This disease has several different clinical signs. These are:
- Mild short term temperature increase (1st sign)
- Mastitis and milk drop ( 2nd sign)
- Abortion – usually occurs 6-12 weeks after initial infection
- Reduced fertility via a decrease in conception rates
Many abortions in British cattle are caused by this disease. The cattle are infected by coming into contact with urine from an infected cow or sheep. This can occur directly or through a water course from a neighbouring farm. Often abortion is the first clinical sign after the animal is infected.
Diagnosis is difficult as the organism doesn’t live very long and is difficult to grow in the laboratory. Antibody levels are high at initial infection, but are low 6 to 12 weeks later when an abortion occurs and so do not give any clear indication that the organism is responsible. The best way to measure it is to use a bulk milk sample to give you an idea of the overall percentage of the herd that are infected. These are cheap and easy to do.
The organism can remain in the fertility tract for quite some time, leading to regular and irregular returns to service, the latter being due to causing early death of the embryo. It is this that will lead to reduced fertility in the herd.
Fortunately there is a good vaccine available Leptavoid-H. This is given as two doses, four weeks apart, with a yearly booster. It is best given in the spring before turnout, as most outbreaks occur when the cows are at pasture. It is also important not just to vaccinate the milking herd, but also any heifers that are being reared prior to their entry to the herd, and any other suckler cows on the farm. Not only will this help defend the herd against abortion and fertility problems, but it will also avoid the reduced yields that are seen in cows that become infected.
Preventing entry into a closed herd is done by reducing the risk factors, which are:
Purchased cattle, including bulls. These cattle should be treated with anti-biotics, vaccinated and isolated. Two weeks after the second dose of vaccine they should then be safe to enter the herd. However there is always a slight risk that they could still be a carrier of the disease.
- Hired or Shared bulls
- Grazing sheep with cattle, as they are carriers of the disease.
- Access to water courses and streams that are shared with other establishments. Excreted organisms can be washed downstream from one farm to the next.
Warning – Leptospirosis Is A Zoonosis
Humans can become infected with Leptospirosis if they are splashed with infected urine i.e. in the parlour. Symptoms include headaches, fever and aching joints, similar to a bad case of flu. Vaccination can reduce the human health risk. The Leptospirosis carried by rats is a different type to that of the cows, and there is no evidence that the vermin are in any way responsible for the spread of the disease in cattle.