Short Takes: 04/04

Predators and outdoor cats; West Nile virus and cats; news on vaccines

Big Cats Versus Regular Size
Cat owners in southern California have another reason for keeping their treasured pets indoors: Mountain lions that leave parks to forage the expanding urban fringe have developed an appetite for house cats, according to researchers at the University of California-Davis.

Scientists from the UC-Davis Wildlife Health Center put radio collars on 20 mountain lions (also called pumas or cougars) to track the big cats movements and dietary preferences. The three-year study in San Diego County was 75 miles from the Orange County site where a puma killed one person and injured another in January 2004.

The movement study found lions definition of home range included human homes. More than 40 percent of some big cats territory was private property – outside state parks where hikers and campers presumably were aware of the danger. Inside park boundaries, lion diet consisted mainly of wild deer and bighorn sheep. Outside the parks, pumas roamed ranches and suburban backyards to dine on goats, chickens, dogs and – yes, Fluffy dearest – cats.

Commented Walter Boyce of the Wildlife Health Center: Ultimately its up to the people who live, work and play in mountain lion habitat to decide if they want to share the environment with an animal that can kill them.


Cats Might Host West Nile Virus
A much smaller predator, the West Nile virus (WNV), was the subject of a study by scientists at Colorado State University and the Centers for Disease Control and Prevention (CDC). Their study, published in the CDC journal, Emerging Infectious Diseases (Vol. 10, No. 1) as Experimental Infection of Cats and Dogs with West Nile Virus, has reassuring news for dog owners and a warning for keepers of cats.

The researchers said they designed the small-scale experiments because, in a country with an estimated 68 million companion dogs and 73 million pet cats, people worry that a mosquito will draw WNV-infected blood from a pet and bite them next.

In the study, four dogs and four cats were bitten by WNV-carrying mosquitoes, and four other cats were fed mice that carried the virus. Low levels of the virus showed up in the blood of all four dogs, but none displayed signs of the disease. The mosquito-bitten cats also became somewhat viremic, the researchers reported, and three showed mild signs of disease – lethargy and modest decreases in appetite.

All cats that ate WNV-infected mice developed similarly low levels of the virus in their blood and none had clinical signs of the disease.

Researchers compared their results to those seen in birds, which can be so-called amplifying hosts for WNV, saying: Neither species (cats or dogs) is likely to function as an epidemiologically important host, although the peak viremia observed in cats may be high enough to infect mosquitoes at low efficiency.


Good News on Vaccinations
Three kinds of shots routinely given to cats on a yearly basis – for feline panleukopenia virus, feline calicivirus and feline herpesvirus – actually last 48 months or longer, according to a revaccination study in the Journal of the American Veterinary Medical Association (JAVMA Vol. 224, No. 1). According to the researchers, the study results suggest that revaccination with the vaccine used in the study provides adequate protection even when given less frequently than the traditional one-year interval.