Further inquiry into the etiology of hoof disease in elk using bacterial metagenomics analysis

Authors: WILD, MARGARET - Washington State University; CHIOK, KIM - Washington State University; SHAW, DEVERDRA - Washington State University; Wilson-Welder, Jennifer; TAYLOR, KYLE - Washington State University; MANSFIELD, KRISTIN - Washington Department Of Fish & Wildlife; HAN, SUSHAN - Colorado State University

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 5/1/2019
Publication Date: N/A
Citation: N/A

Interpretive Summary:

Technical Abstract: Cases of limping elk (Cervus elaphus) exhibiting characteristic hoof lesions reported to the Washington Department of Fish and Wildlife increased markedly in southwest Washington in 2008. Currently, the disease has been documented in localized areas across western and southern Washington, northern Oregon, and western Idaho. Lesions are characterized by deformed, overgrown, broken or sloughed hooves, often with severe sole ulcers, extensive laminar necrosis, and pedal osteomyelitis. Spirochetes are observed on histology. In previous studies, Treponema spp. similar to those reported in digital dermatitis of cattle and sheep were isolated sporadically from lesions, and the presence of treponemes in tissues was supported by immunohistochemistry and PCR. Thus, the disease is currently diagnosed as treponeme-associated hoof disease (TAHD) based on gross lesions and histological presence of spirochetes. While treponeme-associated, additional investigation is warranted to determine the suite of organisms that might contribute to etiology. For example, digital dermatitis in livestock is generally considered to be a polymicrobial disease and predictable changes in the bacterial microbiota have been described through the progression of hoof lesions in cattle. We hypothesize a similar process may occur in elk. In a pilot study, we compared the bacterial (16S rDNA) metagenomes in biopsies collected postmortem from healthy (n=4) and diseased (n=4) elk feet. The bacterial diversity was reduced in the diseased state when compared to control samples. Results supported treponeme association; Spirochetes (Treponema spp.), as well as Tenericutes (Mycoplasma spp.) and Fusobacteria (Fusobacterium spp.), were the most predominant bacteria Phyla associated with lesions. Proteobacteria (Halomonas spp.) were overrepresented in control samples. Ongoing studies are evaluating larger numbers of samples collected from different lesion grades and geographically distant from the area of initial disease detection. Findings are critical for epidemiological investigation, developing a disease challenge model, and identifying potentially effective mitigation actions.