The most common manifestions of leptosporosis are abortion and infertility. Other less common manifestations include milk drop syndrome, mastitis and weak calf syndrome.

Cause

Leptospirosis is a bacterial disease caused by leptosira hardjo. Chronically infected cows are the main means of transmission and maintenance of leptospirosis in herds. Infection in cattle is acquired from contact with infected urine and the products of abortion including foetuses, cleanings and discharges. The bacteria make their way to the kidneys, wombs and udders of infected animals. Chronic infections are established in the kidneys and the animal itself becomes a source of infection for comrades.

It is also important to note that leptospirosis is a zoonosis, ie it can cause disease in humans (flu-like symptoms and occasionally meningitis). Leptospires are spread in urine and uterine discharges from carrier cows. As a result, dairy farmers are at most risk of contracting disease due to urine splashing in the parlour. Farmers may also be exposed to the bacteria from discharges and fluids from the wombs of cows at calving.

Symptoms

As the disease has been endemic in the country for so long, leptospirosis causes subclinical disease in the majority of herds, ie low level of disease that may often go unnoticed. In suckler and dairy cows, abortion occurs usually in the last trimester of pregnancy, ie in cows approximately seven months in-calf.

In some herds calves may be stillborn due to infection of the cow in late pregnancy. Other calves may be born small (5kg to 10kg lighter than normal) and weak, with increased mortality rates among this group. Leptospirosis has been linked to infertility due to inflammation caused by leptospires which persist in the uterine tract of the cow. The main manifestation of this infertility is in the form of early embryonic deaths.

In naïve dairy herds, leptospirosis can cause an acute mastitis and milk drop syndrome, which can affect up to 40% of a herd over a number of weeks. The udder has a soft flabby appearance and the milk is yellow in colour and similar to colostrum in consistency. Fortunately, milk drop syndrome outbreaks are now very rare in Ireland.

Treatment

Antibiotic treatment of the bull on an annual basis, and also of purchased animals that are entering the breeding/milking herd, can be carried out to eliminate the carrier status. Antibiotic treatment of cows which are comrades of cows where leptospirosis has been diagnosed is often warranted. However, it is strongly recommended that you consult your vet before deciding to treat animals with antibiotics.

Prevention and control

Leptospirosis is much more common in larger suckler and dairy herds. Other risk factors include the purchase of carrier animals, the use of a bull, the co-grazing of cattle and sheep and access of cattle to contaminated watercourses.

It is important to reduce risk factors on-farm, to maintain good biosecurity and a closed herd policy if possible. Vaccination plays an important role in the control of leptospirosis in suckler and dairy herds and will also reduce the zoonotic risk to dairy farm workers. Ideally, vaccination programmes should be completed a month before the breeding season starts.