Lyme disease, bubonic plague, and hantavirus pulmonary syndrome--all potentially serious disease threats to people--are carried by non-human vertebrates, most often rodents, who are the host species for a plethora of pathogens. Recent outbreaks of Monkeypox and Severe Acute Respiratory Syndrome have generated fresh concern about how pathogens move from non-human carriers to people. The paper, "Are predators good for your health? Evaluating evidence for top-down regulation of zoonotic disease reservoirs," appears in this month's issue of the Ecological Society of America's journal Frontiers in Ecology and the Environment and explores the role of predators in curbing disease outbreaks in humans.

Authors Richard Ostfeld (Institute of Ecosystem Studies) and Robert Holt (University of Florida) found that different predator types influence rodent populations in a range of ways, with some very effectively regulating rodent numbers while other predators actually cause periodic rodent population booms.

Specifically, Ostfeld and Holt found that predators that are not picky about what small animals they eat and are also highly mobile--such as foxes, coyotes, and falcons--appear to protect human health by constantly suppressing rodent numbers. In contrast, predators such as weasels specialize, eating only certain rodents. As a result those rodent populations fluctuate dramatically and during population peaks conceivably promote transmission of rodent-borne pathogens to people.

"It seems likely that when rodent populations are at chronically low densities, the incidence of disease transmission to people will also be low," says Ostfeld. "During population peaks and when rodents invade houses, we often see a higher incidence of disease outbreaks in people."

However, the researchers say that much more work needs to be done to understand the multiple variables driving the emergence of infectious diseases from wildlife to hum
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Contact: Nadine Lymn
nadine@esa.org
Ecological Society of America
19-Feb-2004

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