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Screening stable flies and house flies as potential vectors of digital dermatitis in dairy cattle.

R. Thibodeaux

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06-24-2020

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Abstract:

W4
Screening stable flies and house flies as potential vectors of digital dermatitis in dairy cattle.
R. Thibodeaux*1, J. Brady2, S. Swiger3, B. Jones1,2. 1Tarleton State University Stephenville, TX, 2Texas A&M Agrilife Research Stephenville, TX, 3Texas A&M Agrilife Extension Stephenville, TX.

Digital dermatitis is a bacterial infection that causes lesions above the heal bulbs on cattle hooves. Treponema bacteria are present on the lesions of an infected hoof. Transmission is suspected through mechanical exposure in dirty bedding areas, but insects as potential vectors have not been explored. Flies can lead to other diseases like mastitis. Thus, the vast number of flies on a dairy may contribute to the spreading of digital dermatitis. Therefore, the objective of this research was to determine if flies captured from a dairy farm known to have digital dermatitis carry Treponema bacteria on their legs and heads. Autoclaved mesh sweep nets were used to collect the stable flies (Stomoxys calcitrans) and house flies (Musca domestica) for transfer to a plastic crate with a fabric opening until transport to the lab. The heads and legs of the fly were cut off with a sterile scalpel to use in the DNA extraction. Flies (n = 417) had DNA extracted using a Qiagen Blood and Tissue Kit. DNA from one tube was qPCR assayed in triplicate to determine if any DNA from Treponema bacteria were present. Three sampling events were used to increase the chance that Treponema DNA was collected if present. The concentration of DNA extracted from samples was measured by using a Qubit 2.0 Fluorometer kit (Life Technologies, Carlsbad, CA). A plasmid with Treponema phagedenis gene sequence was used as a qPCR positive control because this species was most prevalent in digital dermatitis infections. The negative control used was molecular biology grade water. The plasmid was serial diluted 1:10,000 before use as a qPCR positive control. Treponema bacteria were not detected on any of the flies we tested. The DNA of treponemes may not have been detected due to the small sample size compared with the overall population, or that other species of flies need to be analyzed to broaden the possibility of detecting the DNA. Further analysis should be conducted to confirm if other flies may carry Treponema bacteria, and to explore other potential vectors of Treponema bacteria.

Keywords: digital dermatitis, Treponema, qPCR.