. .

Bovine Spongiform Encephalopathy (Mad Cow Disease): FAO recommends precautions FAO estimates that between 1986-96 up to today, meat and bone meal (MBM) from Europe was exported to more than 100 countries. Around 100 countries imported live cattle. Some countries also re-exported MBM to third countries. All countries which have imported cattle or meat and bone meal that originated from Western Europe, during and since the 1980s, can be therefore considered at risk from the disease. Regions that have imported sizeable quantities of meat meal from the UK during and since the 1980s include the Near East, Eastern Europe and Asia.

Apart from scrapie, and excluding the cluster of SE cases in exotic zoo ruminants and felines which appear to be related to BSE, two other "naturally occurring" TSEs have been identified in animals. Both were known before the first identification of BSE.

Transmissible Mink Encephalopathy (TME)

TME is rare, and has largely been confined to the United States of America, although incidents have also occurred in Canada, Finland, East Germany and Russia. The last outbreak was in the USA in 1985, after an outbreak free period of 22 years.

TME takes the form of a rapidly evolving epidemic, usually involving single mink farms, and appears not to spread from mother to offspring. The disease is fatal, with neurological symptoms including locomotor incoordination, somnolence and debilitation. It appears to be associated with the feeding of contaminated food. Most mink are fed on either commercially produced compound food and/or tissues of animals that have died on neighbouring farms. It had always been assumed that the most likely source of infection was scrapie in sheep fed to them.

Since BSE was first recognised there has been debate as to whether or not one American outbreak may have been caused by the feeding of cow tissue rather than sheep. Anecdotal evidence suggests that one farmer did not feed sheep to his mink. If this is so, it is argued that cases of BSE may actually occur in the USA, although to date none have been recorded.

Supporters of the prion theory believe that spontaneous disease may arise in any species that have a PrP gene, even in the absence of recycling of contaminated feed. The theoretical prevalance rate for this is estimated at about one per million population, the rate at which CJD occurs sporadically in humans. It is thought that if such a cow affected with spontaneous BSE was fed to the mink it could have caused TME.

In scientific experiments brain tissue from British BSE cases have been inoculated into mink, and in a separate experiment fed to them. Although the mink were killed by the resulting disease, the symptoms and pathology produced were not however identical to TME.

Reference: Marsh R. F and Hadlow. W. J. 1992. Transmissible mink encephalopathy. Rev.sci.tech. Off. int. Epiz. 11 (2). 539-550.

Chronic Wasting Disease (CWD)

CWD is a rare disease of elk, mule deer, black tailed deer and mule-white tailed deer crosses in the USA. There have been one or two cases elsewhere, possibly linked to American infection. Although most of the cases have occurred in captive populations, many of the animals were originally caught in the wild and are reported not to have been fed ruminant protein. Cases have been identified in wild animals too, so it must be presumed to be a natural disease rather than one introduced through feed. The name of the disease is appropriate in that the animals show progressive wasting rather than the neurological signs seen with BSE. The wasting may however be partly due to interference with brain centres that control rumination, which are also affected in BSE.

References: 

Williams E. S and Young. S. 1992. Spongiform encephalopathies in Cervidae. Rev.sci.tech. Off. int. Epiz. 11 (2). 551-567

Spraker T. R. et al 1997. Spongiform encephalopathy in free-ranging mule deer (Odocoileus hemionus), white-tailed deer (Odocoileus virginianus) and Rocky Mountain elk (cervus elaphus nelsoni) in Northcentral Colorado. Journal of Wildlife Diseases. 33 (1). 1-6.

Feline Spongiform Encephalopathy (FSE)

FSE was first identified in Britain in 1990. Since then there have been 87 cases in Great Britain, one in Northern Ireland, one in Norway and one in Liechtenstein. FSE is not an easy disease to study. Although Britain has a large cat population they would not normally have been subjected to close neurological examination in the past. Nevertheless, sufficient numbers of FSE cases have been seen and investigated to permit an association with BSE to be made. Obtaining lifetime feeding history for cats is not easy, so although all have eaten foods that would be expected to contain specified bovine offals, no particular type of food can be implicated.

The epidemic in cats is often thought to be a useful model for past human exposure to BSE. The number of feline cases has declined dramatically.

Although MAFF has not historically held responsibility for investigating disease, other than rabies, in domestic pets, most of the information gathered about FSE in domestic cats and zoo animals has been provided through the good will of owners and veterinary practitioners. Laboratory diagnosis of a spongiform encephalopathy in any species has however been notifiable since November 1994, thus ensuring that cases would not be missed.

Interestingly, when brain tissue from some of the early cats identified identified as having FSE, was inoculated into mice, the pattern of incubation periods and lesion profiles in the mice was indistinguishable from that produced by BSE.

In exotic cats there have now been nine cases in cheetahs (three were diagnosed abroad but originated in Britain), three in pumas, three in ocelots, two in tigers and two in lions.

In October 1998 the simultaneous occurrence of spongiform encephalopathy in a man and his pet cat was reported. The report from Italy noted that the cat did not display the same clinical features as FSE cases previously seen. Indeed, the presence of a new type of FSE was suggested. The man was diagnosed as having sporadic CJD, and neither case (man nor cat) appeared to be affected by a BSE-related condition.

References: 

Zanusso-G, Nardelli-E Rosati-A Fabrizi-G-M Ferrari-S Carteri-A Desimone-F Rizutto-N Monaco-S. Simultaneous occurrence of spongiform encephalopathy in a man and his cat in Italy. LANCET, 1998 V352, N9134, OCT 3, Pp 1116-1117.

Pearson G. R. et al. 1992. Feline spongiform encephalopathy: fibril and PrP studies. Veterinary Record. 131. 307-310.

Wyatt. J. M. et al. 1991. Naturally occurring scrapie-like spongiform encephalopathy in five domestic cats. Veterinary Record. 129. 233.

Gruffydd-Jones T. J. et al. 1991. Feline spongiform encephalopathy. J. Small Animal Practice. 33. 471-476.

Willoughby K. 1992. Spongiform encephalopathy in a captive puma (Felis concolor). Veterinary Record. 131. 431-434.

Exotic ruminants

For completion it is worth mentioning cases that occurred in British zoos in exotic ruminants, largely antelopes but including two Ankole cattle and one American bison. The antelopes affected are kudu (6), eland (6), arabian oryx (1), scimitar horned oryx (1), nyala (1) and gemsbok (1). With hindsight the nyala was actually diagnosed before the first case of BSE was identified but had no association with farm animals at the time. 

All the exotic ruminants appear to be linked to the BSE epidemic via the consumption of contaminated feed. Although there was speculation that the kudu cases might provide evidence of horizontal transmission, this is now considered unlikely. Maternal Transmission may have occurred in one case. Kudu appeared to be particularly susceptible to BSE, being affected at a younger age than cattle, and with short clinical histories. The incompleteness of the ruminant feed ban was not appreciated at the time that the theory of horizontal transmission was being postulated. 

Reference: Kirkwood J. K. and Cunningham A.A. Epidemiological observations on spongiform encephalopathies in captive wild animals in the British Isles. Veterinary Record. 135. 296-303.

Canine Spongiform Encephalopathy (CSE)

• Priondata: A vital source of regularly upgraded data for scientists, business, the media and the public, Currently sponsored by Microsens Biotechnologies the makers of Seprion, the selective reagent for prions

CJD/BSE: TSE Guidance

• Transmissible spongiform encephalopathy agents: safe working and the prevention of infection: Guidance from the Advisory Committee on Dangerous Pathogens and the Spongiform Encephalopathy Advisory Committee.

Statement on ACDP/SEAC 

Part 1 - Introduction  (44kb) 
Part 2 - Health and Safety management of TSEs (35kb) 
Part 3 - Laboratory containment and control measures (156kb) 
Part 4 - Infection control of CJD and related disorders in the healthcare setting (62kb) 

Annex A.1 - Distribution of TSE Infectivity in Human Tissues and Body Fluids (14kb) 
Annex A.2   Distribution of TSE infectivity in Animal Tissues and Body Fluids - see 1998 guidance, annex A 
Annex B - Diagnostic criteria (19kb) 
Annex C - Decontamination and waste disposal (179kb)
Annex D - Transport of TSE-infected material (98kb) 
Annex E - Quarantining of surgical instruments (9kb) 
Annex F - Decontamination of endoscopes (23kb) 
Annex G - Decontamination of other specialised equipment (see 1998 guidance, annex B) 
Annex H - After death (25kb)

Related Information

• Tracking spongiform encephalopathies in North America: Related Articles, PubMED, National Library of Medicine. 
• Risk management of the transmissible spongiform encephalopathies in North America: J.A. Kellar & V.W. Lees, Rev. sci. tech. Off. int. Epiz., 2003, 22 (1), 201-225 See also: Chronic wasting disease in deer and elk in North America: E.S. Williams & M.W. Miller, Rev. sci. tech. Off. int. Epiz., 2002, 21 (2), 305-316. 
• Chronic Wasting Disease: Update April 2001: ProMED/International Society for Infectious Diseases.