SALMONELLA-DUBLIN INFECTION IN QUEENSLAND DAIRY-CATTLE

Objective To investigate the presence of Salmonella Dublin in Queensla nd cattle. Design An epidemiological study using diagnostic laboratory information and farm records. Procedure Outbreaks of gastroenteritis or pneumonia in calves, and abortions and enteritis in cows were routi nely investigated for the presence of salmonellae. Where S Dublin was isolated, attempts were made to gather further epidemiological informa tion. Results Prior to 1983 only two outbreaks of S Dublin have been r ecorded in Queensland dairy cattle. In 1983 S Dublin abortions were di agnosed in dairy heifers introduced from southern Australia to south-e ast Queensland. Sampling indicated that at least 10% of the 500 introd uced heifers were faecal excretors of S Dublin. On 3 of the 7 farms fr om which S Dublin was recorded, infection spread to other cattle that were in contact. From February 1985 to February 1996, 29 outbreaks of S Dublin in cattle occurred on 29 farms (28 in south east Queensland a nd 1 in north Queensland). Calves were primarily affected. Continuing outbreaks were confirmed on only 4 of these 29 farms. On 15 farms S Du blin infections were associated with the purchase of infected carves o r cows, while another farm adjoined 2 previously infected farms. No so urce of S Dublin was evident for the other 13 farms, where histories w ere often inadequate. Conclusion There has been a marked increase in S Dublin outbreaks in Queensland dairy cattle since 1983. Introduction of S Dublin carrier and aborting dairy heifers from southern Australia , where S Dublin is not uncommon, was associated with the initial outb reaks.