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Leptospirosis is a highly infectious bacterial disease affecting humans and most mammals. For cows, it can cause abortions, mastitis and decrease milk production, while calves can suffer severe symptoms such as fever, loss of appetite and sometimes death. It spreads through infected urine, contaminated water or pastures, from animals to humans and from animal to animal, and it's especially common in New Zealand.
Leptospirosis is a significant human health risk causing flu-like symptoms or severe ongoing illness. Protect the people and animals on your farm by taking appropriate preventative measures.
Leptospirosis occurs in all livestock species in New Zealand.
Multiple Leptospira serovars (strains) occur in New Zealand cattle, including ones not covered by routine vaccination. There are over 200 serotypes currently identified worldwide, and at least five strains are present in New Zealand dairy cattle.
A Massey University study showed that:
Symptoms in animals
The signs seen in animals will depend on whether the animals are primary or secondary hosts and sometimes they can be asymptomatic.
Primary hosts shed infectious bacteria via their urine into the environment and generally show only minor clinical signs.
Leptospira bacteria remain in the host’s kidneys for at least 18 months and potentially, for years.
Infection in secondary hosts will cause more severe clinical signs:
Clinical signs in cows
Clinical signs in calves
Livestock become infected by contact with water or grazing pasture contaminated by urine from infected animals or through mating.
Leptospira can survive for up to six months in damp soil and stagnant water and can spread rapidly after heavy rain or flooding.
When cows are close together, they can infect each other via urine e.g. in the milking shed.
The bacteria are extremely infectious and can penetrate intact mucous membranes, and skin that has been softened by exposure to water. Cuts and abrasions make it easier for the bacteria to enter the body.
The bacteria do not survive well out of water so there is little infection risk from dry surfaces.
Leptospirosis is easy to catch from an infected animal, but transmission from person to person is rare.
Humans can become infected via direct or indirect contact with urine from infected animals either through the eyes, nose and mouth or through cuts and abrasions. This can include:
How common is leptospirosis in humans?
Rates of leptospirosis in New Zealand are high by international standards. Around 50-150 people are diagnosed here each year, and a high proportion are farmers and farm workers.
Results from blood tests of people at risk show that there are about 40-50 people infected each year for every confirmed case.
Symptoms and effects for people
Leptospirosis can cause a minor flu-like sickness, or a serious illness, requiring hospitalisation. Long-term effects can include:
Limit infection by:
Risks and response
It is important that all people working with animals are aware of the risks and know what to do before entering areas where they are exposed to animals or animal urine. Preventative measures for people include:
Employers have a responsibility to manage health and safety risks on their farm under the Health and Safety at Work Act 2015, this includes taking preventative measures for leptospirosis. For more information about reducing the risks on your farm, speak to your veterinarian.
The dynamics of leptospirosis on farms are complex, but an effective animal vaccination programme and a focus on minimising hazards can aid control.
Herd vaccination programmes need to include all classes of stock on farm e.g. cows, calves, heifers, carryover cows, bulls and beef cattle.
Calves should receive an initial and booster vaccination before they pick up an infection, and all other animals should be on an annual vaccination schedule.
Other species on the farm (e.g. pigs and sheep) can also carry Leptospira bacteria so they need to be considered as part of your vaccination programme.
All current vaccines are very effective in controlling leptospirosis caused by the serovars (strains) included in the vaccine if started at the right age, stored and used within manufacturer specifications and given to all stock annually. The available vaccines vary in the serovars they cover, your veterinarian will be able to advise you on the right approach for your herd.