Infection of Leishmania donovani in Phlebotomus orientalis Sand Flies at Different Microhabitats of a Kala-Azar Endemic Village in Eastern Sudan

A study was carried out to compare the infection rates of Leishmania donovani in Phlebotomus orientalis sandflies at different microhabitats of a VL endemic village in Gedarif state, Sudan. DNA extracts of 1078 P. orientalis sand fly females sampled by CDC light traps from indoor, outdoor, peri-domestic, and sylvatic sites, in three transmission seasons, March-June 2016-18, in Helat-Belo village, were subjected to independent PCR amplifications targeting Leishmania kDNA and the cpb gene followed by ITS1 region sequencing. Leishmania kDNA was detected in 1.4% of the 1078 P. orientalis females captured in the area. Two of these specimens showed a characteristic 741 bp band of L. donovani after cpb gene amplification. The DNA sequence of the ITS1 region of the parasites matched the ITS1 L. donovani genotype F. There were no signficant differences between rates of infection of L. donovani in P. orientalis captured at different sites. Blood meals found in infected flies origninated from human (5 specimens), cattle (4 specimens) and donkey (2 specimens). The finding of fresh cow and donkey blood in the infected flies suggests the possible role of these animals in the zoopotentiation and/or zooprophylaxis against VL. The study provides important information for VL transmission models and control programs in East Africa.

Unraveling Key Chloroquine Resistance-Associated Alleles Among Plasmodium falciparum Isolates in South Darfur State, Sudan Twelve Years After Drug Withdrawal

Background

Due to the increasing resistance of Plasmodium falciparum to chloroquine (CQ) in Sudan, a shift from CQ to artesunate combined with sulfadoxine/pyrimethamine as a first-line treatment for uncomplicated falciparum malaria was adopted in 2004. This study aimed to determine the frequency distribution of K76T and N86Y mutations in P. falciparum chloroquine resistance transporter (pfcrt) and P. falciparum multidrug resistance 1 (pfmdr1) genes as key markers of resistance to CQ among P. falciparum isolates from patients in Nyala district of South Darfur state, west of Sudan.

Methods

A descriptive, cross-sectional study was conducted among 75 P. falciparum isolates from Sudanese patients diagnosed with falciparum malaria mono-infection. Parasite DNA was extracted from dried blood spots and amplified using a nested polymerase chain reaction (PCR). Then, restriction fragment length polymorphism (RFLP) was used to detect the genetic polymorphisms in codons 76 of pfcrt and 86 of pfmdr1. PCR-RFLP products were analyzed using 1.5% gel electrophoresis to identify the genetic polymorphisms in the studied codons. The wild-type (pfcrt K76 and pfmdr1 N86), mutant (pfcrt 76T and pfmdr1 86Y) and mixed-type (pfcrt K76T and pfmdr1 N86Y) alleles were expressed as frequencies and proportions.

Results

The wild-type pfcrt K76 allele was observed among 34.7% of isolates and the mutant 76T allele among 20% of isolates, while the mixed-type K76T allele was observed among 45.3% of isolates. On the other hand, 54.7% of isolates harbored the wild-type pfmdr1 N86 allele and 5.3% of isolates had the mutant 86Y allele, while the mixed-type N86Y allele was observed among 40% of isolates.

Conclusion

The key molecular markers associated with CQ resistance (pfcrt 76T and pfmdr1 86Y) are still circulating in high frequency among P. falciparum isolates in South Darfur state, about twelve years after the official withdrawal of the drug as a treatment for uncomplicated falciparum malaria.

Host preference and human blood index of Phlebotomus orientalis, an exophilic sand fly vector of visceral leishmaniasis in eastern Sudan

Visceral leishmaniasis (VL, kala azar), caused by Leishmania donovani, transmitted by Phlebotomus orientalis, is a serious systemic disease that causes high morbidity and mortality rates in Sudan and other parts of East Africa and the world. Despite progress in understanding the epidemiology of the disease in East Africa, little is known about the host preference of P. orientalis in kala azar endemic villages of Sudan, which have some of the highest VL incidence rates in the world. The present study used host choice experiments and blood-meal identification approaches to determine the host preference of P. orientalis in kala azar endemic villages in Gedarif state, eastern Sudan. In the host choice experiment, tent traps were used to compare the attractiveness of cows, donkeys, sheep and goats for host-seeking P. orientalis. In the blood-meal identification study, blood-fed P. orientalis females, captured inside houses and peri-domestic habitats, were subjected to molecular typing using cytochrome b gene (cyt b) amplification and sequence analysis. Cows and donkeys were the most attractive to blood-seeking P. orientalis, followed by goats. Similarly, the blood-meal analysis of P. orientalis showed that the vector preferentially feeds on cows, followed by donkeys, humans and goats. The human blood index of P. orientalis was 19.4% (42/216), indicating a high zoophilic habit of the vector, both inside and outside the houses. Although the order of host preference varied by location, it was clear that cows are the most preferred host of P. orientalis in the area. Results are discussed in relation to the role of domestic/livestock animals in VL zoopotentiation and zooprophylaxis. Inference is made on the potential impact of insecticide treatment of cows in control of the vector and the transmission of VL in Sudan and other parts of East Africa.

The genus Madurella: Molecular identification and epidemiology in Sudan

Eumycetoma (mycotic mycetoma) is the fungal form of mycetoma, a subcutaneous infection occurring in individuals living in endemic areas of the disease. The Sudan is hyperendemic for mycetoma, with the highest incidence being reported from Gezira State, Central Sudan. The present study was conducted at the Gezira Mycetoma Center and aimed to determine the cause of black-grain eumycetoma in the state and describe its epidemiology. Black-grain specimens were collected during the surgical operation and direct detection of the causative agent was performed using M. mycetomatis species-specific PCR and ITS PCR followed by sequencing. Black-grain was reported from 93.3% of all confirmed mycetoma cases (n = 111/119), with a prevalence in young males. Of the 91 samples subjected to direct PCR, 90.1% (n = 82) gave positive results. The predominant species (88.2%) was Madurella mycetomatis. One sample was identified as M. fahalii, one as M. tropicana, and one matched the phytopathogenic species Sphaerulina rhododendricola. The highest endemic zones were Southern Gezira (76.6%) and Northern Sinnar (23.4%). The study confirmed that direct molecular detection on grains provides rapid and specific diagnosis of agents of eumycetoma.

Eumycetoma is a neglected fungal disease endemic in Africa, India, and Latin America. Black-grain eumycetoma is the most common type in Africa and is mainly caused by Madurella spp. The Sudan, and in particular Gezira State, central Sudan is hyperendemic for black-grain eumycetoma. Patients with this type of mycetoma are treated with surgery in combination with antifungal therapy. In this study, we collected surgical biopsies from patients attending Gezira Mycetoma Center to directly identify the etiology of black-grain eumycetoma in this state. We also studied the epidemiology of the disease based on the demography of the patients’ population. Our result showed that the highest endemic regions were Southern Gezira (76.6%) and Northern Sinnar (23.4%). By applying direct PCR and sequencing we confirmed that the most common etiology of the disease is Madurella mycetomatis (88.2%). In addition, we found one case of M. fahalii and the first Sudanese case of M. tropicana and Sphaerulina rhododendricola.

Prevalence and identification of arthropod-transmitted viruses in Kassala state, Eastern Sudan

Vector-borne diseases are responsible for more than 20% of the infectious diseases worldwide. The prevalence of arboviruses transmit diseases to humans in Sudan has not been investigated. Mosquito-borne viral diseases increase globally incidence, including the Sudan. Frequent unknown fever outbreaks have been reported in eastern region, Sudan. However, diagnosis was based exclusively on clinical signs and symptoms without confirmatory laboratory investigations. However, for accurate detection of these viruses in outbreaks, molecular technique is considered. The objective of this study was to determine the prevalence of six arboviruses in the Kassala state of east Sudan during unknown fever outbreak. A cross sectional hospital-based study was conducted in the Kassala, Teaching Hospital. Blood samples from 119 patients suffering from unknown fever were used for screening of six arboviruses, hepatitis E virus and malarial using molecular techniques and serology.  The overall arboviruses seroprevelance was 61.3% (73/119). The highest positivity rate was 73.1% (52/73) chikungunya virus; 29 males and 20 females patients were chikungunya positive. Other arboviruses were circulating in low rate 20.5% (15/73), and 6.8% (5/73) for sindbis and rift valley fever viruses respectively. Hepatitis E virus was negative in all cases and malaria positivity rate 13.4% (16/119). The prevalence of arboviruses among unknown fever patients present to Kassala teaching hospital of eastern region in Sudan is significantly high (61.3%). The chikungunya virus is the predominant causative agent of arboviruses. Molecular techniques such as PCR are important for accurate and rapid diagnosis of this viral outbreak.

Molecular surveillance of antimalarial drug resistance related genes in Plasmodium falciparum isolates from Eritrea

The introduction of artemisinin-based combination therapy has led to extraordinary results in malaria control, however the recent emergence of partial resistance to artemisinin therapy in Southeast Asia jeopardizes these successes. This study aimed at investigating resistance to the antimalarial drugs by evaluating the polymorphisms in the PfK13, Pfcrt and Pfmdr1 genes in Plasmodium falciparum isolates obtained from patients in Eritrea.

Plasmodium vivax Diversity and Population Structure across Four Continents

Plasmodium vivax is the geographically most widespread human malaria parasite. To analyze patterns of microsatellite diversity and population structure across countries of different transmission intensity, genotyping data from 11 microsatellite markers was either generated or compiled from 841 isolates from four continents collected in 1999–2008. Diversity was highest in South-East Asia (mean allelic richness 10.0–12.8), intermediate in the South Pacific (8.1–9.9) Madagascar and Sudan (7.9–8.4), and lowest in South America and Central Asia (5.5–7.2). A reduced panel of only 3 markers was sufficient to identify approx. 90% of all haplotypes in South Pacific, African and SE-Asian populations, but only 60–80% in Latin American populations, suggesting that typing of 2–6 markers, depending on the level of endemicity, is sufficient for epidemiological studies. Clustering analysis showed distinct clusters in Peru and Brazil, but little sub-structuring was observed within Africa, SE-Asia or the South Pacific. Isolates from Uzbekistan were exceptional, as a near-clonal parasite population was observed that was clearly separated from all other populations (F_ST>0.2). Outside Central Asia F_ST values were highest (0.11–0.16) between South American and all other populations, and lowest (0.04–0.07) between populations from South-East Asia and the South Pacific. These comparisons between P. vivax populations from four continents indicated that not only transmission intensity, but also geographical isolation affect diversity and population structure. However, the high effective population size results in slow changes of these parameters. This persistency must be taken into account when assessing the impact of control programs on the genetic structure of parasite populations.

Plasmodium vivax is the predominant malaria parasite in Latin America, Asia and the South Pacific. Different factors are expected to shape diversity and population structure across continents, e.g. transmission intensity which is much lower in South America as compared to Southeast-Asia and the South Pacific, or geographical isolation of P. vivax populations in the South Pacific. We have compiled data from 841 isolates from South and Central America, Africa, Central Asia, Southeast-Asia and the South Pacific typed with a panel of 11 microsatellite markers. Diversity was highest in Southeast-Asia, where transmission is intermediate-high and migration of infected hosts is high, and lowest in South America and Central Asia where malaria transmission is low and focal. Reducing the panel of microsatellites showed that 2–6 markers are sufficient for genotyping for most drug trials and epidemiological studies, as these markers can identify >90% of all haplotypes. Parasites clustered according to continental origin, with high population differentiation between South American and Central Asian populations and the other populations, and lowest differences between Southeast-Asia and the South Pacific. Current attempts to reduce malaria transmission might change this pattern, but only after transmission is reduced for an extended period of time.

Effects of mefloquine use on Plasmodium vivax multidrug resistance

Use of mefloquine against P. falciparum jeopardizes its future use against P. vivax.

Numerous studies have indicated a strong association between amplification of the multidrug resistance-1 gene and in vivo and in vitro mefloquine resistance of Plasmodium falciparum. Although falciparum infection usually is not treated with mefloquine, incorrect diagnosis, high frequency of undetected mixed infections, or relapses of P. vivax infection triggered by P. falciparum infections expose non–P. falciparum parasites to mefloquine. To assess the consequences of such unintentional treatments on P. vivax, we studied variations in number of Pvmdr-1 (PlasmoDB accession no. PVX_080100, NCBI reference sequence NC_009915.1) copies worldwide in 607 samples collected in areas with different histories of mefloquine use from residents and from travelers returning to France. Number of Pvmdr-1 copies correlated with drug use history. Treatment against P. falciparum exerts substantial collateral pressure against sympatric P. vivax, jeopardizing future use of mefloquine against P. vivax. A drug policy is needed that takes into consideration all co-endemic species of malaria parasites.

Molecular genetic analysis of Plasmodium vivax isolates from Eastern and Central Sudan using pvcsp and pvmsp-3α genes as molecular markers

In Sudan, Plasmodium vivax accounts for approximately 5-10% of malaria cases. This study was carried out to determine the genetic diversity of P. vivax population from Sudan by analyzing the polymorphism of P. vivax csp (pvcsp) and pvmsp-3α genes. Blood samples (n=76) were taken from suspected malaria cases from 2012-2013 in three health centers of Eastern and Central Sudan. Parasite detection was performed by microscopy and molecular techniques, and genotyping of both genes was performed by PCR-RFLP followed by DNA sequence for only pvcsp gene (n=30). Based on microscopy analysis, 76 (%100) patients were infected with P. vivax, whereas nested-PCR results showed that 86.8% (n=66), 3.9% (n=3), and 3.9% (n=3) of tested samples had P. vivax as well as Plasmodium falciparum mono- and mixed infections, respectively. Four out of 76 samples had no results in molecular diagnosis. All sequenced samples were found to be of VK210 (100%) genotype with six distinct amino acid haplotypes, and 210A (66.7%) was the most prevalent haplotype. The Sudanese isolates displayed variations in the peptide repeat motifs (PRMs) ranging from 17 to 19 with GDRADGQPA (PRM1), GDRAAGQPA (PRM2) and DDRAAGQPA (PRM3). Also, 54 polymorphic sites with 56 mutations were found in repeat and post-repeat regions of the pvcsp and the overall nucleotide diversity (π) was 0.02149±0.00539. A negative value of dN-dS (-0.0344) was found that suggested a significant purifying selection of Sudanese pvcsp, (Z test, P<0.05). Regarding pvmsp-3α, three types were detected: types A (94.6%, 52/55), type C (3.6%, 2/55), and type B (1.8%, 1/55). No multiclonal infections were detected, and RFLP analysis identified 13 (Hha I, A1-A11, B1, and C1) and 16 (Alu I, A1-A14, B1, and C1) distinct allelic forms. In conclusion, genetic investigation among Sudanese P. vivax isolates indicated that this antigen showed limited antigenic diversity.

Cytokine profiles amongst Sudanese patients with visceral leishmaniasis and malaria co-infections

BACKGROUND

The immune system plays a critical role in the development of co-infections, promoting or preventing establishment of multiple infections and shaping the outcome of pathogen-host interactions. Its ability to mediate the interplay between visceral leishmaniasis (VL) and malaria has been suggested, but poorly documented. The present study investigated whether concomitant infection with Leishmania donovani complex and Plasmodium falciparum in naturally co-infected patients altered the immunological response elicited by the two pathogens individually.

RESULTS

Circulating levels of interferon (IFN)-γ, interleukin (IL)-2, IL-4, IL-6, IL-10, IL-12p70, IL-13, IL-17A and tumor necrosis factor (TNF) were assessed in sera of patients infected with active VL and/or malaria and healthy individuals from Gedarif State, Sudan. Comparative analysis of cytokine profiles from co- and mono-infected patients highlighted significant differences in the immune response mounted upon co-infection, confirming the ability of L. donovani and P. falciparum to mutually interact at the immunological level. Progressive polarization towards type-1 and pro-inflammatory cytokine patterns characterized the co-infected patients, whose response partly reflected the effect elicited by VL (IFN-γ, TNF) and malaria (IL-2, IL-13), and partly resulted from a synergistic interaction of the two diseases upon each other (IL-17A). Significantly reduced levels of P. falciparum parasitaemia (P <0.01) were detected in the co-infected group as opposed to the malaria-only patients, suggesting either a protective or a non-detrimental effect of the co-infection against P. falciparum infection.

CONCLUSIONS

These findings suggest that a new immunological scenario may occur when L. donovani and P. falciparum co-infect the same patient, with potential implications on the course and resolution of these diseases.

Whole genome sequencing of field isolates reveals a common duplication of the Duffy binding protein gene in Malagasy Plasmodium vivax strains

Background

Plasmodium vivax is the most prevalent human malaria parasite, causing serious public health problems in malaria-endemic countries. Until recently the Duffy-negative blood group phenotype was considered to confer resistance to vivax malaria for most African ethnicities. We and others have reported that P. vivax strains in African countries from Madagascar to Mauritania display capacity to cause clinical vivax malaria in Duffy-negative people. New insights must now explain Duffy-independent P. vivax invasion of human erythrocytes.

Methods/Principal Findings

Through recent whole genome sequencing we obtained ≥70× coverage of the P. vivax genome from five field-isolates, resulting in ≥93% of the Sal I reference sequenced at coverage greater than 20×. Combined with sequences from one additional Malagasy field isolate and from five monkey-adapted strains, we describe here identification of DNA sequence rearrangements in the P. vivax genome, including discovery of a duplication of the P. vivax Duffy binding protein (PvDBP) gene. A survey of Malagasy patients infected with P. vivax showed that the PvDBP duplication was present in numerous locations in Madagascar and found in over 50% of infected patients evaluated. Extended geographic surveys showed that the PvDBP duplication was detected frequently in vivax patients living in East Africa and in some residents of non-African P. vivax-endemic countries. Additionally, the PvDBP duplication was observed in travelers seeking treatment of vivax malaria upon returning home. PvDBP duplication prevalence was highest in west-central Madagascar sites where the highest frequencies of P. vivax-infected, Duffy-negative people were reported.

Conclusions/Significance

The highly conserved nature of the sequence involved in the PvDBP duplication suggests that it has occurred in a recent evolutionary time frame. These data suggest that PvDBP, a merozoite surface protein involved in red cell adhesion is rapidly evolving, possibly in response to constraints imposed by erythrocyte Duffy negativity in some human populations.

Malaria results from infection of human red blood cells (RBC) by Plasmodium parasite's merozoite. For Plasmodium vivax the process of RBC invasion has been hypothesized to depend on interactions between the parasite's Duffy binding protein (PvDBP) and human Duffy blood group antigen because Duffy-negative people (most often people of African descent) were shown to be highly resistant to RBC infection and disease. Over the past five years, researchers are reporting with increasing frequency that Duffy-negative individuals are infected with P. vivax. This raises new questions as to how P. vivax infects the RBC when the Duffy blood group antigen is not available. Here we show that the parasite's Duffy binding protein gene has been duplicated in multiple P. vivax strains, especially at high prevalence in Madagascar. The specificity and prevalence of this polymorphism suggest that the parasite genome has responded to the barrier of Duffy negativity through the duplication of the PvDBP gene. Our results indicate that the PvDBP duplication is a recent event and provide novel research avenues to understand alternative pathways for P. vivax RBC invasion.

Concomitant malaria among visceral leishmaniasis in-patients from Gedarif and Sennar States, Sudan: a retrospective case-control study

Background

In areas where visceral leishmaniasis (VL) and malaria are co-endemic, co-infections are common. Clinical implications range from potential diagnostic delay to increased disease-related morbidity, as compared to VL patients. Nevertheless, public awareness of the disease remains limited. In VL-endemic areas with unstable and seasonal malaria, vulnerability to the disease persists through all age-groups, suggesting that in these populations, malaria may easily co-occur with VL, with potentially severe clinical effects.

Methods

A retrospective case-control study was performed using medical records of VL patients admitted to Tabarakallah and Gedarif Teaching Hospitals (Gedarif State) and Al`Azaza kala-azar Clinic (Sennar State), Sudan (2005-2010). Patients positively diagnosed with VL and malaria were identified as cases, and VL patients without microscopy-detectable malaria as controls. Associations between patient characteristics and the occurrence of the co-infection were investigated using logistic regression analysis. Confirmation of epidemiological outcomes was obtained with an independently collected dataset, composed by Médecins Sans Frontières (MSF) at Um-el-Kher and Kassab Hospitals, Gedarif State (1998).

Results

The prevalence of malaria co-infection among VL surveyed patients ranged from 3.8 to 60.8%, with a median of 26.2%. Co-infected patients presented at hospital with deteriorated clinical pictures. Emaciation (Odds Ratio (OR): 2.46; 95% Confidence Interval (95% CI): 1.72-3.50), jaundice (OR: 2.52; 95% CI: 1.04-6.09) and moderate anemia (OR: 1.58; 95% CI: 1.10-2.28) were found to be positively associated with the co-infection, while severity of splenomegaly (OR: 0.53; 95% CI: 0.35-0.81) and, to a less extent, hepatomegaly (OR: 0.52; 95% CI: 0.27-1.01) appeared to be reduced by concomitant VL and malaria. The in-hospital case-fatality rates did not significantly differ between co- and mono-infected patients (OR: 1.13; 95% CI: 0.59-2.17). Conversely, a significantly increased mortality rate (OR: 4.38; 95% CI: 1.83-10.48) was observed by MSF amongst co-infected patients enrolled at Um-el-Kher and Kassab Hospitals, who also suffered an enhanced risk of severe anemia (OR: 3.44; 95% CI: 1.68-7.02) compared to VL mono-infections.

Conclusions

In endemic VL areas with unstable seasonal malaria, like eastern Sudan, VL patients are highly exposed to the risk of developing concomitant malaria. Prompt diagnosis and effective treatment of malaria are essential to ensure that its co-infection does not result into poor prognoses.

Informed decision-making before changing to RDT: a comparison of microscopy, rapid diagnostic test and molecular techniques for the diagnosis and identification of malaria parasites in Kassala, eastern Sudan

OBJECTIVES

Rapid diagnostic tests (RDTs) are promoted for the diagnosis of malaria in many countries. The question arises whether laboratories where the current method of diagnosis is microscopy should also switch to RDT. This problem was studied in Kassala, Sudan where the issue of switching to RDT is under discussion.

METHODS

Two hundred and three blood samples were collected from febrile patients suspected of having malaria. These were subsequently analysed with microscopy, RDT (SD Bioline P.f/P.v) and PCR for the detection and identification of Plasmodium parasites.

RESULTS

Malaria parasites were detected in 36 blood samples when examined microscopically, 54 (26.6%) samples were found positive for malaria parasites by RDT, and 44 samples were positive by PCR. Further analysis showed that the RDT used in our study resulted in a relatively high number of false positive samples. When microscopy was compared with PCR, an agreement of 96.1% and k = 0.88 (sensitivity 85.7% and specificity 100%) was found. However, when RDT was compared with PCR, an agreement of only 81.2 and k = 0.48 (sensitivity 69% and specificity 84%) was found.

CONCLUSION

PCR has proven to be one of the most specific and sensitive diagnostic methods, particularly for malaria cases with low parasitaemia. However, this technique has limitations in its routine use under resource-limited conditions, such as our study location. At present, based on these results, microscopy remains the best option for routine diagnosis of malaria in Kassala, eastern Sudan.

Frequency distribution of antimalarial drug resistance alleles among Plasmodium falciparum isolates from Gezira State, central Sudan, and Gedarif State, eastern Sudan

In 2004, Sudan adopted artesunate + sulfadoxine/pyrimethamine (SP) combination as the first-line drug, in response to the high level of falciparum resistance to antimalarials. In 2007, a molecular study on antimalarial resistance linked genes, pfcrt, pfmdr1, pfdhfr, pfdhps, and pfATPase6, was conducted on 198 isolates from central and eastern Sudan. We observed a high frequency of point mutations at almost all loci analyzed, mainly of pfcrt 76T (72.7%), pfdhfr 51I (75.3%), and pfdhfr 108N (72.7%) alleles. The MARK III in vitro test for chloroquine sensitivity in 45 P. falciparum isolates showed that 37.8% of the isolates were low resistant and 6.7% were fully resistant. This study represents the most recent molecular investigation on antimalarial resistance in this area after the adoption of artemisinin-based combination therapy (ACT), and underlines the importance of the analysis of SP resistance evolution to monitor the efficacy of ACT therapy in endemic areas.

Laboratory evaluation on the sensitivity and specificity of a novel and rapid detection method for malaria diagnosis based on magneto-optical technology (MOT)

Background

This study describes the laboratory evaluation of a novel diagnostic platform for malaria. The Magneto Optical Test (MOT) is based on the bio-physical detection of haemozoin in clinical samples. Having an assay time of around one minute, it offers the potential of high throughput screening.

Methods

Blood samples of confirmed malaria patients from different regions of Africa, patients with other diseases and healthy non-endemic controls were used in the present study. The samples were analysed with two reference tests, i.e. an histidine rich protein-2 based rapid diagnostic test (RDT) and a conventional Pan-Plasmodium PCR, and the MOT as index test. Data were entered in 2 × 2 tables and analysed for sensitivity and specificity. The agreement between microscopy, RDT and PCR and the MOT assay was determined by calculating Kappa values with a 95% confidence interval.

Results

The observed sensitivity/specificity of the MOT test in comparison with clinical description, RDT or PCR ranged from 77.2 - 78.8% (sensitivity) and from 72.5 - 74.6% (specificity). In general, the agreement between MOT and the other assays is around 0.5 indicating a moderate agreement between the reference and the index test. However, when RDT and PCR are compared to each other, an almost perfect agreement can be observed (k = 0.97) with a sensitivity and specificity of >95%.

Conclusions

Although MOT sensitivity and specificity are currently not yet at a competing level compared to other diagnostic test, such as PCR and RDTs, it has a potential to rapidly screen patients for malaria in endemic as well as non-endemic countries.

The spatial-temporal clustering of Plasmodium falciparum infection over eleven years in Gezira State, The Sudan

Background

Malaria infection and disease exhibit microgeographic heterogeneity which if predictable could have implications for designing small-area intervention. Here, the space-time clustering of Plasmodium falciparum infections using data from repeat cross-sectional surveys in Gezira State, a low transmission area in northern Sudan, is investigated.

Methods

Data from cross-sectional surveys undertaken in January each year from 1999-2009 in 88 villages in the Gezira state were assembled. During each survey, about a 100 children between the ages two to ten years were sampled to examine the presence of P. falciparum parasites. In 2009, all the villages were mapped using global positioning systems. Cluster level data were analysed for spatial-only and space-time clustering using the Bernoulli model and the significance of clusters were tested using the Kulldorff scan statistic.

Results

Over the study period, 96,022 malaria slide examinations were undertaken and the P. falciparum prevalence was 8.6% in 1999 and by 2009 this had reduced to 1.6%. The cluster analysis showed the presence of one significant spatial-only cluster in each survey year and one significant space-time cluster over the whole study period. The primary spatial-only clusters in 10/11 years were either contained within or overlapped with the primary space-time cluster.

Conclusion

The results of the study confirm the generally low malaria transmission in the state of Gezira and the presence of spatial and space-time clusters concentrated around a specific area in the south of the state. Improved surveillance data that allows for the analysis of seasonality, age and other risk factors need to be collected to design effective small area interventions as Gezira state targets malaria elimination.

Evaluation of the direct agglutination test based on freeze-dried Leishmania donovani promastigotes for the serodiagnosis of visceral leishmaniasis in Sudanese patients

The direct agglutination test (DAT) based on freeze-dried (FD) Leishmania donovani antigen was evaluated for the serodiagnosis of kala-azar in a rural setting in eastern Sudan. The performance of the FD-DAT was compared with standard liquid antigen (LQ) by testing serum samples and blood samples collected on filter paper of microscopically and PCR-confirmed VL patients, apparently healthy endemic controls and patients with other relevant infectious diseases for the region. In the present study, the FD-DAT had a sensitivity of 96.8% and a specificity of 96.2%. The LQ-DAT had a sensitivity of 91.0% and a specificity of 96.6%. A high degree of agreement (97.3%; r-value 0.94) was observed between the FD-DAT and the LQ-DAT, as well as between the FD-DAT performed on serum samples and corresponding blood samples collected on filter paper (agreement 97.8%; r-value 0.79). The FD-DAT is very suitable as diagnostic test for kala-azar in remote rural conditions as it is sensitive, specific and stable. The antigen is affordable, reproducible and available, which contributes to the sustainability of the DAT as a diagnostic test for VL.