Trypanosome infection rate in Glossina tachinoides: infested rivers of Limmu Kosa District Jimma Zone, Western Ethiopia

Prevalence of Spiroplasma and interaction with wild Glossina tachinoides microbiota

Tsetse flies (Diptera: Glossinidae) are vectors of the tropical neglected diseases sleeping sickness in humans and nagana in animals. The elimination of these diseases is linked to control of the vector. The sterile insect technique (SIT) is an environment-friendly method that has been shown to be effective when applied in an area-wide integrated pest management approach. However, as irradiated males conserve their vectorial competence, there is the potential risk of trypanosome transmission with their release in the field. Analyzing the interaction between the tsetse fly and its microbiota, and between different microbiota and the trypanosome, might provide important information to enhance the fly's resistance to trypanosome infection. This study on the prevalence of Spiroplasma in wild populations of seven tsetse species from East, West, Central and Southern Africa showed that Spiroplasma is present only in Glossina fuscipes fuscipes and Glossina tachinoides. In G. tachinoides, a significant deviation from independence in co-infection with Spiroplasma and Trypanosoma spp. was observed. Moreover, Spiroplasma infections seem to significantly reduce the density of the trypanosomes, suggesting that Spiroplasma might enhance tsetse fly's refractoriness to the trypanosome infections. This finding might be useful to reduce risks associated with the release of sterile males during SIT implementation in trypanosome endemic areas.

Glossina pallidipes Density and Trypanosome Infection Rate in Arba Minch Zuria District of Gamo Zone, Southern Ethiopia

Background

African trypanosomosis is a disease of both animals and humans resulting from infection with parasitaemic protozoa of the genus Trypanosoma transmitted mainly by the tsetse flies (Glossina species). The disease has been reported in different parts of the country. However, information on the apparent density and trypanosome infection rates of the vectors is very limited in the Southern part of Ethiopia. Therefore, this study was conducted to estimate the apparent density, infection rate of trypanosomes in Glossina pallidipes, and the trypanosome species involved in Arba Minch Zuria district of Southern Ethiopia.

Methods

A cross-sectional study was conducted from January to June 2018 in two purposely selected kebeles of Arbaminch Zuria district and in the escarpments of Nech Sar National Park of Southern Ethiopia. For entomological survey, a total of 40 standard NGU traps were deployed around the watering and grazing areas. A total of 300 fresh Glossina pallidipes were examined for trypanosome infection using a dissection procedure as described by the FAO Training manual for tsetse control personnel.

Results

The study revealed the presence of only one Glossina species, known as Glossina pallidipes, and biting flies including Stomoxys and Tabanus. A total of 2176 flies were caught of which 1803 (82.86%) belong to Glossina pallidipes and the remaining 373 (17.14%) were biting flies. The overall apparent density of Glossina pallidipes and biting flies in the study area were 15.03 fly/trap/day (F/T/D) and 3.11 F/T/D, respectively. Relatively higher Glossina pallidipes and biting flies, respectively, were caught in a wood-grass land (15.87 F/T/D and 3.69 F/T/D) and riverine forest (15.13 F/T/D and 3.42 F/T/D) than bush land vegetation types (13.87 F/T/D and 1.76 F/T/D). The overall trypanosome infection rate of Glossina pallidipes was 17.67% (53/300). Two trypanosome species, namely, Trypanosoma congolense (66.04%) and Trypanosoma vivax (33.96%), were responsible for Glossina pallidipes infection in the study area. Trypanosome infection rate was significantly higher in female G. pallidipes than in male (OR = 3.39, 95%CI = 1.53‐7.52). Significantly, higher trypanosome infection rate was observed in flies older than 20 days (OR = 2.5, 95%CI = 1.12‐5.56) and in hunger stage 1 flies (OR = 14.24, 95%CI = 4.01‐50.59). Glossina pallidipes infection was significantly higher in and around park grazing areas (OR = 3.41, 95%CI = 1.76‐6.6) and wood-grass land vegetation type (OR = 2.7, 95%CI = 1.2‐6.5).

Conclusion

The current study revealed high apparent density and trypanosome infection in Glossina pallidipes in Arba Minch Zuria district of Southern Ethiopia. So, this study warrants the need for strengthening both vector and parasite control strategies in the study area.

Seasonal Patterns: Bovine Trypanosomosis, Glossina pallidipes Density, and Infection in Rift Valleys of Gamo Zone, Southern Ethiopia

Bovine trypanosomosis is a parasitic disease causing serious economic losses in livestock productivity and agricultural development. The disease has been reported in different parts of Ethiopia. However, seasonal pattern of trypanosomosis, tsetse fly apparent density, and infection are very limited in the southern rift valley of the country, particularly in Gamo Zone. Therefore, the objective of this cross-sectional study design was to estimate seasonal prevalence of bovine trypanosomosis, assessing tsetse fly apparent density and its infection by trypanosomes. For the parasitological study, a total of 600 cattle (300 in each season) were sampled and assayed using the buffy coat technique. A total of 80 standard NGU traps were deployed around the watering and grazing areas for the entomological survey. An overall prevalence of trypanosomosis was 10.17% (61/600), of which 7.33% (22/300) and 13% (39/300) accounted for the dry and wet seasons, respectively. The prevalence of trypanosomosis was significantly higher during the wet season (OR = 2.47; p < 0.05), in black coat color (OR = 7.2, p < 0.05), and poor body-conditioned (OR = 3.15; p < 0.05) animals. Two species of trypanosomes, Trypanosoma congolense, 68.85% (42/61), and Trypanosoma vivax, 31.15% (19/61), were circulating in the area. The mean PCV value in infected animals (22.56 ± 4.61) was significantly lower than in non-infected animals (25.3 ± 4.75). Entomological result indicated that Glossina pallidipes (G. pallidipes) was the only species of tsetse found in the study area. Totally, 3,789 flies were caught of which 81.42% (3,085/3,789) belong to G. pallidipes and 18.58% (704/3,789) were other biting flies. The overall apparent density of G. pallidipes was 12.85 flies/trap/day (FTD). Relatively higher G. pallidipes/trap/day were caught in the wet season (13.64 F/T/D) than in the dry season (12.07F/T/D). Of the flies caught, 342 G. pallidipes were randomly selected and dissected. The overall proportion of G. pallidipes infection was 18.42% (63/342) of which 12.28% (21/171) and 24.56% (42/171) were accounted in the dry and wet seasons, respectively. Infection in G. pallidipes was significantly higher during the wet season (OR = 2.32; p < 0.05) and in park grazing areas (OR = 2.45; p < 0.05). In conclusion, trypanosomosis is the major challenge for cattle productivity in the district. So this study warrants the need for strengthening the vector and parasite control interventions in the area.

Epidemiological investigation of bovine trypanosomosis and distribution of vectors in Jimma zone, Ethiopia

Trypanosomosis is highly reliant on the distribution of vectors responsible for transmission. A cross-sectional study was conducted to determine the prevalence and associated risk factors of bovine trypanosomosis as well as the distribution of vectors in the Jimma zone, Ethiopia. Blood samples from a total of 2088 cattle were collected and tested using a buffy coat and Giemsa techniques. An overall 13.36% prevalence of trypanosomosis was recorded in study areas. The highest proportion of the infections was caused by T. vivax (44.80%) followed by T. congolense (36.92%) and mixed infection (18.28%) of both species. The study also revealed that trypanosomosis was associated with anemia as the mean PCV was significantly lower among trypanosome-infected animals (20.34 ± 4.39) than non-infected ones (27.98 ± 3.68). Moreover, anemia was more pronounced with T. congolense infection (19.54 ± 3.22) than T. vivax (21.07 ± 3.96) and mixed infection of both species (20.16 ± 2.71). This study identified age, body condition, and agro-ecology as risk factors for the occurrence of trypanosomosis in cattle. Vector survey was conducted by deploying 377 mono-pyramidal traps in selected districts. Accordingly, Glossina species and other biting flies (Stomoxys and Tabanus) were identified with an apparent density of 5.27 and 1.74 fly/trap/day, respectively. Moreover, a higher 4.49 fly/trap/day of G. tachinoides than G. morsitans submorsitans (0.79 fly/trap/day) was noted in study areas. The present study indicated that trypanosomosis is the major cattle production constraint in the areas. Hence, applicable management techniques of the disease and its vector should be implemented and further investigation involving molecular technique should be conducted in different seasons.

Concurrent Infection of Fascioliasis andTrypanosomosis and Associated Risk Factors in Local Zebu Breed Cattle of Western Ethiopia

Background

A cross-sectional study was conducted from late October 2016 to June 2017, with the primary objective of estimating and analyzing the concurrent occurrence of both fascioliasis and trypanosomosis infections and associated risk factors along the tsetse-infested Didessa river basin.

Methods

The methodology applied was based on stratified sampling for the parasitological study, with entomological and malacological surveys, including fly dissection.

Results

The result of variance-ratio testing between trypanosomosis and fascioliasis infections (mean prevalence 0.117±0.322 and 0.283±0.451, respectively), was statistically significant (P[F>f]=0), with higher observed fascioliasis infection (n=147, 28.27%). Severe anemia was observed in trypanosomosis infection, with mean packed cell volume of 19.57 (OR=0.71, P>|z|=0.000), and vast fascioliasis infections identified among cattle with medium and poor body condition in terms of weight (n=91 [32.73%] and n=38 [21.47%]). On entomological study, 578 (62.62%) and 345 (37.38%) female and male Glossina tachinoides fly species were cached, respectively, with overall mean flies/trap/day of 5.19 (n=923). Despite the prevalence of trypanosomosis in infected cattle, of 130 G. tachinoides flies dissected, only three were found to be positive for an infection rate of 2.31%. Malacological study identified three snail species known to maintain fascioliasis: Lymnea truncatula (n=28, 45.16%), Lymnea natalensis (n=23, 37.10%), and Biomphalaria (n=11, 17.74%). Concurrent infection with fascioliasis and trypanosomosis was mainly associated with the co-occurrence of their intermediate host snails and Glossina flies, respectively, with 4.42% (n=23) prevalence.

Conclusion

This study clearly demonstrated that the former parasite was highly associated with emaciation, whereas the second was responsible for anemia. In future,researchers should focus solely on estimating meat and milk production of local cattle to assess the economic impact of the study parasites.