Bertram Harmon a publié une note il y a 6 jours et 1 heure
DiscussionRasero et al. (2010) demonstrated the utility of analyzing microsatellite loci to differentiate between carnivore-associated Sarcoptes mite populations in an analysis between three geographically separated carnivore hosts from Italy and Spain. Using these microsatellite loci, the results in the present study strongly suggest that the difference of host species did not disrupt the gene flow of Sarcoptes mites between domestic/companion dogs and raccoon dogs, which would be caused by the transmission of sarcoptic mange between raccoon dogs and domestic/companion dogs, at least around the Gifu area of Japan. In several cases, S. scabiei could be transmitted from a mangy host to a healthy host, whether they are of the same species or not (e.g., the successful experimental cross-contamination from mangy red foxes to dogs; Bornstein, 1991). In Japan, there was also a case report of mange in a companion dog suspected to have been transmitted from the carcass of a mangy wild raccoon dog (Mizutani et al., 2010). These reports and the results in the present study suggest that contact with mangy raccoon dogs may be one of the general routes of infection in companion dogs.The coexistence of the two mite groups may be explained by the recent introduction of one genotype into an area already inhabited by the other. For some introduced species, it has been reported that genetic diversity was increased by repetitive introduction (Kolbe et al., 2004; Genton et al., 2005). In the present study, when one mite was randomly extracted from each host (=27 mites), allele number (Na) as a median value was calculated as 42. This number (Na=42) and allelic diversity (A=4.7) led by the Na were larger than most comparable data from previous studies (Gakuya et al., 2011; Alasaad et al., 2011; Oleaga et al., 2013), except for Rasero et al. (2010), which were expected to detect a greater variety of cyclooxygenase-2 inhibitors than the present study, as they focused on mite populations from hosts belonging to different taxa (Table 2). These findings of a relatively large number of alleles from parasites on hosts of low taxonomic diversity might be due to repetitive spillover of domestic/companion dog-derived mites, or the repeated introduction of mites from raccoon dogs (or other wild carnivores, e.g. raccoons, masked palm civets, etc.). However, several questions remain to be answered. From the perspective of mite ecology and evolution, the competition and/or avoidance processes (Alasaad et al., 2008) and sympatric differentiation (McCoy et al., 2001) between mite populations might be possible causes for segregation of the two genotypes. Any heterogeneity in the susceptibility of hosts, the virulence of the pathogens, or the degree of connectivity among mangy hosts and susceptible hosts are also not clarified in the present study. Future studies on these aspects are needed to evaluate the hypotheses stated above.In conclusion, the present study is the first report demonstrating a considerably close genetic relationship between companion animal– and wild mammal-derived Sarcoptes scabiei in the natural environment. Despite the limitation of relatively small sample sizes, the results in the present study strongly support the concept of the transmission of mange between wild canids (i.e. raccoon dogs) and domestic/companion dogs, and inversely, the risk of spillover of mange from domestic/companion dogs to wild canids, and re-infection from wild canids to domestic/companion dogs.AcknowledgementsWe thank H. Kitagawa (Gifu University), K. Ito (Amami Animal Hospital), and S. Yamazaki (Japan Wildlife Research Center) for their generous cooperation with their mite collection, as well as many cooperative veterinary hospitals in the Gifu area. We also thank S. F. Walton (University of the Sunshine Coast), A. Dougall (James Cook University), H. Tsuruga, M. Kondo (Hokkaido Research Institute for Environmental Sciences), T. Asai (Gifu University), and M. Tsuruta (Gifu University) for their invaluable technical advice and helpful comments. This study was supported by the Grant from the Ministry of Education, Culture, Sports, Science and Technology, Japan, for Joint Research Program of the Research Center for Zoonosis Control, Hokkaido University.