Abstract
BackgroundThe flea Xenopsylla cheopis (Siphonaptera: Pulicidae) is a vector of plague. Despite this insect’s medical importance, especially in Madagascar where plague is endemic, little is known about the organization of its natural populations. We undertook population genetic analyses (i) to determine the spatial genetic structure of X. cheopis in Madagascar and (ii) to determine the potential risk of plague introduction in the neighboring island of Mayotte.ResultsWe genotyped 205 fleas from 12 sites using nine microsatellite markers. Madagascan populations of X. cheopis differed, with the mean number of alleles per locus per population ranging from 1.78 to 4.44 and with moderate to high levels of genetic differentiation between populations. Three distinct genetic clusters were identified, with different geographical distributions but with some apparent gene flow between both islands and within Malagasy regions. The approximate Bayesian computation (ABC) used to test the predominant direction of flea dispersal implied a recent population introduction from Mayotte to Madagascar, which was estimated to have occurred between 1993 and 2012. The impact of this flea introduction in terms of plague transmission in Madagascar is unclear, but the low level of flea exchange between the two islands seems to keep Mayotte free of plague for now.ConclusionThis study highlights the occurrence of genetic structure among populations of the flea vector of plague, X. cheopis, in Madagascar and suggests that a flea population from Mayotte has been introduced to Madagascar recently. As plague has not been reported in Mayotte, this introduction is unlikely to present a major concern for plague transmission. Nonetheless, evidence of connectivity among flea populations in the two islands indicates a possibility for dispersal by fleas in the opposite direction and thus a risk of plague introduction to Mayotte.
Highlights
The flea Xenopsylla cheopis (Siphonaptera: Pulicidae) is a vector of plague
Eighty-six per cent of suspected cases reported in Madagascar between 2007 and 2011 were classified as bubonic plague [14], reflecting the important role played by flea vectors in the transmission cycle
Our objectives were : (i) to determine the genetic diversity and spatial genetic structure of X. cheopis populations in Madagascar; (ii) to determine the extent and pattern of any gene flow between X. cheopis populations in Madagascar and Mayotte, which may constitute an indication of plague introduction risk
Summary
The flea Xenopsylla cheopis (Siphonaptera: Pulicidae) is a vector of plague Despite this insect’s medical importance, especially in Madagascar where plague is endemic, little is known about the organization of its natural populations. The oriental rat flea, Xenopsylla cheopis (Siphonaptera: Pulicidae) is a holometabolous insect ectoparasite and was first described in Egypt [1], which is believed to represent its origin [2]. This species of flea is cosmopolitan because of widespread dispersal (principally on ships) by its preferred rodent host, the black rat Rattus rattus (Rodentia: Muridae) [3]. Eighty-six per cent of suspected cases reported in Madagascar between 2007 and 2011 were classified as bubonic plague [14], reflecting the important role played by flea vectors in the transmission cycle
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