Emerging pathogens and host species barriers

Abstract number: 1732_247

Kuiken T.

Emerging infectious diseases have a major impact on public and animal health, the economy, and the environment (Science 309: 1680). Human mortality from recently emerged diseases varies, ranging from less than 200 people thus far for H5N1 avian influenza to about 20 million for AIDS. Livestock production has been negatively affected by the direct mortality of animals from emerging infections and depopulation policies to protect the safety of international trade and to control the spread of pathogens. The environmental impact of emerging infections is of special concern for endangered wild animal populations, which can be pushed to the brink of extinction by such events. Animals, and particularly wild animals, are thought to be the source of more than 70% of all emerging infections (Philos Trans R Soc London B 356: 983). Understanding how some infectious agents have breached the barriers that normally limit this interspecies transmission is important. However, these barriers are poorly characterised. The host species barrier for infection can be defined as an interaction of factors that collectively limits the transmission of an infection from one host species (the donor species) to another (the recipient species) (Science 312: 394). Such limiting factors may occur at different levels, of which the functional components are organism, tissue, and cell. At the organism level, barriers limiting contact between two host species, and thus preventing transmission of an infection, may be geographical, environmental, or behavioural. Because of the rapid growth of both human populations and their consumption patterns, these barriers are often breached. Even if two host species share the same geographical area and habitat, pathogen transmission may not occur due to behavioural restrictions. At the tissue level, an emerging pathogen, in particular a virus, needs to gain access to the appropriate tissue or tissues in order to replicate. First it must invade the host through a portal of entry. It may then remain localised and replicate in a tissue near the original portal of entry, or may generate a systemic infection, using various pathways to spread to more distant target tissues in the host. Release of progeny virus from the infected host typically occurs through dissemination by respiratory, enteric, or urogenital secretions, or by an arthropod vector that has ingested blood from a viremic host. There are barriers at each stage of this process that may prevent the virus from developing a productive infection. At the cellular level, a virus needs to enter, replicate in, and exit from the appropriate cell type, simultaneously dealing with any host response to infection. Understanding how a pathogen is able to breach the constraints of the host species barrier and become established in a new host species will help us to detect and control the emergence of zoonotic infections.

Session Details

Date: 31/03/2007
Time: 00:00-00:00
Session name: European Society of Clinical Microbiology and Infectious Diseases
Location: ICC, Munich, Germany
Presentation type:
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