Microbiology Today November 2003
Wildlife is increasingly recognized as a source of
infectious diseases that pose a risk to man and his domesticated stock. This
was highlighted when the masked palm civet was implicated as the likely source
of the SARS coronavirus during the recent outbreak. Extensive international
travel means that new emerging diseases like SARS can spread around the world
with frightening speed. Pathogens that were once confined to a small area or
to one animal host are becoming a threat on a much wider scale. Veterinary and
animal microbiology has never been more important. This issue of Microbiology Today
takes a close look at different aspects of emerging diseases from wildlife.
Emerging infectious diseases of wildlife
In an overview, Sarah Cleaveland (Centre for Tropical Veterinary Medicine, University of Edinburgh) explains that many
pathogens are not fussy about their host species. This means that wildlife hosts can play a central role in the emergence of
human and domestic animal diseases. Ecological changes can lead to increased human-wildlife contact, allowing the spread of
infective agents from animal hosts to people. The interaction between wildlife and human health is complex, with implications
that pose real challenges to microbiologists and veterinarians.
Wildlife disease surveillance by the Veterinary Laboratories Agency
In the UK we may feel safe from diseases such as rabies, plague and anthrax which are spread by wildlife in other countries.
In fact all three have occurred in England historically and as the physical barriers between potential pathogens and hosts
are removed by our modern way of life, could well affect us again. The government has to be vigilant to the risks to health
and has made its Veterinary Laboratories Agency responsible for systematic wildlife disease surveillance. Paul Duff, leader
of the Diseases of Wildlife Project for the VLA, describes how regional labs around the country investigate incidents of
wildlife mortality and emerging disease.
Does West Nile virus pose a threat to the UK?
Antibodies to the West Nile virus, a pathogen that is sweeping the States, have been detected in wild birds in the UK.
Ernie Gould (Centre for Ecology and Hydrology, Oxford), who has been involved in the study, assesses the risks of this
potentially fatal disease to humans in Britain.
Seal distemper outbreak 2002
Several new members of the morbillivirus family have been recognized as the
causes of disease outbreaks and deaths in marine mammals such as whales, dolphins and porpoises in recent years.
Tom Barratt and colleagues from the Institute for Animal Health and London Zoo describe the outbreak of seal distemper
in northern European seals in April 2002 that killed over 22,000 harbour and grey seals.
Now they eat them, now they don't: phagocytes and Borrelia burgdorferi in Lyme disease
Lyme Disease is the most common vector-borne disease in North America. It is caused by bacteria called spirochaetes
which are transmitted from the wildlife host to humans and other animals by ticks. Symptoms include arthritis and
inflammation of the heart. The way that the immune system of the victim reacts to the bacteria is complex and some
aspects of it still baffle microbiologists, as Ruth Montgomery of Yale University describes.
Tick-borne relapsing fever in Tanzania
People in Tanzania are severely affected by a spirochaete infection that is transmitted by ticks which tend to infest their
traditional houses. The disease, known as tick-borne relapsing fever, particularly affects young children and pregnant women
and is spread from person-to-person, but rats and chickens often share the 'tembe' dwellings and researchers are trying to
find out if they act as a reservoir for the infection. Sally Cutler, of the UK Veterinary Laboratories Agency, and
Alison Talbert, a paediatrician in Tanzania, report on recent conference findings.
Christoph Dehio and Anna Sander are experts on Bartonella bacteria - insect-borne pathogens of growing medical
importance. There are many different species, each with their own animal reservoir and insect vector. Animal hosts range
from humans to rabbits, mice, cattle, deer, dogs and cats. Insects which transmit the bacteria include sandflies, fleas and
ticks. In World War 1, a Bartonella species caused trench fever, which was spread by the human body louse.
It has recently re-emerged as a disease in homeless people. Bartonella
henselae has been found to cause human disease worldwide. Cats act as a reservoir of the bacteria, and they often appear
quite healthy, although suffering from a blood condition. In humans the infection caught via cat fleas is called Cat
The significance of genetic control in TSEs
Prions may or may not be microbes, but TSE diseases, such as BSE and CJD, are important around the world. Incubation periods
can be several years and result in the accumulation of prion protein in the tissues. When BSE began to affect thousands of
cattle in the UK, scientists began to wonder why pigs were not infected and why cats, but not dogs, got a form of the
disease. Wilfred Goldmann (University of Edinburgh) assesses the latest findings on TSE susceptibility in different
Prions in the wild: CWD in deer and elk
Chronic Wasting Disease (CWD) is not 'mad deer disease' or BSE in deer or elk. It is a prion disease that seems to be
specific to members of the deer family in western and Midwestern North America. It is the only TSE known to occur in
free-ranging animals. Veterinary pathologist, Beth Williams, and wildlife vet Michael Miller describe the epidemiology of
CWD, how it spread and why it is so unusual.
Comment - The importance of veterinary microbiology: the role of the SGM
Many current infectious disease scares involve animal hosts, as in SARS and vCJD, or the animals themselves, as in
foot-and-mouth disease and BSE. Expertise is needed to deal with these outbreaks, which not only cause suffering but can
have serious social and economic consequences. SGM Council members Colin Howard
and Geoffrey Schild argue in 'Comment' that veterinary microbiology requires a good deal more support.
Hot off the Press highlights some new developments in microbiological research published in the Society's journals -
Microbiology, Journal of General Virology, International Journal of Systematic and
Evolutionary Microbiology and Journal of Medical Microbiology. Topics covered include:
- HME - an emerging human disease
- West Nile virus in the UK?
- A new fast-growing species of Borrelia
- A new threat from bats
- New Zealand rabbit haemorrhagic disease virus
- New member of the CF lung flora
- Real sex in bacteria!
- Degradation of alkanes and highly chlorinated benzenes by a psychrophilic Rhodococcus sp.
Other items include:
Last updated 9 February 2004