Memorandum by the University of Edinburgh,
Centre for Infectious Diseases
1. MAIN PROBLEMS
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.
2. GETTING AHEAD
Zoonotic pathogens receive minimal attention
in this document, and traditionally medical surveillance has tended
to ignore the veterinary aspects of many infectious diseases of
3. ADVANCES AND
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
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.
6. POLICY INTERVENTIONS
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
diseasealthough 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.