Ticks used to be most active in spring through autumn, but rising temperatures attributed to global warming have shortened their long winter naps and in some areas eliminated them entirely. The result: Tick bites have become a year-round risk in many parts of the U.S.
Although blacklegged deer ticks prefer mice, birds and deer, they can bite other warm-blooded mammals — cats, dogs, horses and people. When the ticks are infected with the bacteria Borrelia burgdorferi, they can transmit Lyme disease. In the U.S., it’s now the most common disease spread by arthropods — invertebrate animals with external skeletons.
Lyme disease is very rare in cats, but even those living indoors aren’t safe from it. Other pets can bring infected ticks into our homes and yards, or we can track them inside on clothing. There’s no evidence that pets can spread the disease to people, however.
Scant Information. It’s difficult to tell if a pet — particularly a cat — has Lyme disease. Unlike humans, cats show no skin rashes or neurologic signs. “Cats appear to have a natural resistance to Lyme disease and tend not to show signs,” says Tiva Hoshizaki, BVSc, a resident in Maddie’s Shelter Medicine Program at Cornell University College of Veterinary Medicine. “There is little published information about Lyme disease in cats.”
Meryl Littman, VMD, ACVIM, Professor of Medicine at the University of Pennsylvania School of Veterinary Medicine, whose research interests include canine tick-borne diseases, concurs: “Lyme disease in cats is not well-documented. The percentage of cats which test positive for exposure to Lyme bacteria and show signs of illness is unknown but is probably lower than 5 percent.”
Until the mid-1900s, infected deer ticks mostly inhabited the islands off New York to Massachusetts. Today they’re found as far west as California, south to Virginia and north into Canada. Recently, Northeastern states have been particularly hard hit. The blacklegged tick (Ixodes scapularis) spreads the disease in the Northeastern, Mid-Atlantic and North-Central United States, and the Western blacklegged tick (Ixodes pacificus) spreads the disease on the Pacific Coast.
Blood Samples. Exposure to the bacteria can be confirmed by examining blood samples with a SNAP-4DxPlus test. “An antibody made by the white blood cells fights the antigen — a part of the bacteria made of protein,” Dr. Hoshizaki says. “This SNAP test shows the presence of that antibody, indicating that there has been a past response to the Lyme bacteria antigen, although that exposure could have been long ago.”
The canine SNAP-4DxPlus tests for exposure to several tick-borne diseases, including Lyme disease, Anaplasmosis and Ehrlichiosis, and can be used off-label for cats. A cat could be sick with more than one tick-borne disease and ticks can carry more than one type of organism. “Testing shows only whether a cat has been exposed to these organisms — but not whether or not they are sick because of them,” Dr. Littman says.
“Tick prevention is the first line of defense,” says Dr. Hoshizaki. Keeping cats indoors keeps them safe from ticks, as long as you thoroughly check your dogs and family members for ticks before they come inside. For outdoor cats, Seresto Flea and Tick Collars repel ticks before they bite for up to eight months. Monthly topicals available for cats can kill attached ticks.
One caveat: “It’s important not to use a dog product on a cat,” Dr. Littman says. “For example, the topicals which contain permethrins can cause illness if used on a cat. And if you have both dogs and cats, and want to treat your dogs, you may want to choose products that are safe for both species.”
In the end, says Dr. Littman, “Think of ticks on your cat and a positive SNAP-4Dx result as sentinels, letting you know that there are ticks in your area and that they carry these organisms. It’s an opportunity for you to improve your tick control methods — for everyone’s safety.”