Herd-level prevalence ofMycoplasma spp. mastitis and characteristics of infected dairy herds in Utah asdetermined by a statewide survey

Objective—To determine herd-level prevalence of Mycoplasma spp mastitis in Utah dairy herds and characterize farms and management practices for positive herds. Design—Epidemiologic study. Sample Population—Bulk tank milk samples from 222 of 285 (78%) dairy farms in Utah. Procedures—Milk haulers or dairy producers collected 5 milk samples from all bulk tanks at 3- to 4-day intervals for mycoplasmal culture. Owners of all positive herds were offered follow-up visits. Results—Milk samples from 16 of 222 (7%) herds had positive mycoplasmal culture results. Follow-up information was obtained from 14 of 16 herds; 12 provided complete data. Some characteristics of mycoplasma-positive herds included the following: 8 of 14 herds had \u3e 750 lactating cows, 9 of 11 had bulk tank milk somatic cell count of 140,000 to 240,000 cells/mL, 7 of 11 had actual milk production of 9,535 to 11,622 kg (21,000 to 25,600 lb)/305 d, 11 of 12 had cows with clinical mastitis that was nonresponsive to treatment and involved ≥ 2 mammary gland quarters, 9 of 12 had cows with clinical mastitis that spread from 1 mammary gland quarter to another, 8 of 12 had cows with droopy ears, 7 of 12 had cows with a head tilt, 7 of 12 used common milking towels, 2 of 12 were closed to replacement cattle for \u3e 1 year, and 2 of 12 purchased bulls only. Conclusions and Clinical Relevance—Herd-level prevalence of mycoplasma mastitis in Utah was relatively high, compared with other areas of the United States. Infection with Mycoplasma spp, typically Mycoplasma bovis, is an important disease complex of dairy cattle. Mycoplasma spp affect all ages of cattle, can cause mastitis, arthritis, pneumonia, metritis, agalactia, and septicemia, and can result in death.1,2Standard techniques for bacterial culture of milk samples do not result in the isolation of Mycoplasma spp; special laboratory methods are required.3–5 No published surveys exist regarding the prevalence of mycoplasma mastitis of cattle within a single state, as measured at the herd level (ie, what percentage of dairy farms in a given state have Mycoplasma spp isolated from samples of bulk tank milk). Estimated prevalence of mycoplasma mastitis varies by regions in the United States. From bulk tank milk samples collected from selected herds in New York, Pennsylvania, and Vermont, the herd-level prevalence of Mycoplasma spp mastitis was reported as 2.8%.6 However, the same national dairy survey reported that in the western United States (bulk tank milk sampling of selected herds in California, Colorado, Idaho, New Mexico, Texas, and Washington), the herd prevalence of mycoplasma was 9.4%.6 Utah had not been included previously in any survey of Mycoplasma spp mastitis prevalence in cows. From experience, the authors speculated that Utah, like other areas in the western United States, might have a high herd-level prevalence of mycoplasma mastitis, compared with other regions in the country. Therefore, an objective of the study reported here was to determine the herd-level prevalence of Mycoplasma spp mastitis in Utah dairy herds. A further objective was to describe mycoplasma-positive herds, their farm characteristics, and management practices