BSE High-Risk Cattle
Being Rendered And
Fed To Swine
BSE Surveillance Update

From Patricia Doyle, PhD
The decision to render high-risk cow into swine feed is extremely dangerous. Swine may be infected and asymptomatic for some time. Some research indicates swine that do not show physical signs of the prion disease Do show TSE infecton in some research tests.
On the other hand, we are dealing with semantics here. The high-risk suspect cow may not have entered the human food chain directly...but it DID, eventually, as the swine fed the rendered cow were slaughtered and consumed by humans.
Patricia Doyle
A ProMED-mail post ProMED-mail is a program of the International Society for Infectious Diseases
From Jeffrey L Blair, DVM
May 26, 2004
(The article cited in the previous posting [20040525.1400] contained the statement: "The cow in San Angelo was taken a rendering plant where the Food and Drug Administration (FDA), which regulates rendering plants, approved it for use in swine feed. Swine are thought not to be susceptible to mad cow disease." - Mod.TG)
This newspaper article makes the statement that 'Swine are not thought to be susceptible to mad cow disease.' I would like to point out that swine are not likely to become infected with BSE via oral exposure, but they are susceptible to the agent via parenteral inoculation. The following study describes this:
Studies of the transmissibility of the agent of bovine spongiform encephalopathy to pigs. Gerald A. H. Wells, Stephen A. C. Hawkins, Anthony R. Austin, Stephen J. Ryder, Stanley H. Done, Robert B. Green, Ian Dexter, Michael Dawson and Richard H. Kimberlin (
"Studies to test the transmissibility of the bovine spongiform encephalopathy (BSE) agent to pigs began in 1989. Parenteral inoculation of the agent by 3 routes simultaneously (intracranially, intravenously, and intraperitoneally) produced disease with an incubation period range of 69 and 150 weeks. Preclinical pathological changes were detected in 2 pigs killed electively at 105 and 106 weeks post-inoculation.
Infectivity was detected by bioassay in inbred mice in the CNS of those pigs that developed spongiform encephalopathy. Infectivity was also found in the stomach, jejunum, distal ileum, and pancreas of terminally affected pigs. These findings show that pigs are susceptible to BSE. In contrast, disease did not occur in pigs retained for 7 years after exposure by feeding BSE-affected brain on 3 separate days, at 1- and 2-week intervals. The amounts fed each day were equivalent to the maximum daily intake of meat and bone meal in rations for pigs aged 8 weeks. No infectivity was found in tissues assayed from the pigs exposed orally. This included tissues of the alimentary tract. It is suggested that these pigs did not become infected. The relatively high oral exposure used in these experiments compared with feed-borne exposure in the field may explain the absence of an epidemic of spongiform encephalopathy in domestic pigs concurrent with the BSE epidemic in the UK."
According to Matthews (cited below), the report of the 1st pig shown to be infected with BSE in the above study led to immediate changes in rules in the UK to exclude specified risk materials from the food of all domestic livestock and pets.
The potential for transmissible spongiform encephalopathies in non-ruminant livestock and fish D. Matthews & B.C. Cooke. Rev. sci. tech. Off. int. Epiz., 2003, 22 (1), 283-296
While the questionable cow in San Angelo may have been approved for use in swine feed, I would hazard a guess that this was after specified risk material (brain, spinal cord, tonsil, thymus, spleen, and intestine) were removed. I have no first-hand knowledge of the case, however.
Jeff Blair, DVM Post Doctoral Fellow Department of Pathobiology 162 McElroy Hall College of Veterinary Medicine Oklahoma State University Stillwater, OK 74078 405-744-1182 <>
[BSE can be experimentally produced in cattle -- and in this case in swine -- by inoculating infected material into the brain, the peritoneal cavity, and by intravenous injection. Swine develop a spongiform encephalopathy from this type of agent introduction. However, swine fed the infected material did not develop the clinical signs of the disease, but on assay their tissues indicated the possibility of a prion disease. Therefore, specified risk material was excluded from all animal and pet feeds in the UK as a result of this experiment.
The cow in San Angelo, Texas, did not enter the human food chain. However, the decision to incorporate the products into swine feed may not have been scientifically justified.
Perhaps these studies will prompt FDA and USDA to re-evaluate current rules. - Mod.TG]
Patricia A. Doyle, PhD Please visit my "Emerging Diseases" message board at: Zhan le Devlesa tai sastimasa Go with God and in Good Health



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