Leptospirosis

Leptospirosis (or ‘lepto’) is caused by Leptospira bacteria and can affect a wide range of animals. Leptospirosis is a zoonosis i.e. the infection can be transferred between animals and humans, and represents a workplace health and safety (WHS) hazard particularly for dairy and pig farmers, abattoir workers and veterinarians. In humans, one of the severe forms of lepto is also known as Weil’s disease.

The many types of Leptospira bacteria are commonly referred to by their serovar name. In Tasmania to date, Leptospira serovars hardjo, Pomona, icterohaemorrhagiae and canicola have been detected in domesticated animals. A number of endemic wildlife and feral species (such as rodents and pigs) also carry these serovars. In Tasmania, Lepto is most often detected in cattle, although rare cases have been diagnosed in other species such as dogs. The most important serovars for cattle in Tasmania are hardjo and Pomona.

Leptospira bacteria prefer a warm, moist, alkaline environment and persist in waterways, other wet areas, and associated vegetation, from which infection is acquired via damaged skin and the membranes of the mouth, eyes and nose. The bacteria colonise the kidneys and female reproductive tract of infected animals, and are shed in urine and birth materials back into the environment.

Lepto outbreaks commonly occur in a very wet season or after a flood; circumstances that increase survival and distribution of the bacteria. Animal movements also contribute for example, when animals that have not been previously exposed to the bacteria or have not been effectively vaccinated, are introduced to an infected environment, or when an infected animal is introduced into an uninfected, unvaccinated herd or flock.

Closed herds may be infected via infected waterways or vermin contaminated fodder.

The severity of clinical signs of leptospirosis in animals is related to the serovar, age of the infected animal, other health issues affecting that animal and lepto immune status. Leptospira infection may not produce clinical signs but the bacteria may be shed in urine for lengthy periods (e.g. up to 18 months for infected cattle); this is the main source of infection for other animals and humans. The first clinical signs of lepto may be infertility or abortions and/or sudden drop in milk production and mastitis in dairy herds and/or severe illness with fever, jaundice, anaemia, discoloured urine and death especially in young stock.

Unfortunately, recovery from infection by one Leptosira serovar does not provide effective protection against being infected by another.

Seek advice from your veterinarian promptly if you suspect your animals are unwell to help ensure an early diagnosis and appropriate treatment options can be administered.

Leptospirosis can be managed in herds and flocks by vaccination and implementing an effective farm biosecurity plan. Vaccination with the appropriate serovars reduces the risk of outbreaks and shedding thus also minimising herd-related infection.

In general, all members of a previously unvaccinated herd/flock should receive two doses of vaccine 4-6 weeks apart. An annual booster is required. For cattle, breeding females should receive their annual vaccination in early pregnancy so that they are well protected in late pregnancy as will their newborn offspring. Additional doses may be required depending on particular circumstances, for instance for replacement heifers between 6-9 months of age.

Developing a farm biosecurity plan enables you to assess biosecurity risks that exist in your farm’s context and from which you can identify practical measures to mitigate those risks. With regard to leptospirosis this includes (not exhaustively) managing livestock introductions (sourcing and quarantining), within-herd movements, vermin control, human hygiene and personal protective equipment (PPE) as well as livestock vaccination and veterinary services.

Your veterinarian is best placed to advise you on the most appropriate vaccination regime for your animals and assist in the development of your biosecurity plan.

The risk of infection can be reduced by avoiding contact with infected animals, animal products or contaminated soil or water. For those who work closely with livestock or in environments where Leptospira may survive (warm, humid, wet conditions with potentially contaminated soil and water sources), the following measures to prevent leptospirosis include: