Determining the Distribution of Tsetse Fly in Gurage Zone, Enemorenaener District, SNNPR of Ethiopia

  

    
Site of Deployment
    
No. of Traps
    
Altitude
    
Species
    
Types of Flies
    
Fly/Trap/Day
  
  

    
M
    
F
    
Total
  
  

    
Shmoro
    
10
    
1120-1159
    
G.morsitance
    
-
    
6
    
6
    
1.05
  
  

    
G.paladipes
    
6
    
9
    
15
  
  

    
Stomoxey
    
-
    
-
    
7
  
  

    
Tabanides
    
-
    
-
    
6
  
  

    
Jatu
    
10
    
1159-1180
    
G.morsitance
    
2
    
5
    
7
    
0.8
  
  

    
G.paladipes
    
3
    
6
    
9
  
  

    
Stomoxey
    
-
    
-
    
3
  
  

    
Tabanides
    
-
    
-
    
7
  

Table 1: Tsetse density and species of glossina.

The epidemiology of African animal trypanosomiasis is governed by the distribution of their vectors as a whole and especially by that of tsetse flies (Glossina species). In tropical Africa, tsetse ecology is confines roughly between 150N-250S latitude where the disease as well occurs, although mechanically transmitted trypanosomiasis is distributed wider than this limit [4]. Tsetse fly as the primary vector of trypanosomes in sub-Saharan Africa is, thus, incriminated as the major and continuing threat to the efforts aimed at improving the livelihoods of rural communities [5].

The four species are members of the salivarian group of Trypanosome and are transmitted cyclically via the mouth part of tsetse flies, hence the name salivarian Trypanosome. The three groups of the Glossina, the savannah and the rivrian are the most important vector since they inhibits areas suitable for grazing and watering. Tsetse flies in Ethiopia are confined to the southern and western region between longitude 33⁰E and 38⁰E and latitude 5⁰N and 12⁰N. The infest area in which together amount of 220,000 tsetse infest areas lie in the lowlands and also in the river valley of Abay (Blue nile, Baro, Akobo, Diddesa, Ghibe and Omo) [6].

The vector, tsetse fly, can be classified in to the order Diphtheria (the two winged flies), family Glossinidae and within the genus, Glossina. There about 23 species and 8 sub species of Glossina identified so far [4,7]. From morphological point of view tsetse flies are elongated and roboust of varies shade of brown ranging from yellowish to grayish to dark or blackish brown color and about 6 to 16 mm long excluding the proboscis. Males are smaller than females [8].

The general distribution of tsetse flies determined principally by climate and influenced by the altitude, vegetation and presence of suitable host animals has been known for a long time [4]. Each of these factors may directly affect the birth, death or migration rate of the vector and thus the population size [9]. The limit of distribution is closely correlated with the tropical savanhan (summer rain) climate, which follows the 950mm annual rain fall. Altitude influence tsetse distribution through its effect on climate, particularly temperature [4] in Ethiopia, 1600 m.a.s.l was considered the upper altitudinal limit to tsetse distribution according to [6]. Subsequently, however, G. paladipes was found at altitude up to 2200m [10]. Therefor studies have needed and not yet been carried out on the distribution of tsetse fly in the study area.

The present study was conducted on identification of tsetse fly in two selected kebele and peasant association of gurage zone enemore ener district. It is located on the equator at 802’11’’ N⁰ latitude and 37⁰5’1’’ E⁰ longitude. The altitude of the study area ranges from 1000 to 3000 m.a.s.l and its total area is estimated to be 195,345,013 hectare of land. The distribution of the rain is bio medial with short rain from January to April and high rain from June to September. The average annual rain fall is 950mm and Enemornaener district and its surrounding is characterized by with minimum and maximum temperature ranging from 6 to 28 respectively.

To assess the apparent densities, distribution and species of tsetse flies and other biting flies’ survey conducted NGU traps baited with aceton and three-week-old cow urine [11] cds used for assessing the density. Site selection was done to include suitable tsetse live savanna area, rift valley, livestock grazing areas and watering points and vicinity to assumed wild game reserved areas. In all study sites a total of 20 NGU traps, 10 traps in shumoro river and 10 traps in jatu river side were deployed early in morning and manifested for 48hrs perceive flies densities traps were sited preferably in slender with good visibility and at suitable intervals depending on the ecology of the target species. Glossina species can detect odors from about 50-100 meters. So the traps were spaced at about 100 meter interval. During trapping acetone dispended from open vials while cow urine from open bottles in to the open bottle of cow urine apiece of tissue paper was included to tactile odor diffusion. All odors were placed on the ground about 30 cm up wind of the trap. The trap poles were grassed to exclude insect predators like ants [11].

The different flies cached in each trap were counted, identified and analyzed. The species of tsetse fly was identified based on the characteristics, morphology [6,12] other biting flies were spread according to their morphology characteristics such size, color, wing venation structure and proboscis at the genus level [13].

Sexing was done just by observing the posterior end of the ventral aspect of the abdomen by microscopic lens as a result male flies easily identified by enlarged hypopygium in the posterior ventral part of the abdomen. The fly apparent densities is the mean catch in traps deployed expressed at the number of fly catch per traps per day [14].

Parasitic diseases like mange mites, ticks, gastrointestinal helminthiasis and trypanosomiasis, bacterial diseases including blackleg, anthrax, contagious bovine pleuropneumonia, caprine pleuropneumonia, and mastitis were listed as most important livestock diseases in the area. From the questionnaire it was indicated that trypanosomiasis was the most important and the first cause of morbidity and mortality of cattle in Enemorena ener district, even after control program has been conducted for years by different stakeholders. Of these listed diseases, from 100 farmers 67(67%) of the interviewed farmers ranked trypanosomiasis as the priority disease affecting their cattle and the risk factor is lack of feed in dry season

During entomological survey two species of tsetse fly was identified Glossina paladipes and G. morsitance. A total of 37 tsetse flies were caught and identified at shumoro (river side), jatu (pastural land area). The mean catch G. morsitance and G. paladipes at shumoro (river side) was 0.25 and 0.75 flies/trape/day were at 0.35 and 0.45 flies/trap/day at the main catch jatu (pastural and landarea) respectively. The overall mean catch of G. morsitance and G. paladipes in shumoro and jatu 0.65 and 1.2 flies/trap/day respectively.

A total of 60 flies were captured out of which 61.6% belong to tsetse, 21.4% tabanus and 16.8 stomoxey. The tabanide fly group comprises tabanus, haematopota and chryoops while the muscida group belongs to stomoxys. From tsetse fly trapped female occupied large ratio out of total 37 flies captured 70.7% flies were females and the 29.73% comprises male.

On the present entomological survey G. morsitance and G. paladipes are the two species of tsetse detected in the study area with the apparent densities of 1.85 flies/trap/days and overall mean catch of G. morsitance and G. paladipes is 0.65 and 1.2 flies/trap/day respectively. This result shows closer apparent densities to different works. According to [14] the mean fly catch was 1.42 in gihibe valley the result is closer to this study and another report by [15] in Gamo gofa and Dawero zone infested with G. paladipes with apparent density of 1.8 flies/trap/days this was little higher than our finding. On the other hand the report that the Great Rift Valley was infested with G. paladipes with apparent density of 2.4 flies/trap/days and 0.64 flies/trap/days in wet dry season [16] our finding ranges in between 0.64 and 2.4 flies/trap/day. The overall 1.85 flies/trap/day in this study was aligned with the finding of [17] which is 1.82 flies/trap/day. The variations in flies densities may be due to the area of fly catch which favored trapping ample amount of flies and temperature below 15^oC in active and about 35^oC they seek refuge in rot holes in the trees and animal burrow and deep tissue in the bark, where they remain inactive. Humidity is also important factor for pupa and adult fly development. Cumulative effect long rainy season or dry season is taught to influence advanced and recession in tsetse population [4].

During the study period, for tsetse flies collected the sex ratio was assessed. Greater ratio of female to male (2.1) was recorded and similar results reported by other workers [16,18] in Somali and southern Ethiopia respectively. Leak [4] reported that in un based sample females would comprise 70-80% of the mean populations. The higher population of female may be attributed to the fact they live longer (mean female fly span being 8 weeks than male about 4 weeks). So that more female could be caught.

The result of the study revaluated that tsetse fly is the most important problem for agricultural activity and animal production in the study area acting as vector. From the species of tsetse flies G. paladipes is considered to be the main vector of the pathogenic trypanosome and biting flies such as tabanides and musides were also caught and these are considered very important for the possible mechanical transmission of disease. Based on the distribution of tsetse fly in the study area the control strategies has to be focused on strong sustainable and community based solution designed and implemented. Further epidemiological studies should be carried out and appropriate, feasible control of tsetse flies should be implemented.

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