Leptospirosis

Writing by Andrew Cribb, Director/Veterinarian, East Coast Farm Vets

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Leptospirosis is caused by the bacteria Leptospira interrogans, which is found throughout New Zealand and the world. There are over 150 serovars of L. interrogans, six of which are present in New Zealand. A study conducted by Massey University found that Leptospirosis-positive animals were present on 97% of sheep and beef farms and 76% of deer farms.

Leptospirosis can infect most mammals, including sheep, cattle, deer, goats, and dogs. It is one of New Zealand’s most significant zoonotic diseases—meaning it can be transmitted from animals to humans. The bacteria target the kidneys, causing damage and increasing the risk of infection. As such, Leptospirosis should be a key consideration in every on-farm health and safety policy.

In cattle, Leptospirosis can cause severe disease. Clinical signs may include:

• Loss of appetite

• Abortion, stillborn or weak calves

• Mastitis

• Potential future infertility issues

In sheep, outbreaks in lambing hoggets can be devastating. Some lambs may be found dead, while others will appear lethargic and refuse to eat. Affected lambs may have red-coloured urine that stains the wool around the hocks and crutch area. Jaundice can also occur, leading to pale, muddy-coloured, or yellow mucous membranes. In ewes, Leptospirosis can cause abortion.

Animals that recover from Leptospirosis can continue to excrete Leptospira bacteria in their urine for extended periods. Research indicates that sheep can shed Leptospires for up to 11 months.

Leptospires can survive outside of a host for up to six months, particularly in environments with contaminated effluent, damp soil, and stagnant water. The bacteria can spread rapidly following heavy rain or flooding, further increasing the risk of infection.

Human infection is relatively common among agricultural workers, rural veterinarians, abattoir workers, and forestry workers. The disease is typically transmitted through:

• Contact with infected urine (via splashes to the eyes, nose, or mouth)

• Exposure to abortion or placental material through breaks in the skin

• Consumption of raw milk from an infected cow in the acute phase of infection

In 90% of cases, infected individuals experience severe flu-like symptoms, but their immune system typically mounts an effective response. However, in 10% of cases, without medical intervention, symptoms can progress to liver and kidney failure.

To minimize the risk of a Leptospirosis outbreak on your farm, discuss a comprehensive vaccination program with your veterinarian, maintain effective rodent control, keep pigs separate from cattle and sheep and fence off or drain contaminated or stagnant water sources.

This article was published in the Gisborne Herald on 22/03/25.