File Name: distribution and ecology of sand fly vectors of leishmania donovai in ethiopia .zip
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. All sand fly specimens collected were identified to species level and counted.
In total, , sand fly specimens, belonging to 25 sand fly species nine Phlebotomus and sixteen Sergentomyia were collected and identified. As it could be determined from the proportion of collections from outdoor peri-domestic and agricultural fields and indoor locations, P. The outdoor to indoor index was on m 2 of sticky traps.
Mean density of P. The highest abundance of P. Through July to September, there was a sharp decline in abundance of P. Regarding climatic variables, P. However, non-significant negative correlation was observed with rainfall pattern. Overall, P. Likewise, the people in the area usually sleep in compounds during these months that potentially expose them to a high risk of peri-domestic VL transmission.
Visceral leishmaniasis VL , caused by Leishmania donovani , is an important public health problem in several regions of Ethiopia, with an estimated annual incidence of 3, to 7, cases per year [ 1 ]. In recent years, reports have described increasing numbers of VL cases as well as new foci of disease in the semi-arid lowlands of Tigray Regional State, northern Ethiopia [ 4 , 5 ]. For instance, between and , VL cases were treated in Tahtay Adiyabo district [ 5 ]. So far, 22 species of Phlebotomus have been reported in Ethiopia.
In our study area, natural infection rates of P. However, detailed studies on the bionomics of sand flies in north and north-west Ethiopia in general and Tahtay Adiyabo district in particular, are very limited since the occurrence of the disease was recently recognized [ 4 ].
Knowledge on the distribution, population dynamics, and behavior of sand fly vectors contributes to understanding of where, when, and how humans become infected with L. Moreover, determining the abundance and seasonal dynamics of vector species are crucial for recommending sound vector management methods towards the control of VL transmission in the area.
Because of the limited information available about the sand fly vector s involved, an extensive entomological study aimed at identifying the sand fly fauna and bionomics of P. The topography of the study area is predominantly lowland plain except in the southwest, where it is mountainous.
The villages of Ademeyti and Lemlem are approximately 17 and 6 kms northwest and west of Sheraro town, respectively. The villages are located on hilly outcrops peri-domestic of sandy clay loam soil, which does not form cracks. The villages are surrounded by large fields many of which are vertisols and red clay soil. The dominant soil in the study villages is chromic vertisols [ 8 ], characterized by high contents of smectitic clay minerals.
This soil type is also main agricultural field in the study area. The climate is generally characterized as tropical semi-arid area with an extended dry period of nine to ten months.
During the rainy season, there is frequent cloud cover and thunder. Vertisols also become excessively muddy and even flooded during the rainy seasons. Around the last week of September the rain ceases and there begins a period marked by clear skies and cool winds which continue with gradual warming to February.
The visible moisture line recedes to the bottom of the cracks. Three sand fly sampling habitats were considered: indoor inside tukuls , peri-domestic habitats homesteads shared with animal shelters , and agricultural fields on the periphery of human residence with scattered and mixed trees mainly Acacia-Balanites-Zyzpus-Combretum trees and some scrub vegetation.
The human dwellings comprise stonewalls and wooden roofs covered with flat stones, sandy soil while few houses are made of stone wall and thatched roofs or corrugated iron roofs. The inside walls and floor of these houses are leveled with alluvial soil and plastered with mud frequently. Houses are built close to animal enclosures and are situated approximately 50— meters from farm fields many of which are in vertisols.
The inhabitants are mainly engaged in the production of cereals and oilseeds and raising different domestic animals, cattle, sheep, and goats being predominant. Traps were set-up for three consecutive nights twice a month. These traps were used to sample sand fly species from peri-domestic and agricultural fields. Five CDC light traps were deployed in representative sites i. Another 50 STs were also deployed in agricultural fields. Simultaneously, another five sets of STs were placed horizontally on the cracks of agriculture fields.
Sticky traps were deployed for three consecutive nights twice a month. Indoor resting sand flies were sampled in the morning to from ten randomly selected houses by the application of pyrethrum spray catches [ 9 ] between May and April twice a month. Prior to spraying in each house, all food items and small animals were removed; the openings and eaves of windows and doors were filled with pieces of cloth, and the floor was entirely covered with white plastic sheets.
Species were identified based on the morphology of the external genitalia of males and the pharynx, antennal features and spermathecae of females, using different keys, [ 10 , 11 ] and other publications [ 12 ]. Age grading of wild-caught males of P. In order to make use of this easily discernable physical characteristic to identify young males, P.
Males with un-rotated or partially rotated external genitalia were considered active for the first night of their adult life. Meteorological data on maximum and minimum temperatures, average relative humidity, and rainfall of Tahtay Adiyabo district during May to April were obtained from the National Meteorology Agency of Ethiopia to assess the effect of local weather elements on the seasonal dynamics of P.
Verbal informed consent was obtained from heads of households selected for sampling sand flies from inside houses. When trapping data did not conform to the normal distribution, the non-parametric equivalent tests of Kruskal-Wallis and Mann—Whitney- U were applied.
Kruskal-Wallis test was followed to compare the mean numbers of P. For non-parametric comparisons, multiple-Mann—Whitney U -test was used and, P- values were adjusted with the Bonferroni correction to adjust for the inflation of type I errors when several Mann—Whitney tests are performed [ 15 ].
For habitat preference comparisons, the equivalent non-parametric Mann—Whitney U -test were used. Seasonal abundance of P. Pearson correlation analysis was also applied to compare the effects of mean monthly temperature, relative humidity, and rainfall on the mean number of P. Further, Mann—Whitney U -test was used for comparing the number and proportions of P. The genus Phlebotomus represented six subgenera while four subgenera were identified in Sergentomyia.
Different sand fly species identified in the present study consist of Phlebotomus Larroussius orientalis, P. Anaphlebotomus rodhaini, P. Synphlebotomus martini, P. Phlebotomus bergeroti , P.
Paraphlebotomus alexandri, P. Parvidens lesleyae , P. Sergentomyia schwetzi, S. Sintonius clydei, S. Grassomyia squamipleuris. The most abundant species of Phlebotomus was P. While the other Phlebotomus species constituted only 0. Among the genus Sergentomyia , S. Mean numbers of P. Significant differences were recorded in the mean numbers of P.
In both trapping methods, Ademeyti and Lemlem were the most productive sampling villages for P. More mean number of male and female P. While the mean density in peri-domestic ecotopes for P. Unlike light trap collections, habitat types had significant effects on the abundance of P. A significantly higher mean density of P.
Likewise, more mean number of P. Of 3, indoor resting sand flies captured in the pyrethrum spray collections during house visits, 48 1. In particular, female populations of P. Among Sergentomyia spp. In total, 52 29 males and 23 females from indoors and 15, 14, male; female from outdoors were captured on sticky traps. The result of the outdoor peri-domestic and agricultural fields combined P. The annual mean maximum and minimum temperatures were The main rainy period was between June and September.
The maximum precipitation recorded in the area during sand fly sampling was Seasonal fluctuations in the mean monthly maximum and minimum temperatures, relative humidity, and rainfall in the study area, May to April To assess the overall seasonal changes in abundance of the P. There were significant mean monthly fluctuations in the numbers of P. From July to December, including the rainy season July-September and shortly after that October-December , there was a sharp decrease in abundance of P.
The lowest mean density of P. Seasonal density of P. The highest mean monthly density of P. In light trap catches, monthly abundance of P. In contrast, the mean monthly abundance of P.
Mean monthly density of P.
Visceral leishmaniasis and cutaneous leishmaniasis are important public health problems in Ethiopian lowland and highland areas respectively. Control of leishmaniasis requires proper understanding of human parasites transmissions anthroponotic or zoonotic or both. The aim of this review was to elaborate different ecologies of leishmaniasis based on evidences from previous researches and information from literatures obtained from different sources including PubMed to describe zoonotic leishmaniasis in Ethiopia with possible control methods. Although vectors of leishmaniasis in Ethiopia are not endophelic, night indoor visits of Phlebotomus vectors for possible blood meal on human have been indicated. Thus, application of indoor and domestic residual insecticides spraying, use of insecticide impregnated fine mashed bed net for visceral leishmaniasis, community based manipulation destruction and residual insecticide fogging of hyrax-sand fly habitats for cutaneous leishmaniasis are the visible vector and reservoir control methods that can be used for control of these diseases in Ethiopia. Use of repellants during night outdoor activities of people in the endemic areas requires further investigations. Impact Factor 1.
Leishmaniasis is the third most important vector-borne disease after malaria and lymphatic filariasis. It is common disease in all over the world.
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