Filaroidosis Invasion Levels in Sable and Pine Marten Populations

A comparative study of lungworm Filaroides martis invasion rates in sable and pine marten populations in the Cis-Urals region and Central Siberia was performed on the basis of samples totaling more than 3000 animals. In different sable population groups, the invasion extensiveness (prevalence) varies from 2 to 57%; in pine marten population groups, from 0 to 54%. In the Urals transgression zone, the invasion rate is statistically significantly higher in martens compared to sables. The studied groups form three clusters. Low prevalence values (less than 2%) were noted in two eastern populations: the upper Ob River (martens) and the Vakh River (sables); the highest values (over 50%), in martens in the Urals and in both species in the Uvat district, Tyumen oblast. The rest of the groups with moderate prevalence values (20–38%) form the third cluster. The invasion intensity varies from 2.5 to 3.6 helminth cysts per infected individual in sables, and from 0 to 4.6 cysts in martens; for most pairwise comparisons performed based on these two parameters, differences between samples are statistically significant. In western groups of both species, the invasion intensity is higher compared to eastern groups. In sables, invasion prevalence and intensity correlate in a statistically significant (r = 0.95; p = 0.01) way. One geographical trend was identified: in pine martens, invasion prevalence increases in a northerly direction. Cases with prevalence levels less than 5% can be explained by the absence of formed filaroidosis foci. At the beginning of the 2010s, a twofold increase in prevalence over the previous 20 years was recorded; this phenomenon has no adequate explanation yet.