Leptospirosis is one of the most common causes of abortion in Irish cows. There are two serovars of Leptospirosis commonly found in cattle in Ireland; Leptospira interrogans hardjo and Leptospira borgpetersenii hardjo.
As well as causing abortion in cows, the infectious bacteria effects fertility in other ways, causing low conception rates, abnormal return to heat, stillbirths and weak calves.
First diagnosed in Ireland in the mid-1970s, Leptospirosis is now a very common bacterial infection. It has been found that over 80% of dairy and beef herds are endemically infected.
Bulk milk samples from 312 Irish herds were taken in 2009 to test for antibodies to Leptospira interrogans hardjo. 76% of herds were vaccinated against L. hardjo. However, in unvaccinated herds, the overall prevalence of antibody-positive herds was 86%.
Leptospirosis was reported prevalent in 82% of Irish suckler herds in 2012. Figures were found consistently highest in the South-East.
The bacteria is shed by carriers in urine, milk and calving fluids. Infected cows can recover from infection but may carry the pathogen for months or years. Sheep can also carry leptospires and can be a source of infection for cattle. Younger animals are most at risk of disease in dairy herds.
Leptospirosis is a zoonosis, meaning it can cause serious disease in humans. Farmers, abattoir workers and vets are the main groups at risk, through contact with the urine, afterbirth or aborted foetus of an infected animal. Clinical signs of the disease in humans are flu-like, with headaches and fever, occasionally progressing to meningitis.
- Abortion - mid to late gestation, usually in the last trimester;
- Stillbirths or Perinatal Weak Calf Syndrome - small weak calves that frequently die within 48 hours;
- Infertility - poor conception rates and early/late embryonic death;
- Milk drop - often the first symptom was a sudden decrease in milk yield but rare now due to endemic nature of hardjo in Ireland;
- Often has no clinical signs in the herds.
Main risk factors
- Purchase of infected cattle;
- Common grazing with infected cattle or sheep;
- Purchase or hire of an infected bull;
- Access to contaminated water.
Maintain good biosecurity and keep a closed herd policy where possible. The most common way for L. hardjo to enter a herd is via a carrier animal.
Implement a vaccination programme
Given the risk to farmers and its prevalence, herd vaccination is advised as the most effective control measure against Leptospirosis. Cows should be vaccinated more than two weeks before the start of the breeding season.
Vaccination will reduce the effect of an outbreak should it occur. Herd immunity wanes with increased disease every five to seven years in endemically infected herds. Remember, vaccines will not clear the carrier status.Further reading on the research conducted on Irish dairy herds can be found here.