Mastitis, polyarthritis and abortion caused by Mycoplasma species bovine group 7 in dairy cattle

Objective To report an outbreak of mastitis, polyarthritis and abortion cau sed by Mycoplasma sp bovine group 7 in three large, centrally-managed dairi es and to review the relevant literature. Design Epidemiological, clinical and laboratory data were analysed, collate d and reported. Multidisciplinary procedures were employed. These included clinical assessment and comprehensive laboratory investigations of affected calves, aborted foetuses and milk samples. Mycoplasma cultures and genetic analyses of isolates were undertaken to identify the aetiological agent. Results About 30% of 240 calves usually kept in a calf rearing facility dev eloped severe polyarthritis as a result of Mycoplasma sp bovine group 7 inf ection between 2 and 3 weeks of age, Multiple abortions occurred on these f arms, Mycoplasma sp bovine group 7 was recovered from the fibrinopurulent s ynovial exudates of four 14-day-old calves, from the stomach contents and l ungs of two aborted foetuses, from 14 of 21 bulk milk and four of 10 mastit ic quarters, Three bulk colostrum samples cultured during the outbreak were negative for mycoplasma. Conclusion Mycoplasma sp bovine group 7 caused significant economic losses as a result of polyarthritis, abortion and mastitis. The disease probably o riginated from udder infections with spread being facilitated by the decrea sed use of tetracycline in the treatment of mastitis. Neonatal calves were most likely infected by the consumption of milk contaminated with the organ ism. Abortions presumably resulted from mycoplasmaemia, This appears to be the first report in Australia of bovine abortion resulting from Mycoplasma sp infection.