Tsetse fly disease ecology and population genetics of Uganda

The riverine tsetse fly Glossina fuscipes fuscipes (Gff) is the primary vector for human and animal African trypanosomiasis in Uganda and the Lake Victoria basin in Kenya. Despite eradication efforts, the tsetse fly populations persist and endanger thousands of lives and impose a large economic burden. To improve knowledge of tsetse population size and density, we test the hypothesis that estimates of population size from genetic and trapping data can provide accurate on-the-ground assessments of tsetse fly density and dispersal and subsequent correlation between effective population size and average flies caught per day. Our approach used genetic data that consisted of 11 polymorphic microsatellite loci from 2,414 individual flies collected from 87 localities, and trapping records from 2,580 biconical traps placed in 158 localities. Both data sources span the geographic distribution of Gff across Uganda and the Lake Victoria basin in Kenya, and within the time frame of 2006-2018. To test our hypothesis, we estimated effective population size (Ne) from genetic data and average fly trap yield (flies/trap/day) from trapping records per time step and locality and tested for correlation between these estimates with a generalized linear model. Results indicated variation in Ne and fly trap yield across the landscape, with our hypothesis supported in only some subsets of the data. This indicates there is a need to further develop methods estimating population size of this system, an essential step towards predicting tsetse population density, dispersal, and infectivity, all essential parameters for controlling this neglected tropical disease.