The population structure of Glossina fuscipes fuscipes in the Lake Victoria basin in Uganda: implications for vector control
- Equal contributors
1 Department of Ecology and Evolutionary Biology, Yale University, 21 Sachem Street, New Haven, CT, USA
2 Department of Biology, Makerere University, College of Natural Sciences, School of Bio-Sciences, P.O. Box 7062, Kampala, Uganda
3 Creation of Sustainable Tsetse and Trypanosomiasis Free Areas in Uganda project, Ministry of Agriculture, Animal Industry and Fisheries, P.O. Box 102, Entebbe, Uganda
4 National Livestock Resources Research Institute, Tororo, Uganda, P.O. Box 96, Tororo, Uganda
5 Trypanosomiasis Research Centre, Kenya Agricultural Research Institute, P.O. Box 362–00902, Kikuyu, Kenya
6 Yale School of Public Health, Yale University, 60 College Street, New Haven, CT, USA
Parasites & Vectors 2012, 5:222 doi:10.1186/1756-3305-5-222Published: 4 October 2012
Glossina fuscipes fuscipes is the primary vector of trypanosomiasis in humans and livestock in Uganda. The Lake Victoria basin has been targeted for tsetse eradication using a rolling carpet initiative, from west to east, with four operational blocks (3 in Uganda and 1 in Kenya), under a Pan-African Tsetse and Trypanosomiasis Eradication Campaign (PATTEC). We screened tsetse flies from the three Ugandan PATTEC blocks for genetic diversity at 15 microsatellite loci from continental and offshore populations to provide empirical data to support this initiative.
We collected tsetse samples from 11 sites across the Lake Victoria basin in Uganda. We performed genetic analyses on 409 of the collected tsetse flies and added data collected for 278 individuals in a previous study. The flies were screened across 15 microsatellite loci and the resulting data were used to assess the temporal stability of populations, to analyze patterns of genetic exchange and structuring, to estimate dispersal rates and evaluate the sex bias in dispersal, as well as to estimate demographic parameters (NE and NC).
We found that tsetse populations in this region were stable over 4-16 generations and belong to 4 genetic clusters. Two genetic clusters (1 and 2) corresponded approximately to PATTEC blocks 1 and 2, while the other two (3 and 4) fell within PATTEC block 3. Island populations grouped into the same genetic clusters as neighboring mainland sites, suggesting presence of gene flow between these sites. There was no evidence of the stretch of water separating islands from the mainland forming a significant barrier to dispersal. Dispersal rates ranged from 2.5 km per generation in cluster 1 to 14 km per generation in clusters 3 and 4. We found evidence of male-biased dispersal. Few breeders are successfully dispersing over large distances. Effective population size estimates were low (33–310 individuals), while census size estimates ranged from 1200 (cluster 1) to 4100 (clusters 3 and 4). We present here a novel technique that adapts an existing census size estimation method to sampling without replacement, the scheme used in sampling tsetse flies.
Our study suggests that different control strategies should be implemented for the three PATTEC blocks and that, given the high potential for re-invasion from island sites, mainland and offshore sites in each block should be targeted at the same time.