Leptospirosis is a bacterial disease of cattle that is widespread in Ireland. A recent study showed that 79% of suckler and dairy herds in Ireland had been exposed to leptospirosis. The seroprevalence in County Wexford is higher than average.
How is leptospirosis transmitted?
Chronically infected cattle are the main means of transmission and maintenance of leptospirosis in herds.
The bacteria settle in the reproductive tract and the kidneys and infection is passed through contact with urine, placental material or the aborted foetus of infected animals. It can also be spread via contaminated water.
It is important to know that leptospirosis is a zoonosis i.e. it can cause disease in humans. Leptospirosis in humans is caused by direct contact with infected urine or water contaminated by infected urine. The bacteria gain entry through the eyes, mouth, nose or broken skin. Urine splashing up in the dairy parlour is a major source of infection for herdsmen. Infected herds are a zoonotic risk to anyone working with them. Prolonged flu-like symptoms and severe headaches may be signs of leptospirosis in humans. It can also lead to jaundice, meningitis, kidney failure.
What are the clinical signs in cattle?
As leptospirosis is an endemic infection in Ireland, a proportion will have developed immunity. This immunity lasts for approximately two years.
Abortion usually occurs in the last trimester.
Calves may be stillborn, or born small and weak with higher death rates in this group. Infertility may result due to leptospires persisting in the reproductive tract of the cow causing inflammation. This will lead to early embryonic deaths.
An acute mastitis and milk drop syndrome can occur in dairy herds which have never been exposed to leptospirosis before.
This can also be seen in first/second lactation dairy heifers introduced into the herd.
Diagnosis
Blood testing is useful for milk drop syndrome but not that useful in cases of abortion due to leptospirosis. Abortion is a chronic event so the serological response may have waned at time of blood testing.
The foetus can be sent for post-mortem testing.
A number of animals should always be tested to diagnose leptospirosis.
A young stock screen can show evidence of transmission within the herd.
Bulk milk testing is only useful for monitoring and a diagnostic tool in unvaccinated herds.
Control
You need to know the risk factors you may have on your farm
- not having a closed herd i.e. you buy in carrier animals
- AI versus natural service i.e. the bull may be a carrier
- sheep co-grazed with cattle increases risk (a two month gap between sheep and cattle grazing resolves this)
- access of cattle to contaminated watercourse increases risk
VACCINATION is vital for the control of leptospirosis in suckler and dairy herds.
Excretion of leptospires is highest at grass so spread increases after turnout. Therefore the vaccination course should be completed in Spring before the main season of transmission.
Start vaccinating at five – six months old to protect and decrease risk of renal carriers. Heifers and bought-in stock should get a two shot primary course that is completed two weeks before turnout.
Previously vaccinated stock need an annual booster two weeks prior to turnout. Forward planning is required. Heifers should be getting the second shot of their primary course when the adult cows are getting their booster. This ensures the heifers receive their full two-dose course before turnout.
Antibiotic treatment of the bull on an annual basis can be carried out to eliminate the carrier status.
Isolate and treat bought in stock that are entering the breeding/milking herd.