109 - Ticks

Abstract

•First Described: The earliest written records of ticks date to ancient Greek literature. Homer mentioned ticks in his poem Odyssey (800 BC) as did Aristotle in the History of Animals (335 BC). Rhipicephalus sanguineus adults and nymphs were recovered from a mummified dog dating to Roman Egypt.1 Occurrence of ticks in the fossil record indicate the parasites originated during the Cretaceous period (65–146 mya).2•Causes: Ticks that infest dogs and cats belong to two taxonomic families, the Ixodidae or hard ticks, and the Argasidae or soft ticks. The most common ticks found on dogs and cats in North America are hard ticks and include Amblyomma americanum (lone star tick), Amblyomma maculatum (Gulf Coast tick), Dermacentor andersoni (Rocky Mountain wood tick), Dermacentor occidentalis (Pacific Coast tick), Dermacentor variabilis (American dog tick), Haemaphysalis longicornis (longhorn tick), Ixodes pacificus (western black-legged tick), Ixodes scapularis (deer tick; black-legged tick), and Rhipicephalus sanguineus (brown dog tick; kennel tick). The soft tick most commonly encountered in dogs and cats is Otobius megnini (spinose ear tick). However, other soft ticks including Ornithodoros spp. can also infest dogs and cats.•Affected Hosts: All dogs and cats are susceptible to tick infestation.•Geographic Distribution: Worldwide with the highest abundances in tropical and temperate climates.•Primary Mode of Transmission: Contact with environments contaminated with ticks. Intrastadial transfer of ticks from one infested animal to another.•Major Clinical Signs: Painful bite, erythema, pruritus, inflammation, swelling, ulceration, hypersensitivity reactions, otitis externa, paralysis, and anemia. Ticks are vectors of several pathogens capable of resulting in severe disease with variable clinical signs in dogs and cats.•Differential Diagnoses: Other ectoparasites including mites, fleas, lice, and bed bugs. For tick paralysis, key differential diagnoses include botulism, polyradiculoneuritis, acute peripheral neuropathies, snakebite, and hypokalemia.•Human Health Significance: Several species of ticks (e.g., A. americanum and I. scapularis) readily bite and feed on humans. Pets that are not maintained on tick control can transport ticks indoors increasing the risk of exposure to humans. Owners removing embedded ticks from infested pets with improper technique or without protection risk infections with tick-borne pathogens.