Crossreacting IgG antibodies against fox mite antigens in human scabies

Scabies continues to be an important parasitic disease of mammals. There remain, however, major gaps in the understanding of the human host immune response, and a simple diagnostic test is lacking. In contrast to human mites, red fox mites (Sarcoptes scabiei var. vulpis) can be collected easily and have been used, due to crossreactivity, for enzyme-linked immunosorbent assay (ELISA) studies in dogs and pigs. We wanted to investigate the possibility that crossreactivity might also exist for the human mite, and determined titers against fox mite antigens by ELISA in 41 patients with scabies. Specific IgG was significantly higher in patients with scabies than in healthy controls (P=0.01). The sensitivity was, however, only 48%, although it increased slightly during treatment (P=0.86). A positive correlation was also noted between disease duration and severity of infestation (r=0.5), with specific IgG titers increasing in parallel with severity of symptoms (P=0.01). Patients with symptomatic scabies for more than 4 weeks had furthermore significantly higher IgG titers than patients with a shorter duration of disease (P=0.007). In conclusion, these findings demonstrate IgG antibodies in human scabies that crossreact with fox mite antigens, thus encouraging the search for improved ELISAs with more specific mite antigens to produce a more sensitive detection system for scabies in humans.