Morphological and morphometric differentiation of dorsal-spined first stage larvae of lungworms (Nematoda: Protostrongylidae) infecting muskoxen (Ovibos moschatus) in the central Canadian Arctic

Abstract

Umingmakstrongylus pallikuukensis and Varestrongylus eleguneniensis are the two most common protostrongylid nematodes infecting muskoxen in the North American Arctic and Subarctic. First stage larvae (L1) of these lungworms have considerable morphological similarity that makes their differential diagnosis very difficult. Using light microscopy, we studied in detail the L1 of these two species and identified the key differences in morphological and morphometric attributes. Thirty L1 of each species from naturally infected muskox were heat-killed and then assessed for morphological and morphometric features that could be used for species-level differentiation. Key differentiating features include: length and morphology of the tail extension, curvature of the body, ventral post-anal transverse cuticular striations, and total body length. A laboratory guide for differentiation of L1 based on these species-specific characters was prepared and used by an experienced observer to identify an additional 35 L1 extracted from a different set of fecal samples from free-ranging muskoxen with mixed infections. The identities of these L1 were confirmed by sequence analysis of the ITS-2 region of the nuclear ribosomal DNA. Accuracy of morphological identification was 100 percent, reflecting the reliability of the proposed guide for differentiation. Using the guide, three minimally trained lab assistants each fixed and accurately identified 10 of 10 randomly selected L1. Ability to morphologically differentiate these facilitates the monitoring of overlapping range expansion of both parasites in the Canadian Arctic. Studies enabling species-level parasite identification are also critical for defining biodiversity, detecting mixed infections, and understanding host–parasite interactions. Morphological identification is a simple, reliable and cost-effective alternative to labor and equipment intensive molecular methods and can easily be performed in low resource settings.

Geography, seasonality, and host‐associated population structure influence the fecal microbiome of a genetically depauparate Arctic mammal

“…Fecal samples of wild muskoxen (n = 78) were obtained over a 9-year period from six sampled regions and two genetically defined populations (Table S1). Samples were collected directly from the rectum of animals harvested by subsistence hunters as part of a community-based muskox health monitoring program (Tomaselli, 2018) or fresh (<24 hr old) from the ground as part of a study on lungworm range expansion (Kafle et al, 2015). In total, 33 F I G U R E 1 Location, season, and year of collection for sampling sites analyzed in this study.…”

“…Northern portions of the Arctic are experiencing the most change, with projected rainfall increases to exceed historical averages by over 65% over the course of the twenty‐first century (Bintanja & Selten, ) and rain being documented to form ice sheets over accessible foliage (Putkonen et al, ), posing obvious threats to muskoxen. With these changing environmental conditions, pathogens (e.g., the nematode species Umingmakstrongylus pallikuukensis and Varestrongylus eleguneniensis ) are dispersing northwards into previously inhospitable environments (Kafle, Lejeune, Verocai, Hoberg, & Kutz, ; Kutz et al, ). Additionally, some muskox herds have experienced population declines of >50% concurrent with large mortality events associated with the bacterium Erysipelothrix rhusiopathiae , a pathogen that had been undetected in the species prior to 2009 (Kutz et al, ).…”

Morphological keys to advance the understanding of protostrongylid biodiversity in caribou (Rangifer spp.) at high latitudes

“…Limiting the efficacy of health monitoring, however, is the lack of robust, pertinent and easily accessible monitoring tools to diagnose and accurately assess the severity of the problems. This is particularly true for some parasitic infections such as helminths, where high morphological and molecular similarity within a group often makes diagnosis challenging ( Jenkins et al., 2005 , Kutz et al., 2007 , Kafle et al., 2015 ).…”

“…Traditional microscopy-based parasitological diagnosis is still relevant and widely used, as it can be performed with minimal equipment and lab expertise. Recently, Kafle et al. (2015) demonstrated that DSL produced by the two protostrongylids, Umingmakstrongylus pallikuukensis (subfamily: muelleriinae) and Varestrongylus eleguneniensis (subfamily: varestrongylinae), can be morphologically differentiated, despite having a high degree of structural similarity.…”

Contagious Ecthyma, Rangiferine Brucellosis, and Lungworm Infection in a Muskox (Ovibos moschatus) from the Canadian Arctic, 2014

“…1E, F). A total of 574 protostrongylid larvae per gram of feces were isolated and identified as U. pallikuukensis and Varestrongylus eleguneniensis based on morphology and sequencing (Kafle et al 2015).…”