Leptospirosis

Leptospirosis in people

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:

• Contact with urine-contaminated water e.g. puddles, waterways.
• Handling aborted material or assisting a cow with calving.
• Contact with urine or kidneys from home-kill, or when hunting (pigs and deer) or when dealing with rodents/possums.

Symptoms and effects for people

Leptospirosis can cause a minor flu-like sickness, or a serious illness, requiring hospitalisation. Long-term effects can include:

• Kidney or liver damage
• Chronic fatigue
• Depression
• Inability to work

Preventing leptospirosis

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:

• Good personal hygiene – wash and dry hands prior to eating, and don’t eat, drink, smoke or vape in the cow shed.
• Wear appropriate protective clothing and equipment, such as gloves, milking sleeves, shed aprons and gumboots.
• Seek medical help early if feeling unwell, especially if flu-like signs are present. Immediate diagnosis and treatment can prevent long-term health effects.
• Ensure farm visitors are aware of your leptospirosis management practices.

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 undiagnosed people infected each year for every confirmed case.

Leptospirosis in animals

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 strains currently identified worldwide, and at least five strains are present in New Zealand dairy cattle.

A Massey University study showed that:

• Around 27% of dairy farms have animals shedding Leptospira bacteria
• On these farms, around 9% of the cows were shedders
• Rates of shedding are significantly higher in unvaccinated livestock

How leptospirosis spreads

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.

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 meaning animals can potentially shed bacteria for life.

Infection in secondary hosts will cause more severe clinical signs:

Clinical signs in cows

• Abortions
• Mastitis
• A drop in milk production

Clinical signs in calves

• Depression
• Loss of apetite (anorexia)
• High fever
• Jaundice (yellow mucous membranes)
• Red water (blood in the urine), with deaths commonly occurring.

Vaccinating livestock

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 early in life before they pick up an infection, and all other animals should be on an annual vaccination schedule. Starting calves too late in life can mean they still shed bacteria even after vaccination, so it’s important to work with your vet to identify the best approach.

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.

Additonal farm managment

• Careful effluent management. This includes adequate fencing around effluent ponds and holding tanks, and ensuring effluent paddocks are not grazed soon after spraying. Find out more on managing dairy effluent.
• Fence waterways to make them inaccessible to cattle and people.
• Control rodents and wildlife as they can be a source of feed and water contamination.
• Keep pigs and their effluent away from cattle or people.