Ticks on Companion Animals
Ticks can be more than a nuisance pest for companion animals because of their potential to transmit diseases. This Montguide describes the biology and life cycles of hard ticks in Montana, health concerns and diseases that may be associated with their bites, the proper way to detect and remove ticks from pets, and products that may help to keep pets safe.
Last Updated: 11/18by Marni Rolston, Entomology Research Associate, and Greg Johnson, Veterinary Entomologist, Dept. of Animal and Range Sciences
COMPANION ANIMALS (CATS AND DOGS) HAVE
important and varied roles in Montana, ranging from herding and hunting dogs to therapy animals and house pets. They are susceptible to bites from many blood- sucking arthropods, including mosquitoes, stable flies, deer flies, ticks, fleas, mites and lice. Of these pests, ticks have the greatest potential to transmit diseases that may sicken or even kill an animal if left untreated. During spring and summer, it is important to regularly check your pet for these ectoparasites, since they may be hidden in their hair, and to monitor the health of your pet to ensure it has not contracted any tick-borne diseases. This MontGuide provides information on the biology, detection and control of ticks on companion animals.
IDENTIFICATION AND BIOLOGY
Ticks are not insects but are arthropods more closely related to spiders and mites. They have four distinct life stages – egg, larva, nymph, and adult. Adult and nymphal ticks have four pairs of legs (larval or seed ticks have three pairs of legs), no antennae, and two fused body parts (head and cephalothorax). Conversely, adult insects have three pairs of legs, one pair of antennae, and three distinct body parts (head, thorax and abdomen).
Species frequently found on companion animals in Montana are the Rocky Mountain wood tick (Dermacentor andersoni) and the American dog tick (Dermacentor variabilis) (Figure 1). Other species found less frequently are the brown dog tick (Rhipicephalus sanguineus) and the winter tick (Dermacentor albopictus). The wood tick and winter tick are distributed throughout much of the state and occur in a variety of habitats, including stream and river corridors, sagebrush flats and grassy meadows. The American dog tick has a distribution that extends from the Dakotas into the eastern edge of Montana. This tick is found in wooded areas, abandoned fields with medium height grasses and shrubs, and open areas between wetlands and woods. The brown dog tick, also known as the kennel tick, is distributed worldwide. It is primarily found indoors in areas where dogs are housed, including homes, kennels, sheds, and barns.
FIGURE 1. Adult Rocky Mountain wood tick, left, and American dog tick, right. (photos by James Gathany, Centers for Disease Control and Prevention)
These four species of ticks are reddish-brown and have a dorsal plate (Figure 1) that typically has gray/ silver colorations or other markings used for species identification. The presence of a dorsal plate categorizes them as hard ticks (Family: Ixodidae). Another category of ticks, soft ticks (Family: Argasidae) also occur in Montana, but are rarely encountered on dogs and cats. The skin of hard ticks is leathery with infoldings (called festoons) on the posterior end. They allow the body to stretch to accommodate large blood meals and egg development. What appears to be the “head” of a hard tick is actually a structure which contains the slender mouthparts, called the capitulum.
The mobile stages of most species are active from April through August. They find a host by detecting odors, heat, or vibrations from an animal and then climb onto it as it passes by. Once on the host, ticks use serrated mouthparts to puncture and attach to the skin. They remain firmly anchored in the host’s skin with the help of tiny spines and a cementing substance that is secreted from salivary glands. This process is rarely felt because the saliva has anesthetic properties. When attached, they will suck blood periodically for extended periods varying from a couple of days to two weeks. The body weight of a feeding female tick can increase up to 100 times its normal weight after feeding to repletion (Figure 2). Ticks can be remarkably long-lived, with many species requiring two to three years to complete development from egg to adult. They can also withstand prolonged periods of starvation of a year or more.
FIGURE 2. Engorged, left, and unengorged nymphs of the brown dog tick. (photo by James Newman, University of Florida)
HEALTH CONCERNS
Topical Wounds
The process of tick attachment involves cutting tissue and creating a wound in the skin. When one or a few ticks are involved, the wound usually heals without complications after the tick(s) is properly removed (Figure 3). High infestation levels can cause irritation and extensive damage to the skin. Contact your veterinarian if redness or inflammation develops around a bite wound and these symptoms persist for several days.
FIGURE 3. Procedure for removing a tick. Grasp the tick as close to the skin as possible and pull upward using a steady pressure.
Tick Borne Diseases
Hard ticks are efficient disease vectors because they are persistent blood-feeders, feed on different hosts, and feed for long periods of time, thus allowing for the transfer of pathogens. In the U.S. they are capable of transmitting many diseases, including Rocky Mountain spotted fever, Colorado tick fever, Lyme disease, canine ehrlichiosis, and anaplasmosis. In Montana, the Rocky Mountain wood tick and the American dog tick are capable of transmitting several of these pathogens with the exception of Lyme disease, which is transmitted through the bite of the blacklegged tick (Ixodes scapularis) and the western blacklegged tick (Ixodes pacificus). Neither of these species is known to occur in Montana. The wood tick, and to some extent the American dog tick, are capable of producing a physical reaction to feeding called tick paralysis. The brown dog tick carries the organisms responsible for canine ehrlichiosis and a form of anaplasmosis in dogs and cats.
Rocky Mountain spotted fever (RMSF)
RMSF is one of the more common tick-borne diseases that can infect dogs in the U.S. Although it was discovered in humans in the Bitterroot Valley of Western Montana in the early 1900s, most cases of RMSF now occur in the south-central and southeastern U.S. The primary vector of RMSF in Montana and the western U.S. is the Rocky Mountain wood tick. An infected tick must remain attached for at least 10 hours before the RMSF pathogen can be transmitted. Therefore, early detection of ticks is important. Dogs infected with RMSF may be asymptomatic, or, within 2-14 days after receiving the tick bite, may exhibit symptoms such as loss of appetite, fever, pain in the muscles and joints, swollen lymph nodes, depression, or an unstable gait. If treated with antibiotics within the first several days, most dogs will recover completely. However, if treated too late or left untreated, dogs may experience permanent neurological damage or death. Blood tests have shown that cats may become infected, but symptoms of the disease are negligible.
Tularemia
Tularemia is a relatively rare bacterial disease that may be transmitted to animals through the bites of ticks, deer flies and mosquitoes, or by contact with or ingestion of an infected animal. Ticks are the most effective arthropod vectors of tularemia, and in Montana transmission may occur through the bite of a Rocky Mountain wood tick or the American dog tick. Dogs appear to be relatively resistant to the disease, and may only exhibit mild fever, loss of appetite or listlessness. Cats are much more susceptible and may develop a sudden, high fever and swollen lymph nodes.
Canine Ehrlichiosis
This bacterial disease is transmitted by the brown dog tick. It is prevalent throughout most of the U.S., but most cases tend to occur in the Southwest and Gulf Coast regions where there are high concentrations of the tick. German shepherds are more susceptible than other dog breeds, and cats can also be infected. Initially, ehrlichiosis causes fever, weight loss and depression. If an initial infection is left untreated, it can develop into a more severe chronic infection characterized by anemia and internal bleeding. Treatment of an initial infection with antibiotics carries a good prognosis, whereas a chronic infection has a more variable to guarded prognosis.
Canine Tick Paralysis
Canine tick paralysis is a reaction to neurotoxins secreted in the saliva of the wood tick or American dog tick as they feed on their host. It can occur when ticks attach to the back of the dog's neck, or at the base of the skull, and feed for at least five to six days. Cats are not affected by the toxin. Symptoms include loss of muscle control, beginning with the lower hind legs and progressing to the rest of the body. Paralysis develops rapidly, and may lead to respiratory failure within 24 to 48 hours after the onset of symptoms. Properly removing the tick usually resolves the symptoms within a few hours to a few days, but if the tick remains embedded in the animal, death has been shown to occur in 10 percent of affected dogs.
Other Tick-borne diseases
The Rocky Mountain wood tick and the American dog tick have the potential to transmit other diseases, such as Colorado tick fever, to companion animals in Montana. Although this disease was the most prevalent tick-borne disease of humans in Montana from 1995-2005, there have been very few incidences of the pathogen in dogs and cats in the state. In addition, cases of anaplasmosis and Lyme disease are detected yearly in companion animals in Montana (http://www.dogsandticks.com/ diseases_in_your_area.php), but incidence rates are very low, and the Lyme disease cases were probably acquired in other regions of the country.
TICK DETECTION AND REMOVAL
It is important to check pets regularly for ticks during the spring and summer. Since ticks can feed anywhere on the body, run your fingers through the animal’s coat, feeling for ticks over the entire body. The size of a tick can vary greatly depending on how long it has been attached. Fully bloodfed ticks can expand to the size of a grape (Figure 2). If you find an attached tick, grasp it with fine-tipped tweezers as close to the surface of the skin as possible and pull upward using slow, steady, even pressure until the tick is dislodged (Figure 3). Hasty removal of an attached tick can break off the mouthparts and lead to prolonged inflammation, irritation, and possibly secondary infection. Do not use other methods of tick removal (e.g., petroleum jelly to suffocate the tick, heat from matches or rubbing alcohol to make the tick back out) as they are ineffective and may be harmful to your pet. Be careful not to squeeze or puncture the tick’s body because its fluids may contain infectious organisms. Thoroughly disinfect the bite wound with iodine scrub, rubbing alcohol, or soap and water. Save the tick in a container in the freezer so that it can be identified and/or tested for a disease in the event your pet becomes sick. A sick pet that has recently been exposed to or infested with ticks should be seen by your veterinarian.
PREVENTION AND CONTROL
Pesticides that are used to repel or kill ticks are called acaricides. They can be applied as topical treatments, shampoos, or plastic collars embedded with a pesticide. Some companion animals may be sensitive to or harmed by certain chemicals contained in these products. If breed sensitivity exists, a caution statement is usually included on the product label. Thus, it is important for the pet owner to carefully read and understand the product label to determine whether the product is intended for use on dogs and/or cats, what the correct dosage is, at what age you can safely apply the product to your pet, and how often the product should be applied. There are reports that some tick and flea treatments containing pyrethrin or pyrethroid insecticides routinely used on dogs are poisonous to cats. Thus, it is recommended that only products formulated for cats be used on cats. If you are unfamiliar with selection and application of these products, you should consult your veterinarian.
Once-a-month topical treatment These liquid products are applied to a small area on the back of the pet, usually between the shoulders. Some may be applied as a full body spray. They are easy to use and are applied monthly for season-long protection from ticks as well as fleas. The acaricide moves through the hair coat of the animal and repels or kills ticks that come in contact with it. The product should be allowed to dry before bathing or swimming. Examples of once-a-month treatments for dogs include Frontline® and other brands containing fipronil, and K9 Advantix® II which contains imidacloprid, permethrin and pyriproxyfen. Products formulated for cats typically contain fipronil and include Frontline®, FiproGuard™ and PetArmor®. If you take your pets for frequent outings in areas known to have high populations of ticks, it is recommended that you use products that will give extended protection.
Shampoos Medicated shampoos will help control ticks already on an animal. Shampoos should cover the entire body and should remain on the animal for several minutes before rinsing. Many different shampoos are available at pet stores or veterinary clinics for use on dogs and cats.
Collars An insecticide is continuously released in very small quantities from the collar over a period of two to three months and spreads over the pet in the oil of its skin and haircoat. The insecticide prevents ticks from attaching and feeding and kills new ticks that climb onto your pet. Collars and their associated insecticide are not affected by normal wetting such as rainfall. However, it is suggested the collar be removed before bathing or swimming. Contact your veterinarian if a pet ingests part of the collar. It is safe for children to be near animals with tick collars on, but be careful of prolonged exposure to the collar. Activities such as using the pet’s neck as a pillow or holding onto the tick collar instead of the regular collar may increase exposure. Always wash your hands thoroughly with soap and water after handling the collar.
Carefully read and follow the insecticide label concerning the application of any insecticide to pets. Avoid contact with the skin. Wash hands thoroughly with soap and warm water after handling these products. Keep out of reach of children. Prolonged or frequently repeated skin contact may cause allergic reactions in some individuals. Products are not listed in order of preference or superiority for tick control. Due to constantly changing labels, laws and regulations, MSU Extension can assume no liability for the suggested use of chemicals contained herein. Pesticides must be applied legally, complying with all label directions and precautions on the pesticide container and any supplemental labeling and rules of state and federal pesticide regulatory agencies.