New Cattle Disease

Alert as new brain disease hits beef herds in Britain
Report on idiopathic brainstem neuronal chromatolysis (ICBN)
Another BSE in the making?
Cows mis-diagnosed as having or not having BSE

Alert as new brain disease hits beef herds in Britain

By David Brown, Agriculture Editor
Daily Telegraph ... Tuesday 5 November 1996

Government vets are baffled by another fatal brain disease of cattle which has been discovered by scientists fighting the BSE epidemic.

More than 100 British cattle are known to have died so far from the mystery illness, which has no known cure. The only other single case was reported in Switzerland. The disease, known as idiopathic brainstem neuronal chromatolysis, was found in 1989 - three years after BSE was first identified - when scientists examined the brains of cattle culled mistakenly as victims of BSE. Many showed clinical symptoms almost identical to those of mad cow disease. Most of the victims were in Scottish herds but at least five cattle in England have also succumbed - and there may be more.

The most worrying aspect for farmers is that, unlike BSE, the second disease has mainly targeted beef herds rather than dairy cows. BSE has claimed most of its victims between two and 12 years old; IBNC has mainly hit beef animals between six and 12 years old.

The Ministry of Agriculture has appealed to vets to report any new cases, but the ministry said yesterday: "This is purely a veterinary problem. There are no implications for human health."

A spokesman said that while BSE had so far claimed more than 164,000 cattle in Britain, the second illness had hit very few. Only between eight and 27 cases a year are reported. Since all cattle more than 30 months old are destroyed routinely under the Government's emergency measures to restore confidence in beef, the ministry says that consumers do not have even a remote chance of eating beef from the older cattle.

BSE in Great Britain: consistency of the neurohistopathological findings

Simmons MM; Harris P; Jeffrey M; Meek SC; Blamire IW; Wells GA 
Central Veterinary Laboratory, New Haw, Addlestone, Surrey. 
Vet Rec 138: 175-7 (1996)

Two annual, random samples of clinically suspect cases of bovine spongiform encephalopathy (BSE) were taken in 1992-93 (year 1, 1500 cases) and 1993-94 (year 2, 1000 cases). From each sample, 100 positive cases were examined in detail to establish the severity of the vacuolation in 17 specific neuroanatomical locations. The resultant 'lesion profiles' were compared with the profile obtained from a similar sample of BSE-affected cattle from early in the epidemic (1987-89); the comparison showed that the distribution and severity of vacuolation in BSE has remained unchanged. The cases not confirmed as BSE on histological examination (172 in year 1 and 162 in year 2) were examined for evidence of any alternative neurohistological diagnosis.

As in previous studies, the majority of these cases showed no significant lesions (61.6 and 61.7 per cent). The remainder consisted of bilateral focal spongiosis of unknown significance (26.7 and 21.0 per cent), inflammatory conditions (8.1 and 11.1 per cent) and a small number of cases with tumours, cerebrocortical necrosis or idiopathic brainstem neuronal chromatolysis. No evidence was found of any cases of BSE with an atypical distribution of lesions. These findings support the theory that the BSE epidemic is sustained by a single, stable strain of the BSE agent, and confirm that the existing statutory diagnostic criteria continue to be appropriate.

Another BSE?

London correspondent 11.5.96

'Remember how BSE started out all those years ago? Just a few cattle, no threat to human health, nothing to worry about, etc? Well, I had a distinct feeling of deja vu when I read the first of the two articles attached. This could be nothing at all, or it could be the first inkling of another impending disaster.'

Cows mis-diagnosed as having BSE

Listserve 11.2.96

Under-reporting abroad
The recent Veternary Record article compared the herds of origin and birth cohorts of the (approx) 58,000 pure breeding cattle exported from the UK in 1985-90, estimating that there should have been 1,670 cases of BSE as compared with the 40 or so declared.

This indicates an awfully large estimated disease rate (10-20%?) in some birth cohorts from these herds. Stuart Neilson did estimate figures in that range for the highest observed susceptibility in British herds.

Non-confirmation rates
In the UK we have about 50 animals a week slaughtered as BSE suspects which on post-mortem turn out to have other conditions: hypomagnesaemia, brain tumours, etc., which produce similar symptoms.

Thus since 1990 approximately 15,000 such cases have been reported in the UK, as opposed (for instance) to 151 in France. Has the non-confirmation rate increased in the UK? It used to be (on average) 15 %.

Non-confirmation in Denmark
A very similar number of suspect cases have been histopathologically examined for BSE in Denmark since 1990. All but one were diagnosed as BSE-negative (the single positive was a cow imported from the UK at age 1 year -- originating from the heavily affected 86/87 birth cohort)

Histopathological examination of suspected BSE in Denmark

negative positive
1995 15 0
1994 7 0
1993 12 0
1992 27 1
1991 39 0
1990 47