Dynamics of tsetse natural infection rates in the Mouhoun river, Burkina Faso, in relation with environmental factors

Abstract

In Burkina Faso, the cyclical vectors of African animal trypanosomoses (AAT) are riverine tsetse species, namely Glossina palpalis gambiensis Vanderplank (G.p.g.) and Glossina tachinoides Westwood (G.t.) (Diptera: Glossinidae). Experimental work demonstrated that environmental stress can increase the sensitivity of tsetse to trypanosome infection. Seasonal variations of the tsetse infection rates were monitored monthly over 17 months (May 2006–September 2007) in two sites (Douroula and Kadomba). In total, 1423 flies were dissected and the infection of the proboscis, middle intestine and salivary glands was noted. All the positive organs were analyzed using monospecific polymerase chain reaction (PCR) primers. To investigate the role of different environmental factors, fly infection rates were analyzed using generalized linear mixed binomial models using the species, sex, and monthly averages of the maximum, minimum and mean daily temperatures, rainfalls, Land Surface Temperature day (LSTd) and night (LSTn) as fixed effects and the trap position as a random effect. The overall infection rate was 10% from which the predominant species was T. congolense (7.6% of the flies), followed by T. vivax (2.2% of the flies). The best model (lowest AICc) for the global infection rates was the one with the maximum daily temperature only as fixed effect (p < 0.001). For T. congolense, the best model was the one with the tsetse species, sex, maximum daily temperature and rainfalls as fixed effect, where the maximum daily temperature was the main effect (p < 0.001). The number of T. vivax infections was too low to allow the models to converge. The maturation rate of T. congolense was very high (94%), and G. t. harbored a higher maturation rate (p = 0.03). The results are discussed in view of former laboratory studies showing that temperature stress can increase the susceptibility of tsetse to trypanosomes, as well as the possibility to improve AAT risk mapping using satellite images.

Variations of Glossina sp. and trypanosome species frequency within different habitats in a sleeping sickness focus, Gabon

“…The present findings also showed that trypanosome prevalence is different between male and female flies. These results are similar to those found elsewhere [9,28]. The infection was due to three species and subspecies: T. congolense savannah predominated, followed by T. brucei brucei and T. brucei gambiense.…”

Seasonal variation of tsetse fly species abundance and prevalence of trypanosomes in the Maasai Steppe, Tanzania

“…Temporal abundance of tsetse flies was estimated by monthly sampling for a period of 15 months in 2014 and 2015 in the village of Emboreet, which borders Tarangire National Park (Figure ). Sites were selected through stratified random subsampling of the major vegetation types in the area (Bouyer et al ). A total of ten sites were identified and three epsilon traps were deployed at each site and located at least 200 m apart (Malele et al ).…”

Adult blood-feeding tsetse flies, trypanosomes, microbiota and the fluctuating environment in sub-Saharan Africa

“…Increasing the number of livestock in farmlands drastically alters the subSaharan African environment by modifying not only the livestock distribution, but also the distribution of tsetse flies that feed on it (and possibly their nutritional behavior). Indeed, the importance of environmental factors to transmission intensity and trypanosome distribution is increasingly being recognized (Van den Bossche et al, 2010;Bouyer et al, 2013). Accordingly, a recent study of climate change effects on the evolution of African trypanosomiasis predicts that 46-77 million additional people will be at risk of sleeping sickness by 2090 (Moore et al, 2012).…”