Assessment of pastoralists’ vulnerability to trypanosomiasis and effects of climate on tsetse and trypanosomes distribution in Tanzania’s Maasai steppe

Abstract

For decades, pastoralists have had their adaptation strategies that enable them to thrive in harsh environments. However, changing climate and land management regimes, coupled with under-investments in pastoral areas, threaten to overwhelm pastoralists’ traditional adaptation methods. This could potentially increase vulnerability of pastoral communities to multiple stressors, including trypanosomiasis. Trypanosomiasis is caused by a parasitic protozoan of Trypanosoma spp where tsetse flies are the main vector. Trypanosomiasis is a neglected tropical disease, yet a disease of public health and socio-economic concern. It exacerbates economic hardships due to loss of livestock or through additional costs needed to control and treat the disease. Despite these concerns, information about where and when to expect high burden of tsetse flies and trypanosomes remain limited, and control strategies, if offered, are often ineffective. This study therefore assessed pastoralists’ vulnerability to trypanosomiasis, seasonality of tsetse fly abundance, prevalence of trypanosome infections in the vector, and potential impacts of climate change on tsetse fly distribution. The study incorporated social and ecological analytical techniques including ArcGIS 10.4, polymerase chain reaction (PCR) and species distribution modelling (SDM). Emboreet and Loibor-Sireet Wards in Simanjiro district were identified as the most vulnerable locations to trypanosomiasis. Three tsetse fly species (Glossina m. morsitans, Glossina pallidipes and Glossina swynnertoni) and three trypanosome species (T.vivax, T.congolense and T. brucei) were found in the study area. Tsetse fly relative abundance and trypanosome prevalence peaked in July and October, respectively. Maximum and minimum temperature negatively affected abundance of G. m. morsitans and G. swynnertoni, respectively. Trypanosome prevalence was negatively correlated with tsetse abundance but positively correlated with temperature. The climate tsetse fly relationships were used in the SDM to show that by the year 2050, the habitable area of G. m. morsitans, G. pallidipes and G. swynnertoni may decrease to 23.13%, 12.9% and 22.8% of current suitable habitat (19 224.58 km2 , 7113.37 km2 and 32 335.27 km2 ), respectively in the study area. These results provide useful information to inform communities, health and livestock development sectors and tsetse fly control units on where and when to expect the highest risk of trypanosomiasis infection in the Maasai Steppe and plan accordingly. ii Keywords: Pastoralist, vulnerability, trypanosomiasis, adaptation, tsetse, trypanosome prevalence, seasonality, SDM, Maasai Steppe, Tanzania