Thirty years ago leptospirosis was one of the most common zoonoses in NZ with over 400 human cases a year, mainly in dairy farm workers.
In recent years the widespread vaccination of pigs and dairy cattle has reduced the number of human cases to fewer than 100 a year.
However there are still plenty of infected livestock on farms. It has been estimated that currently meat workers deal with from 5 to 25 lepto-infected sheep and deer carcasses daily. Meat workers are at risk of becoming infected while working on these carcasses. The farmers who are most at risk are those who milk unvaccinated cows, who work with unvaccinated pigs or who deal with possums.
This article will give you an overview of the current situation in New Zealand, to help you understand the significance of lepto for you and your animals.
How does the disease spread?
- Lepto bacteria can infect cattle, pigs, sheep, deer, possums, rats, mice and dogs as well as humans.
- An animal becomes infected when bacteria in urine from an infected animal enter its body, either through the mouth or eyes or through skin cuts.
- Once in the body the bacteria generally localise in the kidney. They multiply there and can be excreted in the urine for months or even years.
- From the urine the bacteria may infect other animals, and so the cycle of infection continues.
- Water sources can be contaminated by bacteria in urine from livestock, rodents and other wildlife.
What's its effect on livestock?
Leptospirosis affects different species in different ways:
- There are two main types of lepto in cattle. Leptospira pomona cause abortion in cows and redwater in calves. L. hardjo infection is more common but it doesn't cause serious disease.
- Nowadays the risk of commercial dairy farmers being infected by cattle is low, because most dairy farmers vaccinate their cows.
- Lifestyle farmers are at risk if their cows are not vaccinated.
- There are two main types of lepto in pigs. Leptospira pomona and L. tarassovi both cause abortion in sows, and piglets may be stillborn or die within a few days.
- Some pigs carry the bacteria in their body, excrete the bacteria in their urine but don't show signs of disease.
- Lifestyle farmers are at risk if their pigs are not vaccinated.
- In deer, there have been occasional outbreaks of leptospirosis causing redwater in young deer and the occasional abortion in hinds.
- Deer can pick up the infection from pigs or wildlife.
- Some types of leptospirosis cause severe liver and kidney disease in dogs, but this is uncommon in New Zealand nowadays.
- Leptospirosis is not usually included in the range of diseases that routine vaccination protects against.
- There are effective vaccines available, and they really should be used wherever there is a risk of infection, especially in cows and pigs. Contact your local vet for advice.
- Vaccination involves two injections about 4 weeks apart for young stock over 12 weeks of age, then a booster each year.
- In some areas your dog may be at risk from lepto and your vet will advise if vaccination is wise.
- It may be wise to vaccinate any deer and alpacas you have if they have contact with sheep or pigs (that may be symptomless carriers). Your vet will advise.
- In humans, lepto causes severe flu-like symptoms and meningitis, liver and kidney disease that can last for up to 6 months.
- Fortunately treatment with antibiotics such as streptomycin is effective especially if begun early.
The bottom line
If you home-kill livestock or handle pigs or possums or hand-milk dairy cows:
- Make sure your personal hygiene is good.
- Wear rubber gloves when handling anything contaminated by urine.
- Put plasters on any cuts on your exposed skin.
- Get your pigs and dairy cows vaccinated.
- In some areas it might be wise to vaccinate your dogs, deer and alpacas. Your vet will advise.