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Bats, Birds, Mice, Ticks and You

Posted By Prucia Buscell, Thursday, July 19, 2012

Flying foxes, also known as Pteropus Vampyrus or fruit bats, are messy eaters, and that has serious implications for human heath.

When a flying fox finds food, it typically crashes into foliage and grabs a branch, swings upside down, and stuffs fruit, flowers, nectar or insects into its mouth with a hind foot or the clawed thumb at the top of its wings. Then it chews the pulp and spits out the juice and seeds. Fruit bats have co-evolved with the henipah virus for millions of years, so the virus doesn’t have much impact on them. But a nightmare can erupt when the virus moves from bats to species with no such immunity.

Scientists suspect that a bat dropped a piece of infected chewed fruit in a piggery in rural Malaysia in 1999. Pigs got the virus, amplified it, and passed it on to humans. Of the 276 people who got sick, 106 died and many others suffered permanent and crippling neurological disorders. There have since been 12 smaller outbreaks in Southeast Asia.

In his New York Times story "Man-Made Epidemics,” science writer Jim Robbins points out 60 percent of the emerging infectious diseases that affect humans today are zoonotic—meaning they originate in animals, and two thirds of those originate in wildlife. As part of a project called Predict, financed by U.S. Agency for International Development (USAID), teams of veterinarians, conservationists, physicians and epidemiologists from 20 countries have joined in a global effort to understand the ecology of disease and create early warning systems. Explosive human population growth, development, changes in land use, climate change, world travel and commerce have altered the ecological balance been pathogens and their human and animal hosts.

Predict scientists are gathering blood, saliva and other samples from high risk wild life species to create a library of viruses so the causes of human outbreaks can be more quickly identified. The potential problems are economic as well as health. The World Bank has estimated a severe influenza pandemic could cost the world $3 trillion dollars.

Jonathan Epstein, a veterinarian with the EcoHealth Alliance, who studies ecological causes of disease, thinks it’s just a matter of time before Henipah or some other virus develops a strain that spreads easily among people. The plague and malaria are examples of diseases that originated in the wild and spread to people. American robins, the harbingers of spring that thrive on lawns and farm fields, are super spreaders of West Nile Virus, which originated in Africa. The mosquitoes that spread the virus especially like robins.

When biodiversity erodes, species that preserve balance in nature are among those lost. For instance, the Robbins story reports, white-footed mice are reservoirs for Lyme disease and other bacterial afflictions such as babeosis and anaplasmosis that are carried by ticks and increasingly frequent. When development depleted predatory populations of hawks, owls, wolves and foxes, mice multiplied. And the problem isn’t just more mice. Lyme disease researcher Richard Ostfield explains white-footed mice have weak immune systems and they are terrible groomers. While Possums and squirrels remove 90% of larval ticks when they grooms, the mice remove only half that. So more people get bitten by ticks.

In another ecological surprise, Raina Plowright a biologist at Pennsylvania State University, found that Hendra virus among flying foxes is more common in the suburbs than in rural areas. She thinks suburban bats are more sedentary, so they have less exposure to the virus in the wild, and are less likely to have immunity and more likely to be infected. That means more infected fruit pulp spit into backyards.

The work of Predict is focusing on primates, rats and bats, the species most likely to carry diseases that affect people. Scientists from EcoHealth, the University of California, Davis, the Wildlife Conservation Society, the Smithsonian Institution, and Global Viral Forecasting, are watching interfaces where potentially deadly viruses are known to exist and where human development is encroaching on forests or other natural habitats. Mapping those edges and talking to people there may predict where the next spreadable disease will emerge. Read the Times story here.

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