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Staphylococcus mastitis pathogens are present in milk and horn fly populations.

E. K. Luc

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06-24-2020

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Abstract:

W51
Staphylococcus mastitis pathogens are present in milk and horn fly populations.
E. K. Luc*, L. G. Schneider, R. T. Trout Fryxell, G. M. Pighetti. The University of Tennessee Knoxville, TN.

Prevention and treatment of mastitis without the use of antibiotics or synthetic products is one of the challenges organic dairies face. Greater understanding of the factors affecting mastitis will aid in developing management programs. Mastitis and fly populations both increase during the summer months, but the relationship between the 2 is unknown in lactating dairy cows housed partly or fully on pasture. Our objective was to identify specific Staphylococcus mastitis pathogens (Staph. aureus, Staph. chromogenes, Staph. hyicus and Staph. agnetis) in quarter milk samples and horn fly populations. Four organic dairies (n = 67 cows) were enrolled in the study. Sampling occurred from May 2019 through October 2019. Aseptic quarter milk samples were collected, regardless of somatic cell count or clinical status, from the same 15 focal cows on each herd (n = 193 samples) once a month, cultured, and Staph. isolates were identified using the API Staph. System (bioMerieux Inc., Hazelwood, MO). Live flies from the back and udder area were collected from the same 15 focal cows on each herd (n = 77 cows) every 2 weeks. Flies were pooled (n = 1,702) by farm, date, cow, back or udder, and sex with a max of 15 flies and minimum of 1 fly per pool. DNA was extracted from whole flies using a QIAcube HT (Qiagen, Germantown, MD) and specific Staph. species were determined in the fly by PCR and visualized using a QiAxcel (Qiagen). PROC FREQ (SAS 9.4, Cary, NC) was used to determine the frequency of select Staph. species in flies and milk samples. To date 384 of 1,702 fly pools have been analyzed. Of those pools tested, 64% were positive for Staph. aureus, 47% for Staph. chromogenes, 54% for Staph. agnetis, and 14% for Staph. hyicus. Of the aseptic milk samples collected, 12% (n = 24) were culture positive for Staph. aureus, 15% (n = 28) for Staph. chromogenes, 0% for Staph. agnetis, and 8% (n = 15) for Staph. hyicus. All Staph. species tested were carried by horn flies and can be potential vectors for intramammary infections and presence in milk. Once all samples are analyzed, the relationship between specific mastitis pathogens from the flies and milk samples will be evaluated.

Keywords: mastitis, horn fly, Staphylococcus.