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

A systematic review and meta-analysis on prevalence of bovine trypanosomosis in East Africa

Bovine trypanosomosis is an incapacitating and lethal ailment brought about by protozoan parasites of the genus Trypanosoma. The disease leads to losses in livestock and agricultural productivity, resulting in significant socio-economic repercussions. In East Africa, trypanosomosis has been endemic for an extensive period due to ecological factors and vector biology that facilitate the persistent circulation of trypanosomes. This investigation outlines the occurrence of bovine trypanosomosis in East Africa through a meta-analysis. A thorough search was conducted on PubMed, Google Scholar, Scopus, Web of Science and AJOL. Suitable studies were chosen using inclusion and exclusion criteria. The prevalence was estimated through a random effect model. Publication bias and the variation in prevalence estimates due to heterogeneity were also evaluated. The analysis was performed on 115 studies that contained relevant prevalence data. The collective estimate of bovine trypanosomosis prevalence across the studies stood at 12% (95% CI: 11, 13), ranging from 1% (95% CI: 0, 2) to 51% (95% CI: 45, 58). The subgroup analysis by country revealed considerable disparities in prevalence. The highest estimated prevalence was 24% (95% CI: 18, 30) in Somalia, whereas the lowest prevalence was observed in Ethiopia at 10% (95% CI: 9, 11). A significant level of heterogeneity was noted in most pooled estimates, even after conducting subgroup analysis. The visual examination of the funnel plot and the Egger's regression asymmetry coefficient (b = -5.13, 95% CI: -7.49, -2.76, p = 0.00) and Begg's plot (p = 0.00) indicate the presence of publication bias. In conclusion, bovine trypanosomosis is a pervasive and noteworthy malady affecting livestock. The findings of this investigation imply a high prevalence of bovine trypanosomosis in the majority of the countries under scrutiny. Despite the well-known hindrance that livestock trypanosomosis poses to livestock production in Africa, little attention has been devoted to the trypanosomosis situation, particularly in East African nations.

Epidemiological study on cattle trypanosomiasis and its vectors distributions in the Gambella regional state, southwestern Ethiopia

African animal trypanosomosis is a parasitic disease that causes significant economic losses in livestock due to anaemia, loss of condition, emaciation, and mortality. It is a key impediment to increased cattle output and productivity in Ethiopia. Cross-sectional entomological and parasitological studies were performed in the Gambella Region state of southwestern Ethiopia to estimate the prevalence of bovine trypanosomosis, apparent fly density, and potential risk factors. Blood samples were taken from 546 cattle for the parasitological study and analyzed using the buffy coat technique and stained with Giemsa. A total of 189 biconical (89) and NGU (100) traps were deployed in the specified districts for the entomological survey. The overall prevalence of trypanosomosis at the animal level was 5.5% (95% CI: 3.86-7.75). Trypanosoma vivax (50.0%), T. congolense (30.0%), T. brucei (20.0%), and no mixed trypanosome species were found. The prevalence of trypanosomosis was significantly (p < 0.05) affected by altitude, body score conditions, age, mean packed cell volume (PCV), and peasant associations, while sex and coat color had no significant effect. According to the entomological survey results, a total of 2303 flies were captured and identified as tsetse (Glossina pallidipes (5.3%)) and G. fuscipes fuscipes (3.3%) and other biting flies (Tabanus (60.1%) and Stomoxys (31.3%)). In the current study, the overall apparent density was 4.1 flies/trap/day. This study shows that trypanosomosis remains a significant cattle disease in the Gambella regional state even during the dry season. Thus, the findings support the necessity to improve vector and parasite control measures in the area.

Prevalence, Risk Factors and Control Practices of Livestock Hirudiniasis in Mirab Abaya District, Southern Ethiopia

Purpose

Hirudiniasis is a disease in people and animals who have been infested by blood sucking leeches. In Ethiopia, it is a neglected disease, causing significant economic loss in the livestock industry. In the study area, information on livestock Hirudiniasis is very limited. Therefore, this study was conducted to assess livestock owners' awareness, knowledge, and control practices toward leech infestation, and to estimate the prevalence and associated risk factors of livestock Hirudiniasis.

Methods

A cross-sectional study was carried out from February to September 2022 on domestic animals randomly selected from livestock owners of Mirab Abaya district, Southern Ethiopia. In total, 384 domestic animals were sampled and examined for the presence of leech infestation. A questionnaire survey was carried out on 150 livestock owners.

Results

This study discovered a 13.54% (52/384) overall prevalence of livestock Hirudiniasis in the study area and the highest prevalence was observed in cattle (22.14%), followed by sheep (10%), goats (8.65%), and equines (5%). Limnatis nilotica was the only leech species identified in the study area. The occurrence of livestock Hirudiniasis was significantly higher in the dry season (OR=3.16, p<0.05), around bodies of water (OR=10.88, p<0.01), in extensive production systems (OR=3.81, p<0.05), and in adult (OR=2.58, p<0.05) and poor body condition animals (OR=9, p<0.01). However, the species and sex of domestic animals were not significantly associated with Hirudiniasis. The questionnaire showed 61.33% and 35.33% of respondents had knowledge about leech infestations in domestic animals and its zoonotic impacts, respectively. Manual removal and traditional medicine are common control measures taken by livestock owners against Hirudiniasis.

Conclusion

The present study showed that leeches were prevalent and significantly affects the health and productivity of livestock in the study area. Hence, cost-effective parasitic control measures need to be implemented to address the setback.

Evaluating the efficacy of various traps in catching tsetse flies at Nech Sar and Maze National Parks, Southwestern Ethiopia: An Implication for Trypanosoma Vector Control

Tsetse flies are the vector of protozoan parasite of the genus Trypanosoma, the causative agent of human African sleeping sickness and animal trypanosomiasis. Traps such as Nguruman (NGU), biconical and sticky traps are in use for tsetse flies sampling and monitoring. However, there is no evidence regarding their comparative efficiency in catching flies using olfactory cues. Therefore, the present study aimed to evaluate the efficiency of different types of traps in catching tsetse flies at Nech Sar and Maze National Parks, Southwestern Ethiopia. The study was done for six consecutive months from February to July 2019. Briefly, a 3×4 Latin square design was performed, and tsetse flies were collected for three days each month in four different vegetation types, including wood grassland, bush land, forest, and riverine forest. To avoid trapping position bias, rotation of traps has been done every day. Almost all (99.5%) of the flies were Glossina pallidipes and the remaining were G. fuscipes. The latter were present only at Maze national park. NGU traps were the most efficient type with 12.1 flies/trap/day at Nech Sar National Park and it was 2.2 flies/trap/day at Maze National Park followed by biconical and sticky traps. The number of tsetse flies collected by biconical trap was three-fold lower than NGU trap, and it was four-fold lower in sticky trap than NGU trap in both Nech Sar and Maze National Parks. A substantial number (41%) of G. pallidipes were collected from woody grassland (WGL). In conclusion, G. pallidipes monitoring and evaluation activities could consider NGU trap model as it performed better in most vegetation types in the region.

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.