3 Using the wildlife trade to uncover the mechanisms behind the missing parasites rule

Tuesday, August 4, 2009: 8:40 AM
Grand Pavillion V, Hyatt
Katherine F. Smith , Ecology, Brown University, Providence, RI
Peter Daszak , The Consortium for Conservation Medicine, New York, NY

International wildlife trade is immense, with an estimated billions of live animals traded globally each year. This trade has led to the introduction of pathogens that threaten public health (i.e. monkeypox virus) and biodiversity (i.e. chytridiomycosis). To assess the scope and scale of U.S. wildlife trade, we obtained and analyzed 2000-2006 shipment records gathered by the U.S. Fish and Wildlife Service for live wildlife imports. Wildlife trade also offers a unique opportunity to study the spread of pathogens across the globe. Recent work suggests that invasive species escape ~50% of the parasites found in their native range, leading to a decrease in the number of parasites and proportion of hosts infected in the introduced range – ‘the missing parasites rule’. The missing parasites of invasive species have been detected in numerous species, yet scientists remain unclear about the mechanisms that drive the pattern as species invasions are inherently difficult to study. One way to overcome this hurdle is to track host-parasite dynamics as species move along an invasion pathway from their native to introduced range, such as occurs in the international trade in wildlife. To understand the mechanisms behind the missing parasites rule, we partnered with a wildlife dealer and initiated preliminary work to track changes in parasite species richness, composition and prevalence in exotic reptiles (Tokay geckos and Panther chameleons) shipped from Indonesia to the U.S.


>1.48 billion live wildlife animals were imported by the U.S. since 2000. The majority was designated for commercial purposes and contained animals from wild populations. >74% of imported live wild animals originated in Southeast Asia: a hotspot for emerging diseases. Only 13% of imports were identified to the species level. Preliminary work on a real life trade route suggests the missing parasite rule varies within and between parasite groups and host species, that animals can accumulate new parasites along the invasion pathway, and carry infectious agents common to other host groups. For example, imported Panther chameleons accumulated novel parasites at a holding facility in Miami while imported Tokay geckos were carriers for human strains of salmonella. This work will advance the conceptual bases of host-parasite dynamics and invasion ecology, but also have broad implications for future research in conservation biology. Results should inform conservation biologists of wildlife trade practices and species invasion dynamics that facilitate the introduction of novel parasites to new regions where they may harm humans, livestock or native species.