Genetically distinct dog-derived and human-derived Sarcoptes scabiei in scabies-endemic communities in northern Australia.

Abstract

Abstract. Overcrowding is a significant factor contributing to endemic infection with Sarcoptes scabiei in human and animal populations. However, since scabies mites from different host species are indistinguishable morphologically, it is unclear whether people can be infected from scabies-infested animals. Molecular fingerprinting was done using three S. scabiei-specific single locus hypervariable microsatellite markers, with a combined total of 70 known alleles. Multilocus analysis of 712 scabies mites from human and dog hosts in Ohio, Panama and Aboriginal communities in northern Australia now shows that genotypes of dog-derived and human-derived scabies cluster by host species rather than by geographic location. Because of the apparent genetic separation between human scabies and dog scabies, control programs for human scabies in endemic areas do not require resources directed against zoonotic infection from dogs.When scabies is endemic in humans and dogs in the same community, it is unclear whether humans and dogs are potential hosts in a single transmission cycle or whether there are two separate transmission cycles. Morphologic studies cannot distinguish mites from dogs (Sarcoptes scabiei var. canis) from those of human origin (var. hominis), and it is not known whether var. canis is capable of infecting and completing a life cycle in humans.

Is ITS-2 rDNA suitable marker for genetic characterization of Sarcoptes mites from different wild animals in different geographic areas?

“…Using microsatellite markers, Walton et al (1999) substantiated previous data that gene flow between sympatric scabies mite populations on humans and dogs is extremely rare in northern Australia. Likewise, genetic…”

Problems in Diagnosing Scabies, a Global Disease in Human and Animal Populations

“…Cross-infection studies describe unsuccessful experimental attempts to transfer scabies mites from dogs to mice, pigs, cattle, goats, and sheep (10). This is supported by molecular genotyping studies that reveal genetically distinct dog and human hostassociated mite populations in Australian indigenous communities where scabies is endemic (106,108). Occasional cases of human scabies have been reported following exposure to animal scabies, but these infestations are generally self-limiting, with no evidence of long-term reproduction occurring on the nonnormal host (15).…”

“…Importantly, a recent study looking at cross-reacting IgG antibodies to the fox mite antigen in human scabies reported a sensitivity of only 48%, in comparison with 80% in pig scabies and 84% in dog scabies (50). This is not surprising, as studies using molecular markers suggest that S. scabiei organisms from humans and animals are genetically distinct and that interbreeding or cross-infection appears to be extremely rare (106,108).…”

“…Over 15 different varieties or strains have been described from various hosts, although morphologically they appear to be similar (38). However, cross-infestation experiments (10) and molecular epidemiology studies (106,108) indicate clear physiological and genetic differences between host strains.…”

Outfoxing a Rash: Clinical Example of Human–Wildlife Interaction

“…The risk of animal strains infecting humans increases with the degree of human-animal contact (Walton et al, 1999). In a population of aborigines with extensive contact with domestic dogs, approximately 25% of adults displayed positive antibodies to the canine strain (Sarcoptes scabiei var canis) (Normaznah et al, 1996).…”