Farm Ireland
Independent.ie

Sunday 26 February 2017

Diseases to keep an eye out for

High-bulk milk titres to IBR indicate infection in the herd. IBR infection in cows is permanent. Supplementary individual blood testing throughout the age groups in a herd may be necessary to define the extent of IBR infection. Management of the environment, stress and use of vaccination are necessary to control IBR.

BVD

The Animal Herd Health protocol for BVD investigation advocates using bulk milk sampling and testing for both antibody and virus. Three-monthly sampling can detect increases in bulk milk antibodies. If the BVD bulk milk antibodies are high it does not necessarily confirm that there is a persistent infected (PI) cow in the milking herd. Further individual testing may be necessary to identify PI animals by blood-testing young, unvaccinated animals from each separate group. The key to the control of BVD involves removing PI animals from the herd. Having removed these animals, vaccination supports immune protection of the herd.

Leptospirosis

This is present in 60-70pc of Irish herds. It causes infertility, abortion and depresses milk production and leads to the birth of weak calves.

Because leptospirosis localises in the kidney and is shed either continuously or intermittently in the urine, it is necessary to test bulk milk in herds three or four times a year to detect antibody trends. A spike in lepto milk antibodies may indicate recent surges in herd infection or perhaps recent vaccination. Vaccination history is essential for interpretation of results. Because leptospirosis can affect humans, vaccination is often used as a prevention strategy in many herds.

Johne's disease

The Johne's Elisa test detects antibodies in blood and milk. Additional tests, together with the herd health history, are very important to diagnose and manage Johne's in the herd. The Johne's bulk milk test will only give a positive result consistently in a herd with a high level of infection. Beware of a negative bulk milk Johne's test. This does not mean that a herd is Johne's-free because its antibodies appear late in the disease process.

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Fluke

A total of 84pc of dairy herds have recently tested positive for fluke. Fluke infections can be associated with depressed milk production. Faecal sampling for fluke eggs and veterinary post mortem of livers at the meat factory provide supplementary evidence of fluke infestation.

The history of fluke treatments in herds is needed for interpretation as fluke antibodies will remain high after using some fluke treatments. In other words, even when fluke is eliminated from the liver by a flukecide, there may be a high reading in the bulk milk test.

Neospora

This is a coccidian protozoa that causes abortion in dairy cattle. It is the most common cause of abortions in dairies in many areas of the world. The dog and other canids (such as foxes) are the animals in which the parasite becomes sexually mature and reproduces. The clinical signs include:

•Abortion, from 3-9 months of pregnancy (particularly 5-7 months).

•Still birth or premature calves.

•Occasionally calves will have brain disease at birth

•No other signs seen in the mother.

•Repeat abortions are possible in the same cow.

Increases in bulk milk antibodies to neospora may indicate recent exposure. It is a valuable aid in monitoring this disease.

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