NADIS disease bulletins are written specifically for farmers, to increase awareness of prevalent conditions and promote disease prevention and control, in order to benefit animal health and welfare.

Farmers are advised to discuss their individual farm circumstances with their veterinary surgeon.

Leptospirosis in Cattle

These spiral bacteria are common causes of disease in cattle. Infection is associated with milk drop syndrome, abortion, weak calves and infertility. Leptospirosis can spread from cattle to man, causing flu-like symptoms and severe headaches

At least five species of Leptospira have been found to affect cattle, in the UK the most important is Leptospira borgpetersenii serovar hardjo. Probably around 60% of herds in the UK have been exposed to leptospirosis.

Clinical Signs

Milk drop syndrome

¨ Sudden large drop in milk production (in some cows it may stop altogether)

¨ All four quarters are affected. The udder is usually soft and flabby and the milk is colostrum-like, with a high cell count but no bacteria.

¨ Affected cows may have a high temperature

¨ Milk drop usually lasts around six days. In some outbreaks 50% of the herd may be affected severely depressing milk production.

Abortion

¨ Unlike milk drop which occurs very soon after infection, abortion occurs 4 to 12 weeks afterwards.

¨ Most cases of abortion occur in the second half of pregnancy.

¨ Infection close to calving usually leads to small weak claves rather than abortion

Infertility

¨ Leptospirosis has been linked to infertility problems such as reduced pregnancy rates and irregular returns to oestrus. However abortion is the most common fertility problem associated with leptospirosis.

Diagnosis

· Milk drop syndrome can be diagnosed on clinical signs, but blood testing of affected animals can be a very useful confirmation.

· Diagnosis of abortion is more difficult as infection is usually distant from the loss of the calf so individual blood testing is less helpful. However testing can show the level of infection in the herd and in some cases show whether there is a link between abortion and leptospiral antibody. Bulk milk testing can also be helpful in dairy herds

· Examination of the aborted calf will occasionally confirm infection in the calf, but is more useful for identifying causes of abortion other than leptospirosis

Treatment

· Large doses of dihydrostreptomycin may help remove the organism in cattle with milk drop. (They can also be used in bought-in cattle of unknown status)

Prevention

Beef cattle:

Many herds are infected without apparent disease. In closed herds, which breed their own replacements, infection may occur in calves before weaning resulting in no effect on reproduction. In such cases, preventive strategies are unlikely to be economic if the majority of the herd are infected. However it is still important to know the status of the herd to confirm that such strategies are unnecessary.

However in herds that buy in replacements, infection is likely to occur at a critical time and can result in significant losses. In such herds it is important to know the status of the herd and put in control measures.

Dairy Cattle

In dairy cattle the risk of spread to humans is increased as there is much greater contact with urine which is the main source of the bacteria. Thus even in herds with no obvious clinical disease prevention is important.

The main methods of preventing leptospirosis getting on farm (whether beef or dairy) are:

1) Fencing off contaminated water (all natural water courses should be assumed to be infected).

2) Treating all bought-in animals with antibiotics, isolating new animals, checking their antibody status and vaccinating.

3) Avoiding contact with sheep (which can be a reservoir of infection)

In infected farms there are two possible control methods:

1) Vaccination. It will significantly reduce the level of abortion, and greatly reduce the spread of disease from cattle to man. Several leptospirosis vaccines are available; your vet should be able to advise on the best to use and the best regime. However, all available vaccines require yearly boosters to maintain effectiveness. This yearly booster is important as vaccination prevents disease but does not eliminate the organism from the farm, so stopping vaccination often results in the recurrence of the disease.

2) Blood testing and removal. A properly planned strategy, combined with good biosecurity will produce a herd free from leptospirosis, resulting in improved health and breeding performance and decreased human disease.

Richard Laven PhD BVetMed MRCVS