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Emerging infectious diseases in wildlife.

ES Williams — 2007-12-17T21:39:14-00:00

Rev Sci Tech, Vol. 21, No. 1. (April 2002), pp. 139-157.

The processes which give rise to emerging infectious diseases of wildlife can be categorised as follows: ecosystem alterations of anthropogenic or natural origin; movement of pathogens or vectors, via human or natural agency; and changes in microbes or in the recognition of emerging pathogens due to advances in the techniques of epidemiology. These are simplistic divisions because factors influencing the emergence of diseases of wild animals generally fall into more than one category. Mycoplasmosis among passerines is related to habitat changes and artificial feeding resulting in increased bird densities and subsequent disease transmission. The origin of this strain of Mycoplasma gallisepticum is not known. Hantavirus infections in rodents have emerged due to human-induced landscape alterations and/or climatic changes influencing population dynamics of hantavirus reservoir hosts, with disease consequences for humans. Movement of pathogens or vectors is a very important process by which diseases of wildlife expand geographic range. Although the origin of caliciviruses of rabbits and hares is somewhat obscure, their movement by humans, either deliberately or accidentally, has greatly expanded the distribution of these viruses. Rabies is an ancient disease, but geographic expansion has occurred by both natural and anthropogenic movements of wild animals. Human movement of amphibians may explain the distribution of the highly pathogenic chytrid fungus around the world. Newly recognised paramyxoviruses may reflect both changes in these pathogens and the development of techniques of identification and classification. Many more such examples of emerging diseases will arise in the future, given the extensive alterations in landscapes world-wide and movements of animals, vectors and pathogens. Those who study and diagnose diseases of wildlife must be alert for emerging diseases so that the impact of such diseases on wild animals, domestic animals and humans can be minimised.

Emerging infectious diseases in wildlife

ES Williams — 2007-12-17T21:25:08-00:00

Revue Scientifique et Technique de l'Office International des Epizooties, Vol. 21, No. 1. (April 2002), pp. 139-157.

The processes which give rise to emerging infectious diseases of wildlife can be categorised as follows: ecosystem alterations of anthropogenic or natural origin; movement of pathogens or vectors, via human or natural agency; and changes in microbes or in the recognition of emerging pathogens due to advances in the techniques of epidemiology. These are simplistic divisions because factors influencing the emergence of diseases of wild animals generally fall into more than one category. Mycoplasmosis among passerines is related to habitat changes and artificial feeding resulting in increased bird densities and subsequent disease transmission. The origin of this strain of Mycoplasma gallisepticum is not known. Hantavirus infections in rodents have emerged due to human-induced landscape alterations and/or climatic changes influencing population dynamics of hantavirus reservoir hosts, with disease consequences for humans. Movement of pathogens or vectors is a very important process by which diseases of wildlife expand geographic range. Although the origin of caliciviruses of rabbits and hares is somewhat obscure, their movement by humans, either deliberately or accidentally, has greatly expanded the distribution of these viruses. Rabies is an ancient disease, but geographic expansion has occurred by both natural and anthropogenic movements of wild animals. Human movement of amphibians may explain the distribution of the highly pathogenic chytrid fungus around the world. Newly recognised paramyxoviruses may reflect both changes in these pathogens and the development of techniques of identification and classification. Many more such examples of emerging diseases will arise in the future, given the extensive alterations in landscapes world-wide and movements of animals, vectors and pathogens. Those who study and diagnose diseases of wildlife must be alert for emerging diseases so that the impact of such diseases on wild animals, domestic animals and humans can be minimised.

The role of wildlife in emerging and re-emerging zoonoses.

RG Bengis — 2005-11-05T08:37:16-00:00

Rev Sci Tech, Vol. 23, No. 2. (August 2004), pp. 497-511.

There are huge numbers of wild animals distributed throughout the world and the diversity of wildlife species is immense. Each landscape and habitat has a kaleidoscope of niches supporting an enormous variety of vertebrate and invertebrate species, and each species or taxon supports an even more impressive array of macro- and micro-parasites. Infectious pathogens that originate in wild animals have become increasingly important throughout the world in recent decades, as they have had substantial impacts on human health, agricultural production, wildlife-based economies and wildlife conservation. The emergence of these pathogens as significant health issues is associated with a range of causal factors, most of them linked to the sharp and exponential rise of global human activity. Among these causal factors are the burgeoning human population, the increased frequency and speed of local and international travel, the increase in human-assisted movement of animals and animal products, changing agricultural practices that favour the transfer of pathogens between wild and domestic animals, and a range of environmental changes that alter the distribution of wild hosts and vectors and thus facilitate the transmission of infectious agents. Two different patterns of transmission of pathogens from wild animals to humans are evident among these emerging zoonotic diseases. In one pattern, actual transmission of the pathogen to humans is a rare event but, once it has occurred, human-to-human transmission maintains the infection for some period of time or permanently. Some examples of pathogens with this pattern of transmission are human immunodeficiency virus/acquired immune deficiency syndrome, influenza A, Ebola virus and severe acute respiratory syndrome. In the second pattern, direct or vector-mediated animal-to-human transmission is the usual source of human infection. Wild animal populations are the principal reservoirs of the pathogen and human-to-human disease transmission is rare. Examples of pathogens with this pattern of transmission include rabies and other lyssaviruses, Nipah virus, West Nile virus, Hantavirus, and the agents of Lyme borreliosis, plague, tularemia, leptospirosis and ehrlichiosis. These zoonotic diseases from wild animal sources all have trends that are rising sharply upwards. In this paper, the authors discuss the causal factors associated with the emergence or re-emergence of these zoonoses, and highlight a selection to provide a composite view of their range, variety and origins. However, most of these diseases are covered in more detail in dedicated papers elsewhere in this Review.