The number of confirmed cases of BSE looks set to rise in Ireland with the introduction of "active surveillance" of the national herd, it emerged at a conference of Bovine Spongiform Encephalopathy in Dublin yesterday.
The introduction of the system in Switzerland last year resulted in the number of confirmed cases increasing from 14 in 1998 to 50 in 1999, according to one of the speakers, Dr Marcus Doherr of the Institute of Animal Neurology, Switzerland. The Swiss, who have so far discovered 327 cases in a national herd of 1.7 million animals, have been using a passive surveillance system of monitoring the disease, the conference was told, with farmers or vets reporting cases.
But, Dr Doherr told the conference, entitled "Transmissible Spongiform Encephalopathies - Problems and Solutions", in the Veterinary College, Dublin, that data from passive surveillance are likely to underestimate the level of disease by more than 50 per cent depending on the disease.
The Swiss, he said, had now introduced a system of examining animals being slaughtered because of accidents or disease, and animals which had died on farms. They were also carrying out random tests on a percentage of the national herd - mainly older cows - which would normally be at risk from the disease. He said the number of confirmed cases had increased in the year after active surveillance from 14 to 50, and he would expect that this pattern would be repeated in other European countries when the same system was introduced.
Dr John Griffin, of the Department of Agriculture and Food, said active surveillance was being introduced here within the next few months and would be in place long before it became mandatory under EU directives.
It was possible, he said, that increased numbers of diseased animals could be found in the herd because of this, but as yet the worrying increase in BSE cases in the Republic during 1996 had yet to be explained. The number of cases jumped from 15 in 1995 to 73 in 1996.
That increase, he said, may have reflected a real increase in the incidence of the disease but other factors may also have been responsible.
"It may have been attributable, in part, to a change in the level of reporting. The increase in public awareness that year may have played a role here," he said.
He also told the conference, organised by the Faculty of Veterinary Medicine Research with the Centre for Food Safety, UCD, that the overall incidence rate of BSE in counties Donegal, Cavan and Monaghan was three times higher than the national average.
In Donegal this may have been caused by cross-Border trade in cattle feed and in the other two counties, there was evidence of contamination of feed at one of the mills.