Effect of LongRange™ eprinomectin on Anopheles arabiensis by feeding on calves treated with the drug.

BACKGROUND: Misuse of long-lasting insecticidal nets together with resistance of vectors to most of the insecticides for indoor residual spraying and impregnated nets threaten malaria vector control interventions, requiring search for alternative control methods. Reports have shown that Anopheles mosquitoes die when they feed on endectocidal drugs used to treat humans and animals. A study was designed to investigate the efficacy of LongRange™ (eprinomectin 5%) on laboratory reared Anopheles arabiensis fed on treated calves. METHODS: Anopheles arabiensis from insectary colony was fed on three calves treated with therapeutic dose of LongRange™ eprinomectin (1 ml/50 kg) and on non-treated three other calves as control arm. For the feeding, mosquitoes were placed in paper cups covered with nylon cloth mesh and then allowed to feed on the necks of calves. Subsequently, mosquito survival, fecundity, egg hatchability, larval development and adult emergence were recorded. Data were entered and analysed by using SPSS version 20. The Kaplan-Meier survival analysis and independent sample t-test were used. RESULTS: All mosquitoes that fed on LongRange™ Eprinomectin treated calves died within 7 days following blood ingestion. The drug also slightly affected fecundity and hatchability of An. arabiensis. CONCLUSION: Treating livestock with LongRange™ (eprinomectin 5%) may serve as a supplementary control method for zoophagic An. arabiensis.

Comparison of two adult mosquito sampling methods with human landing catches in south-central Ethiopia.

BACKGROUND: The human landing catch (HLC) is the standard reference method for measuring human exposure to mosquito bites. However, HLC is labour-intensive, exposes collectors to infectious mosquito bites and is subjected to collector bias. These necessitate local calibration and application of alternative methods. This study was undertaken to determine the relative sampling efficiency (RSE) of light traps with or without yeast-produced carbon dioxide bait vs. HLC in south-central Ethiopia. METHODS: The experiment was conducted for 39 nights in a 3 × 3 Latin square randomized design with Anopheles arabiensis as the target species in the period between July and November 2014 in Edo Kontola village, south-central Ethiopia. Center for Disease Control and Prevention light trap catches (LTC) and yeast-generated carbon dioxide-baited light trap catches (CB-LTC) were each evaluated against HLC. The total nightly mosquito catches for each Anopheles species in either method was compared with HLC by Pearson correlation and simple linear regression analysis on log-transformed [log10(x + 1)] values. To test if the RSE of each alternative method was affected by mosquito density, the ratio of the number of mosquitoes in each method to the number of mosquitoes in HLC was plotted against the average mosquito abundance. RESULTS: Overall, 7606 Anopheles females were collected by the three sampling methods. Among these 5228 (68.7%) were Anopheles ziemanni, 1153 (15.2%) An. arabiensis, 883 (11.6%) Anopheles funestus s.l., and 342 (4.5%) Anopheles pharoensis. HLC yielded 3392 (44.6%), CB-LTC 2150 (28.3%), and LTC 2064 (27.1%) Anopheles females. The RSEs of LTC and HLC for An. arabiensis were significantly correlated (p < 0.001) and density independent (p = 0.65). However, for outdoor collection of the same species, RSEs of LTC and CB-LTC were density dependent (p < 0.001). It was estimated that on average, indoor LTC and CB-LTC each caught 0.35 and 0.44 times that of indoor HLC for An. arabiensis respectively. CONCLUSIONS: Results showed that HLC was the most efficient method for sampling An. arabiensis. LTC can be used for large-scale indoor An. arabiensis surveillance and monitoring when it is difficult to use HLC. CB-LTC does not substantially improve sampling of this major vector compared to LTC in this setting. Trial registration PACTR201411000882128 (retrospectively registered 8 September, 2014).

Malaria incidence and entomological findings in an area targeted for a cluster-randomized controlled trial to prevent malaria in Ethiopia: results from a pilot study.

BACKGROUND: This study was part of the work to prepare for a cluster-randomized controlled trial to evaluate the effect of combining indoor residual spraying and long-lasting insecticidal nets on malaria incidence. A pilot study was done to estimate the variations of malaria incidence among villages, combined with entomological collections and an assessment of susceptibility to insecticides in malaria vectors. METHODS: A cohort of 5309 residents from four kebeles (the lowest government administrative unit) in 996 households was followed from August to December 2013 in south-central Ethiopia. Blood samples were collected by a finger prick for a microscopic examination of malaria infections. A multilevel mixed effect model was applied to measure the predictors of malaria episode. Adult mosquitoes were collected using light traps set indoors close to a sleeping person, pyrethrum spray sheet catches and artificial outdoor pit shelters. Enzyme-linked immunosorbent assays were used to detect the sources of mosquito blood meals, while mosquito longevity was estimated based on parity. The World Health Organization's tube bioassay test was used to assess the insecticide susceptibility status of malaria vectors to pyrethroids and carbamates. RESULTS: The average incidence of malaria episode was 4.6 per 10,000 person weeks of observation. The age group from 5 to 14 years (IRR = 2.7; 95 % CI 1.1-6.6) and kebeles near a lake or river (IRR = 14.2, 95 % CI 3.1-64) were significantly associated with malaria episode. Only 271 (27.3 %) of the households owned insecticide-treated nets. Of 232 adult Anopheles mosquitoes collected, Anopheles arabiensis (71.1 %) was the predominant species. The average longevity of An. arabiensis was 14 days (range: 7-25 human blood index days). The overall human blood index (0.69) for An. arabiensis was higher than the bovine blood index (0.38). Statistically significant differences in Anopheline mosquitoes abundance were observed between the kebeles (P = 0.001). Anopheles arabiensis was susceptible to propoxur, but resistant to pyrethroids. However, An. pharoensis was susceptible to all pyrethroids and carbamates tested. CONCLUSIONS: This study showed a high variation in malaria incidence and Anopheles between kebeles. The observed susceptibility of the malaria vectors to propoxur warrants using this insecticide for indoor residual spraying, and the results from this study will be used as a baseline for the trial.

Evaluation of Endod (Phytolacca dodecandra: Phytolaccaceae) as a Larvicide Against Anopheles arabiensis, the Principal Vector of Malaria in Ethiopia.

Malaria control methods rely mostly on adult mosquito control using insecticide-treated nets and indoor residual spraying with insecticides. Plants such as endod (Phytolacca dodecandra) can potentially be used for the control of mosquito larvae as a supplement to adult control methods. Following the discovery of endod, a molluscicide plant, more than 5 decades ago in Ethiopia, subsequent studies have shown that its potency can further be increased by simple procedures such as aging endod berry powder in water. This study was conducted to evaluate the killing effect of fresh and aged endod solution against 4th-stage larvae of Anopheles arabiensis. Laboratory-reared An. arabiensis larvae exposed to different concentrations of endod preparation using distilled or spring water had 50% lethal concentration (LC(50))  =  49.6 ppm and 90% lethal concentration (LC(90))  =  234 ppm for fresh and LC(50)  =  36.4 ppm and LC(90)  =  115.7 ppm for the aged endod solution in distilled water against the laboratory population. Against field-collected larvae of the same species, aged preparations in habitat water resulted in higher LC(50) (472.7 ppm) and LC(90) (691 ppm) values, with only a slight improvement over fresh preparations in habitat water (LC(50)  =  456.2 ppm; LC(90)  =  896.1 ppm). In general, although aged preparations of endod required lower concentrations than fresh to kill at least 90% of the larvae, these concentrations were much higher (12-70×) than that required for schistosome-transmitting snails.

Repellent efficacy of DEET, MyggA, neem (Azedirachta indica) oil and chinaberry (Melia azedarach) oil against Anopheles arabiensis, the principal malaria vector in Ethiopia.

BACKGROUND: In Ethiopia, Anopheles arabiensis is the main vector responsible for the transmission of malaria in the country and its control mainly involves application of indoor residual spraying (IRS) and use of insecticide-treated bed nets (ITNs). OBJECTIVE: Although the role of repellents for reducing man-vector contact is documented in the literature, the response of An. arabiensis to repellents was not previously evaluated under field conditions in Ethiopia. METHOD: The trial was conducted in Sodere village assessing the repellent activities of four repellents, of which, two of them were commercially available DEET (N, N-diethyl-1,3-methylbenzamide) and MyggA (p-methane diol) and the other two were laboratory- produced, 20% neem oil and 20% chinaberry oil. A 6 by 6 Latin square design was employed by involving six volunteers who received rotated treatments of repellents and the Ethiopian Niger seed, noog abyssinia (Guizotia abyssinia), and locally called as noog oil (diluents to the two plant oils). Each volunteer also served as control. Volunteers were positioned at a distance of 20-40 m from each other and each was treated with one of the repellents, Niger seed/noog/ oil or untreated. Landing mosquitoes were collected from dusk to down using tests tubes. The tests were done in three replicates. RESULTS: Both DEET and MyggA provided more than 96% protection. The mean protection time for DEET was 8 hrs while the time for MyggA was 6 hrs. Protection obtained from neem oil and chinaberry oil was almost similar (more than 70%), however, the complete protection time for neem was 3 hrs, while that of chinaberry oil was one hour. CONCLUSION: The commercial products and laboratory-produced repellents can be utilized by individuals to avoid contact with An. arabiensis in Ethiopia.

Sero-prevalence of Leishmania donovani infection in labour migrants and entomological risk factors in extra-domestic habitats of Kafta-Humera lowlands - kala-azar endemic areas in the northwest Ethiopia.

BACKGROUND: Visceral leishmaniasis (VL) or kala-azar cases in seasonal labour migrants from highland areas are addressed to travel history to the Metema-Humera lowlands, northwestern Ethiopia. Factors that affect the incidence of VL in extra-domestic habitats were not evaluated. The aim of this study was to evaluate sero-prevalence of Leishmania donovani infection in randomly selected labour migrant workers and entomological risk factors which might affect the incidence of kala-azar. METHODS: Sero-prevalence of L. donovani infection in labour migrants was obtained from Direct Agglutination Test (DAT) using blood samples. Logistic regression analysis was used to correlate the possible risk factors with L. donovani infection. The season for L. donovani infection or Phlebotomus orientalis bite was estimated from the study of population dynamic of P. orientalis in areas where the blood was sampled. RESULT: A total of 7, 443 P. orientalis (1,748 female and 5,695 male) were collected from agricultural fields and thickets of Acacia seyal using 461 CDC light traps. The highest mean number of P. orientalis/trap in the thickets of A. seyal and agricultural fields were 46.9 and 43.9 in March and April respectively. The mean P. orientalis/trap for November - May dry season in agricultural fields (11.39) and thickets of A. seyal (25.30) were higher compared to 0.66 in fields and 3.92 in thickets during June - August weeding season. Of the total 359 labour migrants screened using DAT, 45 (12.5%) were DAT-positive (≥1:800) for L. donovani infections. Very high titers (1:12800) were found in 3 (0.8%) individuals who had the risk of kala-azar development. Statistically significant p-values and odd ratio (OR) for staying in the areas both in the weeding and harvesting seasons (p = 0.035; OR = 2.83) and sleeping in the agricultural fields (p = 0.01; OR = 15.096) were positively correlated with L. donovani infection. Night harvest (p = 0.028; OR = 0.133) and knowledge about sign or symptoms (p = 0.042; OR = 0.383) were negatively associated with this infection. CONCLUSIONS: Sleeping in open agricultural fields was related with L. donovani infections in labour migrants during June-August weeding season.

Blood meal sources and entomological inoculation rates of anophelines along a highland altitudinal transect in south-central Ethiopia.

BACKGROUND: The role of anophelines in transmitting malaria depends on their distribution, preference to feed on humans and also their susceptibility to Plasmodium gametocytes, all of which are affected by local environmental conditions. Blood meal source and entomological inoculation rate of anophelines was assessed along a highland altitudinal transect in south- central Ethiopia. METHODS: Monthly adult anopheline sampling was undertaken from July 2008 to June 2010 in Hobe (low altitude), Dirama (mid altitude) and Wurib (high altitude) villages located at average elevations of 1800 m, 2000 m and 2200 m, respectively. Anophelines were collected using CDC light trap, pyrethrum space spray catches (PSC) and artificial pit shelter methods. Upon collection, females were categorized according to their abdominal status and identified to species. Their human blood index, sporozoite rate and entomological inoculation rate was determined. RESULTS: A total of 4,558 female anophelines of which Anopheles arabiensis was the most prevalent (53.3%) followed by Anopheles demeilloni (26.3%), Anopheles christyi (8.9%), Anopheles pharoensis (7.9%) and Anopheles cinereus (3.6%) were caught and tested for blood meal source or sporozoite infection depending on their abdominal status. The proportions of human fed and bovine fed An. arabiensis were generally similar. In the low altitude village, there were 0.3% (1/300) and 0.2% (1/416) Plasmodium falciparum infected An. arabiensis among the CDC trap catches and PSC respectively. The percentage of Plasmodium vivax infected An. arabiensis were 3% (9/300) and 0.7(3/416) among the CDC and PSCs respectively in the village. In addition, there were 1.4% (1/71) and 50% (1/2) P. vivax infected An. pharoensis from the CDC light trap and PSCs, respectively. In the mid altitude village, 2.5% (1/40) and 1.7% (1/58) from among the CDC and PSCs of An. arabiensis respectively carried P. vivax sporozoites. Among the CDC light trap catches; there were 3.7 and 0 P. falciparum infective bites per year per household for An. arabiensis in the years July 2008 to June 2009 and July 2009 to June 2010 respectively in the low altitude village. The corresponding numbers for P. vivax infective bites for An. arabiensis were 33 and 14.5 in the same village. Space spray catches revealed 0.32 P. vivax infective bites per household for An. pharoensis during the first year in the low altitude village. CONCLUSION: Anopheles arabiensis was the most prevalent vector of P. vivax and P. falciparum malaria in the low and mid altitude villages followed by An. pharoensis. Annual entomological inoculation rates showed that vivax malaria transmission was higher than that of the falciparum and both decreased with increase in altitude.

A dynamic model of some malaria-transmitting anopheline mosquitoes of the Afrotropical region. II. Validation of species distribution and seasonal variations.

BACKGROUND: The first part of this study aimed to develop a model for Anopheles gambiae s.l. with separate parametrization schemes for Anopheles gambiae s.s. and Anopheles arabiensis. The characterizations were constructed based on literature from the past decades. This part of the study is focusing on the model's ability to separate the mean state of the two species of the An. gambiae complex in Africa. The model is also evaluated with respect to capturing the temporal variability of An. arabiensis in Ethiopia. Before conclusions and guidance based on models can be made, models need to be validated. METHODS: The model used in this paper is described in part one (Malaria Journal 2013, 12:28). For the validation of the model, a data base of 5,935 points on the presence of An. gambiae s.s. and An. arabiensis was constructed. An additional 992 points were collected on the presence An. gambiae s.l.. These data were used to assess if the model could recreate the spatial distribution of the two species. The dataset is made available in the public domain. This is followed by a case study from Madagascar where the model's ability to recreate the relative fraction of each species is investigated. In the last section the model's ability to reproduce the temporal variability of An. arabiensis in Ethiopia is tested. The model was compared with data from four papers, and one field survey covering two years. RESULTS: Overall, the model has a realistic representation of seasonal and year to year variability in mosquito densities in Ethiopia. The model is also able to describe the distribution of An. gambiae s.s. and An. arabiensis in sub-Saharan Africa. This implies this model can be used for seasonal and long term predictions of changes in the burden of malaria. Before models can be used to improving human health, or guide which interventions are to be applied where, there is a need to understand the system of interest. Validation is an important part of this process. It is also found that one of the main mechanisms separating An. gambiae s.s. and An. arabiensis is the availability of hosts; humans and cattle. Climate play a secondary, but still important, role.

Agro-ecosystems impact malaria prevalence: large-scale irrigation drives vector population in western Ethiopia.

BACKGROUND: Development strategies in Ethiopia have largely focused on the expansion of irrigated agriculture in the last decade to reduce poverty and promote economic growth. However, such irrigation schemes can worsen the socio-economic state by aggravating the problem of mosquito-borne diseases. In this study, the effect of agro-ecosystem practices on malaria prevalence and the risk of malaria transmission by the primary vector mosquito, Anopheles arabiensis, in Ethiopia were investigated. METHODS: In three villages in western Ethiopia practising large-scale sugarcane irrigation, traditional smallholder irrigation and non-irrigated farming, cross-sectional parasitological surveys were conducted during the short rains, after the long rains and during the dry season. Entomological surveys were undertaken monthly (February 2010-January 2011) in each village using light traps, pyrethrum spray collections and artificial pit shelters. RESULTS: Malaria prevalence and the risk of transmission by An. arabiensis assessed by the average human biting rate, mean sporozoite rate and estimated annual entomological inoculation rate were significantly higher in the irrigated sugarcane agro-ecosystem compared to the traditionally irrigated and non-irrigated agro-ecosystems. The average human biting rate was significantly elevated by two-fold, while the mean sporozoite rate was 2.5-fold higher, and the annual entomological inoculation rate was 4.6 to 5.7-fold higher in the irrigated sugarcane compared to the traditional and non-irrigated agro-ecosystems. Active irrigation clearly affected malaria prevalence by increasing the abundance of host seeking Anopheles mosquitoes year-round and thus increasing the risk of infective bites. The year-round presence of sporozoite-infected vectors due to irrigation practices was found to strengthen the coupling between rainfall and risk of malaria transmission, both on- and off-season. CONCLUSION: This study demonstrates the negative impact of large-scale irrigation expansion on malaria transmission by increasing the abundance of mosquito vectors and indicates the need for effective vector monitoring and control strategies in the implementation of irrigation projects.

First record of Phlebotomus (Synphlebotomus) vansomerenae (Diptera: Psychodidae) in Ethiopia.

Male Phlebotomus (Synphlebotomus) vansomerenae, specimens were collected together with two other members of the same subgenus between August 2010 and December 2011 in Melka Guba village near Dawa River in Liben district, southeastern Ethiopia. This is the first record of the species in Ethiopia and the first time it has been found outside of Kenya where it was originally described, extending the known distribution of this species in East Africa.

Environmental factors associated with larval habitats of anopheline mosquitoes (Diptera: Culicidae) in irrigation and major drainage areas in the middle course of the Rift Valley, central Ethiopia.

BACKGROUND & OBJECTIVES: Larval control is an integral part of malaria vector management in Ethiopia and elsewhere. For effective larval control, a sound understanding of the factors responsible for spatio-temporal variation in larval production is essential. A study was thus conducted to characterize larval habitats of anopheline mosquitoes in irrigation and major drainage areas between Adami Tulu and Meki towns, in the middle course of the Ethiopian Rift Valley. METHODS: Aquatic habitats were sampled for anopheline larvae and the associated environmental variables (water temperature, turbidity, water current, water pH and other variables) were measured, characterized and analyzed. RESULTS: Microscopic identification of the late instars (III and IV) of anopheline larvae collected throughout the study period yielded nearly 47.6% Anopheles pharoensis, 32.1% An. arabiensis, 17.1% An. squamosus and only 3.2% of other species (An. coustani and An. cinereus). Larvae of the local malaria vectors, An. arabiensis and An. pharoensis were most abundantly sampled from sand pools and natural swamps, respectively. Logistic regression analysis detected four best predictor variables associated with larval abundance of malaria vector species. Thus, relative abundance of An. arabiensis larvae was significantly and inversely associated with aquatic vegetation and water current, whereas the relative abundance of An. pharoensis larvae was significantly and positively associated with water temperature and the presence of algae in the water bodies. CONCLUSION: Dry season anopheline larval habitats such as riverine sand pools that are created and maintained by perennial water bodies and their associated water development projects need to be considered in vector control operations.

Species composition, blood meal hosts and Plasmodium infection rates of Anopheles mosquitoes in Ghibe River Basin, southwestern Ethiopia.

BACKGROUND: Vector control interventions using long-lasting insecticidal nets (LLINs) and indoor residual spraying (IRS) are commonly practiced tools for the control of malaria in Ethiopia. In order to evaluate the effectiveness of these control interventions, and understand the prevailing malaria vectors, their incrimination in disease transmission, and their resting and feeding behavior, we set out to identify the Anopheles species, their blood meal sources, and entomological inoculation rate (EIR) in Ghibe and Darge within the Ghibe River basin, southwestern Ethiopia. METHODS: Adult Anopheles mosquitoes were sampled both indoors and outdoors from January 2015 to October 2016 using Centers for Disease Control and Prevention (CDC) light traps, pyrethrum spray catch (PSC), artificial pit shelters and mouth aspirators. Mosquito species were morphologically identified, and their blood meal sources and malaria sporozoite rates were assessed using enzyme-linked immunosorbent assays. RESULTS: In total, 13 species of Anopheles mosquitoes were identified, among which Anopheles gambiae (s.l.) was the predominant species: 87.9 and 67.7% in Ghibe and Darge, respectively. The mean density of An. gambiae (s.l.) collected per night using CDC light traps was 1.8 and 0.7 outdoors and indoors, respectively, in Ghibe, and 0.125 and 0.07 indoors and outdoors, respectively, in Darge. Anopheles mosquito abundance was higher in houses near the river than in houses far from the river in both study sites. Among Anopheles mosquitoes sampled using CDC light trap catches, 67.6% were unfed and the indoor and outdoor human blood indices of An. gambiae (s.l.) were 58.4 and 15.8%, respectively in Ghibe, while in Darge, they were 57.1 and 50%, respectively. Sporozoite rates were 0.07% for P. vivax and 0.07% for P. falciparum in Ghibe and zero in Darge. In Ghibe, the overall EIRs for P. falciparum and P. vivax were zero and 8.4 infective bites/person/year, respectively, in 2015, while zero and 5.4 infective bites/person/year for P. vivax and P. falciparum, respectively, in 2016. No Plasmodium-positive Anopheles mosquitoes were identified from Darge. CONCLUSIONS: Anopheles gambiae (s.l.), the principal vector of malaria in Ethiopia was the most abundant species both indoors and outdoors, fed both on human and cattle blood and occurred at higher frequencies near rivers. Anopheles gambiae (s.l.) that were circumsporozoite-positive for Plasmodium species were collected from Ghibe, but not Darge.

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.

Study on the species composition and ecology of anophelines in Addis Zemen, South Gondar, Ethiopia.

BACKGROUND: Malaria is a public health problem in Ethiopia and its transmission is generally unstable and seasonal. For the selection of the most appropriate vector control measures, knowledge on the ecology of the vector is necessary at a local level. Therefore, the objectives of this study were to document the species composition, breeding habitat characteristics and occurrence of anopheline larva in Sheni stream and the vectorial role of the prevailing Anopheles in relation to malaria transmission in Addis Zemen, Ethiopia. METHODS: Immature anophelines were sampled from breeding habitats and characteristics, such as water temperature, turbidity, water current, water pH and other variables, of the habitats were measured from October 2011 to February 2012. Adult anophelines were sampled inside human dwellings using space spray and Center for Disease Control light traps. Artificial pit shelters and clay pots were also used for outdoor adult collections. Anophelines collected were identified using morphological key. The enzyme-linked immunosorbent assay was applied to detect circumsporozoite proteins of Plasmodium and source of blood meals. RESULTS: A total of 6258 Anopheles larvae were collected and identified morphologically. Five anopheline species were found: An. gambiae (s.l.), An. cinereus, An. demeilloni, An. christi and An. pretoriensis. Anopheles gambiae (s.l.) existed in most of the habitats investigated. Only the former three species were captured in the adult collections. Sun-lit Sheni stream, rain pools, hoof prints, drainage and irrigation canals were found to be habitats of larvae. Anopheles gambiae (s.l.) larvae were most abundantly sampled from sand mining and natural sand pools of Sheni stream. Multiple regression analysis showed that clear, permanent and temporary habitats devoid of mats of algae were the best predictors of An. gambiae (s.l.) larval abundance. It is also the responsible malaria vector in the study area and exhibits anthropophilic and endophagic behaviour. CONCLUSIONS: The malaria vector An. gambiae (s.l.) was found in Addis Zemen throughout the study period from both adult and larval collections. Sheni stream is the main larval habitat responsible for the occurrence of anopheline larvae during the dry season of the study area when other breeding sites perish.

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.

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

Non-biting cyclorrhaphan flies (Diptera) as carriers of intestinal human parasites in slum areas of Addis Ababa, Ethiopia.

A study was conducted to determine the role of non-biting cyclorrhaphan flies as carriers of intestinal parasites in slum areas of Addis Ababa from January 2004 to June 2004. A total of 9550 flies, comprising of at least seven species were collected from four selected sites and examined for human intestinal parasites using the formol-ether concentration method. The dominant fly species was Chrysomya rufifacies (34.9%) followed by Musca domestica (31%), Musca sorbens (20.5.%), Lucina cuprina (6.8%), Sarcophaga sp. (2.8%), Calliphora vicina (2.2%) and Wohlfahrtia sp. (1.8%). Six intestinal helminths (Ascaris lumbricoides, Trichuris trichiura, hookworms, Hymenolepis nana, Taenia spp. and Strongyloides stercoralis) and at least four protozoan parasites (Entamoeba histolytica/dispar, Entamoeba coli, Giardia lamblia and Cryptosporidium sp.) were isolated from both the external and gut contents of the flies. A. lumbricoides and T. trichiura among the helminths and E. histolytica/dispar and E. coli among the protozoans were the dominant parasites detected both on the external and in the gut contents of the flies, but occurring more in the latter. Among the flies, C. rufifacies and M. sorbens were the highest carriers of the helminth and protozoan parasites, respectively. The public health significance of these findings is highlighted.

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.

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.

Comparative study on the nocturnal activity of phlebotomine sand flies in a highland and lowland foci of visceral leishmaniasis in north-western Ethiopia with special reference to Phlebotomus orientalis.

BACKGROUND: Leishmania donovani, the causative agent of visceral leishmaniasis (VL), is most probably vectored by Phlebotomus orientalis in north-western Ethiopia. The aim of this study was to determine and compare the nocturnal activity patterns of Ph. orientalis in VL endemic foci of Libo-Kemkem (highland) and Metema (lowland) districts of north-western Ethiopia. METHODS: Sampling of sand flies was conducted bimonthly from January-May 2012 in the highland and from March-June 2013 in the lowland. Sand flies were sampled using two CDC light traps placed in compounds occupied by both cattle and humans. Sampling of sand flies started at 18:00 h and ended at 06:00 h. Every hour, a cage was replaced by another cage. RESULTS: In total, 9479 nocturnally active sand flies were collected from both study areas. Six Phlebotomus species (Ph. orientalis, Ph. duboscqi, Ph. papatasi, Ph. bergeroti, Ph. rodhaini and Ph. martini) and several Sergentomyia spp. were identified. In both areas, of the six Phlebotomus spp., Ph. orientalis was the preponderate. In the highland, the hourly activity pattern of Ph. orientalis females was higher before midnight with a peak in density between 22:00-23:00 h, whereas in the lowland after midnight between 03:00-04:00 h. CONCLUSIONS: The present study showed that Ph. orientalis females exhibited different nocturnal activity patterns with a peak in the early part of the night in the highland and in the latter part of the night in the lowland areas. As the risk of acquiring L. donovani infections vary in the two areas, appropriate control strategies should be developed according to the activity of Ph. orientalis in the respective areas.