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Prurigo, Pets, Vets

Cheyletiella Mite

Some patients with unexplained itchy bumps may be infested with miters from dogs or cats.  One of the best articles on the subject appeared in the British Medical Journal in 1979.  The  Cheyletiella mite can infest dogs, cats, rabbits and other mammals.

Prurigo and pets: the benefit from vets.
M Kieffer, S Kristensen, and T E Hallas
Br Med J. 1979 June 9; 1(6177): 1539–1540.

Scabies Update

Scabies:  A Parasite for our Time by Ian Burgess (Cambridge, U.K.) is a helpful presentation and a valuable educational tool. 

One authority I found felt that the mite can infest the head and neck.  If so, this may explain treatment failures.  It really makes no sense that the mite can not be on the head and neck - it was probably an "urban legend."

"I have been unable to find the origin of this myth.  Mites do occur on the face and neck in humans, just like in other mammals.  I suspect the myth has arisen due to therapeutic inadequacies.  Perhaps the story went like this: the only therapies available in the early days (e.g., benzyl benzoate) was very irritant on the face, so the original prescribers said don't use it on the face because it is too irritant.  When people asked others "why not treat the head?", I suspect they then said because mites don't occur there, rather than admit they were prescribing inadequate treatment. One of the causes of treatment failure is not treating the whole epidermis, and this definitely includes the head, the finger nails, the external genitals and the natal cleft. Now less irritant treatments are available, there is no excuse not to treat scabies adequately."

Scabies Treatment

The standard therapy in 2012 for scabies is 5% permethrin cream (Elimite or a generic).  One application is 99% effective.  Two applications, a week apart, are recommended -- so that if someone has scabies there is a 0.01 percent failure rate.  Re-infestation is common unless all contacts are treated.

Five percent permethrin cream is applied over the entire skin from the neck down, especially between the fingers and toes after a warm bath or shower. It is important to reach all areas, except the face, with especially careful attention to the sites of greatest involvement. The medicine should be left on for 12-24 hours and then washed off.  In infants and small children there may be scalp involvement, so that area should be treated as well.  For unknown reasons, lesions above the neck in adults do not occur.

Two applicants of permethrin are all that are necessary. Permethrin is safe to use for children and even infants.  The only contraindication is allergy to chrysanthemums. A second treatment should be performed in one week. It is of the utmost importance that all other household members and close contacts be treated.

An oral medicine, stromectal (Ivermectin), has been approved for use, as well. Stromectol is not approved, at this time, for young children.  In  studies, it appears to be slightly less effective than topical permethrin.

Ordinary laundering or dry cleaning of clothing, bed linens, and blankets is all that is required. Some patients, because of their scratching developed impetigo, and this will have to be treated with appropriate antibiotics. After treatment, it is common for itching to persist for 2-4 weeks.

Re-infestation, unfortunately, can occur. This is suspected in patients who persist in itching for more than two-four weeks after treatment. If evidence of active scabies is found, then re-treatment may be advisable. The patient should be questioned closely about the possible source for re-infestation.  Usually, this turns out to be a close contact who was not treated.

Printable version: Download Scabies Treatment

Scabies

Jane Brody wrote an important introduction to scabies in the September 23, 2008 NY Times.

"Scabies is frequently misdiagnosed and mistreated, partly because most physicians are unfamiliar with it and partly because its symptoms mimic so many other skin diseases.

A correct diagnosis is further complicated by the fact that symptoms can often appear six to eight weeks after a person becomes infested with the microscopic arthropod, making it seem as if the problem came from nowhere. But unlike other skin diseases, scabies is usually accompanied by a tell-tale sign: one or more burrows in the skin where female mites lay their eggs.

Scabies is easily cured, but only if patients and their close contacts conscientiously follow directions for medical treatment and environmental cleanup. However, even after a person is rid of the mites and their eggs, itching can persist for up to four weeks."

To read the full article click on "An Itchy Torment, Frequently Misdiagnosed."

Picture of mite taken from Stanford Medical School's article on Scabies.