Recolonizing gray wolves increase parasite infection risk in their prey

Abstract

The recent recolonization of Central Europe by the European gray wolf (Canis lupus) provides an opportunity to study the dynamics of parasite transmission for cases when a definitive host returns after a phase of local extinction. We investigated whether a newly established wolf population increased the prevalence of those parasites in ungulate intermediate hosts representing wolf prey, whether some parasite species are particularly well adapted to wolves, and the potential basis for such adaptations. We recorded Sarcocystis species richness in wolves and Sarcocystis prevalence in ungulates harvested in study sites with and without permanent wolf presence in Germany using microscopy and DNA metabarcoding. Sarcocystis prevalence in red deer (Cervus elaphus) was significantly higher in wolf areas (79.7%) than in control areas (26.3%) but not in roe deer (Capreolus capreolus) (97.2% vs. 90.4%) or wild boar (Sus scrofa) (82.8% vs. 64.9%). Of 11 Sarcocystis species, Sarcocystis taeniata and Sarcocystis grueneri occurred more often in wolves than expected from the Sarcocystis infection patterns of ungulate prey. Both Sarcocystis species showed a higher increase in prevalence in ungulates in wolf areas than other Sarcocystis species, suggesting that they are particularly well adapted to wolves, and are examples of “wolf specialists”. Sarcocystis species richness in wolves was significantly higher in pups than in adults. “Wolf specialists” persisted during wolf maturation. The results of this study demonstrate that (1) predator–prey interactions influence parasite prevalence, if both predator and prey are part of the parasite life cycle, (2) mesopredators do not necessarily replace the apex predator in parasite transmission dynamics for particular parasites of which the apex predator is the definitive host, even if meso‐ and apex predators were from the same taxonomic family (here: Canidae, e.g., red foxes Vulpes vulpes), and (3) age‐dependent immune maturation contributes to the control of protozoan infection in wolves.

Large-Scale Sheep Losses to Wolves (Canis lupus) in Germany Are Related to the Expansion of the Wolf Population but Not to Increasing Wolf Numbers

“…Odds ratio exp β was measured as the effect size and we also considered its 99% confidence interval resultant from a conservative p-value. Odds ratio indicates an increase if > 1 (e.g., by 20% if it is equal to 1.20), decrease if < 1 (e.g., by 60% if it is 0.40) or no change if = 1 (Lesniak et al, 2018;Khorozyan, 2020). Although information-theoretic and hypothesis testing approaches are conceptually different and their concurrent use is debated for long (Qian, 2014), we checked the AIC c -based best models for statistical significance to be sure that they are indeed robust and not selected as the best out of all bad models (Poudyal et al, 2016).…”

High genetic diversity of immunity genes in an expanding population of a highly mobile carnivore, the grey wolf Canislupus, in Central Europe

“…In TLRs, the number of private alleles was higher in Carpathian populations compared with lowlands, what may be explained either by the genetic distinctiveness of this population (as indicated in neutral markers, see Szewczyk et al., 2019) and/or different selective pressures associated with the highland habitats. The wolf microbial pathogen fauna depends on many ecological factors, such as predator–prey interactions, or presence of other predators (Lesniak et al., 2018), yet the data on microbial pathogens infecting wolves in each of the studied populations are limited (Čabanová et al., 2017). Thus, further studies are needed to verify whether differences in microbial communities between lowlands and highlands may drive TLR diversity in wolves.…”

Cross‐continental comparison of parasite communities in a wide‐ranging carnivore suggests associations with prey diversity and host density

“…Further research could help clarify the extent to which naturally transmitted parasites (i.e., from natural wolf prey) versus anthropogenically transmitted parasites (transmitted from feeding on or contact with domestic animals or human refuse) influence the health of wolves and other carnivores. Recent findings also highlight the importance of monitoring recolonizing wolf populations, as wolf-specific parasites could increase in prevalence following the return of wolves (Lesniak et al, 2018). Parasites might thus contribute to re-establishing ecosystems toward a more naturalized state in ways not typically observed or reported by humans.…”