The mites are fairly host-specific, but animals (including humans) that come in contact with infested dogs can also be affected. Adult mites are 0.3-0.5 mm long, roughly circular in shape, without a distinctive head, and have 4 pairs of short legs. Females are almost twice as large as males. The entire life cycle (17-21 days) is spent on the dog. Females burrow tunnels in the stratum corneum of the skin to lay eggs. Sarcoptic mange is readily transmitted between cats by direct contact; infestation by indirect contact is less frequent but may occur. The incubation period is variable (10 days to 8 wk) and depends on level of exposure, body site, number of mites transmitted, and individuals. Asymptomatic carriers may exist.
Intense pruritus (itching) is characteristic and is probably due to hypersensitivity to mite products. Primary lesions consist of a papular eruption that, due to self-trauma, develops thick crusts. Secondary bacterial and yeast infections may occur. Typically, lesions start on the ventral abdomen, chest, ears, elbows, and legs and, if untreated, become generalized. Dogs with chronic, generalized disease develop seborrhoea, severe thickening of the skin with fold formation and crust build up, peripheral lymphadenopathy, and emaciation; dogs so affected may even die. “Scabies incognito” has been described in well-groomed dogs; these dogs, infested with Sarcoptic mites, are pruritic, but demonstrating the mites on skin scrapings is difficult because the crusts and scales have been removed by regular bathing. Untypical clinical forms that are probably linked to the extensive use of insecticides or acaricides may be observed.
Diagnosis is based on the history of severe pruritus of sudden onset, possible exposure, and involvement of other animals, including humans. Making a definitive diagnosis is sometimes difficult because of negative skin scrapings. Concentration and flotation of several scrapings may increase chances of finding the mites, eggs, or faeces. Several extensive superficial scrapings should be done of the ears, elbows, and hocks; non-excoriated areas should be chosen. Faecal flotation may reveal mites or eggs. Recently, a specific and sensitive ELISA for detection of specific antibodies became commercially available.
Signs of pruritus can be confused clinically with other causes of pruritus, including:
- other mites (Neotrombicula autumnalis, Notoedres spp, Otodectes spp, Pulex irritans, Cheyletiella spp, Lynxacarus radovskyi)
- fleas (Ctenocephalides felis, Echidnophaga gallinacea, Eutrombicula alfreddugesi)
- miliary dermatitis (which includes food allergy dermatitis)
- eosinophilic granuloma complex
- fungal infections
It is imperative that all in-contact pet mammals, their paraphernalia, and their environment be included in the treatment program. However, environmental treatment is not always performed nowadays, as long as treatment duration is adequate. Indeed, treatment duration, which should cover a minimum period of 6 to 8 wk, is directly influenced by the severity of the infestation, the number of animals involved, the acaricidal product chosen, and whether or not there is concomitant topical or environment decontamination, or both.
Options include one of the following:
- weekly bathing in pyrethrin shampoo
- lime sulfur dips every five to seven days for three weeks
- fipronil spray one spritz/lb body weight repeated again in three weeks
- selamectin topically one dose every 15 days for a total of three doses
- ivermectin 200 micrograms/kg every week for three weeks (must be heartworm negative first and not used in herding breeds or crosses thereof — also avoid ivermectin in older patients)
- milbemycin 2 mg/kg once weekly for three weeks (one study treated for up to nine weeks)
- The environment must be treated with a house and carpet spray such as those that are used for fleas. Remember to treat any pet exposed to the affected animal and not just the affected animal.
Vaccines have not been developed as yet for this parasitic disease.
- Xhaxhiu D et al (2009) Ectoparasites of dogs and cats in Albania. Parasitol Res 105(6):1577-1587
- Malik R et al (2006) Crusted scabies (sarcoptic mange) in four cats due to Sarcoptes scabiei infestation. J Feline Med Surg 8(5):327-339
- Ghubash R (2006) Parasitic miticidal therapy. Clin Tech Small Anim Pract 21(3):135-144
- Merck Vet Manual
- Nisbet AJ & Huntley JF (2006) Progress and opportunities in the development of vaccines against mites, fleas and myiasis-causing flies of veterinary importance. Parasite Immunol 28(4):165-172