A serosurvey for Trichinella in Arctic foxes (Vulpes lagopus) in Svalbard

After infection with Trichinella spp. was first demonstrated in the arctic fox population in Svalbard 30 years ago, there have been changes in the Svalbard ecosystem related to abundance of polar bear and walrus, both reservoir species for Trichinella. In order to update the assessment of the infection rate and search for differences between sex, age, trapping season and location of trapping sites, we examined arctic foxes from Svalbard in 1996-2004 (n = 429) for antibodies against Trichinella spp. For support and muscle larvae (ML) identification, the diaphragm of a subsample of 330 of the foxes, 40 foxes from 2007 to 2008, and a polar bear (Ursus maritimus) tongue sample, were examined for ML by an HCl-pepsin digestion method. The antibody assay (enzyme-linked immunosorbent assay, ELISA) demonstrated a seroprevalence of 11.7 %. The prevalence increased with age, was similar in females and males, and body condition was similar in seropositives and seronegatives. There were differences in prevalence between trapping seasons and sites. A previously reported spatial (north-south) difference appeared to be eliminated. The seroprevalence was significantly higher in males (50.0 %) than females (20.0 %) of age 4 years and older. An ML prevalence of 6.7 % was demonstrated for the foxes. This was probably an underestimate due to small sample weights. ML were found also in the polar bear. Multiplex PCR identified eleven ML isolates, ten from the arctic foxes and the polar bear isolate, as Trichinella nativa.