Emergence of the arterial worm Elaeophora schneideri in moose (Alces alces) and tabanid fly vectors in northeastern Minnesota, USA

Abstract

BackgroundMoose (Alces alces) are a culturally and economically valued species in Minnesota. However, the moose population has experienced a sudden, marked decline in their range, including extirpation in the northwest and a 66% decline in the last decade in the northeast portions of the state. Although the exact cause of this decline is unclear, parasitic metastrongylid and filarioid nematode infections are known causes of morbidity and mortality in moose across North America.MethodsTo determine if these parasitic nematodes could be contributing to the Minnesota moose population decline, we molecularly examined banked tissues obtained from moose that died of known and unknown causes for the presence of nematode DNA. Extracted brain DNA of 34 individual moose was amplified utilizing primers targeting the 18S rRNA gene and internal transcribed spacer regions of nematodes.ResultsDNA sequencing revealed that PCR products obtained from 15 (44.1%) of the moose were 99% identical to Parelaphostrongylus tenuis, a metastrongylid known to cause neurological disease and death. Additionally, brain tissue from 20 (58.8%) individuals yielded sequences that most closely aligned with Elaeophora schneideri, a parasite associated with neurological impairment but previously unreported in Minnesota. Setaria yehi, a common filarioid parasite of deer, was also detected in the brain tissue of 5 (14.7%) moose. Molecular screening of 618 captured tabanid flies from four trapping sites revealed E. schneideri was present (6%) in the Minnesota environment and transmission could occur locally. Prevalence rates among the flies ranged between 0–100% per trapping site, with Chrysops spp. and Hybomitra spp. implicated as the vectors.ConclusionsUltimately, these data confirm that P. tenuis is widespread in the Minnesota moose population and raises the question of the significance of E. schneideri as a contributing factor to morbidity and mortality in moose.Electronic supplementary materialThe online version of this article (10.1186/s13071-018-3077-0) contains supplementary material, which is available to authorized users.

Adverse effects of Diptera flies on northern ungulates: Rangifer, Alces, and Bison

“…Rumenfilaria spp. and Setaria yehi ) to many individual Alces alces , causing severe disease, neurological impairment, peritonitis, and death (Grunenwald et al 2018).…”

“…However, the costs of immune function rise with secondary infections and transmission of pathogens from the bite of adult or larval flies, or from contact of flies with an open wound. High costs of infection coincided with declines in Alces alces populations from 2004 to 2015 in north-east Minnesota, USA (DelGiudice 2020), where flies transferring nematode parasites cause neurological impairment, peritonitis, and death (Grunenwald et al 2016(Grunenwald et al , 2018. The added immunological costs of fly bites therefore depend greatly on what the fly leaves behind and the time course of the physiological response.…”

Trapped between food, heat, and insects: Movement of moose (Alces alces) and exposure to flies in the boreal forest of Alaska

“…Both mosquitoes and black flies are tolerated by moose and make up the majority of flies in the boreal forests of the Kenai Peninsula, creating repeated spring and summer exposure. Nematode parasites have also been found to cause neurological impairments, peritonitis, and death in a declining moose population in northern Minnesota (Grunenwald et al., 2016 , 2018 ; Murray et al., 2006 ).…”

Prevalence and Mortality of Moose (Alces alces) Infected with Elaeophora schneideri in Montana, USA

“…Geographic patterns of elaeophorosis in the western US may relate to abundance of the definitive host (O. hemionus), tabanid intermediate hosts, or both, aligning with drier habitats in this region (Boyce et al 1999;Anderson 2001). However, detection of E. schneideri in the eastern US indicates that reservoirs of the parasite are sustained in whitetailed deer populations, as well (Couvillion et al 1986;Grunenwald et al 2018). Henningsen et al (2012) noted that E. schneideri presence among Wyoming moose increased during the decades preceding their 2009 survey.…”