"it's speculation, but I am perfectly serious. Experimental work has shown that pigs are especially sensitive to the disease. How ironic if 11 million British caslle should be slaughtered in a pre-emptive strike to eliminate CJD, only to find belatedly that the real villains were pigs or chickns which were also fed contaminated nutritional supplements," Brown wrote in a letter to the British Medical Journal.
Until late March, 996, pigs and chickens could be legally fed rations made from sheep infected with scrapie. The animals are normally slaughtered so young that they would be unlikely to manifest clinical symptoms of the disease. However, sub-clinical infection coul provide a massive titre of infectious agent to people eating tainted meat.
The identification of 10 cases of a highly stereotyped clinicopathological variant of Creutzfeldt-Jakob disease (CJD) in adolescents and young adults occurring in Britain within the past 24 months (R G Will, J Ironside, et al, personal communication) is cause for serious rethinking about the possibility of human infection from bovine spongiform encephalopathy (BSE).
Typically, "sporadic" (idiopathic) cases of Creutzfeldt-Jakob disease begin in the sixth or seventh decade of life with a loss of memory or, less commonly, with behavioural changes or higher cortical function deficits such as dysphasia or dyslexia. Over several weeks the mental deterioration progresses to frank dementia in association with abnormalities of vision or coordination, rigidity, and involuntary movements (especially myoclonic jerks), which often occur in synchrony with periodic spike waves on electroencephalography.[ii] Death usually occurs within six months, and at necropsy the brain shows a pathognomonic spongiosis with neuronal loss and gliosis in the cortex, deep nuclei, and cerebellum. Amyloid plaques are found in only about 5% of cases.[iii] Creutzfeldt-Jakob disease contracted from infected growth hormone also begins in a stereotyped way but with ataxia or other abnormalities of coordination.
By contrast, the newly reported variant syndrome is characterised clinically by onset with psychiatric symptoms and progressive neurological deficits with an unusual neuropathological profile (R G Will, I Ironside, et al, personal communication). This syndrome vividly recalls kuru, the epidemic spongiform encephalopathy in the eastern highlands of Papua New Guinea, which is thought to have been orally transmitted through the practice of ritual cannibalism, particularly the eating of brain tissue.[ii] All types of human and animal spongiform encephalopathy, including kuru, scrapie, and bovine spongiform encephalopathy, are experimentally transmissible in animals.
The ill defined early emotional and behavioural symptoms of the new variant will obviously open the floodgates to hundreds if not thousands of suspected cases of Creutzfeldt-Jakob disease over the next few years, and it will be a matter of enormous practical importance to be able to screen real from imagined cases. A soon to be reported spinal fluid test has shown itself to be both sensitive (97%) and specific (98%) for diagnosing the disease in even its early clinical stages and should prove extremely valuable in evaluating suspect cases (G Hsich, K Kenney, C I Gibbs Jr, et al, personal communication.)
Last November, the BMJ published a debate about the possibility of a link between bovine spongiform encephalopathy and Creutzfeldt-Jakob disease, to which I submitted a short article entitled "The jury is still out. "[iii] Despite this even handed title, I must confess to having felt that the available evidence favoured the idea that bovine spongiform encephalopathy constituted a negligible risk to humans. It now appears I was wrong. I am still astonished, in view of all of the earlier negative epidemiological and laboratory evidence concerning the risk of human infection from scrapie (the analogous disease in sheep), and from the failure to detect infectivity in the muscle of cattle with bovine spongiform encephalopathy, that human infection might be occurring from the ingestion of beef (or, even more improbably, from milk).
Especially distressing is the fact that no unusual dietary history characterises these cases - for example, the regular ingestion of calf brain, black puddings, sausage, or tripe because of the implication that a "normal" British diet has been sufficiently contaminated to have caused their infections. It is possible, of course, that these cases are not related to bovine spongiform encephalopathy, but it must be confessed that no better explanation is presently forthcoming. However, it must also be emphasised that the link to cattle products is itself only a presumption; how ironic, for example, if 11 million British cattle should be slaughtered m a preemptive strike to eliminate the risk of zoonotic Creutzfeldt-Jakob disease, only to find belatedly that the true villains were pigs or chickens which were also fed contaminated nutritional supplements but were brought to market at such a young age that the disease had not had time to become manifest.
A good deal of work remains to be done in order to establish the link between bovine spongiform encephalopathy and Creutzfeldt-Jakob disease, much of which has already been initiated. None of it will be of any help to those who may have been exposed to the infectious agent in the 1980s before precautionary measures were put in place to minimise the risk of human disease. Nor will it remedy the possible failure of the scientific pundits (including me) to foresee a potential medical catastrophe.
PAUL BROWN Medical director US PHS Laboratory of Central Nervous System Studies National Institute of Neurological Disorders and Stroke
i. Brown P, Gibbs CJ Jr, Rodgers-Johnson P, Asher DM, Sulima MP, Bacote A, et al Human spongiform encephalopathy: the National Institutes of Health series of 300 cases of experimentally transmitted disease. Ann Neurol 1995;35:513-29.
ii. Gajdusek DC, Zigas V. Degenerative disease of the central nervous system in New Guinea. The endemic occurrence of kuru in the native population. N Engl J Med 1957;257:974-8.
iii. Brown P. The jury is still out. BMJ 1995;311:1416.
Chicago Tribune (CT) - MONDAY, April 1, 1996
LONDON - Britain's food inspectors have warned slaughterhouses of a potentially dangerous outbreak of tuberculosis in pigs, linked to animal feeding practices, The Observer newspaper reported Sunday. Scientists believe the increase in pig tuberculosis is due to breeders feeding the animals peat contaminated with bird droppings, the newspaper said. The peat is used to bulk out the animals' food.
The Observer quoted from a Meat Hygiene Service memor andum written in January--well before the scare over evidence of a new human strain of mad cow disease--drawing attention to "evidence of a new problem." Up to half the animals in two large pig slaughterhouses had been infected.
The bacterium infecting pigs is common in wild birds, where it causes avian tuberculosis. It also can be passed to people. The Observer said it has been known to cause enlargement of the lymph glands in the neck or cause lung infection in people prone to lung disease.
Agriculture ministry officials told the newspaper it is different from the bacteria that cause tuberculosis in humans. They said humans with the bacterium, microbacterium avium complex, normally would show no symptoms. The bacterium is destroyed by normal cooking.
The animal feed manufacturers' association told The Observer that peat was used for a short period until six months ago.
USA TODAY (US) - THURSDAY April 11, 1996
'Right place, right time' for ostrich meat
By: Shannon Tangonan
A North Carolina company expects to cash in on ostrich meat it's shipping to England, where citizens are wary of tainted beef. Oro Verde Farms International, based in Raleigh, will ship 40,000 pounds of ostrich meat next week for distribution in supermarkets, pubs and inns, company president Jim Kirk says.
The company started marketing in England eight months ago, but the going was slow until British citizens began avoiding beef for fear of contracting Creutzfeldt-Jakob disease, a condition in humans similar to ``mad cow'' disease.
Ostrich shipments will increase to about 100,000 pounds a month, Kirk says. Britons can expect to pay from $14 to $16 a pound for the meat. Tender cuts of ostrich have the same flavor as a beef filet, Kirk says. ``I don't like to look at myself as gaining on someone else's hardships,'' he says. ``But now that mad cow disease is here, we are at the right place at the right time.''
Oro Verde gained approval to sell ostrich in England, Wales, Scotland and Ireland. Kirk expects to enter other world markets, including Singapore, Japan and Taiwan. ``Those are on the back burner -- cooking slowly,'' he says.
[Ironically, ostriches are the only species of bird known to contract TSE -- webmaster]