By Michelle Evason, BSc, DVM, DACVIM (SAIM)

Tick-borne disease in dogs and cats is almost entirely preventable. Client education is needed to inform about the risk to pets associated with different tick species, canine and kitty lifestyles, importation concerns, and travel (particularly as summer advances). Public health (i.e. human) risks surrounding ticks and tick-borne disease is also now part of our veterinary One Health accountability, in addition to preventing ticks on pets.

Tick-borne concerns in U.S. and Canada

Tick-borne diseases in dogs include Lyme disease (Lyme borreliosis), anaplasmosis, ehrlichiosis, tularemia, Rocky Mountain spotted fever (RMSF), hepatozoonosis, babesiosis, and tick paralysis (Table).^1,2 In cats, cytauxzoonosis and anaplasmosis are concerns, and potentially Lyme borreliosis.^1,3,4

Sadly, many of these diseases can have severe outcomes and potentially cause death in dogs and cats if they are not diagnosed promptly or go untreated. Dogs, and probably cats, can also serve as "sentinels" for human disease (e.g. RMSF, Lyme borreliosis), and veterinary identification of disease and test positive status can have implications for human health.^5,6

The table summarizes U.S. and Canadian tick and tick-borne disease information.^2,8 The maps this information is drawn from are based on tick distribution (for different tick types), tick-borne disease (i.e. Lyme disease risk maps), and/or canine tick-borne disease seroprevalence maps, i.e. test positive results from dogs in the U.S. and Canada.

Education needs and 'tick-risk'

Despite the obvious concern and need for communication on, tick-borne disease, many pet owners are unaware of regional and travel-related tick risk. As such, client knowledge may lag considerably behind the rapid increases in tick numbers, distribution, infection, and disease risk, that have occurred over the past several years, which has presently resulted in ticks now found in higher abundance (and in new regions) of the U.S. and Canada.^7,8

One example of this change in the U.S. is ticks are now seen in higher numbers in residential areas of south-central Indiana, with Amblyomma americanum ticks as the predominant species.⁹ Another example is the Gulf Coast tick (Amblyomma maculatum), which can now be found in the mid-Atlantic and Midwest states (Arkansas, Oklahoma, Kansas, Tennessee), and in southern Arizona, with higher reported tick abundance.^10-12

As more ticks often equates to more tick-borne pathogens, and from there to heightened disease risk (and disease) in dogs and cats, updating and informing clients on ticks and tick-related disease risks is key to prevention.^6,13,14

Common clinical signs

Tick-borne disease can be a challenge to diagnose in dogs, and even more so in cats. This is because clinical signs are often vague, or nonspecific, and vary with infecting pathogen. Importantly, tick-borne disease must be on clinician differential lists to be diagnosed.

Below is a summary of key presenting clinical signs in dogs and cats associated with the more common tick-borne diseases in the U.S. and Canada.

Lyme borreliosis: The two most common clinical forms in dogs are: 1) acute onset of shifting limb lameness (+/- fever), and, less commonly, 2) Lyme nephritis, a severe form of protein-losing nephropathy.^1,6 In cats, reported clinical signs are vague, i.e. anorexia, lethargy.³

With anaplasmosis, dogs can present with fever, reduced appetite, weakness, lethargy, and bleeding tendencies, e.g. petechiation. In cats, clinical signs can consist of fever, anorexia, and lethargy.^3,4

Ehrlichiosis can occur due to infection with Ehrlichia canis or Ehrlichia ewingii, and potentially with E. chaffeensis and E.muris-like agent.^1,15 In dogs, clinical signs may include fever, reduced appetite, weakness, lethargy, and bleeding tendencies, e.g., petechiation.¹

Rocky Mountain spotted fever (RMSF) can cause acute onset of fever, reduced appetite, weakness, lethargy, vomiting and diarrhea in dogs. Bleeding tendencies (e.g. petechiation), polyarthritis, and peripheral edema can occur, along with signs related to vasculitis and neurologic dysfunction. Rapid diagnosis of RMSF is critical for patient management and to advise on human risk, as diagnosis in one species (dog) can assist in diagnosis/management of the other (human). ^1,5

American canine hepatozoonosis can occur after ingesting an infected nymph or adult Ambylomma maculatum tick (e.g. self-grooming) or through ingesting cysts (Hepatozoon americanum), e.g. dog eating a carcass containing cysts. Lethargy, muscle pain (reluctance to walk, stiff gait, bone, or spinal pain), and weight loss can be the observed clinical signs. ¹

Cytauxzoonosis can cause severe disease in cats. Clinical signs can include acute fever, weakness, pale mucous membranes (anemia), jaundice, reduced appetite, and gastro-intestinal signs. ¹

Prevention strategies for cats and dogs

Tick and tick-borne disease prevention strategies are based on risk assessment of the individual dog, cat, and pet owner. As such, recommendations for prevention will vary based the following:

1) Regional risk for different tick species.

2) Lifestyle risks of the cat or dog, e.g. hunter, outdoor lifestyle, etc.

3) Travel risk, i.e. travel to other regions (U.S. and Canada) with different tick species.

4) Importation concerns, imported to the U.S. or Canada, or international travel risk.

5) Owner level tolerance of risk.

Dogs: Prevention of tick exposure, attachment, and tick-borne disease in dogs means a veterinarian-approved tick prevention product, tick checks, and prompt tick removal. Other aspects of tick prevention might include reduction of tick exposure as practical (e.g. tick environmental reduction strategies, choice of area for dog walks, runs, etc.), Lyme disease vaccination, and, if indicated, blood donor screening prior to transfusion.

DVM-directed administration of 1) tick prevention products, and (based on region and risk) 2) Lyme disease vaccination will reduce disease risk in most dogs.⁶

Cats: Prevention of tick exposure, attachment, and tick-borne disease in cats means consistent application of a veterinarian-approved tick prevention product, tick checks, and prompt tick removal, along with reduction of tick exposure as practical.

PREVENTION PRODUCTS

The array of available tick prevention products can feel overwhelming, and, in Canada, the Ontario Animal Health Companion Animal Expert Network helps with this by providing its (updated for 2022) anti-parasitics tables for dogs and cats. Pet-owner specific: https://www.oahn.ca/resources/anti-parasitics-table-for-cats-and-dogs Veterinarians (must be registered and logged in): https://www.oahn.ca/resources/anti-parasitics-table-for-cats-and-dogs-for-veterinarians Ideally, tick prevention is discussed at the first puppy or kitten exam and repeated at every health check thereafter, to ensure timely and consistent prevention compliance. Regular client reminders regarding tick risk (regional and seasonal) and prevention needs, pointing pet owners towards resources, such as those included in this article, and emphasizing the "ounce of prevention is worth a pound of cure" message can assist with practical tick prevention. Fortunately, there are numerous evidence and expert-based information sources veterinary team members can provide to help keep patients and clients aware and as safe as possible, despite the upticks in tick risk.

Michelle Evason, BSc, DVM, DACVIM (SAIM), has worked in general practice, academia, specialty clinical practice, and in the animal health industry. She serves as a small animal internal medicine and nutrition consultant in North America and consults for IDEXX UK. Dr. Evason has published on numerous infectious diseases, antimicrobial stewardship, nutrition, and pet-owner education-related topics.

References

1. Weese JS, Evason M. Infectious Diseases of the Dog and Cat. CRC Press. July 2019.
2. Evason M. Tick-borne diseases in dogs: A Canadian Perspective. Island Studies Press. July 2020.
3. Hoyt K, Chandrashekar R, et al. Evidence for Clinical Anaplasmosis and Borreliosis in Cats in Maine. Top Comp Animal Med. 2018;33(2):40-44.
4. Schäfer I, Kohn B. Anaplasma phagocytophiluminfection in cats: A literature review to raise clinical awareness. J Fel Med Surg. 2020;22(5):428–441.
5. Warner, RD, Marsh WW. Rocky Mountain Spotted Fever. J Am Vet Med Assoc. 2002; 221(10):1413-17.
6. Littman MP, Gerber B, Goldstein RE. ACVIM Consensus update on Lyme borreliosis in dogs and cats. J Vet Int Med. 2018; 32:887-903.
7. Sonenshine DE. Range Expansion of Tick Disease Vectors in North America: Implications for Spread of Tick-Borne Disease. Int J Environ Res Public Health. 2018;15(3): 478.
8. Maps, as accessed April 2022: A - Companion Animal Parasite Council (CAPC), Tick-borne pathogen seroprevalence: USA: https://capcvet.org/maps/#2020/all/lyme-disease/dog/united-states; Canada: https://capcvet.org/maps#2020/all/lyme-disease/dog/canada/; B - Tick distribution Centers for Disease Control and Prevention (CDC, US): https://www.cdc.gov/ticks/geographic_distribution.html; C - Lyme disease risk maps (Government of Canada): https://www.canada.ca/en/public-health/services/diseases/lyme-disease/risk-lyme-disease.html
9. OmodiorO, KianersiS. Active surveillance of ticks in peri-domestic areas of Indiana, Midwest United States. J Vector Borne Dis. 2021;58(4):352-358.
10. Allerdice MEJ, Beati L, Yaglom H, et al. Rickettsia parkeri(Rickettsiales: Rickettsiaceae) detected in ticks of theAmblyomma maculatum (Acari: Ixodidae) group collected from multiple locations in southern Arizona. J Med Entomol. 2017; 54:1743–1749.
11. Monzón JD, Atkinson EG, Henn BM, et al. Population and Evolutionary Genomics of Amblyomma americanum, an Expanding Arthropod Disease Vector Genome. Biol Evol. 2016; 8:1351–1360.
12. Teel PD, Ketchum HR, Mock DE, et al. The Gulf Coast tick: A review of the life history, ecology, distribution, and emergence as an arthropod of medical and veterinary importance.J Med Entomol.2010; 47:707–722.
13. Dewage BG, Little SE, Payton M, et al.Trends in canine seroprevalence toBorrelia burgdorferiand Anaplasma spp. in the eastern USA, 2010–2017. Paras & Vect. 2019; 12: 476; 1-13.
14. Evason ME, Stull JS, Pearl DL, et al. Prevalence of Borrelia burgdorferi, Anaplasma spp., Ehrlichia spp. and Dirofilaria immitis in Canadian dogs, 2008 to 2015. Paras & Vect. 2019; 12:64; 1-11.
15. Hegarty BC, Maggi RG, Koskinen P, et al. Ehrlichia muris infection in a dog from Minnesota. J Vet Int Med. 2012;26(5), 1217–1220.