Cheyletiellosis or Walking Dandruff in the Cat

24 05 2011

Cheyletiellosis or Walking Dandruff in the Cat

Is your cat constantly scratching?  Does he have scabby areas of hair loss?  Does he have dandruff that you think may be moving?  Then your cat could be suffering from cheyletiellosis.

Cheyletiellosis is a dermatologic condition caused by a mite so large that it is sometimes visible to the naked eye. The mite infecting cats is called Cheyletiella blakei.  Although primarily a parasite of cats, cross-infections with dogs, rabbits, and foxes may occur.

The entire life cycle of Cheyletiella takes 21 days.  During the mite’s life cycle it will rotate through five different stages:  egg, prelarva, larva, first-nymph, second-nymph, and adult.   These mites have four sets of legs, and on close examination, a yellow coloring.   The eggs are also large and will attach to the hair of the host by cocoon-like strands.  On microscopic examination, Cheyletiella eggs may be mistaken for those of hookworm eggs but tend to be much larger, approximately three times the size.

The mite is spread by direct contact with an infected individual or infested bedding. The mite is non-burrowing and will feed on the keratin layer of the skin, sebaceous secretions, or hair.  The mite most often inhabits the dorsal coat (area along the backbone or spine) but have been seen crawling in and out of the nostrils of cats.  The female mite may live off, a host in the environment for up to 10 days, thereby allowing for the environmental spread of the mite.

Once exposed to Cheyletiella, it typically takes three to five weeks before the disease is clinically apparent. Symptomatic cats develop crusting of the dorsal coat and puritic hair loss, which is also known as a generalized military dermatitisFacial pruritus, excoriation, sneezing, and periocular involvement (around the eyes) may occur. Occasionally lesions will resemble an eosinophilic granuloma complex.   Immunocompromised and young cats tend to be the most greatly affected.  An asymptomatic carrier state may occur in the cat.

The diagnosis may be confirmed through the demonstration of the mite or eggs on microscopic examination.  The mites may be combed out with a fine comb with the scale being observed under the microscope.  Alternatively, the mite may be picked up on acetate tape or the eggs may be demonstrated on fecal flotation of the combed-out

coat scale.

Systemic treatment in the cat includes the use of selamectin or Revolution®, available from Pfizer Animal Health.  The medication is applied topically every 15 days or three doses.

Topical treatment in cats also includes the use of lime-sulfur dips every five to seven days for three to four applications.  Lime-sulfur is very soothing to the skin and will help ease the pruritus associated with the infection.  Lime-sulfur does, however, smell like rotten eggs and gloves should be worn when applying the dip.  Alternatively, pyrethrin shampoos may be used weekly for three to four weeks or Frontline® spray, marketed by Merial, may be used every three weeks for two applications.  Remember when treating for Cheyletiella that all pets should be treated regardless of the presence of clinical signs.  It is important to eliminate the inapparent carrier state.  The environment may be treated with various house and carpet sprays that are used for fleas.

Cheyletiella is considered to be a possible zoonosis (capable of being transmitted to people).  Most people are exposed through the handling of infested pets.  In humans, there is often pruritus without lesions, although the lesions may include papules with a central area of necrosis most commonly seen on the arms, trunk, and buttocks.  .  Additional symptoms may include sneezing. Infection is typically transient and self-limiting in people because constant animal contact is needed to maintain human infection.

References:

Jeromin, Alice.  “Cheyletiella Mites:  Population on the Move.”  DVM In Focus.  May 2008.  Pp. 20-24.

Jeromin, Alice.  “Cheyletiella:  the Under-Diagnosed Mite.”  DVM Newsmagazine.  August 2006.  Pp. 8S-9S.

Kahn, Cynthia.  The Merck Veterinary Manual.  9th Edition.  Merck and Co. 2005. P.747.

Scott, Danny and William Miller, et all.  “Muller & Kirk’s Small Animal Dermatology.” 5th. Edition. W.B. Saunders Co. Pp. 412-417.

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