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How to manage bacterial disease Leptospirosis

Leptospirosis, a bacterial disease, is mainly spread via urine from carrier animals.
Leptospirosis due to Leptosira Hardjo is a bacterial disease that is widespread throughout the suckler and dairy cattle population in Ireland. Research conducted at the UCD Veterinary School has shown that 80% of suckler and dairy herds have evidence of exposure to the disease.

Chronically infected cows are the main means of transmission and maintenance of leptospirosis in herds, and there is recent evidence to show that sheep can also transmit the disease to cattle. Leptospirosis manifests mainly as disease affecting the reproductive system, i.e. abortion, infertility and the birth of stillborn or weak calves. It is also important to note that leptospirosis is a zoonosis, i.e. 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 slashing in the parlour.

Symptoms

As the disease has been endemic in the country for so long, leptospirosis causes subclinical disease in the majority of herds, i.e.low level of disease that may often go unnoticed. In suckler and dairy cows, abortion occurs usually in the last trimester of pregnancy, i.e. 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 to10kg 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 naive 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.

Diagnosis

Individual blood testing can be unrewarding and, therefore, a number of animals should always be tested to help arrive at a diagnosis. A young stock screen can show evidence of transmission within a herd. Bulk milk antibody testing is only useful as a monitoring and diagnostic tool in unvaccinated herds.

Treatment

Antibiotic treatment of the bull on an annual basis, and of purchased animals that are entering the breeding/milking herd, can be carried out to eliminate the carrier status. Most commonly, two injections of streptomycin or longacting oxytetracycline are given 10 days apart.

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. There are two good vaccines available in Ireland, i.e. Le tavoid-H and Spirovac.

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.

Cattle should be vaccinated more than two weeks before the start of the breeding season.

Source: Irish Farmers Journal


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