Rev Sci Tech. 2004 Aug;23(2):497-511.

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

*Bengis RG, Leighton FA, Fischer JR, Artois M, Morner T, Tate CM.*

Veterinary Investigation Centre, PO Box 12, Skukuza, Kruger National
Park, 1350, South Africa.

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.

PMID: 15702716 [PubMed - in process]