Samson Leta; Thi Ha Thanh Dao; Frehiwot Mesele; Gezahegn Alemayehu

“ Endemic regions have been spreading further and there has been a sustained transmission cycle. The public health impact of VL often becomes more evident in areas that are remote, where health facilities are absent or undeveloped [27] . In these areas, most critical cases are neither treated nor reported, so they act as a reservoir of infection, passing on the parasite to non-infected people and keeping the transmission sustained.
Future Needs
The epidemiology of leishmaniasis, especially that of VL, in Ethiopia is complex, and a number of key questions remain unanswered. ”

“ VL control through sandfly control could be successful, especially in domestic and peridomestic transmission habitats. The use of insecticide-treated bed nets (ITNs) prevents VL and other vector-borne diseases. In Ethiopia, using bed nets was found to decrease the risk of VL [41] . The use of ITNs avoids human–vector contact and thereby decreases the chance to be infected and also decreases the likelihood that sandflies will feed on infected individuals. However, in Ethiopia, bed net distribution and insecticide spraying take place in the context of malaria control. ”

“ Almost all livestock owners and urban dwellers keep at least one dog to safeguard their properties from wild carnivores and thieves. These, and other, socioeconomic realities are considered to be conducive to the maintenance and further propagation of the disease. ”

“ In northwestern foci, VL epidemics are associated with migration and the movement of non-immune workers into the VL-endemic extensive farm lands [5] . Workers from the non-endemic highlands are often victims of VL in these foci.
A recent study conducted by Bashaye et al. [20] investigating risk factors associated with the outbreak in Libo Kemkem identified dog ownership to be a risk factor. In Ethiopia, culture and tradition of inhabitants favours the keeping of dogs in urban and rural households often in close association with the family and farm animals. ”

“ HIV/AIDS and VL are locked in a vicious circle of mutual reinforcement. VL accelerates the onset of AIDS by infecting macrophages throughout the reticuloendothelial system, rendering the body more susceptible by stimulating replication of the virus. ”

“ This is especially more evident in nomadic populations and in men who work in agricultural or pastoral settings due to increased time spent outdoors and thus higher exposure to the sandfly. Part of a community that lives and/or has frequent contact with acacia trees and termite hills are at increased risk, since acacia trees and termite hills are common breeding and resting sites for certain species of sandflies [5] , [30] .
Epidemics of leishmaniasis are often associated with migration and the introduction of non-immune people into areas with existing transmission cycles [17] . ”

“ This is the only recorded VL outbreak from highland areas in Ethiopia; however, Ashford et al. [15] reported a few cases of VL in Belessa, a highland area in the Amhara regional state in the 1970s.
VL is becoming a growing public health threat; the spatial distribution and burden of VL is upsurging year after year [16] . VL–HIV co-infection is rising in Ethiopia, and it poses a new and difficult challenge to VL control effort. VL–HIV co-infection is characterized by a number of complexities, including challenging diagnosis, increased drug toxicity, and poor treatment response. ”

“ Leishmaniasis is caused by obligate intracellular protozoa of the genus Leishmania, belonging to the family Trypanosomatidae (order Kinetoplastida) [17] , [18] . Human infection is caused by about 21 of 30 species that infect mammals. Leishmania donovani complex (L. donovani and Leishmania infantum) are the causative agents of VL in Ethiopia. L. donovani is regarded as the major cause of VL in Ethiopia, although L. infantum was identified as a main causative agent of the recent VL outbreak in Libo Kemkem, in the Amhara regional state [6] , [14] . ”

“ In Ethiopia, the first case of VL was documented in 1942 in the lower Omo plains, the southwestern part of the country [8] . The disease has spread to become endemic in many parts of the country. The disease is prevalent mostly in lowland, arid areas, and the parasite involved is mainly Leishmania donovani, with an estimated annual incidence of more than 4,000 cases [9] . Most important endemic foci include the Humera and Metema plains in the northwest [10] , the Omo plains, the Aba Roba focus, and the Weyto River Valley in the southwest [11] , [12] . ”

“ Moreover, Hassan et al. [21] reported highly significant attraction of different sandfly species to dog-baited traps. On the other hand, in East Africa, the transmission of L. donovani (the predominant causative agent of VL in the region) is thought to be anthroponotic, indicating that humans are a potential reservoir host for the disease [22] . Hence, the definitive reservoir of VL in East Africa in general and Ethiopia in particular remains to be determined. ”

“ Poverty increases the risk for VL. Poor housing and poor sanitary conditions may increase sandfly breeding and resting sites, as well as their access to humans. The flies are mainly attracted to crowded housing, as these provide a good source of blood-meals [5] . Sleeping outside or on the ground may increase the risk of infection. ”

“ The efficiency and acceptability of zoonotic VL control based on surveillance and culling of infected dogs is increasingly being debated. Treating infected dogs is not an effective control strategy, as relapses are frequent and dogs can regain infectivity weeks after treatment, despite being clinically cured. ”

“ The distribution of viseral leishmaniasis in Ethiopia. Am J Trop Med Hyg 33: 548–552.# Gebre-Michael T, Malone JB, Belkew M, Ali A, Berhe N, et al. (2004) Mapping the potential distribution of Phlebotomus martini and P.orientalis (Diptera: Psychodidae) , vectors of kala-azar in East Africa by use of geographic information systems. Acta Tropic 90: 73–86.# Alvar J, Bashaye S, Argaw D, Cruz I, Aparicio P, et al. (2007) Kala-azar outbreak in Libo Kemkem, Ethiopia: epidemiologic and parasitologic assessment. ”