Diversity of gastrointestinal helminths in Dall's sheep and the negative association of the abomasal nematode, Marshallagia marshalli, with fitness indicators

Authors: ALEUY, O.A. - University Of Calgary; RUCKSTUHL, K. - University Of Calgary; Hoberg, Eric; VEITCH, A. - University Of Calgary; SIMMONS, N. - Diamond Willow Ltd; KUTZ, S. - University Of Calgary

Submitted to: International Journal for Parasitology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/6/2017
Publication Date: 3/4/2018
Citation: Aleuy, O., Ruckstuhl, K., Hoberg, E.P., Veitch, A., Simmons, N., Kutz, S. 2018. Diversity of gastrointestinal helminths in Dall's sheep and the negative association of the abomasal nematode, Marshallagia marshalli, with fitness indicators. International Journal for Parasitology. 13:3. https://doi.org/10.1371/journal.pone.0192825
DOI: https://doi.org/10.1371/journal.pone.0192825

Interpretive Summary: Gastrointestinal helminths can have a detrimental effect on the fitness of domestic and free-ranging wild ungulates. Arctic and Subarctic ecosystems are ideal for the study of host-parasite interactions due to the comparatively simple ecological interactions and limited confounding factors. We used a unique dataset collected in the early 1970's to study the diversity of gastrointestinal helminths and their effect on fitness indicators of Dall's sheep, Ovis dalli dalli, in the Mackenzie Mountains, Northwest Territories, Canada. These collections are one of most extensive baselines ever assembled to document parasite diversity in a free-ranging ungulate species. The parasite diversity included nine different species among which the abomasal nematode Marshallagia marshalli occurred with the highest prevalence and infection intensity. The intensity of M. marshalli increased with age and was negatively associated with body condition and pregnancy status in Dall's sheep across all the analyses performed. The intensity of another nematode, the whipworm, Trichuris schumakovitschi, decreased with age. No other parasites were significantly associated with age, body condition, or pregnancy. Our study suggests that M. marshalli might negatively influence fitness of adult female Dall's sheep. Understanding the distribution and occurrence of parasites is a critical adjunct in identifying the factors that influence helath status for individuals and herds of wild ungulates. Further with accelerating climate change, and the expansion of domestic ungulates on northern trajectories, such baseline information is essential in identifying the potential for exchange and impact of parasites in areas of contact between managed and wild systems. These data and their interpretation are essential for veterinarians, disease ecologists and wildlife biologists in managing ungulate populations in the mix of increasingly complex zones where parasite exchange may occur.

Technical Abstract: Gastrointestinal helminths can have a detrimental effect on the fitness of wild ungulates. Arctic and Subarctic ecosystems are ideal for the study of host-parasite interactions due to the comparatively simple ecological interactions and limited confounding factors. We used a unique dataset collected in the early seventies to study the diversity of gastrointestinal helminths and their effect on fitness indicators of Dall's sheep, Ovis dalli dalli, in the Mackenzie Mountains, Northwest Territories, Canada. The parasite diversity included nine different species among which the abomasal nematode Marshallagia marshalli occurred with the highest prevalence and infection intensity. The intensity of M. marshalli increased with age and was negatively associated with body condition and pregnancy status in Dall's sheep across all the analyses performed. The intensity of Trichuris schumakovitschi decreased with age. No other parasites were significantly associated with age, body condition, or pregnancy. Our study suggests that M. marshalli might negatively influence fitness of adult female Dall's sheep.