Further studies on the phlebotomine sandflies of the kala-azar endemic lowlands of Humera-Metema (north-west Ethiopia) with observations on their natural blood meal sources

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.

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.

Seroprevalence of visceral leishmaniasis and its associated factors among asymptomatic pastoral community of Dire District, Borena zone, Oromia Region, Ethiopia

Visceral leishmaniasis (VL) is a vector-borne protozoan neglected tropical disease. In some parts of Ethiopia, it is a public health problem and its main causative agent is the Leishmania donovani complex. The objective of the study was to determine the seroprevalence of VL and factors associated among the asymptomatic pastoral community of Dire District, Borena Zone, Oromia Region, Ethiopia. A community-based study was conducted among 432 pastoralist communities from June to July 2021. A systematic random sampling method was used to select households. Pretested structured questionnaires and face-to-face interviews were used to collect data. A single finger-prick blood sample was collected and tested for Leishmania donovani complex using an immune-chromatographic test (rk39-ICT). A logistic regression model was used to assess factors associated with VL infection and a p-value of < 0.05 was considered statistically significant. A total of 432 study participants were included (their mean age was 26.69) and 218 (50.5%) were females. The overall seroprevalence of VL was 33/432(7.6%) (95%CI: 5.32-15.60). Sero-prevalence was significantly associated with high family size (>5) (adjusted odds ratios (AOR) = 5.134; 95% CI: 2.032-9.748), sleeping or/and staying under acacia tree (AOR = 2.984; 95%CI = 1.074-8.288), presence of cracked house walls (AOR = 1.801; 95%CI: 1.026-4.926), presence of termite hills (AOR = 1.938; 95%CL: 1.002-7.050), availability of water points (AOR = 3.893; 95%CI: 1.034-7.426) and presence of domestic animals (AOR = 2.124; 95% CI: 2.341-5.108). It is recommended that community awareness on the transmission and prevention methods of Leishmania donovani complex and taking appropriate interventions on the identified factors play a greater role to prevent and control infection in the area. Further investigation is also needed to characterize the pathogens and risk factors and tackle the problem.

Livestock infected with Leishmania spp. in southern Iran

BACKGROUND

Query ID="Q1" Text="Graphical abstract: As per journal requirements, graphical abstract is necessary. Kindly check and provide the same."The magnitude of the health problems caused by leishmaniasis has been a major driving factor behind the development and implementation of leishmaniasis control programs by the national authorities in Iran, with a priority for health and environmental management. Such programs are not achievable unless all of the factors leading to the infection, including the parasite's life-cycle, vectors and reservoirs, are recognized. So far in Iran, humans and rodents have been considered the principal reservoirs of Leishmania tropica and Leishmania major, respectively, both associated with cutaneous leishmaniasis (CL), with domestic dogs considered to be the main reservoir for Leishmania infantum, associated with visceral leishmaniasis (VL). The role of other mammals in maintaining the Leishmania parasite has remained unclear. This study aimed to investigate Leishmania infection among livestock in endemic areas of VL and CL in Fars province, southern Iran, using serological and molecular methods.

METHODS

Blood samples from 181 clinically healthy livestock, including 49 sheep, 114 goats, 16 cattle and two donkeys, were screened to detect Leishmania DNA and anti-Leishmania antibodies using qPCR (quantitative PCR) and the direct agglutination test (DAT), respectively. Four qPCR-positive samples were amplified using the internal transcribed spacer one (ITS1) primers in conventional PCR and sent for directional sequencing.

RESULTS

Of the 181 livestock tested, 51 (28.2%) were infected with Leishmania, using serological and molecular methods. Anti-Leishmania antibodies were detected in 70 (38.7%) (95% confidence interval [CI]: 31.5-46.2) and Leishmania DNA in 93 (51.4%) (95% CI: 43.9-58.9) livestock. The identified Leishmania spp. were L. infantum and L. major.

CONCLUSIONS

The findings of the present study show a relatively high prevalence of Leishmania infection among livestock in endemic areas of the disease, in Fars province, southern Iran. Given the large population of this group of animals and the fact that they live in the vicinity of the main reservoirs of the disease and vectors, it seems that sand flies regularly bite these animals. Further studies are needed to determine the role of livestock in the parasite's life-cycle and the epidemiology of Leishmania infection.

Blood Meal Analysis and Molecular Detection of Leishmania DNA in Wild-Caught Sand Flies in Leishmaniasis Endemic Areas of Turkey and Northern Cyprus

INTRODUCTION

Phlebotomine sand flies (Diptera: Psychodidae) are known as the vector of diseases such as leishmaniasis, bartonellosis and viral diseases. The aim of this study is to detect the host feeding pattern of sand flies in the endemic areas for leishmaniasis in Turkey (Antalya, Kayseri) and Northern Cyprus (TRNC) as well as the presence of Leishmania DNA in the specimens.

METHODS

One-hundred seventy-six blood-fed sand fly specimens were examined for blood meal analysis. A SYBR Green-PCR assay was performed with specific forward primers for each host and a universal reverse primer. Primers of human and goat were used together in multiplex PCR while goat and cow were studied separately. ITS-1 qPCR assay was also performed on both blood-fed and non-blood-fed females to detect Leishmania parasites.

RESULTS

Blood sources could be detected in 69 out of 176 blood-fed sand fly specimens. The results of blood meal analysis showed that specimens were fed mostly on cows (22.2%) followed by humans (5.7%), goats (2.8%) and dogs (0.6%). Multiple feeding patterns were also detected as human + cow (3.4%), cow + goat (2.8%) and human + goat (1.7%). Five of the blood-fed specimens were Leishmania spp. positive: P. major s.l. (n = 1), P. tobbi (n = 2) were L. tropica positive from Antalya, P. simici was positive for L. infantum from Kayseri and P. papatasi (n = 1) was positive for L. major from Cyprus. Leishmania infection rates were determined as 3.79%, 1.69% and 2.63% among the blood-fed sand fly specimens in Antalya, Kayseri and TRNC, respectively.

CONCLUSION

The SYBR-Green-based multiplex PCR assay is a cost-effective and promising tool for blood meal identification of wild-caught sand flies as well as other blood-sucking arthropods. Feeding patterns of important vector species detected in the present study show the high risk in these endemic areas. As a next step, to identify the blood source in a shorter time and to make the test more sensitive, development of this assay to probe-based and multiplex PCR will be also planned.

Domestic mammals as reservoirs for Leishmania donovani on the Indian subcontinent: Possibility and consequences on elimination

Leishmania donovani is the causative agent of historically anthroponotic visceral leishmaniasis (VL) on the Indian subcontinent (ISC). L. donovani is transmitted by the sand fly species Phlebotomus argentipes. Our collaborative group and others have shown that sand flies trapped outside in endemic villages have fed on cattle and dogs in addition to people. Domestic animals are reservoirs for L. donovani complex spp., particularly L. infantum, in other endemic areas. Multiple studies using quantitative PCR or serological detection methods have demonstrated that goats, cattle, rats and dogs were diagnostically positive for L. donovani infection or exposure in eastern Africa, Bangladesh, Nepal and India. There is a limited understanding of the extent to which L. donovani infection of domestic animals drives transmission to other animals or humans on the ISC. Evidence from other vector-borne disease elimination strategies indicated that emerging infections in domestic species hindered eradication. The predominant lesson learned from these other situations is that non-human reservoirs must be identified, controlled and/or prevented. Massive efforts are underway for VL elimination on the Indian subcontinent. Despite these herculean efforts, residual VL incidence persists. The spectre of an animal reservoir complicating elimination efforts haunts the final push towards full VL control. Better understanding of L. donovani transmission on the Indian subcontinent and rigorous consideration of how non-human reservoirs alter VL ecology are critical to sustain elimination goals.

Diversity and Within-Host Evolution of Leishmania donovani from Visceral Leishmaniasis Patients with and without HIV Coinfection in Northern Ethiopia

Visceral leishmaniasis (VL) is a fatal disease and a growing public health problem in East Africa, where Ethiopia has one of the highest VL burdens. The largest focus of VL in Ethiopia is driven by high prevalence in migrant agricultural workers and associated with a high rate of coinfection with HIV. This coinfection makes VL more difficult to treat successfully and is associated with a high rate of relapse, with VL/HIV patients frequently experiencing many relapses of VL before succumbing to this infection. We present genome-wide data on Leishmania donovani isolates from a longitudinal study of cohorts of VL and VL/HIV patients reporting to a single clinic in Ethiopia. Extensive clinical data allow us to investigate the influence of coinfection and relapse on the populations of parasites infecting these patients. We find that the same parasite population is responsible for both VL and VL/HIV infections and that, in most cases, disease relapse is caused by recrudescence of the population of parasites that caused primary VL. Complex, multiclonal infections are present in both primary and relapse cases, but the infrapopulation of parasites within a patient loses genetic diversity between primary disease presentation and subsequent relapses, presumably due to a population bottleneck induced by treatment. These data suggest that VL/HIV relapses are not caused by genetically distinct parasite infections or by reinfection. Treatment of VL does not lead to sterile cure, and in VL/HIV, the infecting parasites are able to reestablish after clinically successful treatment, leading to repeated relapse of VL. IMPORTANCE Visceral leishmaniasis (VL) is the second largest cause of deaths due to parasite infections and a growing problem in East Africa. In Ethiopia, it is particularly associated with migrant workers moving from regions of nonendemicity for seasonal agricultural work and is frequently found as a coinfection with HIV, which leads to frequent VL relapse following treatment. Insight into the process of relapse in these patients is thus key to controlling the VL epidemic in Ethiopia. We show that there is little genetic differentiation between the parasites infecting HIV-positive and HIV-negative VL patients. Moreover, we provide evidence that relapses are caused by the initially infecting parasite population and that treatment induces a loss of genetic diversity in this population. We propose that restoring functioning immunity and improving antiparasitic treatment may be key in breaking the cycle of relapsing VL in VL/HIV patients.

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.

Global genome diversity of the Leishmania donovani complex

Protozoan parasites of the Leishmania donovani complex - L. donovani and L. infantum - cause the fatal disease visceral leishmaniasis. We present the first comprehensive genome-wide global study, with 151 cultured field isolates representing most of the geographical distribution. L. donovani isolates separated into five groups that largely coincide with geographical origin but vary greatly in diversity. In contrast, the majority of L. infantum samples fell into one globally-distributed group with little diversity. This picture is complicated by several hybrid lineages. Identified genetic groups vary in heterozygosity and levels of linkage, suggesting different recombination histories. We characterise chromosome-specific patterns of aneuploidy and identified extensive structural variation, including known and suspected drug resistance loci. This study reveals greater genetic diversity than suggested by geographically-focused studies, provides a resource of genomic variation for future work and sets the scene for a new understanding of the evolution and genetics of the Leishmania donovani complex.

A molecular analysis of sand fly blood meals in a visceral leishmaniasis endemic region of northwestern Ethiopia reveals a complex host-vector system

Background

Visceral leishmaniasis (VL, or “kala-azar”) is a major cause of disability and death, especially in East Africa. Its vectors, sand flies (Diptera: Psychodidae: Phlebotominae), are poorly controlled and guarded against in these regions, owing in part to a lack of understanding about their feeding behavior.

Methods

A total of 746 freshly fed female sand flies were collected in five population centers in Kafta Humera (northwestern Ethiopia), where VL is endemic. Flies were collected from habitats that ranged from inside houses to open fields, using light traps and sticky traps. Sources of sand fly blood meals were identified using enzyme-linked immunosorbent assays (ELISA) and DNA amplification with reverse-line blot analysis (PCR-RLB); 632 specimens were screened using ELISA, 408 of which had identifiable blood meals, and 114 were screened using PCR-RLB, 53 of which yielded identifications. Fly species determinations were based on morphology, and those specimens subjected to PCR-RLB were also screened for Leishmania parasites using conventional PCR to amplify the nuclear marker ITS1 (internal transcribed spacer 1) with Leishmania-specific primers.

Results

More than three-fourths of all sand flies collected were Phlebotomus orientalis, and the remaining portion was comprised of nine other species. Nearly two-thirds of P. orientalis specimens were collected at village peripheries. The most common blood source for all flies was donkey (33.9% of all identifications), followed by cow (24.2%), human (17.6%), dog (11.8%), and goat or sheep (8.6%); mixtures of blood meals from different sources were found in 28.2% of all flies screened. Unidentified blood meals, presumably from wildlife, not domestic animals, were significantly higher in farm fields. Leishmania parasites were not detected in any of the 114 flies screened, not surprising given an expected infection rate of 1–5 out of 1,000. Meals that included a mixture of human and cow blood were significantly more frequent relative to all cow meals than human blood meals were to non-cow meals, suggesting a zoopotentiative interaction between cows and humans in this system.

Conclusions

Habitat and host preferences of sand fly vectors in Kafta Humera confirmed the finding of previous reports that the main vector in the region, Phlebotomus orientalis, is a highly opportunistic feeder that prefers large animals and is most commonly found at village peripheries. These results were similar to those of a previous study conducted in a nearby region (Tahtay Adiabo), except for the role of cattle on the prevalence of human blood meals. Preliminary examinations of blood meal data from different settings point to the need for additional surveys and field experiments to understand the role of livestock on biting risks.

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.

Zoonotic impact and epidemiological changes of leishmaniasis in Ethiopia

Leishmaniasis is one of the growing public health challenges in Ethiopia and estimated over 7,000 and 50,000 new cases of visceral leishmaniasis (VL) and cutaneous leishmaniasis (CL) per year, respectively. The aim of the review is to address zoonotic impact and epidemiological changes of leishmaniasis in Ethiopia. VL is caused by L. donovani and it is endemic in many parts of the country with one third of the country’s landmass is highly suitable for VL. CL is principally caused by L. aethiopica. CL is endemic and widespread in the highland of Ethiopia. Northern lowland foci are Humera and Metema plains in the Tigray and Amhara regional states constitute the main VL endemic areas in the country, contributing over 60% of the total burden. The southern foci are the south-western savannah, and the south-eastern semi-arid lowlands which account for approximately 20 % of the total VL burden in Ethiopia. Leishmaniasis is a serious zoonotic disease in Ethiopia with more reservoir hosts maintaining the disease. Dogs and hyraxes are the main reservoir hosts for visceral and cutaneous leishmaniasis in the country, respectively. Epidemiological changes of leishmaniasis may relate to environmental changes and expansion of mega projects such as irrigations and sugar cane factories, knowledge and socio-economic factors, development of new settlements, migration of peoples and HIV/AIDS co-infection. Expansions of mega projects such as sugar factories and irrigations are suitable for reproduction of stray dogs, rodents, wild canids and vectors. VL is one of the major challenges to prevent and control in the endemic areas of the country. Therefore, new research should be imperative, especially in the mega projects to design strategic control and prevention methods.

A fine scale eco-epidemiological study on endemic visceral leishmaniasis in north ethiopian villages

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We conducted fine-scale eco-epidemiological analyses of factors associated with visceral leishmaniasis transmission.

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The population densities of Phlebotomus orientalis, the vector, were negatively correlated with distance from vertisols.

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Sero-positivity to Ph. orientalis saliva, was found in people living close to vertisol areas.

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Apparent clustering of infections indicates that transmission occurs around houses located close to vertisols.

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Our data suggest that asymptomatic individuals serve as reservoir hosts for anthroponotic transmission inside villages.

Visceral Leishmaniasis (VL) is a disseminated protozoan infection caused by Leishmania donovani that affects almost half a million people annually. In Northern Ethiopia, VL is common in migrant agricultural laborers returning from the lowland sesame fields of Metema and Humera. Recent VL foci have emerged in resident rural populations near the town. In the current study, we evaluate multilevel entomological, epidemiological and ecological factors associated with infection and disease through fine-scale eco-epidemiological analyses in three villages. Satellite images showed that villages constructed in or close to vertisols, were likely to become endemic for VL. Vertisols or black-cotton soil, are characterized by high contents of smectitic clay minerals, which swell when hydrated and shrink upon desiccation, causing extensive deep cracking during the dry season. The population densities of Phlebotomus orientalis, the vector, were negatively correlated with distance from vertisols and persons living close to vertisols were more likely to be bitten by sand flies, as evidenced by sero-positivity to Ph. orientalis saliva. Apparent (albeit non-significant) clustering of VL cases and abundant asymptomatic infections close to vertisols, suggest anthroponotic transmission around houses located close to vertisols. Comparable rates of male and female volunteers, mostly under 15 years of age, were infected with L. donovani but a significantly higher proportion of males succumbed to VL indicating a physiological gender-linked male susceptibility. Our data suggest that the abundant infected persons with high parasitemias who remain asymptomatic, may serve as reservoir hosts for anthroponotic transmission inside villages. Only limited insights on the transmission dynamics of L. donovani were gained by the study of environmental factors such as presence of animals, house structure and vegetation cover.

Visceral leishmaniasis in selected communities of Hamar and Banna-Tsamai districts in Lower Omo Valley, South West Ethiopia: Sero-epidemological and Leishmanin Skin Test Surveys

Background

Visceral leishmaniasis [VL] is a debilitating parasitic disease which invariably kills untreated patients. The disease is caused by Leishmania (L.) donovani or L. infantum, and transmitted by the bite of female phlebotomine sandflies. VL often remains subclinical but can become symptomatic with an acute/subacute or chronic course. Globally, the Eastern Africa region is one of the main VL endemic areas. The disease is prevalent in numerous foci within Eritrea, Ethiopia, Kenya, Somalia, Sudan South Sudan, and Uganda. In Ethiopia, the Lower Omo plain is one of the many VL endemic regions.

Objectives

The objective of this study was to determine the prevalence of asymptomatic visceral leishmaniasisin Hamar and Banna-Tsamai districts of the South Omo plains where VL is becoming an emerging health problem of neglected communities.

Methods

A community based cross-sectional survey was conducted in 2013 between 25th of July and 14^th of August. A total of 1682 individuals living in 404 households were included in the study. Socio-demographic and clinical data were collected from each of the participants and venous blood was also collected for the detection of antibodies to visceral leishmaniasis using Direct Agglutination Test. Leishmanin Skin Test was performed to detect the exposure to the parasite.

Results

The surveys included 14 villages located in areas where VL had been reported. In a study population of 1682 individuals, the overall positive leishmanian skin test and sero-prevalence rates respectively were 8.6% and 1.8%. A statistically significant variation in the rate of positive LST response was observed in different study sites and age groups. Positive LST response showed an increasing trend with age. The sero-prevalence rate also showed a statistically significant variation among different study sites. Higher rates of sero-prevalence were observed in children and adolescents. The LST and sero-prevalence rates in Hamar District exceeded significantly that of Banna-Tsamai District (10.7% versus 5.8% for LST; and 2.6% versus 0.7% for sero-prevalence).

Conclusion

The prevalence of asymptomatic VL infection in Hamar and Banna-Tsamai districts during the study period in 2013 was low compared to rates previously reported in other endemic areas of Ethiopia. This could be due to the fact that the disease is emerging in Hamar and Banna-Tsamai districts. Based on records of a nearby Hospital, increasing numbers of active VL cases have been reported in these districts through the years 2006–2012, especially in Hamar District. Both districts are important destinations of tourism, and thus the importance of surveillance should be emphasized. Detailed epidemiological and entomological studies are recommended.

Some aspects of entomological determinants of Phlebotomus orientalis in highland and lowland visceral leishmaniasis foci in northwestern Ethiopia

Visceral leishmaniasis (VL) is one of the major public health problems in northwest Ethiopia, mainly in Libo-Kemkem and Metema districts, where Phlebotomus orientalis is the most probable vector of the disease. The aim of this study was to determine the physiological age, host preference and vectorial potential of P. orientalis in the highland and lowland foci of the region. Sand flies were collected using CDC light traps between May 2011 and April 2012 in Libo-Kemkem and October 2012 and September 2013 in Metema from household compounds, farm field and mixed forest. Females belonging to Phlebotomus were dissected for physiological age determination and Leishmania detection and isolation. Leishmania infections in sand flies were investigated using molecular methods. Freshly fed Phlebotomus females were tested to identify blood meal sources using PCR-RLB and ELISA. A total of 1149 (936 from Libo-Kemkem and 213 from Metema) blood unfed female P. orientalis were dissected for age determination. The parity rate was 45.6% and 66.2% in Libo-Kemkem and Metema, respectively. None of 798 female P. orientalis dissected (578 from Libo-Kemkem and 220 from Metema) was infected with Leishmania parasites. A total of 347 P. orientalis specimens collected from Libo-Kemkem were processed using PCR, of which 10 (2.8%) specimens were found with DNA of Leishmania spp. Of a total 491 freshly fed female P. orientalis analyzed for blood meal origins by RLB-PCR and ELISA, 57.6% (67.8% from Libo-Kemkem and 49.8% from Metema) were found to contain bovine blood while 4.9% (3.7% from Libo-Kemkem and 5.7% from Metema) were of human blood. In conclusion, the present study showed parity difference between the two populations of P. orientalis and that both populations have strong zoophilic behavior. Based on the presented evidences, the species is strongly implicated as a vector of kala-azar in both areas. Therefore, vector control should be a component of a strategy to manage visceral leishmaniasis in both study areas.

Serological investigation of visceral Leishmania infection in human and its associated risk factors in Welkait District, Western Tigray, Ethiopia

Visceral leishmaniasis (VL) is major neglected public health problem in terms of geographical spread and incidence in Ethiopia. Magnitude, public health impact and dynamics of VL were not well studied in Welkait District, Western Tigray, though the area is known for VL. Hence, this study aimed to determine sero-prevalence of human VL and associated risk factors in Welkait as new foci. A cross sectional study design was employed in this study. Two stage stratified random sampling method was used to select study participants. Hence, a total of 329 human study participants were included for serological survey using ITleish and leishmanin skin tests. Semi structured questionnaire was also used to identify VL associated risk factors. Univariate and multivariate logistic regression statistical methods were used to determine the degree of association. The overall sero-prevalence of human VL in the study area was found to be 8.81%. Statistical significant difference in the prevalence of the disease was found among Sub-districts, sex, re-settlement, sleeping outdoor and dog ownership (P < 0.05). Participants who resettled from their original place were found 2 times (AOR = 2.143; 95% CI = 1.02, 14.20) more vulnerable to VL infection. Those who had an experience of sleeping outdoor were found almost 4 times (AOR = 4.29; 95% CI = 1.58, 11.69) more likely to be at risk of acquiring VL infection than those sleep indoor. Furthermore, individuals who owned dogs were 3 times more prone to the VL infection than their counterparts (AOR = 3.37; 95% CI = 1.29, 8.76). Alarming sero-positivity of human VL was recorded from new foci. Hence, it is recommended to improve the VL health services in the study area. The investigation also invites further study on VL dynamics in the study area.

Genome wide comparison of Ethiopian Leishmania donovani strains reveals differences potentially related to parasite survival

Leishmania donovani is the main cause of visceral leishmaniasis (VL) in East Africa. Differences between northern Ethiopia/Sudan (NE) and southern Ethiopia (SE) in ecology, vectors, and patient sensitivity to drug treatment have been described, however the relationship between differences in parasite genotype between these two foci and phenotype is unknown. Whole genomic sequencing (WGS) was carried out for 41 L. donovani strains and clones from VL and VL/HIV co-infected patients in NE (n = 28) and SE (n = 13). Chromosome aneuploidy was observed in all parasites examined with each isolate exhibiting a unique karyotype. Differences in chromosome ploidy or karyotype were not correlated with the geographic origin of the parasites. However, correlation between single nucleotide polymorphism (SNP) and geographic origin was seen for 38/41 isolates, separating the NE and SE parasites into two large groups. SNP restricted to NE and SE groups were associated with genes involved in viability and parasite resistance to drugs. Unique copy number variation (CNV) were also associated with NE and SE parasites, respectively. One striking example is the folate transporter (FT) family genes (LdBPK_100390, LdBPK_100400 and LdBPK_100410) on chromosome 10 that are single copy in all 13 SE isolates, but either double copy or higher in 39/41 NE isolates (copy number 2-4). High copy number (= 4) was also found for one Sudanese strain examined. This was confirmed by quantitative polymerase chain reaction for LdBPK_100400, the L. donovani FT1 transporter homolog. Good correlation (p = 0.005) between FT copy number and resistance to methotrexate (0.5 mg/ml MTX) was also observed with the haploid SE strains examined showing higher viability than the NE strains at this concentration. Our results emphasize the advantages of whole genome analysis to shed light on vital parasite processes in Leishmania.

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.

Studies on sand fly fauna and ecological analysis of Phlebotomus orientalis in the highland and lowland foci of kala-azar in northwestern Ethiopia

BACKGROUND

Visceral leishmaniasis (VL) also known as kala-azar is a growing health problem in Ethiopia with an estimated annual VL incidence between 3700 and 7400. The disease is mainly endemic in northwestern parts of the country. The aim of the current study was to determine the sand fly fauna and ecology of Phlebotomus orientalis in two endemic and ecologically distinct areas of northwestern Ethiopia.

METHODS

Sand flies were collected using CDC light traps, sticky traps and pyrethrum spray catches from peri-domestic, mixed forest, farm field and indoor habitats from both Libo-Kemkem (May 2011-April 2012) and Metema (October 2012-September 2013) districts.

RESULTS

A total of 51,411 sand fly specimens were collected and identified (10,776 from highland and 40, 635 from the lowland areas). Seven species were found in the highland area: two Phlebotomus spp. (P. orientalis and P. rodhaini) and five Sergentomyia species. Whereas 19 species were found in the lowland area: six Phlebotomus (P. orientalis, P. rodhaini, P. bergeroti, P. duboscqi, P. papatasi and P. martini) and 13 Sergentomyia species. Of the Phlebotomus spp., P. orientalis was the predominant species in both the highland (99.9%) and lowland (93.7%) areas. Indoor collections using pyrethrum spray catches and sticky traps indicated that P. orientalis has a strong exophilic and exophagic behaviors in both districts. In both areas, this species showed seasonal occurrence and showing abundance during the dry months (March-May/June) of the year and increasing in numbers till the rain season, when numbers dropped dramatically. Mean density of P. orientalis in the two areas had positive and significant correlation with mean temperature in light trap collections (P<0.05). However, mean density of P. orientalis in the two areas in sticky trap collections had positive and insignificant association with the temperature (P>0.05). Regarding the rainfall pattern, density of P. orientalis had negative and statistically insignificant correlation (for light trap collections for both areas) and significant correlation (for sticky trap collections for lowland area).

CONCLUSIONS

The current study indicated the variation in sand fly fauna between the highland and lowland districts, wherein, P. orientalis was found to be the most abundant Phlebotomus species. The study also determined that P. orientalis exhibits distinct seasonality, where its abundance increases during the dry season and disappears when the rainy period starts in both study areas. This entomological observation on the bionomics of P. orientalis provides significant evidence for considering vector control or preventive measures in the areas studied.

Preliminary study on investigation of zoonotic visceral leishmaniasis in endemic foci of Ethiopia by detecting Leishmania infections in rodents

OBJECTIVE

To investigate the zoonotic visceral leishmaniasis (ZVL) by identification of the most probable reservoir hosts using parasite isolation and analysis of a possible transmission dynamics of the disease in extra-domestic agricultural fields and rural villages.

METHODS

Rodents were collected from selected study sites in kala-azar endemic areas based on information for localities of kala-azar cases for screening of Leishmania infections using parasitological, serological and polymerase chain reaction (PCR) from March, 2013 to January, 2014. Ketamine (Clorketam Veterinary) was used to anaesthesize the rodents according the prescribed dosage (average 2 mg/kg for intra-venous route). The blood obtained using sterile needle was dropped into sterile filter paper and allowed to air dry before sealing in plastic bags. The tissues from liver, spleen and skin were macerated in Locke's solution before transferring them into NNN medium. Blood and touch smears of liver, spleen, skin and bone marrow were prepared for fixing using methanol and staining by Giemsa stain for microscopy. These tissues were also used for DNA extractions and PCR amplification of Leishmania infection.

RESULTS

A total of 335 rodents (13 species) were analyzed by sampling internal organs. The infection rate by PCR was 11.1% (6/54) for Arvicanthis nilothicus compared to 17.6% (3/17) and 12.5% (2/16) for Acomys cahirinus and Tarera (G) robustus respectively. Almost all the infections were found from bone marrow samples (8/48 or 16.7%) compared with 1/91 (1.1%) liver, 2/87 (2.2%) spleen and 0/87 (0%) skin. In all study sites with past human VL cases, rodents and proved vectors shared similar habitats.

CONCLUSIONS

Leishmania donovani might circulate among different species of rodents in kala-azar endemic lowlands and valleys of Ethiopia by Phlebotomus orientalis and Phlebotomus martini. Detailed studies to substantiate the preliminary data on the possible role of these rodents are urgently needed.

Habitat preference and seasonal dynamics of Phlebotomus orientalis in urban and semi-urban areas of kala-azar endemic district of Kafta Humera, northwest Ethiopia

Visceral leishmaniasis is a significant public health problem in northwest Ethiopia, particularly in Kafta Humera district. The study was designed to determine the species composition and population dynamics of sand flies in five villages representing urban and semi-urban areas of Kafta Humera district namely, Setit Humera, Mykadra, Rawyan, Bereket and Adebay. Sand flies were collected for two to three nights monthly from May 2011 to April 2012 using CDC light-traps and sticky traps. Traps were placed in villages, at periphery of villages and farm fields. Sticky traps were also used for sampling indoor active sand flies. In total, 13,097 sand fly specimens of eight Phlebotomus species and 91,949 Sergentomyia specimens were collected. Among the Phlebotomus, P. orientalis was the predominant species (58.1%) followed by P. papatasi (29.6%), P. lesleyae (5.6%), P. bergeroti (3.8%), P. duboscqi (2.1%), P. alexandri (0.4%), P. heischi (0.2%) and P. rodhaini (0.2%). Significantly, higher number of P. orientalis was caught in Adebay village and the least in Setit Humera town. Seasonal abundance of P. orientalis increased during the dry season (January-May) and dropped drastically in the wet season (late June-September). Significant positive correlation was found between monthly abundance of P. orientalis and the monthly average air and surface soil temperature, while a negative correlation was found with monthly average rainfall and relative humidity. Higher number of P. orientalis was collected outdoors, especially in the farm fields followed by periphery of villages. Thus, various observations strongly suggested P. orientalis to be the principal vector in the study areas, where farm lands and periphery of villages were identified as the most risky habitats, whereas the indoors were the least ones. Appropriate control methods should be designed and implemented according to the knowledge of P. orientalis habitat preferences and seasonal dynamics in the district.

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.

Recombinant Salivary Proteins of Phlebotomus orientalis are Suitable Antigens to Measure Exposure of Domestic Animals to Sand Fly Bites

Background

Certain salivary proteins of phlebotomine sand flies injected into the host skin during blood-feeding are highly antigenic and elicit strong antibody-mediated immune responses in repeatedly-exposed hosts. These antibodies can be measured by enzyme-linked immuno sorbent assays (ELISAs) using salivary gland homogenates (SGHs) as the source of antigens and serve as a markers for exposure to biting sand flies. Large-scale screening for anti-sand fly saliva antibodies requires replacement of SGH with recombinant salivary proteins. In East Africa, Phlebotomus orientalis is the main vector of Leishmania donovani, a trypanosomatid parasite causing visceral leishmaniasis. We tested recombinant salivary proteins derived from Ph. orientalis saliva to study exposure of domestic animals to this sand fly species.

Methodology/Principal Findings

Antigenic salivary proteins from Ph. orientalis were identified by immunoblot and mass spectrometry. Recombinant apyrase rPorSP15, yellow-related protein rPorSP24, ParSP25-like protein rPorSP65, D7-related protein rPorSP67, and antigen 5-related protein rPorSP76 were tested using ELISA with sera of domestic animals from L. donovani foci in Ethiopia where Ph. orientalis is present. Our results highlighted recombinant yellow-related protein rPorSP24 as the most promising antigen, displaying a high positive correlation coefficient as well as good sensitivity and specificity when compared to SGH. This recombinant protein was the most suitable one for testing sera of dogs, sheep, and goats. In addition, a different antigen, rPorSP65 was found efficacious for testing canine sera.

Conclusions/Significance

Recombinant salivary proteins of Ph. orientalis, specifically rPorSP24, were shown to successfully substitute SGH in serological experiments to measure exposure of domestic animals to Ph. orientalis, the vector of L. donovani. The results suggest that rPorSP24 might be a suitable antigen for detecting anti-Ph. orientalis antibody-mediated reactions also in other host species.

The sand fly Phlebotomus orientalis is the main vector of Leishmania donovani, the causative agent of visceral leishmaniasis in East Africa. During bloodfeeding, sand flies inject saliva into the host skin and repeated bites result in a specific antibody response in the bitten hosts. Antibody responses are directed against sand fly salivary proteins and the levels of these antibodies reflect the intensity of exposure to biting sand flies. The antibody reactions can be measured using salivary gland homogenates (SGHs), but for large-scale testing its use is impractical because of the amount of work required to obtain sufficient quantities of SGH. Recombinant proteins prepared based on the antigens in the sand fly saliva can substitute whole SGH in large-scale studies. We tested five recombinant proteins from Ph. orientalis saliva expressed in Escherichia coli and demonstrated that the yellow-related protein rPorSP24 can replace the SGH in estimating exposure to sand flies of dogs, goats, and sheep in Ethiopia. Immune reactions to vector saliva in endemic areas, provides useful information on levels of exposure and, thereby, on the effectiveness of vector control programs.

One Health Approach Prospect for Integrated Control and Elimination of Visceral Leishmaniasis in Ethiopia: A Narrative Review Article

BACKGROUND

Leishmaniasis is an obligate intercellular protozoon that affects animals and human. It has zoonosis and/or anthroponosis transmission. Human and veterinary medicine, environmental science and wildlife conservation specialists have many commonalities in case of visceral leishmaniasis. Still the above disciplines respond against leishmaniasis in a separate way. The aim of this review is to indicate inter- and intra- sectoral collaboration for planning future control strategies.

METHODS

literatures written on visceral leishmaniasis and one health approach were systematically reviewed from the year 1969 to 2014 from Pub Med, Scopus, Medline and Google scholar sources.

RESULT

Such a one health approach would enhance biomedical progress; improve medical and veterinary serves, entomological control and wildlife conservation for Visceral Leishmaniasis especially in endemic areas.

CONCLUSION

Inter- and intra - sectoral collaboration in the leishmaniasis control is limited in Ethiopia. Therefore, incorporating one health approach or integrated inter- and intra - sectoral collaboration for visceral leishmaniasis control is an effective control strategy in endemic areas.

Determinants of Visceral Leishmaniasis: A Case-Control Study in Gedaref State, Sudan

BACKGROUND

Improving knowledge on local determinants of visceral leishmaniasis (VL) is crucial to guide the development of relevant control strategies. This study aimed to identify individual and household level determinants of primary VL in 24 highly endemic villages of Tabarak Allah hospital's catchment area, Gedaref State, Sudan.

METHODS

From September 2012 to July 2013, in an unmatched case-control design, 198 patients with primary VL were compared to 801 controls free of VL symptoms and with a negative VL rapid test. Using random spatial sampling, controls were selected with a distribution of age, sex and village of residence proportionate to the distribution of the target population. Data were collected using a structured questionnaire.

RESULTS

Children and men were at higher risk of VL. Reporting VL patient(s) in the household in the previous year was the strongest VL risk factor. In a multivariate analysis, VL risk increased with household size, sleep location (outside the yard, not in the farm), evening outdoor activities in the rainy season (playing, watching TV, radio listening), use of ground nut oil as animal repellent and of smoke of Acacia seyal as indoor repellent, presence of dogs in the yard at night, Acacia nilotica in the yard's immediate surroundings and of a forest at eye range. VL risk appeared to decrease with the use of drinking water sources other than the village water tank, a buffer distance from the adjacent house yard, and with the presence of animals other than dogs in the yard at night. In contrast with previous studies, housing factors, mosquito-net use, black cotton soil, ethnicity, socioeconomic index, presence of Balanites aegyptica and Azadirachta indica in the yard were not independent VL determinants.

DISCUSSION AND CONCLUSION

Although these results do not provide evidence of causality, they provide useful suggestions for guiding further intervention studies on VL preventive measures.

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.

Exposure to Leishmania spp. and sand flies in domestic animals in northwestern Ethiopia

Background

Human visceral leishmaniasis caused by Leishmania donovani is considered an anthroponosis; however, Leishmania-infected animals have been increasingly reported in L. donovani foci, and the role of these animals as reservoirs for human L. donovani infection remains unclear.

Methods

We conducted a study of domestic animals (goats, sheep, cows, dogs, and donkeys) in three L. donovani foci in northwestern Ethiopia. Domestic animals were screened for Leishmania DNA and for anti-L. donovani IgG. Serum anti-sand fly saliva antibodies were used as a marker of exposure to the vector sand fly, Phlebotomus orientalis.

Results

Of 546 animals tested, 32 (5.9 %) were positive for Leishmania DNA, with positive animals identified among all species studied. Sequencing indicated that the animals were infected with parasites of the L. donovani complex but could not distinguish between L. infantum and L. donovani. A total of 18.9 % of the animals were seropositive for anti-L. donovani IgG, and 23.1 % of the animals were seropositive for anti-P. orientalis saliva IgG, with the highest seroprevalence observed in dogs and sheep. A positive correlation was found between anti-P. orientalis saliva and anti-L. donovani IgGs in cows, goats, and sheep.

Conclusions

The detection of L. donovani complex DNA in the blood of domestic animals, the reported seroprevalence to the L. donovani antigen, and the widespread exposure to sand fly saliva among domestic animals indicate that they are frequently exposed to Leishmania infection and are likely to participate in the epidemiology of Leishmania infection, either as potential blood sources for sand flies or possibly as parasite hosts.

Electronic supplementary material

The online version of this article (doi:10.1186/s13071-015-0976-1) contains supplementary material, which is available to authorized users.

Host-feeding preference of Phlebotomus orientalis (Diptera: Psychodidae) in an endemic focus of visceral leishmaniasis in northern Ethiopia

Background

Blood-feeding behavior studies are important for estimating the efficiency of pathogen transmission and assessing the relative human disease risk. However, in Ethiopia and other parts of East Africa there are large remaining gaps in identifying the feeding habits of Phlebotomus orientalis, the vector of Leishmania donovani. The aim of the study was to determine the blood feeding patterns of P. orientalis in Tahtay Adiyabo district, northern Ethiopia.

Methods

For bloodmeal analysis, sandflies were collected from three different villages of Tahtay Adiyabo district using CDC light traps, sticky traps, and pyrethrum spray catches. Bloodmeal of engorged female sandflies was identified using cytochrome (cyt) b-PCR and reverse-line blotting (RLB) and enzyme linked immunosorbent assay (ELISA) assays.

Results

Most (637/641) of the females analyzed were P. orientalis. Successful identification of the host from bloodmeals was achieved in 83.03 and 92.1 % using cyt b PCR-RLB and ELISA, respectively. Bloodmeal analysis of P. orientalis females revealed that they have a range of hosts with predominant preference to bovines followed by donkey, human, goat, sheep, dog, and camel.

Conclusion

Results obtained from bloodmeal analyses demonstrate that the feeding preference of P. orientalis is mainly zoophilic, which could vary depending on the availability of hosts.

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.

Host choice of Phlebotomus orientalis (Diptera: Psychodidae) in animal baited experiments: a field study in Tahtay Adiyabo district, northern Ethiopia

Background

Host choice and feeding success of sand fly vectors of visceral leishmaniasis (VL) are important factors in understanding the epidemiology and for developing efficient control strategies. The aim of the present study was to determine the host preference of Phlebotomus orientalis in the VL focus of Tahtay Adiyabo district, northern Ethiopia.

Methods

Two separate experiments were conducted testing attraction of P. orientalis to humans, domestic animals, and small wild animals. The host choice of P. orientalis and other sand fly species was assessed using tent traps baited with seven different animals (human, cow, sheep, goat, donkey, dog and chicken) and a blank control. Baited traps were rotated every night in a Latin square design for two consecutive full rounds totaling 16 trap-nights. The second set of experiments tested attraction to small wild animals including; ground squirrel (Xerus rutilus), hare (Lepus sp.), gerbil (Tatera robusta) and spiny mouse (Acomys cahirinus). Animals were caged in standard rodent traps or cylindrical wire-mesh cages. The bait animals were placed in agricultural field and the attracted sand flies were collected using unlit CDC traps for 10 trapping nights. Sand fly specimens collected from each of the experiments were identified to species level and counted.

Results

Significant difference (P < 0.05) was observed in the attraction and feeding rate of P. orientalis to different baits. In the first experiment, cow-baited tent traps attracted the highest mean number of P. orientalis (mean = 510 flies). The engorgement rate of P. orientalis on donkey was the highest followed by cow, and much lower on goat, sheep, dog and chicken. In the case of smaller wild animals, more numbers of P. orientalis females were attracted to squirrels followed by hares, gerbils and the spiny rat. However, the engorgement rates for P. orientalis in the smaller animals were very low (1.08%) compared with larger domestic animals (30.53%).

Conclusion

The tendency of female P. orientalis to engorge in large numbers on certain species of domestic as well as wild animals strongly indicated that the species is primarily zoophilic in its host preference with feeding habits that may vary depending on the availability of hosts.

The influence of moonlight and lunar periodicity on the efficacy of CDC light trap in sampling Phlebotomus (Larroussius) orientalis Parrot, 1936 and other Phlebotomus sandflies (Diptera: Psychodidae) in Ethiopia

BACKGROUND

Phlebotomus orientalis is the main sandfly vector of visceral leishmaniasis in the north and northwest of Ethiopia. CDC light traps and sticky traps are commonly used for monitoring sandfly populations. However, their trapping efficiency is greatly influenced by various environmental factors including moonlight and lunar periodicity. In view of that, the current study assessed the effect of moonlight and lunar periodicity on the performance of light traps in collecting P. orientalis.

METHODS

Trapping of P. orientalis and other Phlebotomus spp. was conducted for 7 months between December 2012 and June 2013 using CDC light traps and sticky traps from peri-domestic and agricultural fields. Throughout the trapping periods, collections of sandfly specimens were carried out for 4 nights per month, totaling 28 trapping nights that coincided with the four lunar phases (viz., first quarter, third quarter, new and full moon) distributed in each month.

RESULTS

In total, 13,533 sandflies of eight Phlebotomus species (P. orientalis, P. bergeroti, P. rodhaini, P. duboscqi, P. papatasi, P. martini, P. lesleyae and P. heischi) were recorded. The predominant species was P. orientalis in both trapping sites and by both methods of collection in all lunar phases. A significant difference (P < 0.05) was observed in the mean numbers of P. orientalis and other Phlebotomus spp. caught by CDC light traps among the four lunar phases. The highest mean number (231.13 ± 36.27 flies/trap/night) of P. orientalis was collected during the new moon phases, when the moonlight is absent. Fewer sandflies were attracted to light traps during a full moon. However, the number of P. orientalis and the other Phlebotomus spp. from sticky traps did not differ in their density among the four lunar phases (P = 0.122).

CONCLUSION

Results of the current study demonstrated that the attraction and trapping efficiency of CDC light traps is largely influenced by the presence moonlight, especially during a full moon. Therefore, sampling of sandflies using light traps to estimate population density and other epidemiological studies in the field should take the effect of moonlight and lunar periodicity into account on the trapping efficacy of light traps.

Nocturnal activities and host preferences of Phlebotomus orientalis in extra-domestic habitats of Kafta-Humera lowlands, Kala-azar endemic, Northwest Ethiopia

Background

Phlebotomus orientalis feeds on a variety of wild and domestic animals and transmits Leishmania donovani from hitherto unknown reservoir hosts to humans in extra-domestic habitats in the Metema - Humera lowlands. The aim of this study was to determine the nocturnal activities of P. orientalis and its preferred blood meal hosts.

Methods

Collections of Phlebotomus orientalis were made by using CDC light traps to determine the density as P. orientalis/hour CDC trap and preference to rodents by using Turner’s traps in agricultural fields, animal shelters and thickets of Acacia seyal in Baeker site-1 and Gelanzeraf site-2. The blood meal sources were detected by Reverse Line Blot (RLB) of cytochrome b polymerase chain reaction (PCR) amplification in August, 2012 from collections of sand flies in thickets of A. seyal (March 2011) and dense mixed forest (July 2011) in Baeker site 1. RLB PCR involved first amplification of animal specific sequences of cytochrome b using PCR techniques. Then the amplified sequence was hybridized with 11 species-specific probes for domestic animals adsorbed on nitrocellulose membrane for calorimetric color detection.

Results

A total of 6,083 P. orientalis (2,702 males and 3,381 females) were collected at hourly intervals using 22 CDC traps from January to May 2013. The peak activities of P. orientalis were at 1.00 a.m (134.0 ± 7.21) near animal shelters, 3.00 a.m (66.33 ± 46.40) in agricultural fields and 21:00 pm (40.6 ± 30.06) in thickets of A. seyal. This species was not attracted to the different species of rodents in trials carried out in March and April 2013. RLB PCR identified 7 human (28%), 9 mixed (human and cattle) (36%) and 2 cattle (8%) blood meals while 7 were unknown (28%).

Conclusion

Female P. orientalis can bite humans in extra-domestic habitats of Kafta-Humera lowlands at any hour of the night with peak biting after midnight.

Characterization of breeding sites of Phlebotomus orientalis - the vector of visceral leishmaniasis in northwestern Ethiopia

We studied breeding sites of Phlebotomus orientalis (Diptera: Psychodidae) the vector of visceral leishmaniasis in northern Ethiopia. Although numbers were rather small, 165 sand flies were captured emerging from vertisol cracks. The most productive breeding sites were cracked vertisols, dry river banks and close to trees. No sand flies were caught emerging from sandy clay loam soils in peri-domestic habitats but a few were captured emerging from gaps in a stone wall. Abiotic parameters in vertisols close to trees and in open field from which P. orientalis had emerged, were compared. Soil pH was slightly alkaline and salinity was low. Organic matter contents were similar in both sites. Temperatures and RH remained relatively stable near trees from the end of the rainy season through mid dry season, yet fluctuated markedly at the shallower depth in the open field. During the rainy season, cracks in the soil were sealed resulting in significant lowering of the oxygen concentrations near the tree. Gravimetric water content of soil near trees was lower than open field at shallow depth but similar deeper down. We conclude that ambient conditions suitable for sand fly larvae at shallow depths (45cm) are restricted to areas close to trees. However, deeper in vertisols (90cm) suitable conditions are apparently maintained throughout the dry season even in open fallow fields.

Risk factors of visceral leishmaniasis: a case control study in north-western Ethiopia

Background

Visceral leishmaniasis (VL, also called ‘’kala-azar”), is a life threatening neglected tropical infectious disease which mainly affects the poorest of the poor. VL is prevalent in Ethiopia particularly in the northwest of the country. Understanding the risk factors of VL infection helps in its prevention and control. The aim of the present study was to identify the factors associated with VL.

Methods

A case–control study was carried out during the period of January-July 2013 in northwest Ethiopia. Cases and controls were diagnosed using clinical presentation, the rk39 rapid diagnostic test and Direct Agglutination Test (DAT). A total of 283 (84.8% males versus 15.2% females) participants were interviewed. 90 cases and 193 controls were involved, matched by age, sex and geographical location with a ratio of 1:2 (case: controls). Univariate and backward multivariate conditional logistic regression were used to identify risk factors of VL.

Results

Elevated odds of VL was associated with goat ownership (OR = 6.4; 95%: confidence interval [Cl]: 1.5-28.4), living in houses with cracked wall (OR = 6.4; 95% Cl: 1.6-25.6), increased family size (OR = 1.3; 95% Cl: 1.0-1.8) and the number of days spent in the farm field (OR = 1.1; 95% Cl: 1.0-1.2). However, daily individual activities around the home and farm fields, mainly sleeping on a bed (OR = 0.2; 95%: Cl 0.03-0.9), sleeping outside the house under a bed net (OR = 0.1; 95% Cl: 0.02-0.36)] and smoking plant parts in the house during the night time (OR = 0.1; 95% Cl: 0.01-0.6) were associated with decreased odds of being VL case.

Conclusion

Our findings showed that use of bed net and smoke could be helpful for the prevention of VL in the area particularly among individuals who spend most of their time in the farm. VL control effort could be focused on improving housing conditions, such as sealing cracks and crevices inside and outside houses. Further research is warranted to elucidate the role of goats in the transmission of L. donovani, assess the impact of bed nets and the role of the traditional practice of smoking plants.

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.

Attraction of Ethiopian phlebotomine sand flies (Diptera: Psychodidae) to light and sugar-yeast mixtures (CO(2))

BACKGROUND

Visceral leishmaniasis (VL) known as Kala-Azar is a serious systemic disease caused by Leishmania donovani parasites (Trypanosomatidae: Kinetoplastida). The disease is prevalent in the Indian Sub-continent, East Africa and Brazil. In Africa, the worst affected regions are in Sudan, with an estimated 15,000-20,000 cases annually and Ethiopia with 5,000-7,000 cases a year. The main vector of VL in Sudan and Northern Ethiopia is Phlebotomus orientalis, a sand fly frequently found in association with Acacia spp and Balanite spp woodlands.

METHODS

To optimize sampling of sand flies for epidemiological studies in remote areas we tested different means of attraction. Miniature suction traps employing 2AA batteries (3 V) were deployed in the up-draft orientation and baited with chemical light-sticks (Red, Yellow and Green), or bakers' yeast in sugar solution (emitting CO2 and perhaps other attractants). These traps were compared with standard CDC incandescent light traps employing 6 V batteries. Trials were conducted during two consecutive years at different localities around Sheraro, a town in West Tigray, Northern Ethiopia.

RESULTS

The sand fly species composition was similar but not identical in the different locations tested with different Sergentomyia spp. predominating. Phlebotomus spp. comprised less than 1% of the catches during the first year trials (November - December 2011) but increased markedly during the second year trials performed later in the dry season at the height of the sand fly season in February 2012. Although there did not appear to be a species bias towards different light wave-lengths, fermenting yeast in sugar solution attracted relatively more Phlebotomus spp. and Sergentomyia schwetzi.

CONCLUSIONS

Although the standard 6 V CDC incandescent light traps captured more sand flies, light-weight (~350 g) 3 V suction traps baited with chemical light-sticks were shown to be effective means of monitoring sand flies. Such traps operated without light and baited with yeast in sugar solution caught relatively more Phlebotomus spp.

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.

Phlebotomus orientalis sand flies from two geographically distant Ethiopian localities: biology, genetic analyses and susceptibility to Leishmania donovani

BACKGROUND

Phlebotomus orientalis Parrot (Diptera: Psychodidae) is the main vector of visceral leishmaniasis (VL) caused by Leishmania donovani in East Africa. Here we report on life cycle parameters and susceptibility to L. donovani of two P. orientalis colonies originating from different sites in Ethiopia: a non-endemic site in the lowlands - Melka Werer (MW), and an endemic focus of human VL in the highlands - Addis Zemen (AZ).

METHODOLOGY/PRINCIPAL FINDINGS

Marked differences in life-cycle parameters between the two colonies included distinct requirements for larval food and humidity during pupation. However, analyses using Random Amplified Polymorphic DNA (RAPD) PCR and DNA sequencing of cytB and COI mitochondrial genes did not reveal any genetic differences. F1 hybrids developed successfully with higher fecundity than the parental colonies. Susceptibility of P. orientalis to L. donovani was studied by experimental infections. Even the lowest infective dose tested (2×10(3) per ml) was sufficient for successful establishment of L. donovani infections in about 50% of the P. orientalis females. Using higher infective doses, the infection rates were around 90% for both colonies. Leishmania development in P. orientalis was fast, the presence of metacyclic promastigotes in the thoracic midgut and the colonization of the stomodeal valve by haptomonads were recorded in most P. orientalis females by day five post-blood feeding.

CONCLUSIONS

Both MW and AZ colonies of P. orientalis were highly susceptible to Ethiopian L. donovani strains. As the average volume of blood-meals taken by P. orientalis females are about 0.7 µl, the infective dose at the lowest concentration was one or two L. donovani promastigotes per sand fly blood-meal. The development of L. donovani was similar in both P. orientalis colonies; hence, the absence of visceral leishmaniasis in non-endemic area Melka Werer cannot be attributed to different susceptibility of local P. orientalis populations to L. donovani.

Sandflies (Diptera: Psychodidae) in a focus of visceral leishmaniasis in White Nile, Sudan

Visceral leishmaniasis (VL) has been known to occur since the 1980s on the western bank of the White Nile River (Central Sudan), 150 km south of Khartoum, and has resulted in high mortality. The most recent outbreak of the disease in this area began in 2006. Entomological surveys were carried out during May 2008, June 2010 and May and July 2011 in the White Nile area. Sandflies were collected using Centers for Disease Control light traps and sticky oil traps in the village of Kadaba and the nearby woodland. Phlebotomus females were dissected for the presence of Leishmania promastigotes. A total of 17,387 sandflies, including six species of Phlebotomus and 10 species of Sergentomyia, were identified. The Phlebotomus species recorded were Phlebotomus orientalis, Phlebotomus papatasi, Phlebotomus bergeroti, Phlebotomus duboscqi, Phlebotomus rodhaini and Phlebotomus saevus. P. orientalis was collected in both habitats. The relative abundance of P. orientalis in the woodland habitat was higher than that recorded in the village habitat. In the woodland habitat, there was a notable increase in the relative abundance of P. orientalis during the surveys conducted in 2008 and 2010 compared to 2011. None of the 311 P. orientalis females dissected were infected with Leishmania promastigotes, although relatively high parous rates were recorded in both habitats. Based on the distribution of P. orientalis recorded in this study, this species is the most likely vector of VL in the endemic focus in the White Nile area. Further investigation is required to elucidate the seasonal abundance and distribution of the vector, as well as the transmission season of VL in both habitats so that appropriate control strategies for the vector can be designed.

Polymorphism in the HASPB repeat region of East African Leishmania donovani strains

BACKGROUND/OBJECTIVES

Visceral leishmaniasis (VL) caused by Leishmania donovani is a major health problem in Ethiopia. Parasites in disparate regions are transmitted by different vectors, and cluster in distinctive genotypes. Recently isolated strains from VL and HIV-VL co-infected patients in north and south Ethiopia were characterized as part of a longitudinal study on VL transmission.

METHODOLOGY/PRINCIPAL FINDINGS

Sixty-three L. donovani strains were examined by polymerase chain reaction (PCR) targeting three regions: internal transcribed spacer 1 (ITS1), cysteine protease B (cpb), and HASPB (k26). ITS1- and cpb--PCR identified these strains as L. donovani. Interestingly, the k26--PCR amplicon size varied depending on the patient's geographic origin. Most strains from northwestern Ethiopia (36/40) produced a 290 bp product with a minority (4/40) giving a 410 bp amplicon. All of the latter strains were isolated from patients with HIV-VL co-infections, while the former group contained both VL and HIV-VL co-infected patients. Almost all the strains (20/23) from southwestern Ethiopia produced a 450 bp amplicon with smaller products (290 or 360 bp) only observed for three strains. Sudanese strains produced amplicons identical (290 bp) to those found in northwestern Ethiopia; while Kenyan strains gave larger PCR products (500 and 650 bp). High-resolution melt (HRM) analysis distinguished the different PCR products. Sequence analysis showed that the k26 repeat region in L. donovani is comprised of polymorphic 13 and 14 amino acid motifs. The 13 amino acid peptide motifs, prevalent in L. donovani, are rare in L. infantum. The number and order of the repeats in L. donovani varies between geographic regions.

CONCLUSIONS/SIGNIFICANCE

HASPB repeat region (k26) shows considerable polymorphism among L. donovani strains from different regions in East Africa. This should be taken into account when designing diagnostic assays and vaccines based on this antigen.

Factors associated with Leishmania asymptomatic infection: results from a cross-sectional survey in highland northern Ethiopia

BACKGROUND

In northern Ethiopia the prevalence of visceral leishmaniasis is steadily rising posing an increasing public health concern. In order to develop effective control strategies on the transmission of the disease it is important to generate knowledge on the epidemiological determinants of the infection.

METHODOLOGY/PRINCIPAL FINDINGS

We conducted a cross-sectional survey on children 4-15 years of age using a multi staged stratified cluster sampling on high incidence sub-districts of Amhara regional state, Ethiopia. The survey included a socio-demographic, health and dietary questionnaire, and anthropometric measurements. We performed rK39-ICT and DAT serological tests in order to detect anti-Leishmania antibodies and carried out Leishmanin Skin Test (LST) using L.major antigen. Logistic regression models were used. Of the 565 children surveyed 56 children were positive to infection (9.9%). The individual variables that showed a positive association with infection were increasing age, being male and sleeping outside [adjusted odds ratios (95% CI): 1.15 (1.03, 1.29), 2.56 (1.19, 5.48) and 2.21 (1.03, 4.71) respectively] and in relation to the household: past history of VL in the family, living in a straw roofed house and if the family owned sheep [adjusted OR (95% CI): 2.92 (1.25, 6.81), 2.71 (1.21, 6.07) and 4.16 (1.41, 12.31) respectively].

CONCLUSIONS/SIGNIFICANCE

A behavioural pattern like sleeping outside is determinant in the transmission of the infection in this area. Protective measures should be implemented against this identified risk activity. Results also suggest a geographical clustering and a household focalization of the infection. The behaviour of the vector in the area needs to be clarified in order to establish the role of domestic animals and house materials in the transmission of the infection.

Evaluation of three feed-through insecticides using two rodent and two sand fly species as models

The efficacy of 3 rodent feed-through insecticides (novaluron, pyriproxyfen, and ivermectin) was determined against larvae of the sand flies Phlebotomus duboscqi and P. papatasi using Syrian hamsters (Mesocricetus auratus) and Mongolian gerbils (Meriones unguiculatus) as laboratory models. For each insecticide, there were no significant differences between the longevity or percentage survival of sand fly larvae that had been fed feces of treated rodents for each sand fly or rodent species pairing. The results of this study suggest that larvae of P. duboscqi and P. papatasi are equally susceptible to the concentrations of the rodent feed-through insecticides tested in this study and that these insecticides are pharmacologically compatible with different rodent/sand fly interactions.

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

Background

Visceral leishmaniasis (VL, kala azar), caused by Leishmania donovani is a major health problem in Sudan and other East African countries. In this region the only proven vectors of L. donovani are Phlebotomus orientalis in eastern Sudan, Ethiopia and Upper Nile areas of Southern Sudan and Phlebotomus martini in Ethiopia, Kenya and Southern Sudan. In this report, we present the first evidence that Phlebotomus rodhaini may also play a role in maintaining transmission of L. donovani between animal reservoir hosts in eastern Sudan. The study was conducted in a zoonotic focus of visceral leishmaniasis in Dinder National Park, eastern Sudan, where previous work showed high infection rates of L. donovani in P. orientalis. Sand flies, captured by CDC traps were dissected and examined for infection with Leishmania parasites. Parasite isolates were subjected to L. donovani specific PCR. Field experiments were also carried out to compare efficiency of rodent baited and un-baited CDC traps in collection of P. rodhaini and determine its man-biting rate.

Results

Three female P. rodhaini were found infected with Leishmania parasites in an astonishingly small number of flies captured in three separate field trips. Two of these isolates were typed by molecular methods as L. donovani, while the third isolate was inoculated into a hamster that was subsequently lost. Although P. rodhaini is generally considered a rare species, results obtained in this study indicate that it can readily be captured by rodent-baited traps. Results of human landing collection showed that it rarely bites humans in the area.

Conclusion

It is concluded that P. rodhaini is a possible vector of L. donovani between animal reservoir hosts but is not responsible for infecting humans. It is suggested that the role of P. rodhaini in transmission of L. donovani in other zoonotic foci of visceral leishmaniasis in Africa should be re-examined.

Epidemiological and geographical aspects of leishmaniasis in Tigray, northern Ethiopia: a retrospective analysis of medical records, 2005-2008

Leishmaniasis is one of the most neglected tropical diseases and epidemic outbreaks often occur worldwide. This paper reports some epidemiological features of the disease in Tigray, northern Ethiopia, with the aim of studying the disease distribution and the environmental factors that may have influenced it. Medical records from patients with Leishmania attending the Italian Dermatological Centre of Mekele in the period 2005-2008 were retrospectively reviewed. Age and gender distribution, clinical types, occupation, co-morbidity, urban/rural origin, altitude and rainfall were investigated. The result was 471 patients affected and the prevalent clinical form was cutaneous leishmaniasis (86%). Five main risk areas were identified in the Tigray highlands and only isolated cases were reported at altitudes below 1700m. The variables related to a higher risk of catching leishmaniasis were male gender, age over-14, poor education, outdoor activities and living at high altitudes. Climatic and environmental changes occurring in this region and land degradation are discussed as factors influencing leishmaniasis distribution. Further research including field missions and geomapping is needed to quantify the actual disease burden in the region.

Serological evidence of Leishmania donovani infection in apparently healthy dogs using direct agglutination test (DAT) and rk39 dipstick tests in Kafta Humera, north-west Ethiopia

Leishmania (Kinetoplastida: Trypanosomatidae) are protozoan parasites of significant medical and veterinary importance. Over the last decade, visceral leishmaniasis (VL) has emerged as a major opportunistic infection associated with HIV/AIDS in North Western Ethiopia. This paper reports on serological evidence of possible Leishmania donovani (L. donovani) infection in dogs using two serological tests: direct agglutination test (DAT) and Kalazar detect rapid test (KDRT). Two hundred and seventeen asymptomatic local breed dogs were examined for L. donovani antibodies. Performance of the DAT and KDRT was assessed in 162 matching samples of blood collected on filter paper and serum, respectively. Using DAT and KDRT testing in parallel, the overall seroprevalence of L. donovani infection was 27.7% and 14.8%, respectively. The degree of agreement was found to be fair (68.8%, k = 0.234). Univariable logistic regression analysis of some risk factors for L. donovani infection in dogs using DAT indicates that place of residence, sex, age, dog keeping purpose and dog housing condition were not significantly associated with seropositivity. The high proportion of positive dogs suggests the exposure of these animals to L. donovani infection and needs further investigation. Isolation and typing of the parasite aiming at confirming the role of these animals in maintenance and transmission of kala-azar is advocated.

Ecology and control of the sand fly vectors of Leishmania donovani in East Africa, with special emphasis on Phlebotomus orientalis

A literature review is provided on the state of knowledge of the ecology and control of the sand fly vectors of Leishmania donovani in East Africa, with a special emphasis on Phlebotomus orientalis. Visceral leishmaniasis caused by L. donovani is a major health problem in several areas in East Africa. Studies conducted in the past 70 years identified P. orientalis Parrot and P. martini Parrot as the principal vectors of L. donovani in Sudan, Ethiopia and Kenya and P. celiae Minter as the secondary vector of the parasite in one focus in Ethiopia. Findings on sand fly fauna and other circumstantial evidence indicate that P. martini is also responsible for transmission of L. donovani in VL endemic foci of Somalia and Uganda. Several studies showed that P. orientalis occupy distinct habitat characterized by black cotton soil and Acacia seyal-Balanites aegyptiaca vegetation, whereas P. martini and P. celiae are associated with termite mounds. Little knowledge exists on effective control measures of sand fly vectors of L. donovani in East Africa. However, recent evidence showed that use of insecticide impregnated bednets and insect repellents may reduce exposure to the bites of P. orientalis.