Is your dog scratching, does he have bad dandruff, is he rubbing his eyes or sneezing? Does that dandruff appear to be moving? Then Cheyletiella yasquri, a large mite that parasitizes dogs, could be the source of your problem.

The Cheyletiella yasquri mite is so large that it may appear visible to the naked eye. Although primarily a parasite of dogs, Cheyletiella species are not host-specific and cross-infections with cats, rabbits, and foxes are not uncommon.

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 or sebaceous secretions on the epidermis. The mite most often inhabits the dorsal coat (area along the backbone or spine) but 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.

The time before infestation is clinically apparent typically takes three to five weeks after exposure has occurred. The most commonly seen clinical sign in the dog is pruritus (itching) with scaling along the dorsal surface and trunk. There have been reports of the mite sequestrating (becoming isolated or separated) in the nasal passages resulting in sneezing, facial pruritus, excoriation and periocular involvement (around the eyes). Immunocompromised and young animals tend to be more greatly affected.

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-toothed comb with the scale taken for observation 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.

Possible remedies that can be used for the treatment of Cheyletiella are numerous. Since nasal sequestration of the mite is possible, systemic therapies may prove to be more effective. Ivermectin may be given by subcutaneous injection or orally once weekly for three weeks at a dose rate of 200 mcg/kg. Interceptor®, manufactured by Novartis Animal Health, may be given at a rate of 1 mg/kg every other day for 14 days or at 1 mg/lb once weekly for three weeks. Advantage Multi ®, marketed by Bayer, may be given once monthly for two months or Revolution®, from Pfizer Animal Health, may be given topically every 15 days for a total of three doses. When using Ivermectin, Interceptor, Advantage Multi, or Revolution the dog should be tested for heartworms before initiating therapy to avoid systemic reactions and possible anaphylaxis. Additional systemic treatment includes amitraz dips or Mitaban ® dips, also available from Pfizer Animal Health, once weekly for three weeks or a dip every two weeks for two dips.

Non-systemic therapies include lime-sulfur dips every five to seven days for three to four applications. Lime-sulfur is very soothing to irritated skin but will smell like rotten eggs. Be sure to wear gloves. Additional non-systemic treatments include pyrethrin shampoos given weekly for three to four weeks or Frontline spray®, marketed by Merial, at a dose of one spritz/lb of body weight every three weeks for two applications.

Cheyletiella is considered to be a possible zoonotic (capable of being transmitted to people) infection. Most people are exposed through handling of infested pets. Infection is typically transient and self-limiting in people because constant contact with infected animals is needed to maintain infection with humans.   


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.

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