Researchers tracking the spread of Toxoplasma gondii – a parasite
that reproduces only in cats but sickens and kills many other
animals – have found infected wildlife throughout a 1,500-acre
(600-hectare) natural area in central Illinois.
The researchers also found dozens of free-ranging cats in the area,
the Robert Allerton Park, near Monticello, Ill. Two years of
tracking, trapping and motion-triggered night photography at eight
sites in the park found no evidence of bobcats, but plenty of
examples of feral or abandoned house cats, many of them infected
with Toxoplasma.
The research appears in the Journal
of Wildlife Diseases.
T. gondii reproduces in cats and is shed in their feces.
Other animals pick it up from soil or water or by eating infected
animals. Infection can lead to neurological problems, and sometimes
death, in humans and other animals.
The researchers trapped, sedated and collected blood samples from
18 cats and hundreds of other mammals, including raccoons,
opossums, squirrels, mice, woodchucks, chipmunks and rabbits. All
of the animals were tagged and released where they were found.
(Watch a slide show about the research.)
One third of the cats sampled were infected with T
gondii, as were significant numbers of the wild animals found
at every site. Animals that inhabit or range over territories of
247 acres (100 hectares) or more, such as raccoons and opossums,
were more likely to be infected than those with smaller ranges.
But these animals "could have acquired T.
gondii infection somewhere outside of the park," said
Nohra Mateus-Pinilla, a wildlife veterinary epidemiologist at the
University of Illinois Prairie Research Institute and leader of the
study. Animals with smaller home ranges likely picked up the
infection close to where they were trapped, she said. This makes
these animals good sentinels of disease in a natural area.
"The small animals are screening the environment for us," she said.
"So when we sample one of those animals, we are really sampling
their lifestyle."
The absence of bobcats in the park combined with the occurrence of
domestic cats and T.
gondii infection in wildlife that inhabit small
territories strongly suggest that feral, free-ranging or abandoned
house cats are the source of the infection, Mateus-Pinilla said.
Cats are vital for the survival of the parasite, and so they are –
either directly or indirectly – spreading T.
gondii to the wildlife in the park. "There's no other
option," she said.
The researchers also found that "small-home-range" animals were
more likely to test positive for T.
gondii if they lived near human structures in the park or
in areas where there were a lot of cats, said lead author Shannon
Fredebaugh, a graduate student who completed her master's degree
with the study. But the researchers also found infected
small-home-range animals in remote areas where fewer cats were
seen.
"If one infected cat defecates there, any area can become
infected," Fredebaugh said. "It just takes one cat to bring disease
to an area."
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Thanks to University of Illinois at Urbana-Champaign for this
article.