Dr. Susan VandeWoude

Colorado State University scientists have evidence that domestic cats, bobcats and mountain lions that live in the same area share diseases – and may bring them into family homes, according to results of an unprecedented study of what happens when wild and domestic cats cross paths.

The study provides evidence that domestic cats and wild cats that share the same outdoor areas in urban environments also can share diseases such as bartonellosis and toxoplasmosis, both of which can be spread from cats to people. The study looked at urban areas of California and Colorado, showing that these diseases can spread through contact with shared habitat, and showing how the diseases can be clustered due to urban development and major freeways that restrict animal movement.

“These results are relevant to the big picture of domestic cats and their owners in urban areas that are frequented by wild cats such as bobcats and pumas,” said Dr. Sue VandeWoude, the Associate Dean of Research for the College of Veterinary Medicine and Biomedical Sciences and co-leader of the project. “The moral of this story is that diseases can be transmitted between housecats and wildlife in areas they share, so it’s important for pet owners to keep that in mind.”

Initial results of the multi-year study were published in the most recent issue of PLoS One, a scientific journal, and in a recent edition of the Journal of Molecular Ecology. The study was conducted jointly by the College of Veterinary Medicine and Biomedical Sciences, and the Warner College of Natural Resources. The study involved collaboration with field biologists, federal and state agencies, animal shelters, and other institutions, and was funded by the National Science Foundation.

In the study, researchers tracked whether or not wild and domestic cats in several regions of Colorado and California had been exposed to various diseases by looking for antibodies in their blood. The massive, multi-year effort includes data comprised of 800 blood samples from cats of all sizes, including 260 bobcats and 200 mountain lions, which were captured and released, and 275 domestic cats.

Domestic cat captured by a motion-activated camera

“As human development encroaches on natural habitat, wildlife that reside there may be susceptible to diseases we or our domestic animals carry and spread,” said Dr. Kevin Crooks, a Professor in the university’s Department of Fish, Wildlife and Conservation Biology, who is a co-leader on the project. “At the same time, wildlife can harbor diseases that humans and our pets can get. This all means that diseases may be increasingly transmitted as formerly natural areas are developed.”

The research project also looked at whether bobcats in Southern California were segregated into different populations by major highways. By looking at genetic and pathogen data, they found that bobcats west or east of Highway 5 south of Los Angeles rarely interbred, but that they did cross into each other’s territory often enough to share diseases, such as feline immunodeficiency virus.

“The evidence suggests that bobcats are moving across major highways but are not able to easily set up new home territories. They can, however, spread diseases to one another when they cross into each other’s territory,” Dr. VandeWoude said. “This could result in inbreeding of the bobcats trapped by urban development —and the spread of diseases.”

Drs. VandeWoude and Crooks both say that the study doesn’t necessarily mean that all domestic cats that are allowed to roam outdoors are doomed or at a high level of risk, and they plan further studies to better assess that risk. It does mean that domestic cats and wild cats that share the same environment – even if they do not come into contact with each other – also can share diseases.

The findings show that mountain lions were more likely to be infected with FIV than bobcats or domestic cats. While FIV cannot be transmitted to people, it is highly contagious among cats. The rate of infection by Toxoplasma gondii was high in mountain lions and bobcats across Colorado and California. All three diseases that the group looked for – toxoplasmosis, cat-scratch disease and FIV – were present in each area.

Toxoplasma gondii is a parasite that, when carried by healthy people, has no impact but can cause complications for infants and people with a compromised immune system. Cats only spread Toxoplasma gondii in their feces for a few weeks following infection with the parasite. Like humans, cats rarely have symptoms when first infected. Bartonella is a bacteria that causes bartonellosis, sometimes called cat-scratch disease. If a person is scratched by a cat infected with Bartonella, the scratch may become infected – usually a mild infection.

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