Abstract:
Resistance of rodents to anticoagulant rodenticides has emerged in several areas across the
world. Single nucleotide mutations in the vkorc1 gene have been shown to elicit various levels of
anticoagulant resistance, and these mutations are prevalent in several Rattus and Mus musculus
populations. In sub-Saharan Africa, the Natal multimammate mouse, Mastomys natalensis, is
one of the most damaging pests to crops, and anticoagulant poisons such as bromadiolone are
frequently used to control these rodents in agricultural fields. Here, we investigate if vkorc1 shows
any polymorphism in natural populations of M. natalensis. We sequenced the third exon of vkorc1
of 162 M. natalensis captured from 14 different agricultural sites in Morogoro Region, Tanzania. In
addition to 6 SNPs in the noncoding flanking region, we detected 3 nonsynonymous SNPs in this
exon: 10 animals (6.2%) carried a Leu108Val variant, 2 animals (1.2%) an Ala140Thr variant, and 1
animal (0.6 %) an Arg100His variant, all 3 in heterozygous form. Ala140Thr is just one residue from
a mutation known to be involved in anticoagulant resistance in Rattus and Mus. While in vitro or
in vivo experiments are needed to link vkorc1 genetic polymorphisms to level of VKOR activity
and anticoagulant susceptibility, our results suggest that M. natalensis individuals may vary in
their response to anticoagulant rodenticides. This is the first vkorc1 sequence data from a species
outside the Rattus or Mus genera, and for the first time from a rodent species endemic to Africa.
