September, there was a sharp decline in abundance of P. orientalis population. Regarding climatic variables, P. orientalis density in light traps and on sticky traps showed a significant positive and negative association with temperature and relative humidity, respectively. However, non-significant negative correlation was observed with rainfall pattern.

Conclusions

Overall, P. orientalis was found to be the most abundant Phlebotomus species, showing marked seasonal abundance that mainly peaks during the dry season (March to April). Likewise, the people in the area usually sleep in compounds during these months that potentially expose them to a high risk of peri-domestic VL transmission.

Visceral leishmaniasis in Ethiopia: an evolving disease

Visceral leishmaniasis (also known as kala-azar) is classified as one of the most neglected tropical diseases. It is becoming a growing health problem in Ethiopia, with endemic areas that are continually spreading. The annual burden of visceral leishmaniasis (VL) in Ethiopia is estimated to be between 4,500 and 5,000 cases, and the population at risk is more than 3.2 million. There has been a change in the epidemiology of VL in Ethiopia. Over the last decades, almost all cases and outbreaks of VL were reported from arid and semi-arid parts of the country; however, recent reports indicated the introduction of this disease into the highlands. Migration of labourers to and from endemic areas, climatic and environmental changes, and impaired immunity due to HIV/AIDS and malnutrition resulted in the change of VL epidemiology. HIV spurs the spread of VL by increasing the risk of progression from asymptomatic infection towards full VL. Conversely, VL accelerates the onset of AIDS. In Ethiopia, VL epidemiology remains complex because of the diversity of risk factors involved, and its control is becoming an increasing challenge. This paper reviews the changes in epidemiology of VL in Ethiopia and discusses some of the possible explanations for these changes. The prospects for novel approaches to VL control are discussed, as are the current and future challenges facing Ethiopia's public health development program.

Sergentomyia schwetzi is not a competent vector for Leishmania donovani and other Leishmania species pathogenic to humans

BACKGROUND

Sand fly species of the genus Sergentomyia are proven vectors of reptilian Leishmania that are non-pathogenic to humans. However, a consideration of the role of Sergentomyia spp. in the circulation of mammalian leishmaniasis appears repeatedly in the literature and the possibility of Leishmania transmission to humans remains unclear. Here we studied the susceptibility of colonized Sergentomyia schwetzi to Leishmania donovani and two other Leishmania species pathogenic to humans: L. infantum and L. major.

METHODS

Females of laboratory-reared S. schwetzi were infected by cultured Leishmania spp. by feeding through a chicken membrane, dissected at different time intervals post bloodmeal and examined by light microscopy for the abundance and location of infections.

RESULTS

All three Leishmania species produced heavy late stage infections in Lutzomyia longipalpis or Phlebotomus duboscqi sand flies used as positive controls. In contrast, none of them completed their developmental cycle in Sergentomyia females; Leishmania promastigotes developed within the bloodmeal enclosed by the peritrophic matrix (PM) but were defecated together with the blood remnants, failing to establish a midgut infection. In S. schwetzi, the PM persisted significantly longer than in L. longipalpis and it was degraded almost simultaneously with defecation. Therefore, Leishmania transformation from procyclic to long nectomonad forms was delayed and parasites did not attach to the midgut epithelium.

CONCLUSIONS

Sergentomyia schwetzi is refractory to human Leishmania species and the data indicate that the crucial aspect of the refractoriness is the relative timing of defecation versus PM degradation.