Abstract

Topic: Moose management and monitoring

Parasite and pathogen monitoring to inform and improve management of wild Norwegian moose

Jaelle C. Brealey¹, Erling J. Solberg², Rebecca K. Davidson³, Christer Moe Rolandsen²

Norwegian Institute for Nature Research, Høgskoleringen 9, 7034 Trondheim, Norway
Norwegian Institute for Nature Research, Trondheim, Norway
Norwegian Veterinary Institute, Tromsø, Norway

Abstract
Background: Fennoscandia has some of the highest moose population densities in the world. However, in many populations, body condition and recruitment rates of moose are declining, even in areas where population size is managed. Several interacting factors are likely contributing to these declines, including climate, food availability and infectious diseases like parasite infections. Parasites are ubiquitous in ungulates and can have important effects on health, survival and reproduction. However, parasite monitoring has been infrequently included in deer management programs. Objectives: We explored the feasibility and value of monitoring parasites and pathogens in wild Norwegian moose, particularly in regions with low-performing moose populations. Methods: We combined DNA metabarcoding (N=242) with traditional parasitological methods (N=138) to characterise the gastrointestinal nematode (GIN) community from moose faecal samples submitted by hunters during autumn 2023–2024. Quantitative PCR was used to screen ear tissue for the bacterial pathogen Anaplasma phagocytophilium (N=240). We explored differences in GIN diversity and parasite prevalence and abundance among moose age groups, sexes, different body conditions (based on carcass mass) and geographic regions (county-level). Results: Significant age and regional differences were found in the GIN community of Norwegian moose. Adult moose had higher species richness compared to younger animals. GIN species richness was also significantly higher in calves with low carcass mass, compared to calves in better condition. Some GIN species were associated with age, mass or region. For example, calves had higher abundance of Nematodirella longissimespiculata, while adults had higher abundance of the sheep parasite Oesophagostomum venulosum. Several other parasites of domestic livestock were identified in moose at high prevalence, such as Haemonchus contortus, Nematodirus battus and A. phagocytophilium, particularly from low-performing populations in southern Norway, suggesting a risk of spillover between domestic animals and wildlife. Conclusions: Our results support the inclusion of parasite investigations in programs monitoring the health and fitness of wildlife populations. While many factors interact to influence moose population performance, our results indicate that in low-performing areas, monitoring of parasites is feasible, informative and can contribute to better understanding of the mechanisms behind declining body conditions.