The tsetse fly, which serves as the vector for human African trypanosomiasis (HAT), may have very selective feeding preferences when choosing its wildlife hosts, according to a PLOS ONE study by Harriet Auty of the Epidemiology Research Unit at Scotland’s Rural College and her colleagues.
HAT, also called acute sleeping sickness, is endemic to sub-Saharan Africa and is transmitted by the tsetse fly, which picks up parasites known as trypanosomes from infected humans or animals. Although past research has identified numerous host wildlife species through tsetse blood meals, the tsetse fly’s relative preference for different hosts has been unclear.
To investigate tsetse fly feeding preferences, Auty and colleagues quantified the density of wildlife at a study site in the Serengeti National Park, Tanzania, and analyzed the blood meals of two different tsetse species, Glossina swynnertoni and Glossina pallidipes, for the presence of trypanosomes. Genetic sequencing technology enabled them to identify the specific host species recently bitten by the flies.
The researchers found that the tsetse flies exhibited strong host feeding preferences regardless of wildlife density. G. swynnertoni preferentially took blood meals from warthogs and giraffes, which were present at relatively low density compared to other potential hosts, while G. pallidipes fed selectively on buffaloes, elephants and giraffes.
In spite of their abundance, the impala, Thomson’s gazelle, zebra and wildebeest were not fed on by the G. swynnertoni tsetse flies in the study. Similarly, G. pallidipes did not feed on the impala, Thomson’s gazelle or wildebeest. The researchers noted that these animals may exhibit more defensive strategies, such as skin-rippling, kicking and tail-flicking, which could deter tsetse flies. The authors also hypothesize that the wildlife species most commonly fed on may share a tolerance for trypanosome infections.
The researchers note that some animals, including the impala, Thomson’s gazelle, zebra and wildebeest, were not selected as hosts despite their abundance. These animals may exhibit more defensive strategies, such as skin-rippling, kicking, and tail-flicking, which could deter tsetse flies. The authors also hypothesize that the wildlife species most commonly fed on may share a tolerance for trypanosome infections.
This is the first study to use genetic sequencing technology to collect robust data on the hosts of tsetse blood meals while also assessing the density of wildlife hosts. The findings could aid further study of the epidemiology of HAT in rural wilderness areas of sub-Saharan Africa.
Research Article: Auty H, Cleaveland S, Malele I, Masoy J, Lembo T, Bessell P, et al. (2016) Quantifying Heterogeneity in Host-Vector Contact: Tsetse (Glossina swynnertoni and G.pallidipes) Host Choice in Serengeti National Park, Tanzania. PLoS ONE 11(10): e0161291. doi:10.1371/journal.pone.0161291
Image Credit: Oregon State University, Flickr