The most common cause of pruritus in guinea pigs is sarcoptiform mange, caused by the mite Trixacarus caviae that burrows into the skin, creating epidermal tunnels and eliciting a cell-mediated immune response. The mite’s life cycle is 10–14 days. Most transmission is direct from carrier animals. Lesions are typically on the head, shoulders, dorsum, or flanks but can become generalized. Lichenification can occur with chronic infection. Secondary bacterial infections are common, and seizures have been reported.

Affected guinea pigs become thin and lethargic; the disease can be fatal. Diagnosis is made via skin scrapings and visualization of eggs and mites. The mites resemble Sarcoptes scabiei var canis; however, T caviae mites are smaller and have longer hair-like dorsal setae. There are no licensed antiacaricidal drugs for guinea pigs.

Seventeen mixed-breed guinea pigs with active mite infestations received either topical selamectin (15 mg/kg, n = 9) as a single dose or ivermectin (400 µg/kg) SC q10d (n = 8) for 4 injections. Pruritus resolved in 10 days for all animals; all were microscopically mite-free on day 30 (selamectin group) or day 40 (ivermectin group). Neither infection recurrence nor adverse reactions were noted in either group.

Commentary Some animals can be subclinical carriers and can introduce the disease into a colony. As with other species of sarcoptic mites, they can cause transient dermatitis in humans. Although there was no significant difference in treatment outcomes, most owners would much prefer a one-time topical than an injection series. Topical ivermectin has also been suggested, but >1 treatment is recommended. These are extralabel uses of antiparasiticides, and owners should be advised. Cleaning bedding and living quarters is also important in management.—Patricia Thomblison, DVM, MS

Source Comparison of efficacy, safety, and convenience of selamectin versus ivermectin for treatment of Trixacarus caviae in pet guinea pigs (Cavia porcellus). Eshar D, Bdolah-Abram T. JAVMA 241:1056-1058, 2012.