The mathematical likelihood of there being BSE in sheep

Ignorance of the realities of farm life has misled scientists

The fear of "scrapie masking BSE" - a terror of vCJD that has resulted in the National Scrapie Plan, the Animal Health Bill and the killing of thousands of sheep in Europe - rests on the fact that the FSA and SEAC appear to have have accepted the mathematical modelling of the "theoretical likelihood" of BSE in sheep.

Hundreds of thousands of pounds-worth of well-meaning research has gone into trying to prove that BSE does indeed occur naturally in sheep. Even more has been spent on experiments involving the injecting of BSE material into the brains of living animals. Yet no single case of naturally occurring BSE in sheep has been found.

Assuming that BSE was indeed "caused" by the feeding of contaminated MBM, the thinking is that since both cows and sheep consumed the feed, that BSE could have been passing silently through the sheep flocks by maternal transmission ever since, perhaps "masked" by scrapie.

But what the mathematical modellers may be unaware of - as was the case with FMD - are the realities of farm life. Sheep are not cows - and this difference is not confined to their brains. First, dairy cows, poor manipulated creatures of today, are bred to produce enough milk to be able to feed far more than a single calf. In the days of the "contaminated feed" they were consuming between 1 ton and 1½ tons of dairy cake a year. In contrast, the ewe's contracted stomach while lambing naturally once a year needed to receive only about a kilo for a very short period.

If any ewe had succumbed to "BSE" in the days of infected feed, the only way BSE could have been passed on would have been through the survival of a female lamb born at the crucial and short time of infectivity before the sheep's visible illness would have caused it to be slaughtered.

But new lambs have only a 5% chance of surviving early slaughter. Even if - considering the small amount of feed consumed by sheep - a few lambs with undetected disease had survived into this new generation, what would have been the statistical likelihood of those (female) lambs in turn passing on the disease to their own offspring, born in that short critical period. And then, again assuming that a few of those survived from the 95% slaughtered, what chance of THOSE lambs being able to transfer disease to their offspring? Generations of freakish survival would have had to take place for any BSE to be present in the national sheep flock today.

Looked at this way, the practical and realistic way, the chances of BSE being anywhere at all in British sheep are about the same as the chances of lightning striking the members of the same family every year for ten years.

Yet it is just such a "theoretical possibility" that is driving legislation - legislation such as the Animal Health Bill - which is harming the sheep industry and affecting thousands of lives. The new Act will make participation in the National Scrapie Plan compulsory and appears to provide, with its "precautionary principle", a justification for the removal of other rights of ownership.

Meanwhile, the pronouncements of the FSA , raising serious public fears about the safety of lamb, are driving ever deeper the coffin nails of the British sheep industry.

Is it not time that such theoretical science joined forces with some common sense?