Abstract
Genetic-modification strategies are currently being developed to reduce the transmission of vector-borne diseases, including African trypanosomiasis. For tsetse, the vector of African trypanosomiasis, a paratransgenic strategy is being considered: this approach involves modification of the commensal symbiotic bacteria Sodalis to express trypanosome-resistance-conferring products. Modified Sodalis can then be driven into the tsetse population by cytoplasmic incompatibility (CI) from Wolbachia bacteria. To evaluate the effectiveness of this paratransgenic strategy in controlling African trypanosomiasis, we developed a three-species mathematical model of trypanosomiasis transmission among tsetse, humans, and animal reservoir hosts. Using empirical estimates of CI parameters, we found that paratransgenic tsetse have the potential to eliminate trypanosomiasis, provided that any extra mortality caused by Wolbachia colonization is low, that the paratransgene is effective at protecting against trypanosome transmission, and that the target tsetse species comprises a large majority of the tsetse population in the release location.
Highlights
African trypanosomiasis infects 30,000 people in sub-Saharan Africa
We evaluated the effectiveness of a paratransgenic strategy, transgenic Sodalis driven by Wolbachia, to control African trypanosomiasis
Previous mathematical models have examined the invasion of Wolbachia into populations of fruit flies [9], mosquitoes [16], and tsetse [17], but the analysis we present here is the first to incorporate the epidemiology of the trypanosome disease system with the population genetics of cytoplasmic incompatibility (CI) dynamics
Summary
African trypanosomiasis infects 30,000 people in sub-Saharan Africa. Losses in livestock production due to African trypanosomiasis are estimated at US$1 billion annually [2]. Control efforts primarily target the tsetse vector by insect traps, insecticide spraying of land and livestock, and sterile-insect technique [3]. Instead of trypanosomiasisrefractory genes being incorporated into the tsetse genome directly, these genes may be encoded in Sodalis, commensal bacteria that colonize the gut of tsetse [8]. This mode of gene expression is termed paratransgenesis, where changes in the insect are induced by modifying genes of a commensal organism
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