Ticks

Synopsis

CAPC Recommends

• All dogs should be treated year round and throughout their life with tick control products to limit infestations on the pet, reduce the number of ticks in the environment around the home, and prevent establishment of brown dog tick populations in the home

• Recognize that home infestations with brown dog ticks (Rhipicephalus sanguineus), once established, may take several months to bring under control and that, in addition to consistently treating pets with tick control product, the services of a licensed exterminator are necessary to eliminate the infestation from buildings

• Because ticks transmit a wide variety of disease agents to pets and people and are active throughout the year, tick control must be practiced consistently to protect the health of the pet and to prevent untreated pets from bringing ticks – which may then infest people - into the home

• Stay current on tick population shifts and new threats from ticks that develop over time. Tick distributions are dynamic and ever changing, and practice protocols often need to evolve to meet the growing threat ticks pose to pet health.

Species

Canine

• Amblyomma americium (Lone star tick)
• Amblyomma maculatum (Gulf Coast tick)
• Dermacentor variabilis (American dog tick)
• Dermacentor andersoni (Rocky Mountain Wood Tick)
• Haemaphysalis longicornis (Asian longhorned tick)
• Ixodes pacificus (Western black-legged tick)
• Ixodes scapulars (Black-legged tick)
• Otobius megnini (Spinose ear tick)
• Rhipicephalus sanguineus (Brown dog tick)

*Other tick species may on occasion parasitize dogs.

Amblyomma americanum (Lone star tick)

Click here to view a video on the Lone star tick

Amblyomma maculatum (Gulf Coast tick)

Click here to view a video on the gulf coast tick

Dermacentor variabilis (American dog tick)

Click here to view a video on the American dog tick

Dermacentor andersoni (Rocky Mountain Wood Tick)

Click here to view a video on the Rocky Mountain wood tick

Haemaphysalis longicornis (Asian longhorned tick)

Dorsal (left) and ventral (right) of an adult female Haemaphysalis longicornis. Photo courtesy of Tadhgh Rainey.

A nymph of Haemaphysalis longicornis (left) next to a nymph of Amblyomma americanum (lone star tick, right) next to a penny for size comparison. Photo courtesy of Graham Hickling.

Ixodes pacificus (western black-legged tick)

Click here to view a video on the western black-legged tick

Click here to view specific CAPC Guidelines for Ixodes pacificus

Ixodes scapularis (black-legged tick or deer tick)

Click here to view a video on the black-legged tick (deer tick)

Click here to view specific CAPC Guidelines for Ixodes scapularis

Ixodes scapularis adult female

Ixodes scapularis adult male

Otobius megnini (spinose ear tick)

Click here to view a video on the spinose ear tick

Rhipicephalus sanguineus (brown dog tick)

Click here to view a video on the brown dog tick

Overview of Life Cycles

• A variety of tick species infest dogs and cats in North America, and each has a unique life cycle and life history pattern. The comments here are general in nature to refer to all the common North American ticks of dogs for more specific life cycle information, please see the recommendations for the tick species of interest.

• Ticks infesting dogs and cats include the Ixodidae (hard ticks) and the Argasidae (soft ticks); the life cycles of these two groups are markedly different.

Hard Ticks

• The most common ticks found on dogs throughout North America are the Ixodidae (hard ticks).

• Hard tick species common on dogs and cats in North America are all ‘three-host’ ticks, which means that each motile stage (larva, nymph, and adult) will molt off of the host between their requisite blood meals, often feeding on a different host after molting to the subsequent stage.

• Female hard ticks deposit a single, large clutch of eggs in the environment. Within weeks to months, depending on environmental conditions, the six-legged larval stage hatches from the egg. The larva must then find a host, feed for several days, and then drops to the ground and molts to an eight-legged nymph. The nymph then finds an appropriate host and feeds for several days to a week. Once the nymph has engorged, it drops to the ground and molts to the eight-legged adult, which then must find a third host.

• Adult hard ticks may mate on (all species) or off (Ixodes spp.) a host. Once mated and fully engorged, the female will detach, crawl to a suitable environmental location, oviposit a clutch of several thousand eggs, and then die.

Soft Ticks

• Argasidae (soft ticks) are less common on pets. The soft tick life cycle includes a larval stage and multiple nymphal stages.

• The only important soft tick of dogs in North America is Otobius megnini, the spinose ear tick.

• Unlike most soft ticks, which feed on hosts intermittently and spend much of their time in the environment, Otobius megnini establishes long-term infestations deep in the ear canal of its hosts, first attaching as a larva and remaining through subsequent nymphal molts until finally leaving the host as an adult.

• Adults of Otobius megnini are non-feeding and free-living in the environment.

Stages

• Egg
• Larva
• Nymph
• Adult

Hard Ticks

• Adult hard ticks are characterized by a highly sclerotized dorsal shield (a “scutum”) and anterior mouthparts with a basis capitulum that is visible from the dorsal surface. Both males and females attach and feed on the host.
• Female hard ticks have a partial dorsal scutum that allows their tegument to expand as they grow as much as 100 times their original weight before they detach from the host.
• Male hard ticks possess a full scutum that covers their entire dorsal surface, so males do not undergo such a large increase in size and will still appear somewhat ‘flat’ after taking a blood meal.
• Hard tick larvae and nymphs will expand several fold in size as they engorge on host blood before they detach to molt.
• The Asian longhorned tick differs from many other ticks in that it can reproduces parthenogenetically. This means that a female tick does not need a male tick to mate with to produce viable eggs. Each female tick is capable of producing thousands of eggs that are all going to all be cloned female ticks which each can reproduce on her own. In the native range of the Asian longhorned tick (i.e. East Asia) there is a bisexual population that has males and females that reproduce similar to other tick species, but this parthenogenetically lineage of ticks is what has been introduced and established in other countries such as the US, Australia, and New Zealand.

Soft Ticks

• Argasid (soft) ticks lack a highly sclerotized scutum; the mouthparts of adult soft ticks originate on the ventral surface and are not visible when ticks are viewed dorsally. The mouthparts of immature stages are visible when ticks are viewed dorsally.
• In the common soft tick of dogs in North America (Otobius megnini), only larvae and nymphs are parasitic; the adults are free-living and have vestigial, non-functional mouthparts.

Disease

Direct disease caused by ticks

• Ticks may cause irritation and pruritus around the attachment site as well as anemia from blood loss. Secondary infections can develop at the tick attachment site, leading to sepsis.
• The Asian longhorned tick in particular can result in large numbers of ticks feeding on individual hosts. These highly infested animals can develop anemia which may cause morbidity or mortality. In the United States mortality due to Asian longhorn tick infestations has been reported on domestic cattle and white tailed deer. But, theoretically any host that develops severe infestations may develop anemia.
• Tick-borne toxicoses can also develop due to localized inflammation, allergic hypersensitivity, or severe toxic reactions. Tick paralysis is a form of tick toxicosis characterized by an acute, ascending, flaccid, motor paralysis and caused by a neurotoxin produced by females of several tick species. In the United States, tick paralysis is most commonly associated with Dermacentor spp.

Pathogen transmission

• Transmission of a given pathogen is often restricted, ecologically or physiologically, to a particular tick genus or species. For example, only members of the genus Ixodes are known to be competent vectors of spirochetes that cause Lyme disease.

• However, vector competence of some ticks for different pathogens has been shown in recent years to have some fluidity (Table 1), and novel tick-borne pathogens continue to be identified. In general, although the suite of pathogens transmitted may vary, all hard tick species should be considered potential vectors.

• The feeding time required to allow disease transmission varies between ticks and disease agents. Ehrlichia spp. and Rickettsia spp. can be transmitted within 3-6 hours of tick attachment, while Borrelia burgdorferi transmission can require 24-48 hours of feeding before a host is infected.

• Most tick-borne pathogens are acquired by immature ticks when feeding as larvae or nymphs, and then transmitted by nymphs or adults in subsequent feedings after molting. Because the infections are maintained through developmental stages, this process is referred to as transstadial transmission.

• Some infections, such as Rickettsia spp., are passed from an infected adult female tick through the eggs so that larvae hatch out of the egg mass already infected, a process referred to as transovarial transmission.

• For those genera in which the adult male ticks must take a blood meal before mating (the genera Amblyomma, Dermacentor, and Rhipicephalus), interhost transfer of the male ticks may occur, which offers opportunity for intrastadial transmission.

North American ticks and the diseases they transmit

Amblyomma americanum

• Common Name: Lone star tick
• Pathogens transmitted (Disease Name):
  • Ehrlichia chaffensis (Monocytic ehrlichiosis)
  • Ehrlichia ewingii (Granulocytic ehrlichiosis)
  • Ehrlichia sp. PME (ehrlichiosis)
  • Rickettsia amblyommii (Rickettsiosis)
  • Francisella tularensis (Tularemia)
  • Cytauxzoon felis (Cytauxzoonosis)
  • Unidentified (Southern tick-associated rash illness (STAR))**
  • Heartland virus**
  • Bourbon virus**

Amblyomma maculatum

• Common Name: Gulf coast tick
• Pathogens transmitted (Disease Name):
  • Hepatozoon americanum (American canine hepatozoonosis)
  • Rickettsia parkeri (Rickettsiosis)

Dermacentor variabilis

Note: that this tick species is now recognized to be 2 distinct species with D. variabilis occurring in the eastern United States and the new species, D. similis, occurring in the western United States

• Common Name: American dog tick
• Pathogens transmitted (Disease Name):
  • Rickettsia rickettsii (Rocky Mountain spotted fever)
  • Francisella tularensis (Tularemia)

Dermacentor similis

• Common Name: dog tick
• Pathogens transmitted (Disease Name):
  • Rickettsia rickettsii (Rocky Mountain spotted fever)
  • Francisella tularensis (Tularemia)

Dermacentor andersoni

• Common Name: Rocky Mountain wood tick
• Pathogens transmitted (Disease Name):
  • Rickettsia rickettsii (Rocky Mountain spotted fever)
  • Francisella tularensis (Tularemia)

Haemaphysalis longicornis

Common name: Asian longhorned tick

Pathogens transmitted (Disease name): Because the invasive Asian longhorned tick has only been recognized in the United States for a relatively short period of time, researchers are still investigating what pathogens this tick can or is capable of transmitting. There are also extensive surveys being conducted of wild tick to see what pathogens they may be acquiring from our native hosts and experimental studies are being conducted in the laboratory to see what pathogens the tick may transmit. Therefore, for the list of pathogens for this tick species below, it is incomplete and some pathogens are still being investigated.

• Pathogens transmitted experimentally (Disease Name):
  • Heartland virus
  • Rickettsia rickettsii (Rocky Mountain spotted fever)
  • Theileria orientalis IKEDA strain (theileriosis in cattle only to date)
• Pathogens detected in naturally-infected ticks but transmission ability unknown (Disease Name):
  • Bourbon virus
  • Borrelia burgdorferi (Lyme disease)
  • Anaplasma phagocytophilum (Anaplasmosis)
  • Rickettsia felis (flea-borne rickettsiosis)

Ixodes pacificus

• Common Name: Western black-legged tick or deer tick
• Pathogens transmitted (Disease Name):
  • Borrelia burgdorferi (Lyme disease)
  • Anaplasma phagocytophilum (Anaplasmosis)

Ixodes scapularis

• Common Name: Eastern black-legged tick or deer tick
• Pathogens transmitted (Disease Name):
  • Babesia microti (Human babesiosis)**
  • Borrelia burgdorferi (Lyme disease)
  • Borrelia miyamotoi (Borreliosis)**
  • Anaplasma phagocytophilum (Anaplasmosis)
  • Ehrlichia muris eauclairensi (EML agent/Ehrlichiosis)
  • Borrelia mayonii (Borreliosis)**
  • Powassan virus**

Otobius megnini

• Common Name: Spinose ear tick
• Pathogens transmitted (Disease Name): None known

Rhipicephalus sanguineus

• Common Name: Brown dog tick
• Pathogens transmitted (Disease Name):
  • Anaplasma platys* (Anaplasmosis)
  • Babesia gibsoni (Canine babesiosis)
  • Babesia vogeli (Canine babesiosis)
  • Ehrlichia canis (Ehrlichiosis)
  • Hepatozoon canis (Hepatozoonosis)
  • Rickettsia rickettsii (Rocky Mountain spotted fever)

*Transmission suspected but not yet documented in North America

**These pathogens can cause disease in humans but infections in dogs and cats are currently not known to occur.

Where Do We Find Ticks?

• Ticks are found throughout the United States; the prevalence and geographic range of individual ticks are described in the specific recommendations according to tick species.
• Brown dog ticks (Rhipicephalus sanginueus) live inside and around homes and kennels and infest homes and kennels anywhere there are dogs, including in colder regions of North America such as Canada and Alaska.
• Amblyomma americanum, Ixodes scapularis, and I. pacificus are most commonly found in the understory or leaf litter associated with natural wooded areas frequented by wildlife. The edge habitat often found surrounding a home or yard provides ample habitat to support these ticks.
• Dermacentor spp. and Amblyomma maculatum are more commonly found in tall, grassy meadows; open woods, particularly along trails; and open fields in agricultural areas.
• Otobius megnini occurs in arid areas west of the Mississippi, particularly in the southcentral and southwestern United States.

Maps showing the general distribution of the most common pet-biting species of ticks. These maps are courtesy of the CDC (https://www.cdc.gov/ticks/geographic_distribution.html). Note that these tick species may occur outside of these shaded areas due to range expansion or movement on people or animals.

Maps showing the general distribution of the most common pet-biting species of ticks. These maps are courtesy of the CDC (https://www.cdc.gov/ticks/geographic_distribution.html). Note that these tick species may occur outside of these shaded areas due to range expansion or movement on people or animals.

Host Associations and Transmission Between Hosts

• Each tick species has individual host preferences and timing of activity. However, ticks often adapt their phenology to the environment, shifting host preferences and timing of activity to accommodate local conditions.
• Dogs acquire tick infestations when in areas with actively questing ticks or in a home or kennel infested with brown dog ticks. Ticks, particularly males, may also transfer between co-housed pets.
• Both immature and adult stages of brown dog ticks prefer dogs and can be active in homes and kennels throughout the year, extending their questing activity to yards and gardens around the home during the warmer months. Brown dog ticks will also occasionally feed on people, but infestations in the U. S. have only been reported where there are dogs.
• In general, immature Ixodes spp., Dermacentor spp., and Amblyomma maculatum feed on small vertebrates in the environment, including rodents, birds, and lizards, although different host preferences have been described in different geographic areas. Nymphs of some species feed on medium sized mammals.
• Adult Dermacentor spp. and Amblyomma spp. also commonly feed on medium to large mammals, including deer and cattle.
• Immature and adult Amblyomma americanum, and adult Ixodes scapularis, have a strong proclivity for white-tailed deer and dense populations of these ticks are often linked to presence of deer. Immature A. americanum will also feed on ground dwelling birds such as wild turkey.
• Haemaphysalis longicornis feed on a wide diversity of avian and mammalian hosts. Common hosts include dogs, cats, livestock, and wildlife (deer, raccoon, opossums).
• Larvae and nymphs of Otobius megnini feed in the ears of a wide variety of mammals; adults are not parasitic.

Environmental Factors

• Seasonal tick activity varies widely by geographic region and climatic cues, and tick populations can vary dramatically within a given area due to local vegetation and wildlife host abundance.
• In recent years, a number of tick species have dramatically expanded their range, moving into areas of higher latitude and higher altitude than they were previously found.
• Most tick species require protection from desiccation to survive, and populations tend to thrive in years with higher humidity and precipitation. However, both Rhipicephalus sanguineus and Otobius megnini are quite drought tolerant and thrive under high temperature, low humidity conditions.
• Rhipicephalus sanguineus can be found in cracks and crevices in houses, garages, and dog runs. These ticks often crawl up walls in homes and kennels and can be found in false ceilings. Although found everywhere there are dogs, brown dog tick pressure is higher in warmer areas of the country where tick activity extends to outside infested buildings.

Diagnosis

• Diagnosis is made on physical examination of host and recognition of attached ticks.

• Identification of adult ticks removed from a dog is readily achieved. Images of individual tick species are available in the Species section (above) and in the recommendations for each species. If clinic staff are not confident in their ability to identify adult ticks to species, ticks may be submitted to a diagnostic laboratory.

• Identification of larval and nymphal ticks is more challenging; immature ticks should be sent to a diagnostic laboratory for identification.

• Ticks should be secured in specimen tubes with or without alcohol for submission.

Treatment

• When only a few ticks are present, individual ticks can be removed manually with forceps and gloved hands.

• To remove ticks manually, use fine forceps to grasp the tick it as close to the skin as possible and then directly extract using slow, steady, rearward pressure. Gloves should be worn to prevent zoonotic infection in the event a tick is inadvertently crushed during removal.

• Care should be taken to avoid crushing, twisting, or jerking the tick out of the skin because this may result in increased host exposure to pathogens within the tick or cause the mouthparts to break off in the skin, which may lead to granuloma formation.

• When dogs are heavily infested with hundreds or thousands of ticks, chemical treatment with a fast-acting acaricide such as a pyrethroid or pyrethrin spray followed by manual extraction of the few remaining ticks may be more feasible than manual extraction alone.

• Regular use of acaricides is often necessary to protect dogs from ticks and the pathogens they transmit. Acaricides may be administered topically, in long acting collar formulations, or orally. Care must be taken to use acaricides only in the species for which they are approved. Dog products should not be given to cats, and cat products should not be given to dogs.

• In North America, several acaricides have efficacy against a broad spectrum of ticks, including Preventic® (amitraz), Frontline® and Parastar, (fipronil), EFFITIX Topical Solution for Dogs (fipronil and permethrin), isoxazolines (Nexgard® (afoxolaner), Simparica ™ (sarolaner), Simparica TRIO® (sarolaner), Credelio® (lotilaner) and Bravecto® (fluralaner)), and pyrethroids (Fiproguard Max®, Frontline Tritak®, Parastar Plus®, and Pronyl® (cyphenothrin), deltamethrin, Biospot® (etofenprox), Seresto® (flumethrin), ), Vectra 3D®, and K9 Advantix® (permethrin)). Some pyrethroids, such as permethrin, also have repellent activity.

• Nexgard® (afoxolaner), Activyl® (amitraz), Frontline® (fipronil), Credelio® (lotilaner), Bravecto® (fluralaner), and the pyrethroids are approved for use in dogs.

• Revolution® (selamectin) is labeled against D. variabilis in dogs.

  Click here to view CAPC's Quick Product Reference Guide

Control and Prevention

• Because substantial annual, seasonal, and geographic differences occur in tick prevalence, and because brown dog ticks can infest homes and kennels every month of the year, CAPC supports year-round use of tick-control products on pets. Reactive or attempted seasonal use of tick-control products allows home infestations to establish and permits transmission of disease agents because products are often not applied until tick activity has commenced.

• Occasionally, ticks may be found on pets even when acaricides are routinely administered. This apparent failure in tick control is usually due to heavy burdens of ticks in the environment which result in high re-infestation rates. In these situations, additional control measures, including environmental treatment, are often needed, particularly when homes are infested with brown dog ticks. 

• When ticks have established in a home or kennel (R. sanguineus), acaricides such as cyfluthrin, permethrin, or other pyrethroids can be sprayed into cracks and crevices, behind and under cages, and along the boards in the ceiling. Acaricides may be applied by licensed pest-management professional (exterminator) or by the home owner, but targeted treatment of both indoor and outdoor areas is usually indicated.

• When ticks are acquired from outdoors (Amblyomma spp., Dermacentor spp., Ixodes spp.), the habitat around the home can be modified to render it less supportive of ticks and wildlife hosts that can amplify tick populations. Such measures include closely cutting grass, removing brush piles and leaf litter, limiting ground cover around the home, and selecting plants that do not attract deer. Detailed outdoor tick habitat management advice can be found here.

• Preventing roaming by dogs by keeping them on leash or behind a fence, as recommended in the general CAPC guidelines, also limits the risk of tick infestation in pets. At certain times of the year, particularly in the spring and summer when tick populations are blooming, it may be necessary to keep pets out of habitats harboring heavy numbers of questing ticks.

• In addition to modifying the habitat and managing pets, treating outdoor environments with products such as carbaryl, cyfluthrin, permethrin, or s-fenvalerate can help control tick pressure. Acaricides should be judiciously applied to the perimeter of a yard rather than broadcast over a large area, and chemicals must be allowed to dry before animals or humans are bought back into the treated area.

• Bait boxes and permethrin-impregnated cotton has been used to limit ticks on rodents, and four-poster corn feeders can be used to apply acaricides to deer.

Public Health Considerations

• Ticks that infest dogs also feed on people and can transmit numerous zoonotic agents (described in Disease section).
• People become infested with ticks in the same way as their pets, i.e., by encountering questing ticks in tick-infested habitats.

• Pets not maintained on acaricides may bring ticks into the home which can then move to people and other pets, creating a risk of infection. Keeping pets treated with acaricides creates a safer environment for pets and people.
• The following measures will aid in preventing human infestation with ticks and infection with tick-borne disease agents.
  • Maintain pets on tick-control products year-round.
  • Avoid-tick infested areas whenever possible.
  • Wear light-colored clothing when entering infested areas to facilitate visualization of ticks as they crawl on clothing.
  • Tuck pant cuffs into socks to limit access to legs
  • Walk in the center of trails; avoid vegetation at trail margins.
  • Use a chemical repellent such as DEET, picaridin, or permethrin.
  • Perform frequent tick checks when vacationing or visiting tick-infested areas. It is especially important that such checks be performed on children.
  • Shower, shampoo, and put on clean clothes after visiting areas where ticks might be present.
    • When a tick is found on a person, remove it with fine forceps as described for pets above. Prompt removal is necessary; some rickettsial infections can be transmitted after as little as 3-6 hours of tick feeding.
  • Save the removed tick, wrapped in cellophane tape or in a vial with alcohol, in case it is needed for identification later. The tape or vial can be sealed in a plastic bag, labeled with the date found, and frozen. If illness develops, identification of the tick and the day it was discovered may aid the physician in recognizing which infection was most likely transmitted and allow prompt, appropriate treatment.

Selected References

• Dryden MW, Payne PA. 2004. Biology and control of ticks infesting dogs and cats in North America. Vet Therapeutics 26:4a.

• Piesman J, Eisen L. 2008. Prevention of tick borne diseases. Annu. Rev. Entomol. 53:323–43.

• Starkey L, Little S. 2012. Defeating ticks – practical tips for preventing tick-borne disease in pets. Today’s Veterinary Practice 5:40-44.