Feline tick-borne diseases
by Jenny Alonge
Vector-borne diseases (VBD) are often disregarded in felines, primarily because they are considered fastidious groomers who typically remove parasites before they attach. However, fleas, ticks, mosquitoes, and sand flies transmit diseases that can affect cats, leading to issues ranging from subclinical infection to death. Ticks, and the diseases they spread, are becoming increasingly prevalent across the United States, and most tick-borne diseases recognized in dogs have been found in cats. More research is needed to determine the tick-borne disease incidence in cats, but regional prevalence in dogs can be used as evidence to indicate risk for felines. The following article reviews feline ticks and tick-borne diseases in the United States.
Common feline ticks
Ticks that commonly infest domestic cats include:
- Amblyomma americanum — Lone star ticks live in woody areas, particularly those with large white-tailed deer populations. The ticks are widely distributed in the eastern, southeastern, and south-central United States. The lone star tick is an important vector for cytauxzoonosis, tularemia, and ehrlichiosis in domestic cats.
- Dermacentor andersoni — The Rocky Mountain wood tick, which is found in western Rocky Mountain states, is an important vector for tularemia in domestic cats.
- Dermacentor occidentalis — Pacific coast ticks, which live along the Pacific coast, are another important vector for tularemia in cats.
- Dermacentor variabilis — The American dog tick is found in grassy meadows and along forested trails east of the Rocky Mountains and in limited areas along the Pacific coast. These ticks can transmit cytauxzoonosis, tularemia, and ehrlichiosis in cats.
- Ixodes scapularis — The black-legged or deer tick lives in dense, humid, wooded areas, and is widespread throughout the eastern, south central, and midwestern states. These ticks are an important vector for Lyme disease and anaplasmosis in cats.
- Ixodes pacificus — The western black-legged tick is found in the west, primarily along the Pacific coast, and can transmit Lyme disease and anaplasmosis in cats.
- Rhipicephalus sanguineus — The brown dog tick is prevalent throughout the country and is thought to transmit ehrlichiosis to cats.
Feline tick-borne diseases
Tick-borne diseases identified in cats include:
- Cytauxzoonosis — Transmitted by the lone star tick and the American dog tick, Cytauxzoon felis is the most concerning feline tick-borne disease. The reservoir hosts are infected bobcats, who typically have a short-lived illness followed by a persistent carrier state. Important information includes:
- Signs — Cytauxzoonosis signs include fever, inappetence, dyspnea, and icterus. The disease typically progresses quickly and can lead to death in as little as one day after clinical signs manifest.
- Diagnosis — C. felis piroplasms seen on erythrocytes are diagnostic, but may not be present in the early disease stages. Detecting C. felis DNA by polymerase chain reaction (PCR) is considered the gold standard, and can detect infection prior to clinical signs.
- Treatment — Cytauxzoonosis treatment includes atovaquone (15 mg/kg PO q 8 hrs), azithromycin (10 mg/kg PO q 24 hrs), and intensive supportive care. Treatment is successful in about 60% of cases.
- Feline granulolcytotropic anaplasmosis — Anaplasma phagocytophilum is transmitted by the black-legged tick and the western black-legged tick. Important information includes:
- Signs — Signs include fever, lethargy, inappetence, joint pain, enlarged lymph nodes, weight loss, periodontal disease, conjunctivitis, and neurologic signs.
- Diagnosis — Finding morulae inside neutrophils in cats who exhibit clinical signs is considered diagnostic, but morulae may be hard to find if rickettsemia is low. Serologic testing and PCR assays are commercially available, but cats with suspected anaplasmosis may need consecutive serum samples to prove infection.
- Treatment — Anaplasmosis treatment includes doxycycline (10 mg/kg PO q 24 hrs) for at least 28 days, and supportive care.
- Tularemia — Cats are exposed to Francisella tularensis infection from infected lone star ticks, American dog ticks, Rocky Mountain wood ticks, and Pacific coast ticks, and can be infected by eating infected wildlife. Cats are more susceptible to tularemia than dogs. Important information includes:
- Signs — Clinical signs include fever, inappetence, depression, lymphadenopathy, splenomegaly, hepatomegaly, icterus, and oral or lingual ulcers.
- Diagnosis — Diagnosis is typically confirmed by rising antibody titers.
- Treatment — Gentamicin (5 to 6.6 mg/kg SC, IV, or IM q 24 hrs) for 7 to 14 days is considered the treatment of choice for tularemia.
- Feline borreliosis — Borrelia burgdorferi infection is known to cause clinical illness in dogs and humans, but consensus on the disease impact on cats is controversial. Cats are hosts for the disease vectors, the black-legged tick and the western black-legged tick. Important information includes:
- Signs — Experimentally infected cats exhibit lameness and multi-localized inflammation, such as arthritis and meningitis.
- Diagnosis — Diagnostic criteria have not been established for cats, but positive serology in cats exhibiting clinical signs supports a diagnosis.
- Treatment — Recommended treatment is doxycycline (10 mg/kg PO q 24 hrs) for at least 28 days.
- Feline monocytotropic ehrlichiosis — Little is known about ehrlichiosis in cats, but an Ehrlichia canis-like agent is the suspected cause. Important information includes:
- Signs — Signs include fever, inappetence, weight loss, and polyarthritis.
- Diagnosis — Diagnostic criteria have not been established for cats, but positive serology in cats exhibiting clinical signs supports a diagnosis.
- Treatment — Recommended treatment is doxycycline (10 mg/kg PO q 24 hrs) for at least 28 days.
Preventing feline tick-borne disease
Prevention is important, since many tick-borne diseases are difficult to diagnose and treat in cats. Cats should be kept indoors, and all cats should receive year-round veterinary approved acaricidal products.
Tick-borne diseases are becoming more prevalent, and recognizing these infections is important to provide the appropriate treatment. Consider a tick-borne illness when you examine a cat who has a fever of unknown origin and promote year-round flea and tick medication for all your feline patients.
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