Abstract
Resistance of the snail Biomphalaria glabrata to the trematode Schistosoma mansoni is correlated with allelic variation at copper-zinc superoxide dismutase (sod1). We tested whether there is a fitness cost associated with carrying the most resistant allele in three outbred laboratory populations of snails. These three populations were derived from the same base population, but differed in average resistance. Under controlled laboratory conditions we found no cost of carrying the most resistant allele in terms of fecundity, and a possible advantage in terms of growth and mortality. These results suggest that it might be possible to drive resistant alleles of sod1 into natural populations of the snail vector for the purpose of controlling transmission of S. mansoni. However, we did observe a strong effect of genetic background on the association between sod1 genotype and resistance. sod1 genotype explained substantial variance in resistance among individuals in the most resistant genetic background, but had little effect in the least resistant genetic background. Thus, epistatic interactions with other loci may be as important a consideration as costs of resistance in the use of sod1 for vector manipulation.
Highlights
Vector-borne diseases account for approximately onesixth of the global human disease burden [1,2], we still lack effective drugs and vaccines for many of these diseases
We investigated the utility of one gene for driving resistance associated alleles into populations of the snail Biomphalaria glabrata, a vector of the trematode parasite of humans, Schistosoma mansoni
Under controlled laboratory conditions we found no evidence for costs of resistance associated with carrying the most resistant allele at sod1
Summary
Vector-borne diseases account for approximately onesixth of the global human disease burden [1,2], we still lack effective drugs and vaccines for many of these diseases. In the absence of vaccines, eradication efforts that include both drug therapy and vector control can be the most effective approach [4]. Vector control methods most often utilize chemicals for eradication [1,4]. This approach has obvious drawbacks because it results in habitat degradation and risk of human exposure to pesticides. Recurrent pesticide application is often necessary because it is nearly impossible, with a single treatment, to completely remove all possible vector individuals from an epidemiologically relevant site [5]
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