Testing For Brucellosis Gains Momentum

Press, Volume CIII, Issue 30442, 16 May 1964, Page 8

Testing For Brucellosis Gains Momentum

As far as he knew Christchurch was the only place in the world where a scheme for eradication of brucellosis from the milk supply had been carried to the point where the disease had virtually been eliminated, Dr. C. S. Hopkirk, who is in charge of the milk research laboratory at Lincoln College, said this week.

It was something of which the city and milk producers could be very proud, he said.

The area had virtually been a guinea pig to prove the reliability of the method used to test cows in milk and now from the laboratory at Lincoln, testing was being extended to other South Island centres. As yet, however, no other scheme of eradication had been formulated. It appeared as though this was awaiting Government action on compensation for affected cattle.

Tracing the history of brucellosis eradication in Christchurch, Dr. Hopkirk said that in 1959 Dr. H. S. Cameron, from the University of California at Davis, had come to Wallaceville Animal Research Station under a Fulbright scholarship to work on testing of milk for brucellosis as compared with blood testing. The Canterbury Dairy Farmers Ltd., and the Metropolitan Milk Company had invited Dr. Cameron to look over the herds in the Christchurch area and it had been arranged that 10,000 milk and blood samples should be sent from the area to Wallaceville. It had been found that the incidence of brucellosis in Christchurch town milk supply herds was about 4.3 per cent, which was really quite low, but subsequently the Canterbury Dairy Fanners and then the Metropolitan Milk Company had decided to proceed with a voluntary scheme of eradication and had asked Lincoln College to undertake the testing. This the college had done since 1960.

Where there was a positive reaction to a ring test on the bulk supply from a herd the milk from each cow in the herd was submitted to the

whey agglutination test, and where there were weak reactions to this test, Dr. Hopkirk said, milk from each quarter had also been tested and it had been found that cows were sometimes infected in only one or two quarters. Farmers had been asked to have infected cows slaughtered and for these a compensation payment of £lO had been made over and above the carcase value, and the Canterbury Dairy Farmers had also instituted a halfpenny a gallon premium on milk from disease free herds.

Up to April 1 of this year, Dr. Hopkirk said, 1325 cows had been slaughtered under the scheme and the result was that only one on town milk supply now had the infection, and it was not in the voluntary scheme. Two hundred and eighty-six herds had been in the scheme. It was creditable that company members had carried the cost of this achievement. From time to time breakdowns occurred in herds, said Dr. Hopkirk, and he believed that repeat ring tests at this stage should be made on herds at not more than two-monthly intervals. Breakdowns occurred where a farmer bought in an affected animal or had a cow with an infected gland and the trouble moved out to the udder. The trouble was that once a farmer had an infected cow the disease spread quickly to susceptible diseasefree cows. The spread was facilitated by the milking machine. So far he said that it had been necessary to blood test a herd on only three occasions. Dr. Hopkirk said that vaccination which prevented animals aborting did not provide protection from infection of the udder, but dairy farmers should continue to vaccinate

calves only to avoid abortion storms. They should not, however, vaccinate older cattle, as it upsets testing, which could not be restarted for at least nine months.

At the request of the South Island Milk Producers’ Federation the bulk supply from herds in Greymouth, Westport, Nelson, Blenheim, Kaikoura, Ashburton, Timaru and Dunedin had been submitted to the ring test, and individual cows from affected herds in Greymouth, Kaikoura, Blenheim and Timaru and a few in Nelson had been submitted to the whey agglutination test. However, as yet no eradication scheme had been organised by any of the associations in these centres. In Kaikoura, however, farmers had slaughtered infected animals.

In the meantime, Dr. Hopkirk said, he had suggested that these outside areas should continue to send in bulk samples for ring testing so that it could be determined whether any further herds had broken down.