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LEPTOSPIROSIS SUMMARY
Bovine leptospirosis is the disease of cattle caused by infection with the bacteria known as Leptospira interrogans serovar hardjo. This disease is believed to be widespread in Scottish cattle having first been imported and subsequently identified around 1970. It is important not only because it causes disease in cattle but also because it can cause disease in man.
The main features of infection are abortion and the birth of weak and premature calves. It is also believed to result in poor herd fertility. Acute infection results in high temperature with a sharp decrease in milk yield (“flabby bag”) and abortion often occurring 2 to 3 months later. In humans infection causes headaches, join pains and occasionally fatal meningitis. It therefore poses a particular Health and Safety problem to farm owners. Antibody to this agent may be a barrier to export live cattle. There are vaccines available to help minimise clinical disease but they do not eliminate herd infection.
The agent is carried in the kidneys and transmitted by infected urine splashing the eyes, mouth, nose or wounds of other susceptible cattle. It can also be transmitted by infected bulls during service, through the placenta, through the products of abortion/calving and even in the milk during the acute phase.
Those herds that remain free from infection with leptospirosis should make every effort to retain this status. Exclusion of leptospirosis is a sensible option given the potential losses associated with herd infection and concerns over human health. Eradication may be worth attempting in herds where the level of infection is low and there is no evidence of active disease.
Leptospirosis Accreditation Programme
To show freedom from this disease all cattle of 2 years or older and all
animals intended for breeding that are one year or older are tested twice
at an interval of 6 to 12 months. Thereafter each year a statistically
based sample of breeding animals of one year of age and older, from each
separately managed group, must be sampled. This would usually mean a sample
from the cow herd and a sample from the followers. Following accreditation
dairy herds must have bulk milk tested quarterly in addition to the annual
screen testing.
If the number of reactors is low they may be culled and the initial herd test can be repeated after a minimum of six months. If large numbers of reactors are found in young stock and young cows there are two options:
Maintain herd health security and retest a sentinel group of serologically negative animals every six months;
Vaccinate the herd. Once a vaccination programme has been implemented the current blood test is unable to differentiate infection from vaccination so accreditation cannot begin until all vaccinated animals have left the herd.
An eradication programme is not offered for Leptospirosis.
Leptospirosis Biosecurity Measures
Added animals must be placed in isolation and tested according to the CHeCS
rules before the animals can enter the herd. Ideally the animals should
also have previously been tested on the farm of origin because if positive
there will be considerable savings in time and expense.