FRANCE COULD be sitting on a variant CJD time bomb, according to two French academics.

The claim is made on the grounds that over 300,000 cows are thought to have been infected with the BSE agent in the 1980s and 1990s, many of which entered the human food chain.

Their estimate appears in a paper published in the latest issue of the Veterinary Research journal.

The authors conclude that there was “considerable BSE case under-reporting throughout the epidemic”.

“Despite uncertainty over the beginning of the epidemic, we show that the French BSE epidemic in the late 1980s was completely undetected, and only the second wave, after 1990, was observed.”

At the heart of the issue is the fact that the French authorities only started looking for the disease in 1990 and this was done passively – farmers and vets were responsible for reporting animals with clinical signs.

It was over 10 years before active surveillance of all over-30-month cattle came in.

“Implementation of active surveillance revealed the inefficiency of the passive surveillance, both in France and elsewhere,” says the report.

“Comparisons showed that only 20% of BSE cases were identified by passive surveillance.”

The report notes that these cases only related to animals in the latter stages of incubating the disease. Infection with BSE is reckoned to happen shortly after birth.

Also, the 103 cases identified by passive surveillance only covered the period from 1990.

“Meat and bonemeal was already being imported by France from the UK in 1985. As the earliest birth cohort of a BSE case dates back to 1983, French cattle were already potentially exposed to the BSE agent at that time.”

Using a method of back calculation, allowing for such things as French cattle mortality, exposure to meat and bonemeal and BSE reporting, the authors estimate that 301,200 cattle were infected by the BSE agent between 1980 and 1997.

Of these, around 49,000 are thought to have been in the late stages of incubation and slaughtered for human consumption.

The report explains that the level of BSE infection in French cattle is still considerably less than in the UK, where up to four million cattle may have been infected over a similar period.

But, while bovine offal was banned in the UK in 1989, it was not until 1996 that the same steps were taken in France.