Leptospirosis 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. In these hosts the Leptospira bacteria remain in the kidneys for long periods of time – at least 18 months and perhaps for years.
Infection in secondary hosts will cause more severe clinical signs:
- A drop in milk production
- High fever
- Jaundice (yellow mucous membranes)
- Red water (blood in the urine), with deaths commonly occurring.
How leptospirosis is spread in livestock
Livestock become infected by contact with water or grazing pasture contaminated by urine from infected animals or through mating. Leptospira can survive for extended periods of time in damp soil and stagnant water and can spread rapidly after heavy rain or flooding.
Cows can also pick up the infection directly from each other when they are close together and urinating on each other, like 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.
How common is leptospirosis in livestock
Leptospirosis occurs in all livestock species in New Zealand. A study conducted by Massey University showed that around 27% of dairy farms have animals shedding Leptospira bacteria and on these farms around 9% of the cows were shedders. Rates of shedding are higher on unvaccinated livestock.
Leptospirosis in people
Humans usually become infected via direct or indirect contact with urine from infected animals. This can include contact with urine contaminated water e.g. puddles. The bacteria invade either through the body’s mucous membranes (eyes, nose and mouth) or through cuts and abrasions.
Aborted material or assisting a cow with calving can also cause infection as well as contact with urine or kidneys from home-kill or when hunting (pigs and deer) or when dealing with rodents/possums.
In people it can cause a minor flu-like sickness, but may also make some people seriously ill, needing intensive care at hospital. They may be off work for several months, have lasting kidney or liver damage, and may suffer long term fatigue and depression.
Traditionally the disease has mostly been occupationally-acquired with strong links to the meat processing, farming and forestry industries. Overseas, leptospirosis has also been linked with outdoor recreational pursuits and flooding events.
How common leptospirosis in humans?
Rates of leptospirosis in people in New Zealand are high by international standards. In 2015 there were 63 notified cases, 44 of whom were hospitalised. Farmers and farm workers accounted for 36 of these cases. Results from blood tests of people at risk show that there are about 40-50 people infected each year for every one confirmed case.
Infection can only be limited by preventing exposure to the bacteria. A key part of this is minimising the number of bacteria shed by animals to reduce the environmental contamination. This can be done very effectively with herd vaccination programmes.
However, it is important to note that not all species of leptospirosis shed by cattle are prevented by current vaccines, so minimising contact with urine is important even in vaccinated herds.
It is also 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 practicing good personal hygiene – this includes washing and drying hands prior to eating, and not eating, drinking or smoking in the cow shed. Everyone should wear and use the appropriate protective clothing and equipment, and seek medical help early if feeling unwell, especially if flu-like signs are present. Immediate diagnosis and treatment can prevent long-term health effects.
For more information see Leptospirosis: working with dairy cattle.
The dynamics of leptospirosis on farm are complex, however control is possible with an effective animal vaccination programme and a focus on minimising hazards.
Herd vaccination programmes need to include all classes of stock on farm, this includes cows, calves, heifers, carryover cows, bulls, beef cattle etc. Calves should receive an initial and booster vaccination before they pick up infection, and all other animals should be on an annual vaccination schedule. Your veterinarian will be able to advise you on the right approach for your herd.
All current vaccines are very effective in controlling leptospirosis caused by the serovars included in the vaccine, if started at the right age and given to all stock annually.
Additional herd management
Minimising hazards such as reducing stock access to stagnant water, controlling rodents and other wildlife, and general hygiene will help reduce the risk of transmission and infection.
Other species on farm such as deer, sheep, goats and pigs need to be vaccinated as they contribute to the cycling of disease. Keeping pigs on a dairy farm is a high risk for infection in both cattle and people. Pigs and their effluent should not come in contact with cattle and any pigs on the farm need to be included in the farm vaccination programme.