Tuberculosis - the new threat

Since restocking Cumbria after foot and mouth there have been over 90 herds, which have had tuberculosis. This has resulted in over 295 cows being slaughtered. Not all of these cases have occurred in restocked herds, but the majority are associated with cattle that have been brought into the county, writes Graham Brooks, of Coomara Veterinary Practice, Carleton, Carlisle.

There are two means by which Tuberculosis can be spread. Within a herd or between herds then close contact between an infected animal and a non-infected animal is required. The bacteria are normally excreted in nasal and mouth secretions, milk and occasionally urine and faecaes. Because it is not possible to tell just by viewing if a cow is infected cow or not, it is necessary to keep your cattle separate from other possibly infected cattle.

The other means of spread is by environmental contamination from infected wildlife species. Because Cumbria was free of tuberculosis before Foot and Mouth, hopefully we can assume that our native wildlife is not infected with the disease. However, if it does become infected then from the examples set by other parts of the country it is unlikely that the county will be free of the disease for a considerable time.

At present in this country Tuberculosis is diagnosed by using the comparative intra dermal tuberculin test. However, this test is by no means 100 per cent efficient at detecting all infected animals. An outbreak of Tuberculosis on your farm can have serious implications. These include movement restrictions preventing you from selling except under licence direct to slaughter and from buying in replacement animals.

The length of time the movement restrictions stay in place depends on the severity of the disease but they will until all bovine animals on the premises have had a second intra dermal test a minimum of 42 days after the initial test. All animals have to pass this test for the restrictions to be lifted. Some animals are classified as inconclusive. These animals have to be placed in isolation and are retested after 42 days.

What can you do to prevent your herd being infected? As already stated the two main sources of infection for your cattle are other infected cattle and wildlife. Therefore to prevent infection entering your herd you need to maintain suitable biosecurity measures. These would include ensuring all your fences are such that your stock cannot make contact with your neighbours. A three-meter gap is a minimum between two fields. Ensure that all food stores are secure against wildlife to prevent contamination.

A lot of wildlife are attracted to molasses feed blocks etc. therefore these should be raised off the ground by at least 30 inches. The same applies to all water and feed troughs. If you are buying in cattle then it is wise to inquire when the herd was last tested for Tuberculosis and at what frequency the tests have been carried out. If the herd has not been tested in the last three months consider having a private intra-dermal test carried out before buying.

Because of the inefficiencies in the test, all cattle entering the farm should be isolated and re-tested after 42 days. Tuberculosis bacteria can survive in damp places in the environment for several months. Therefore all farm buildings that have been used for isolation should be cleaned and disinfected before reuse. Ensure that you have your routine tuberculosis test carried out as soon as possible after it becomes due. If your herd is infected the sooner it is found the less animals that will need culling.

Please try to have your herd tuberculin tests carried out as soon after the due date as possible. The use of an isolation period for cattle entering the farm is an ideal time to test cattle for other diseases such as BVD and IBR and to carry out any necessary vaccination programmes to prevent newly introduced stock becoming infected with diseases that are endemic in your herd.

All herd health plans should have a section in them dealing with the procedures for introducing new livestock to the farm. This is best arranged with your own Veterinary Surgeon who should know the disease status of your herd and can instigate the correct vaccination and testing regime for you.