Most cat owners understand the reasons why it’s best not to let their pets roam outdoors without supervision or protection. Indoor cats live on average twice as long as do cats that roam freely primarily because of their reduced risk of infectious disease and traumatic injury.

Cats with access to the outdoors are also responsible for killing millions of birds and other small animals every year. Finally, feral cat colonies originating from lost or released pets and their offspring present huge animal welfare challenges.

Scientists in Colorado and California have now discovered several more excellent reasons to keep housecats indoors – disease transmission between domestic and wild animals, and a potential risk to human health.

The results of a large, multiyear study were recently published in the online journal PLoS ONE. Researchers took blood samples from bobcats and puma that were captured and released and from free-ranging domestic cats upon admission to shelters or through trap, neuter, release programs from the Colorado Western Slope, Colorado Front Range, Ventura County California, Orange County California, and Riverside/San Diego Counties, California.

The scientists evaluated 791 blood samples for the presence of antibodies against Bartonella spp., Feline Immunodeficiency Virus (FIV) , and Toxoplasma gondii, and found the following rates of exposure:

 Even if you are not particularly interested in feline health, you should take note that both Bartonella spp. and Toxoplasma gondii are zoonotic diseases, meaning that they can be transmitted from animals to humans.

This study shows that feline populations could be significant reservoirs for some highly prevalent human diseases — most notably feral cats as a source of Bartonella spp., and bobcats and especially puma for toxoplasmosis. Toxoplasma oocysts can persist in the soil or water for months and are of particular concern to pregnant women and people who are immunosuppressed by disease or chemotherapy. Also, Toxoplasma contaminates a significant percentage of the meat supplied for human consumption and is implicated as a factor in declining sea otter populations on the western coast of the U.S.

As the authors put it:

The fundamentals of zoonotic disease ecology are often poorly understood despite the fact that they can have serious public health consequences and are emerging with alarming frequency. In addition, threatened species, as well as overall biodiversity, can be negatively impacted by disease. This study incorporated data collected over a ten year period on 791 pumas, bobcats, and domestic cats, sampled across five study areas that varied in both ecosystem characteristics and degree of urbanization. Data provide new and unanticipated findings about the distribution of three pathogens capable of infecting and being transmitted among three felid species whose ranges overlap, particularly along urban edges.

Dr. Jennifer Coates

Image: AnetaPics / via Shutterstock