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
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
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
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.