Exposure and resistance to anticoagulant rodenticides in invasive and endemic Chadian urban rodent species to develop a rational management strategy

Abstract

Rodent management involves the use of anticoagulant rodenticides (ARs). This use has resulted in the selection of numerous resistance alleles in the Vkorc1 gene, encoding the target enzyme of ARs. In Africa, while rodents are a major problem due to their transport and transmission of zoonotic pathogens and damage to crops, the use of ARs and the spread of resistance alleles are poorly documented. We attempted to address both issues in Chad which is one of the largest countries in Africa. Due to this location at the crossroads of central and northern Africa, Chad is representative of many African countries. Using a sampling of nearly 300 rodents composed of invasive and endemic rodents collected in 6 of Chad's largest cities, exposure to ARs was analyzed by their quantification in the liver; the spread of AR resistance alleles was analyzed by Vkorc1 sequencing. We demonstrate the use of both ARs generations in Chadian cities and report the total sequencing of the Vkorc1 for 44 M. natalensis with detection of two different haplotypes, the sequencing of the Vkorc1 for 2 other endemic rodent species, M. kollmannspergeri and A. niloticus, and finally the detection of three new missense mutations, V29E, V69E, D127V in R. rattus. potentially associated to resistance to ARs.

These results should argue for the implementation of a reasoned management of rodent populations in Africa to avoid the spread of ARs resistance alleles.

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