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Certain moose (Alces alces) populations in the northeastern United States are in decline because of increasing frequency of winter tick (Dermacentor albipictus) epizootics characterized by high calf mortality and reduced productivity in the population. Previous research identified soil fungi in wallows of bull moose that are pathogenic to larval winter ticks. We analysed skin/hair samples of moose harvested in Maine, USA, to further understand this fungus–tick–moose relationship. A total of 32 keratinophilic fungi from moose fur and skins were isolated, predominately Penicillium, Cladosporium, Aspergillus, Alternaria, Trichoderma, Beauveria, and Scopulariopsis. Each displayed pathogenic activity against unfed winter tick larvae (sole infestation stage) by topical application of spore inoculums and Koch's postulates. Bulls had more entomopathogenic fungi, pathogenic fungal isolates to ticks, and infected larvae than cows and calves. We propose a disease cycle with interactions of soil fungi, moose, and on-host winter tick larvae killed by entomopathogenic soil fungi. Bull moose presumably experience enhanced exposure and protection from abundant soil fungi due to their wallowing behaviour during the breeding season that is coincidental with questing by winter tick larvae. [ABSTRACT FROM AUTHOR]

Eastern moose (Alces alces americana) are heavily parasitized by winter ticks (Dermacentor albipictus), the dominant cause of increased calf mortality in the northeastern US. Although much work has focused on the direct negative effects of winter tick on moose, it remains unknown whether diseases transmitted by ticks may also affect moose health or pose a risk to other species. We explored the role that moose and winter ticks play in transmission of the tick-borne bacterial pathogens, Anaplasma spp., which cause mild to severe illness in humans and domestic animals. Our objectives were to 1) estimate the prevalence of Anaplasma spp. in moose and winter ticks; 2) determine the phylogenetic placement of these strains with respect to those found in other hosts and vectors; and 3) explore risk factors of Anaplasma infection in moose. A total of 157 moose (142 calves, 15 adults) were captured in western (n=83) and northern (n=74) Maine in 2017 and 2018. We screened for Anaplasma spp. in moose whole blood samples using a genus-specific PCR assay targeting the 16S rRNA gene. Over half (54%) of the moose were infected with Anaplasma bacteria, with a greater proportion of moose harboring Anaplasma-infections in the western (67%) versus northern study areas (38%). Male moose exhibited a higher prevalence than did females (63% vs. 47%). In contrast, Anaplasma spp. prevalence in winter ticks was low (<1%). Sequencing and phylogenetic analysis revealed that the single Anaplasma strain in moose was highly divergent from the strain in winter ticks and most closely related to an uncharacterized North American cervid strain. We conclude that winter ticks are unlikely to play a significant role in Anaplasma transmission to moose; however, high infection prevalence warrants further investigation into the impacts of Anaplasma spp. infection on moose health., (© Wildlife Disease Association 2021.)