That distinction makes it hard to use the animals to test treatments or vaccines.

The disease has an incubation period of at least several years, so many animals may test positive even if they look healthy.

But the animals can't test for toxic waste, so they drink it and die.

They did not identify themselves then, and the animal later tested positive for rabies, city officials have said.

If an animal does test positive, the European Union requires the slaughter of the entire herd.

At once the Mwellret's head snapped up, as if an animal testing the air.

But some experts question the assumption that only downers are at risk, since many healthy-looking animals in Europe have tested positive.

The department said 8,585 animals had tested negative since June 1.

So far this year, 321 animals have tested positive for rabies across the state, said Claire Pospisil, a department spokeswoman.

In all of last year, 29 animals tested positive.