Merck Manual

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Pet Owner Version

Ticks of Dogs


Karen A. Moriello

, DVM, DACVD, Department of Medical Sciences, School of Veterinary Medicine, University of Wisconsin-Madison

Reviewed/Revised Jun 2018 | Modified Oct 2022
Topic Resources

Ticks are blood-sucking parasites that attach themselves to animals and people. Once attached to a host, ticks feed voraciously. As they feed, ticks can transmit a large number of diseases, including Rocky Mountain spotted fever, ehrlichiosis, Q fever, and Lyme disease. Ticks also release toxins that can harm their hosts Tick Paralysis in Dogs Tick paralysis is a rapidly progressive motor paralysis caused by a toxin in the tick's saliva that attacks the nervous system. Certain species of ticks are known to cause tick paralysis. People... read more . Skin wounds caused by ticks can lead to secondary bacterial infections and screwworm infestations. Severe tick infestations can lead to anemia and death.

Technically, ticks are not insects. They are arachnids and are related to spiders and mites. There are numerous species of ticks belonging to 3 biological families. The Ixodidae family (commonly known as “hard” ticks) contains more than 650 species while the next largest family, the Argasidae (“soft” ticks), contains about 185 species in 4 genera (Argas, Carios, Ornithodoros, and Otobius). Notably, many hard tick spend >90% of their lifetime off the host. Ticks have 4 life stages—egg, larva, nymph, and adult.

Ticks can be found worldwide. Some ticks prey on specific animals, though other species can prey on many species of animals, including humans. Blood-sucking behavior is different depending on the species. Ticks can survive from several months to several years without food if environmental conditions permit.

Most species of ticks have a favored feeding area on a host, although in dense infestations, ticks may attach themselves wherever they can find a feeding location. Some ticks feed chiefly on the head, neck, shoulders, and pubic area. In other species, the favored sites may be ears, near the anus and under the tail, or in nasal passages.

The definitive sign of tick infestation is the presence of a tick on the animal. Direct contact with ticks frequently results in tick infestation. Animals that spend time outdoors, especially in wild areas, are more often affected. Thus, among dogs, hunting breeds or dogs that roam are mostly likely to be infested, though any dog spending time outside can acquire ticks.

Otobius megnini is a tick species that can hide unusually well. These ticks prefer to attach themselves in the ears of their hosts and are often overlooked by pet owners. These ticks are found in low rainfall areas of the western US and in Mexico and western Canada. Dogs and humans can suffer severe irritation from ear canal infestations. Toxins from these ticks may cause paralysis. Secondary infections by larval screwworms are reported. Otobius megnini ticks can transmit Q fever, tularemia, Colorado tick fever, and Rocky Mountain spotted fever.

Diagnosis is by appearance of tick bite marks on the dog and the presence of the parasite. Ticks that have been on an animal only a short time (an hour to a few days) appear flat. Ticks that have been on an animal for days appear much more rounded due to the blood they have consumed.

Engorging ticks

Engorging ticks

Ticks should be removed as soon as possible to minimize disease and damage. To do this, use tweezers to carefully grasp the tick close to the skin and pull gently. Never try to remove a tick with your bare hands, as some tick-borne diseases (for example, Rocky Mountain spotted fever) can be immediately transmitted through breaks in your skin or contact with mucous membranes. The use of hot matches should also be avoided. Infested dogs should also be treated with anti‑tick insecticides that kill attached larvae, nymphs, and adults. These can be given by spot-on solutions (which are applied on the back and spread rapidly over the entire body surface), sprays, and dusts. Care needs to be taken in selecting the correct anti-tick product. Contact your veterinarian for a recommendation for the best tick control product for your pet. Some of the products that are given monthly for flea control also effectively control ticks. Be sure to tell the veterinarian about any other pets you have in your household because this will make a difference in the veterinarian’s recommendation.

If your dog is severely infested with ticks, you should promptly take it to a veterinarian for tick removal. Heavy infestations will not only severely damage the skin, but the chances of anemia, paralysis, and other complications are high. Your veterinarian is in the best position to provide a heavily infested pet with the care it needs. A clinic stay for such pets is likely.

Even if your pet has acquired only a few ticks, you should have your pet checked for any of the many diseases spread by these parasites. Monitor any site(s) from which you have removed ticks. If a tick bite site turns red or swells a prompt trip to the veterinarian is warranted.

Keeping animals away from tick-prone areas is the most effective step you can take to control exposure. Most ticks live in particular microhabitats, such as tall grass or the border between wooded areas and lawns. Destruction of these microhabitats reduces the number of ticks. Removing tall grass and weeds and trimming vegetation can help protect your animal. Insecticide treatment of vegetation can slightly reduce the risk of ticks. However, it is not recommended for wide use because of environmental pollution and the cost of treatment of large areas.

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