Cats can be infected with the bacteria that causes Lyme disease, though illness is very rarely seen in cats. Cats do not always develop symptoms like dogs and humans, so diagnosis can be trickier.
What Is Lyme Disease?
Lyme disease is a tick-borne illness that affects a variety of species and is commonly seen in humans and dogs. It has been shown that cats can become infected with B. burgdorferi bacteria (the causative agent of Lyme disease), but many cats do not show signs of the disease. Nevertheless, it is a diagnosis to consider when cats have symptoms compatible with Lyme disease, especially in areas where Lyme disease is common. The great majority of confirmed Lyme disease cases have been reported in 14 states: Connecticut, Delaware, Maine, Maryland, Massachusetts, Minnesota, New Hampshire, New Jersey, New York, Pennsylvania, Rhode Island, Vermont, Virginia, and Wisconsin.
Cats and dogs can become infected with Borrelia burgdorferi without ever developing symptoms of Lyme disease. Where Lyme disease is common, cats may test positive for exposure to the bacteria despite not showing any signs of the disease.
Symptoms of Lyme Disease in Cats
If a cat were to develop Lyme disease, their symptoms would probably be similar. It is important to note, however, that another tick-borne disease called anaplasmosis does occur in cats and leads to fever, lethargy, and a poor appetite.
Causes of Lyme Disease
Lyme disease is caused by Borrelia burgdorferi, a type of bacteria that is transmitted by ticks. These ticks become infected with the bacteria by feeding on infected mice and other small animals. When an infected tick bites other animals, it can transmit the bacteria to these animals. Lyme disease is transmitted by the deer tick (also called Ixodes scapularis or the black-legged tick) and a group of other closely related ticks. The exact tick species varies by location, but the deer tick is small enough to bite animals and people without being easily detected.
Cats that spend a lot of time outdoors, especially in areas with bush or tall grass, are most at risk of being infected with Lyme disease bacteria. It is important to remember that ticks can be carried into yards on other animals, so even cats that don't roam far could potentially be bitten by a tick. Ticks are frequently found on dogs, so if you have a dog, the tick can hitch a ride into the home on the dogs and then bite the pet cat. There is currently no evidence that Lyme disease is spread by direct contact between animals, including between infected pets and their owners.
Diagnosis of Lyme Disease in Cats
Because so many cats do not develop symptoms after infection with B. burgdorferi, a diagnosis of Lyme disease must be made on a combination of factors, including history (especially exposure to ticks), clinical signs, laboratory tests, and ruling out other causes of a cat's symptoms. An antibody test is not enough to make a diagnosis on its own because not all cats that are exposed to B. burgdorferi get sick, and the antibodies can persist in the blood for a period of time after exposure. Other diagnostic tests such as blood tests, urine tests, X-rays, and sampling of joint fluid would need to be done as well.
In dogs with Lyme disease, treatment with antibiotics usually produces a rapid improvement in symptoms and the same should hold true for cats. If there are more serious issues that might be secondary to Lyme disease, such as kidney disease, a longer course of antibiotics along with additional treatments is usually necessary. Your vet will come up with a treatment plan that is aligned with your cat's needs and medical situation.
How to Prevent Lyme Disease
Tick control is extremely important for the prevention of Lyme disease (and other diseases that can be transmitted by ticks). This is true for both pets and humans. Check outdoor cats daily for ticks and safely remove them as soon as possible. Be sure to pull back the fur and examine the cat at the skin level. A tick will attach itself to the animals' skin, not its fur if it is feeding. Since ticks must feed for at least 12 hours (possibly 36 to 48 hours) before transmitting the bacteria that causes Lyme disease, removing the tick as soon as possible can help prevent transmission. Be careful handling ticks as they are potentially infective to people too.
Products that kill ticks should also be used in at risk cats, but be sure to follow your veterinarian's advice when using these products, because cats are extremely sensitive to a variety of chemicals. Keep grass and brush trimmed in your yard and remove leaf litter and other materials where ticks may hide. You can also treat your yard for ticks if you live in a high-risk area.
Lyme Disease (Lyme Borreliosis) In Cats. Veterinary Manual, 2020
Lyme Disease: A Potential, But Unlikely, Problem For Cats. Cornell University College Of Veterinary Medicine, 2020
Preventing Ticks on Your Pets. Centers for Disease Control and Prevention, 2020