Studies on the geographic distribution, prevalence, intensity and bone pathology of sinus worm (Skrjabingylus spp.) infection in mustelid species

Mink (n = 880), otter (n = 43), fisher (n = 360), marten (n = 37) and weasel (n = 55 short-tailed; n = 12 long-tailed) skulls from various geographic regions within Ontario, Quebec, and Newfoundland were examined for sinus infection by the parasite Skrjabingylus spp. Prior to dissection, left and right sinuses were examined and individually scored for discoloration, swelling, bone thinning and perforation/exposure of the sinus cavity as potential indicators of infection intensity. Presence of Skrjabingylus spp. was confirmed and intensity determined by exposing and counting adult worms present in each sinus. With respect to mink in Ontario, site differences in both infection prevalence and infection intensity were found but definitive geographic trends (north-south or east-west) were not apparent. Mink from Newfoundland had both the lowest infection prevalence and the lowest infection intensity of all mink populations examined. Interspecies differences in both prevalence and intensity were found among mink and the two species of weasel from Quebec, with infected short-tailed weasels harboring almost double the parasitic burden of either long-tailed weasel or mink from the same region. No Skrjabingylus parasites were found in fisher or marten, while only two otter specimens were infected with S. lutrae. Sinus lesion scores were found to be reliable predictors of infection prevalence and intensity, even when fresh skulls were subjected to most museum preparation/cleaning methods. Despite marked levels of sinus enlargement, heavily-infected mink failed to show a significant reduction in braincase volume, suggesting that most of the sinus swelling associated with Skrjabingyliasis in mink is directed externally. Variations in parasitic infection rate with respect to geographic sites, interspecies differences, and resulting patterns of sinus bone pathology incurred in the host are discussed in relation to findings previously reported in the literature.