- Email: [email protected]
Looking out for wildlife
The last word
Looking out for wildlife Bernard Dixon 130 Cornwall Road, Ruislip Manor, Middlesex HA4 6AW, UK
Microorganisms are innocent of national, regulatory, and, to some degree, taxonomic distinctions. Influenza viruses and their genes, recombining or reassorting in human beings, wild birds, and domesticated pigs, are a classic example. Other recent incursions come readily to mind: West Nile virus in New York, Nipah virus in Malaysia, and Hendra virus in Australia. Strange, then, that our surveillance over biospheric animalcules should be so lopsidedly incomplete. We monitor human pathogens reasonably well. We investigate conspicuous outbreaks of zoonotic disease and keep an eye on certain infections in farm animals. Yet many countries largely ignore the rich microbial populations supported by their native fauna. Since these organisms are constantly evolving, this neglect seems strange. Foolhardy might be a more apposite adjective, given the propensity of those teeming reservoirs to spill over into humankind and to equip our own pathogens with genes to boost virulence, transmissibility, or invasiveness. Zoologists have been less neglectful. They have long been interested in the impact of communicable diseases on the population dynamics and conservation of wild animals. Recent research has shown, for example, that the parasite Trichostrongylus tenuis can regulate the numbers of free-living red grouse in Britain. More broadly, two decades of vigorous debate have followed Bill Hamilton’s suggestions regarding sexual selection in animals ranging from pheasants to tree frogs. He believed that only males who are resistant to parasites express to the full “showy” traits (brightly coloured plumage, vigorous courtship displays). The advantage to females attracted by these stratagems is clear. Aside from investigations into such interesting biological issues, microbial diseases in wildlife have received comparatively little attention. This is all the more perplexing when we remember that, following well recognised zoonoses such as rabies and tularaemia, many recent “new” infections have been associated with other animals. Consider just four of the pathogens whose origins have come to light over the past 25 years. First, Martin Skirrow 66
highlighted Campylobacter jejuni, now recognised as a major cause of human diarrhoeal illness with reservoirs in waterfowl, pigeons, chickens, and many other species. Then followed discoveries of the Lyme disease spirochaete in deer ticks, influenza B virus in seals, and Escherichia coli O157 in cattle, sheep, and even reindeer. The impact of infections in wildlife on the health of human beings and domesticated animals must remain a matter of conjecture. We simply do not command reliable, comprehensive evidence. Three countries have created appropriate machinery to deal with the problem. Canada’s national surveillance programme, which not only investigates outbreaks but also monitors changes over time, is vested in the Canadian Cooperative Wildlife Health Centre. There is a similar body in the USA and a nationwide surveillance network in France. Yet the arrangements in many other countries are at best poor. Britain is particularly unimpressive. “There has never been a coordinated, methodical and wide-ranging approach to the investigation of wildlife diseases in the UK,” Tony Sainsbury and his Institute of Zoology colleagues write in the Veterinary Record (2001; 148: 558–63). “As a result, there is little knowledge of the range of diseases, infectious or non-infectious, which occur, or of when or where epizootics have occurred or their impact on individual animals or populations.” Such criticisms apply in many other regions of the world. Not only that. They need to be augmented by concern at a genetic level. Now that we know much more about horizontal gene flow than we did two decades ago, the microbial monitoring of wildlife is correspondingly more necessary than we hitherto recognised. Earlier this year, at the Royal Society in London, virologists deliberated over whether the flu virus, which killed 40 million people in the 1918–19 pandemic, arose by recombination or reassortment with pig or bird strains. Fine. That’s an important issue, with huge practical implications. But isn’t it just as important to understand precisely how microorganisms are evolving in other animals today? THE LANCET Infectious Diseases Vol 1 August 2001
For personal use. Only reproduce with permission from The Lancet Publishing Group.
Looking out for wildlife Bernard Dixon 130 Cornwall Road, Ruislip Manor, Middlesex HA4 6AW, UK
Microorganisms are innocent of national, regulatory, and, to some degree, taxonomic distinctions. Influenza viruses and their genes, recombining or reassorting in human beings, wild birds, and domesticated pigs, are a classic example. Other recent incursions come readily to mind: West Nile virus in New York, Nipah virus in Malaysia, and Hendra virus in Australia. Strange, then, that our surveillance over biospheric animalcules should be so lopsidedly incomplete. We monitor human pathogens reasonably well. We investigate conspicuous outbreaks of zoonotic disease and keep an eye on certain infections in farm animals. Yet many countries largely ignore the rich microbial populations supported by their native fauna. Since these organisms are constantly evolving, this neglect seems strange. Foolhardy might be a more apposite adjective, given the propensity of those teeming reservoirs to spill over into humankind and to equip our own pathogens with genes to boost virulence, transmissibility, or invasiveness. Zoologists have been less neglectful. They have long been interested in the impact of communicable diseases on the population dynamics and conservation of wild animals. Recent research has shown, for example, that the parasite Trichostrongylus tenuis can regulate the numbers of free-living red grouse in Britain. More broadly, two decades of vigorous debate have followed Bill Hamilton’s suggestions regarding sexual selection in animals ranging from pheasants to tree frogs. He believed that only males who are resistant to parasites express to the full “showy” traits (brightly coloured plumage, vigorous courtship displays). The advantage to females attracted by these stratagems is clear. Aside from investigations into such interesting biological issues, microbial diseases in wildlife have received comparatively little attention. This is all the more perplexing when we remember that, following well recognised zoonoses such as rabies and tularaemia, many recent “new” infections have been associated with other animals. Consider just four of the pathogens whose origins have come to light over the past 25 years. First, Martin Skirrow 66
highlighted Campylobacter jejuni, now recognised as a major cause of human diarrhoeal illness with reservoirs in waterfowl, pigeons, chickens, and many other species. Then followed discoveries of the Lyme disease spirochaete in deer ticks, influenza B virus in seals, and Escherichia coli O157 in cattle, sheep, and even reindeer. The impact of infections in wildlife on the health of human beings and domesticated animals must remain a matter of conjecture. We simply do not command reliable, comprehensive evidence. Three countries have created appropriate machinery to deal with the problem. Canada’s national surveillance programme, which not only investigates outbreaks but also monitors changes over time, is vested in the Canadian Cooperative Wildlife Health Centre. There is a similar body in the USA and a nationwide surveillance network in France. Yet the arrangements in many other countries are at best poor. Britain is particularly unimpressive. “There has never been a coordinated, methodical and wide-ranging approach to the investigation of wildlife diseases in the UK,” Tony Sainsbury and his Institute of Zoology colleagues write in the Veterinary Record (2001; 148: 558–63). “As a result, there is little knowledge of the range of diseases, infectious or non-infectious, which occur, or of when or where epizootics have occurred or their impact on individual animals or populations.” Such criticisms apply in many other regions of the world. Not only that. They need to be augmented by concern at a genetic level. Now that we know much more about horizontal gene flow than we did two decades ago, the microbial monitoring of wildlife is correspondingly more necessary than we hitherto recognised. Earlier this year, at the Royal Society in London, virologists deliberated over whether the flu virus, which killed 40 million people in the 1918–19 pandemic, arose by recombination or reassortment with pig or bird strains. Fine. That’s an important issue, with huge practical implications. But isn’t it just as important to understand precisely how microorganisms are evolving in other animals today? THE LANCET Infectious Diseases Vol 1 August 2001
For personal use. Only reproduce with permission from The Lancet Publishing Group.