Overview of Mites
Almost all domestic mammals can be infested by S scabiei.
Skin, otic, and respiratory conditions commonly affect dogs and cats; the prevalence for each is estimated at 15%1, 21%2, and 23%3 respectively. A multitude of etiologies exist (eg, allergic, infectious, parasitic). Because more than one etiology is commonly present in a patient, a thorough diagnostic protocol should be followed to allow detection of parasitic organisms and secondary bacterial or fungal infections. The following are common mites that lead to these conditions in small animals.
Sarcoptes scabiei (Sarcoptic Mange Mite)
With the exception of cats and guinea pigs, almost all domestic mammals can be infested by S scabiei.4 Cats may be infested by Notoedres cati, a mange mite very similar to Sarcoptes. Lesions appear first on thin-haired parts of the body (eg, ear margins, elbows, hocks, inguinal and axillary regions).5 A hallmark of sarcoptic mange is intense pruritus; infested animals will self-traumatize attempting to relieve the itching, which may lead to secondary infections, hair loss, thickened skin, and eventually lichenification. If a dog scratches with a hindlimb when the ear margin is rubbed or scratched, S scabiei should be suspected.1 Transmission of S Scabiei is by direct contact and is extremely zoonotic.
Demodex spp (Demodectic Mange Mite)
These mites are considered normal fauna of the host hair follicles and sebaceous glands. They are routinely detected in younger patients with localized alopecia and will usually resolve once the patient is mature. However, in genetically predisposed or immunocompromised patients, Demodex spp may become debilitating and even life-threating.6 Clinical signs occur in these immunodeficient or genetically predisposed patients.7 Pustular demodicosis, characterized by moist, purulent dermatitis with an unpleasant, rancid odor, may develop. The prognosis is poor without proper treatment.
Otodectes cynotis (Ear Mite)
Ear mites are common in dogs, cats, and ferrets worldwide. All developmental stages of Otodectes live deep in the external ear canal.4,8 Transmission occurs through direct contact with an infected animal; younger patients tend to be more affected. Unlike Sarcoptes and Demodex, ear mites live as surface parasites only, piercing the skin to feed on blood, lymph, and serum. Clinical signs range from asymptomatic to severe otitis externa; debris is typically dark brown to black and thick. Secondary bacterial infection, yeast infection, and aural hematomas may develop as a result of excessive head shaking.
Pneumonyssoides caninum (Nasal Mite)
These mites are commonly referred to as nasal mites because of the infestation site (ie, the nasal sinuses of dogs). Details of the life cycle are not completely understood; however, adults with 4 pairs of legs and larvae with 3 pairs have been identified.9 Clinical signs include hyperemia of the nasal mucosa, nasal secretions, tearing of the eyes, chronic sneezing, facial pruritus, and epistaxis.10
Cheyletiella spp (Fur Mite)
Like ear mites, these mites are nonburrowing and pierce the skin to feed on blood, lymph, and serum.4 Although most infested patients are asymptomatic, clinical signs can include mild alopecia, pruritus, and skin scaling that resembles eczema. Fur mites can survive several days off the host, so infested bedding and household furniture may be a source of infection.
Editor's note: Dr. Chris Adolph is affiliated with Zoetis Animal Health.