A cluster of three cases of leptospirosis in dairy farm workers in New Zealand.

AIMS: We report a cluster of three cases of leptospirosis on a New Zealand dairy farm, with regard to clinical, laboratory, and environmental findings. The cluster is discussed against the annual incidence of leptospirosis in humans and cattle, and the vaccination of cattle as one means of preventing human cases on farms.

METHDOS: The three cases were investigated by case interview and review of clinical and laboratory information. A site visit was made to the farm to assess environmental risk. Relevant veterinary information relating to the cattle herds was reviewed.

RESULTS

Most of the symptoms exhibited by the three patients were consistent with primary phase leptospirosis. Different methods of laboratory diagnosis were used with each case. However, two cases were confirmed as leptospirosis and in both the causative agent was Leptospira borgpetersenii serovar (sv) Hardjo. The third case had a milder illness, received doxycycline early, and was regarded as a 'probable' case as there were no confirmatory diagnostic results. All three cases had worked on the same dairy farm during their incubation period, where the highest risk environment was the milking shed and potential exposure to urine splashes from infected cattle. Also there were inadequacies in the herd vaccination programme.

CONCLUSIONS

There are options for minimising risk to dairy farm workers in New Zealand. No human vaccine exists in this country. Leptospira borgpetersenii serovar (sv) Hardjo (serovar Hardjo) is endemic in New Zealand dairy cattle without causing apparent disease. L. Pomona is a sporadic infection but can cause abortions. A cattle vaccine against these serovars was introduced in New Zealand in 1979, after which there was a general fall in notifications of human cases of leptospirosis. This was attributed to the overall decrease in these two serovars among the livestock population. Vaccination of farm livestock for leptospirosis is an integral factor in preventing human cases. We note the New Zealand initiative to combine vaccination with a risk management programme operated by veterinarians, called Leptosure, to reduce the risk of human leptospirosis on dairy farms. The efficacy of using doxycycline as a prophylaxis for preventing human infection in trials is reviewed. Other preventative strategies include the use of personal protective equipment to cover the mouth and nose, eyes and all skin breaks, farm workers and rural clinicians being aware of the signs and symptoms of leptospirosis, and prompt treatment of cases with antibiotics.