Leptospirosis in dairy cattle; the effectiveness of long-term vaccination of dairy cattle on New Zealand farms

Abstract

Recently, there has been an observation of high leptospirosis titres in vaccinated dairy herds. This study was conducted to answer the question whether vaccination totally eliminates urine shedding of Leptospira in dairy herds or not. The outcome of this study could act as a model for predicting the possible outcome of vaccination in deer and beef cattle. This study was conducted in November 2010 at 17 farms all serviced by Massey University Farm Services Veterinary Clinic. Ten out of the 17 farms were open farms and bought new animals. Of each farm urine was collected of 10 cows. A questionnaire was filled in with questions about the livestock, other animals on the farm, vaccination program against leptospirosis, the leptospirosis history and movement of cattle. Three different vaccines were included: Leptavoid®-2, Ultravac® 7-in-1 and Leptoshield®-3. The vaccination protocol for calves varied from farm to farm. Vaccination of adult cows was between February and August. The urine was tested by dark-field microscopy and Polymerase Chain Reaction (PCR). Positive PCR samples where confirmed by agarose gel electrophoresis. One sample was PCR and agarose gel electrophoresis positive, dark-field microscopy negative and one sample was dark-field microscopy positive and PCR negative. In this study, animals on two farms were shedding Leptospira in urine. This may implicate that vaccination was not fully effective. It is not possible to identify the cause of infection in this research. Therefore, further research is necessary on these farms. To make clear conclusions about the effectiviness of vaccination against leptospirosis, further study is needed. It is recommanded to sample more farms and take urine and blood samples of more animals of the positive tested farms, to find out which serovar causes the infections. For optimizing the vaccination strategy of the different farms, a well conducted vaccination program with a regular follow-up by the veterinarians is needed.