Veterinary parasitologists warn of high tick risk

Hot or cold? Drought or floods? With the unpredictability of recent weather conditions across the country, it's hard to know what to expect from Mother Nature this summer. But one thing is clear—whatever the weather, it's sure to bring ticks. In fact, they're already here.

Cytauxzoonosis, an often fatal tick-borne disease in cats, is becoming more prevalent, says parasitologist Dr. Dwight Bowman.

Ticks are known carriers of a number of infectious diseases, some of which have been on parasitologists' radar for some time and others that are less well-known but quickly gaining popularity. One of the more common tick-borne diseases that rears its ugly head every year—and shows no sign of relenting—is Lyme disease. And according to initial assessments from the Companion Animal Parasite Council (CAPC), which works with statisticians to evaluate a variety of weather and disease-predicting factors, the threat of Lyme disease for dogs and cats is going to be extremely high this summer.

Dwight Bowman, MS, PhD, professor of parasitology at Cornell University College of Veterinary Medicine, has a similar prediction and says that although veterinarians may see some fluctuations in case load from year to year, Lyme disease continues to spread and is expected to be a problem this year as well. "As long as we have more deer, more rodents and more places for them to live, the number of cases will increase yearly," he says.

And it's not just due a larger reservoir host population. Susan E. Little, DVM, PhD, DEVPC, professor of parasitology at Oklahoma State University Center for Veterinary Health Sciences, states that weather conditions—primarily warmer winters—have created an ideal environment for many tick populations to thrive in and actively seek hosts. "Adults of the deer tick, the one that transmits Lyme disease and anaplamosis to dogs, are out in cooler months," says Little. "Mild winters allow for more days when these ticks can be actively questing and thus put more dogs at risk."

But even harsh weather conditions—last summer's drought, for example—haven't slowed these parasites down. While it was thought that the drought might have put a dent in the lone star tick population, which is responsible for the most common Ehrlichia species infecting dogs in the United States, it's shown a tremendous amount of endurance and is still going strong, according to Little. And the brown dog tick, known to carry Rocky Mountain spotted fever in the U.S. and by nature tolerant to low humidity and high temperatures, took advantage of the drought conditions and continues to thrive.

However, it's not just the most common ticks and the diseases they carry that have parasitologists concerned this year. Emerging protozoan diseases such American canine hepatozoonosis, carried by the Gulf Coast tick, and cytauxzoonosis, carried by both the American dog tick and the lone star tick, are becoming more of a problem and rapidly becoming evident in larger parts of the country, says Bowman.

The power of prevention

Amidst the apparent doom and gloom of the current tick situation, one common theme is echoed in parasitology camps—preventives are crucial. CAPC continues to recommend year-round parasite control for both dogs and cats. Additionally, the organization recommends regular examinations—at least annually—by a veterinarian. "While virtually all infestations of parasites are preventable, estimates indicate that fewer than half the dogs in the country are protected," says Chris Carpenter, DVM, MBA, executive director for CAPC.

So why are so few animals protected throughout the year? Little states that many pet owners think they can take their animals off tick preventives in the winter, because it's too cold for ticks to survive in their area. And that's a problem. "It only takes a day or two of nice weather for the ticks to become active and start questing," she says. "Every season is tick season."

Although year-round preventive compliance rates are low among dog owners, they're almost nonexistent among cat owners. "Cats are not getting to the veterinarians often enough," says Bowman. "All cats should be on some sort of flea control. And if they're going to go outside, they need flea and tick protection."

Little backs up this point by citing recent research from her colleague Mason Reichard, MS, PhD, associate professor of veterinary pathobiology at Oklahoma State University Center for Veterinary Health Sciences. Reichard recently showed in an experimental model that using persistent acaricides on cats protects them from cytauxzoonosis, an often-fatal but preventable disease.

"Cats, as we all know, are the underserved companion animal species when it comes to preventive care," says Little. "And that is true for protection from vector-borne infections as well."

Manufacturers of antiparasite products have made it increasingly easier for pet owners to comply with year-round preventive recommendations. From long-lasting flea and tick collars to monthly oral or topical preventives that often combat multiple internal and external parasites, there are a wide range of choices available for even the most reluctant pet owner. But it still starts with a recommendation and education from the veterinarian.

"We know now that ticks are out every month of the year," says Little. "We also know that they transmit more pathogens than we previously realized. Tick control protects pets from all of these infections—the known and the unknown. It really is a central part of wellness care."