NR AJZH
AU Ridley,R.M.; Baker,H.F.; Windle,C.P.
TI Failure to transmit bovine spongiform encephalopathy to marmosets with ruminant-derived meal
QU Lancet 1996 Jul 6; 348(9019): 56
PT letter
VT
Sir - We have kept a large breeding colony of common marmosets (Callithrix jacchus) for use in neuropsychological research for almost 20 years. This primate species develops spongiform encephalopathy with an incubation period of 3.5 or 4 years after intracerebral injection of scrapie-affected or bovine spongiform encephalopathy (BSE)-affected brain homogenate.1 The majority of marmosets in the colony are used for experimental purposes and are killed when under 3 years of age, but the breeding animals are aged 3-10 years and a small number of animals have been kept for up to 15 years in an investigation of ageing.2 All animals are fed a daily diet of egg sandwiches, fruit, and a proprietary brand of UK-produced New World monkey pellets. According to the manufacturers these pellets contained a 20% inclusion of ruminant-derived meat-meal protein until April 1996 (cattle-feed supplements before 1988 contained about 4% of meat and bone meal). From 1985 onwards, ruminant-derived feed probably contained increasing amounts of BSE agent from affected cattle and although the Ruminant Feed Ban of 1988 prohibited the feeding of this material to ruminants, its use in other animal feeds was legal until April 1996.
We estimate that more than 100 marmosets born in our colony between 1980 and 1990 lived for more than 5 years and were exposed to ruminant-derived protein in their diet for their entire life. Each adult marmoset (weight 350 g) was fed about 2 g meat meal per day. It seems likely, therefore, that the mature monkeys in our colony were exposed to significant amounts of infective agent for more than 5 years and in some cases for up to 10 years. With the exception of those animals which were injected intracerebrally with infected brain in our primary transmission studies, no animal in our colony has ever developed spongiform encephalopathy. As part of general husbandry all animals are monitored daily for signs of ill-health and any with severe illness or persistent poor condition are killed. Unexpected deaths are rare in adult animals in our colony and necropsy examination has usually shown a cause of death. Since our main focus of research has been concerned with the study of neurological and neurodegenerative conditions, staff are experienced in the assessment of subtle neurological signs in marmosets including those of spongiform encephalopathy. After death, the brains of all animals are examined histologically either because the animals were in an experiment or because brains provide valuable control material. The brains of older animals are examined with particular care for signs of neurodegenerative change.
It is most unlikely that a case of spongiform encephalopathy would have been missed in our colony. Although the quantitative level of contamination in ruminant-derived meat meal has not been established experimentally, it is known that the infectious agent of BSE can be detected in meat and bone meal produced in industrial pilot-scale versions of the rendering processes used in Europe.3 Our observation serves as a reminder that the oral route is probably an inefficient mode of infection for spongiform encephalopathy across the species barrier.
1 Baker HF, Ridley RM, Wells GAH. Experimental transmission of BSE and scrapie to the common marmoset. Vet Rec 1993; 132: 403-06.
2 Baker HF, Ridley RM, Duchen LW, Crow TJ, Bruton CJ. Induction of ß(A4)-amyloid in primates by injection of Alzheimer's disease brain homogenate: comparison with transmission of spongiform encephalopathy. Mol Neurobiol 1994; 8: 25-39.
3 Taylor DM. Exposure to, and inactivation of, the unconventional agents that cause transmissible degenerative encephalopathies. In: Baker HF, Ridley RM, eds. Prion Diseases. Totowa, New Jersey: Humana Press, 1996: 105-18.
IN Die Autoren halten es für angebracht, ihren Fehlversuch zur Übertragung von BSE auf Krallenaffen per Wiederkäuerfleisch zu publizieren.
ZR 3
MH Animal; *Animal Feed; *Callithrix; Cattle; Encephalopathy, Bovine Spongiform/*transmission; Food Contamination; *Meat; Monkey Diseases/*transmission
AD R M Ridley, H F Baker, C P Windle, MRC Comparative Cognition Team, Department of Experimental Psychology, School of Clinical Veterinary Medicine, Madingley Road, Cambridge CB3 0ES, UK
SP englisch
PO England
OR Prion-Krankheiten 7