Br. vet .
7. (1990) . 146, 485
GUEST EDITORIAL BOVINE SPONGIFORM ENCEPHALOPATHY (BSE) : MENACE OR MIRAGE?
R . M. BARLOW Department of Veterinary Pathology, Royal Veterinary College, Hatfield, Herts AL-9 7TA
For the British people the 1980s was a decade tinged by Lear, the fear of mortality from diseases difficult to control or in some cases even to understand . First, there was the spectre of AIDS that rocked complacent belief in a wholly sanitized human existence . Then came Salmonella in eggs, shortly to be followed by listeriosis from cook-chill meat and soft cheese . Meanwhile a third `zoonotic' condition, BSE, was steadily climbing the charts to become what media people call a `runner' . It is perhaps interesting to speculate on the psychological mechanisms by means of which public opinion is so roused, but it is the consequences of that arousal that contain lessons relevant to some of the roles of the veterinary profession in the fabric of society . By now the bare bones of the BSE situation must be familiar to almost everyone . 'Mad cow disease' is a transmissible spongiform encephalopathy (TSE) with similarities to scrapie in sheep and CreutzfeldtJakob disease in man . The BSE epidemic is thought to have arisen from scrapie infected sheep residues having been incorporated as meat and bone meal into cattle rations . Also survival of the agent in meat and bone meal may have been facilitated by changes in rendering methods . One view- is that as BSE is presumably scrapie in cattle it poses little risk to human health . The opposite speculation is that as it has apparently crossed the `species barrier' from sheep to cattle it may more readily do so again, to man . Experimental work with other TSEs has shown that passage through one species of laboratory animal may facilitate the establishment of disease in another, initially insusceptible species . However, with respect to BSE there is a plethora of speculation and a dearth of facts . The legislation now in force was introduced as a precaution against the more sensible worst scenarios that have been conceived . The transmissibility to certain strains of mice by intracerebral inoculation or by incorporation into the diet of brain tissue from affected cattle has been demonstrated . However, the feeding of large amounts of extraneural tissues such as spleen, lymph nodes, placenta, mammary tissue and milk to susceptible mice has not resulted in disease (luring their lifetimes . Furthermore, intracerebral subpassages of CNS tissue and spleen from mice fed the extraneural tissues have not yet given any indication that the latter were subclinically infected, even towards the end of their lives . Though it is perhaps premature to conclude that there is no risk of people becoming exposed to the BSE agent through consumption of dairy products and meat it is clear now that the risk is small . The evidence also allows for the tentative suggestion that the infection in cattle is unlikely
486
BRITISH VETERINARY ,JOURNAL, 146, 6
to be transmitted horizontally or vertically . In other words, however the infection has been acquired, cattle seem likely to be end hosts . Though many important questions concerning the biology and pathogenesis of BSE remain, the results of these first directly relevant experiments must be reassuring . Nevertheless, public concern over BSE has brought a number of matters into sharp focus . First, assuming that the presumed source of infection is correct, the outcome could have been predicted had veterinary personnel been more widely involved in food hygiene and aware of changes taking place in the residue rendering industry . Hopefully the lesson has now been learnt that adequate appropriately trained and skilled veterinary supervision is essential in the whole food chain through animals to people . Such is the position in most other European countries . Second, the scale of the BSE epidemic and the publicity it has received have inflicted serious damage to the cattle industry in all its ramifications . The economic costs to the industry and the nation resulting from loss of public confidence must be some orders of magnitude greater than the funding made available for scrapie research over the last decade . To this must be added the several million pounds of compensation to owners of confirmed cases of BSE and the several million more which have suddenly been found for research . Whilst such funding is more than welcome to those scientists with experience in the field and those with well researched sound new ideas, it is inevitable that in an era of increasingly fierce competition for grant support, the prospect of the golden guinea will also attract those whose real interests and aims are more questionable . The burden of responsibility for the wise disbursal of such funding is a heavy one . Finally, it may not be entirely coincidental that the problems mentioned erupted during a decade of monetarism in which profit was the sole criterion of excellence, a decade also in which veterinary schools and research institutes have been repeatedly squeezed and restructured to the point of scientific impotence . Here surely there are lessons to be learnt by those in command of policy .
7. (1990) . 146, 485
GUEST EDITORIAL BOVINE SPONGIFORM ENCEPHALOPATHY (BSE) : MENACE OR MIRAGE?
R . M. BARLOW Department of Veterinary Pathology, Royal Veterinary College, Hatfield, Herts AL-9 7TA
For the British people the 1980s was a decade tinged by Lear, the fear of mortality from diseases difficult to control or in some cases even to understand . First, there was the spectre of AIDS that rocked complacent belief in a wholly sanitized human existence . Then came Salmonella in eggs, shortly to be followed by listeriosis from cook-chill meat and soft cheese . Meanwhile a third `zoonotic' condition, BSE, was steadily climbing the charts to become what media people call a `runner' . It is perhaps interesting to speculate on the psychological mechanisms by means of which public opinion is so roused, but it is the consequences of that arousal that contain lessons relevant to some of the roles of the veterinary profession in the fabric of society . By now the bare bones of the BSE situation must be familiar to almost everyone . 'Mad cow disease' is a transmissible spongiform encephalopathy (TSE) with similarities to scrapie in sheep and CreutzfeldtJakob disease in man . The BSE epidemic is thought to have arisen from scrapie infected sheep residues having been incorporated as meat and bone meal into cattle rations . Also survival of the agent in meat and bone meal may have been facilitated by changes in rendering methods . One view- is that as BSE is presumably scrapie in cattle it poses little risk to human health . The opposite speculation is that as it has apparently crossed the `species barrier' from sheep to cattle it may more readily do so again, to man . Experimental work with other TSEs has shown that passage through one species of laboratory animal may facilitate the establishment of disease in another, initially insusceptible species . However, with respect to BSE there is a plethora of speculation and a dearth of facts . The legislation now in force was introduced as a precaution against the more sensible worst scenarios that have been conceived . The transmissibility to certain strains of mice by intracerebral inoculation or by incorporation into the diet of brain tissue from affected cattle has been demonstrated . However, the feeding of large amounts of extraneural tissues such as spleen, lymph nodes, placenta, mammary tissue and milk to susceptible mice has not resulted in disease (luring their lifetimes . Furthermore, intracerebral subpassages of CNS tissue and spleen from mice fed the extraneural tissues have not yet given any indication that the latter were subclinically infected, even towards the end of their lives . Though it is perhaps premature to conclude that there is no risk of people becoming exposed to the BSE agent through consumption of dairy products and meat it is clear now that the risk is small . The evidence also allows for the tentative suggestion that the infection in cattle is unlikely
486
BRITISH VETERINARY ,JOURNAL, 146, 6
to be transmitted horizontally or vertically . In other words, however the infection has been acquired, cattle seem likely to be end hosts . Though many important questions concerning the biology and pathogenesis of BSE remain, the results of these first directly relevant experiments must be reassuring . Nevertheless, public concern over BSE has brought a number of matters into sharp focus . First, assuming that the presumed source of infection is correct, the outcome could have been predicted had veterinary personnel been more widely involved in food hygiene and aware of changes taking place in the residue rendering industry . Hopefully the lesson has now been learnt that adequate appropriately trained and skilled veterinary supervision is essential in the whole food chain through animals to people . Such is the position in most other European countries . Second, the scale of the BSE epidemic and the publicity it has received have inflicted serious damage to the cattle industry in all its ramifications . The economic costs to the industry and the nation resulting from loss of public confidence must be some orders of magnitude greater than the funding made available for scrapie research over the last decade . To this must be added the several million pounds of compensation to owners of confirmed cases of BSE and the several million more which have suddenly been found for research . Whilst such funding is more than welcome to those scientists with experience in the field and those with well researched sound new ideas, it is inevitable that in an era of increasingly fierce competition for grant support, the prospect of the golden guinea will also attract those whose real interests and aims are more questionable . The burden of responsibility for the wise disbursal of such funding is a heavy one . Finally, it may not be entirely coincidental that the problems mentioned erupted during a decade of monetarism in which profit was the sole criterion of excellence, a decade also in which veterinary schools and research institutes have been repeatedly squeezed and restructured to the point of scientific impotence . Here surely there are lessons to be learnt by those in command of policy .
