106 - Fleas and Lice

Abstract

Fleas•First Described: Familiar since antiquity, fleas (Pulex irritans, Tunga penetrans) were first described in the 10th edition of Systema Naturae published by Linnaeus in 1758. Ctenocephalides canis was first described by Curtis in 1826, Ctenocephalides felis by Bouché in 1835, Ctenocephalides gallinacea by Westwood in 1875, and Pulex simulans by Baker in 1895.•Cause: Ctenocephalides felis (cat flea) most common on dogs and cats worldwide; also Ctenocephalides canis (dog flea), Echidnophaga gallinacea (sticktight flea), Pulex spp. (human flea), Xenopsylla cheopis (rat flea) (family Pulicidae, order Siphonaptera); Tunga penetrans (chigoe flea, jigger) (family Hectopsyllidae (formerly Tungidae), order Siphonaptera).•Affected Hosts: Dogs, cats, other domestic animals, and peridomestic wildlife.•Geographic Distribution: Most fleas of companion animals (Ctenocephalides spp., Pulex spp., E. gallinacea) are found worldwide, sparing high altitude and arid regions; T. penetrans is native to the Caribbean, Central America, and South America, and has been introduced to and established in sub-Saharan Africa, especially East Africa, and India.•Primary Mode of Transmission: Infestations are most often acquired through direct contact with emerging fleas from pupae in the environment. Fleas are persistent or permanent ectoparasites of the host; although considered a secondary infestation route, a few fleas may occasionally move directly from an infested animal to another animal in close, prolonged proximity.•Major Clinical Signs: Pruritus; anemia; flea allergy dermatitis consisting of tail head or abdominal alopecia, seborrhea, pyotraumatic dermatitis, and secondary infections (dogs); or miliary dermatitis especially around the neck (cats). Pruritus may be the primary clinical sign or, in some flea-infested animals, absent. Direct evidence of flea infestation (fleas, flea frass) is absent in the majority of dogs and cats with flea allergy dermatitis. Fleas also serve as vectors for common pathogens, including Bartonella spp. and Dipylidium caninum.•Differential Diagnoses: Atopic dermatitis; dermatophytosis, bacterial pyoderma, Malassezia dermatitis, mite infestations (Cheyletiella spp., Demodex spp., Notoedres cati, Otodectes cynotis, Sarcoptes scabiei, Lynxacarus radovskyi), lice infestation, mosquito allergy, cutaneous adverse food reactions, autoimmune disease.•Human Health Significance: Humans, especially those sharing a home with infested pets, are at risk of experiencing flea bites, particularly on the feet, ankles, and lower legs. The bites occur when adult fleas emerge from pupae and feed on humans instead of pets. Children less than 10 years of age are particularly likely to develop a localized allergic reaction to the bites.