Select Committee on Science and Technology Written Evidence

Memorandum by the University of Edinburgh, Centre for Infectious Diseases


  More than half of all human pathogens are zoonotic, that is, they are transmitted between animals and humans. Many zoonotic pathogens are of public health importance in the UK, including variant CJD, E. coli O157, salmonellae and Borrelia burgdorferi. Worldwide, there have been recent outbreaks of zoonotic pathogens such as influenza H5N1 and H9N2, hantaviruses and Nipah virus. There is also concern that antibiotic resistance may transfer between animal and human populations.


  Zoonotic pathogens receive minimal attention in this document, and traditionally medical surveillance has tended to ignore the veterinary aspects of many infectious diseases of humans.


  For zoonotic pathogens surveillance must be integrated across the medical and veterinary services. At the very least good surveillance in reservoir species can provide an "early warning" of possible public health problems. It should be noted that any surveillance programme needs to be carefully designed for maximum effectiveness. It is widely accepted that passive surveillance often provides relatively poor quality information and active surveillance may often be warranted (eg TSEs in sheep in the UK). The statistical design of surveillance programmes is currently an important research topic, and advances are being made.


  Again, for zoonotic pathogens an effective public health intervention may be one targeted not at the human population but at the animal reservoir. A possible example of this is for rabies in East Africa, where vaccination campaigns targeted at domestic dogs appear to have had a significant impact on the public health burden imposed by rabies. Also in East Africa, chemotherapy of cattle may make a significant contribution to reducing human exposure to sleeping sickness. In the UK, effective interventions aimed at the major livestock species are likely to have significant public health benefits. For example, there is currently a substantial research effort aimed at developing vaccines against E. coli O157 in cattle. O157 is not, itself, a major veterinary problem so it is the public health impact of this intervention which is important.


  Future threats are inherently very difficult to assess. However, new human (and animal) pathogens have been recognised at a rate of more than one per year over the past 20 years and there is no reason to suppose that this trend will not continue. Almost 200 different pathogens are currently regarded as "emerging" or "re-emerging", that is, their incidence is increasing and/or they are spreading geographically. Three-quarters of these pathogens are zoonotic. The potential emergence of pathogens, both zoonotic and non-zoonotic, is significantly enhanced by globilisation, that is, increased human mobility and the widespread movement of animals and animal products.


  The key to controlling disease outbreaks is early intervention. The importance of this is illustrated in the veterinary context by early interventions to halt the transmission of BSE, in contrast to the disastrous consequences of failing to intervene quickly and effectively in the case of foot-and-mouth disease—although it should be noted that the time scales of those two epidemics were very different.

  Early intervention requires high quality surveillance. For zoonotic pathogens surveillance begins not in the human population but in the animal reservoir, so it is important that medical and veterinary surveillance are effectively integrated.

  An obvious policy intervention here is to have a post, at the national or regional level, whose responsibilities specifically include liaison with the veterinary services. This should cover not just operational matters but also scientific research aimed at zoonotic pathogens.

October 2002

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