Observations on acute salmonellosis in four Waikato dairy herds.

Acute epidemic salmonellosis was investigated in the winter of 1978 in 4 dairy herds in the Waikato district. The outbreaks involved pregnant or recently calved cows. Calves were affected on only one farm. Salmonella bovismorbificans was isolated from the faecal, uterine and environmental samples from the herd most severely affected. In this herd 20, (20%) of the cows died; 10 calves were either born dead or died soon after birth; and 10 cows were culled as unlikely to return to production. S. typhimurium was involved in the outbreaks in the other 3 herds and from one of these farms salmonellae were isolated from the faeces of the 2 farm dogs and from a 12-month-old infant with dysentery. Salmonellae were recovered from all of the clinically ill cows and from 36% of the asymptomatic animals. Salmonellae were widespread on the properties and were isolated from 81% of soil samples; 36% of drain swabs; and from all the pairs of rubber boots worn while collecting samples.