Common Fur Mites or Cheyletiellosis
Esther van Praag Ph.D.
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Rabbits can be infested with non-burrowing skin mites Cheyletiella parasitovorax and Leporacarus gibbus. These parasites are encountered around the world and affect mainly rabbits but also cats and dogs.
Cheyletiella parasitovorax parasites live in close association with the keratin layer of the skin but they do not burrow into the skin. It is suspected that mites may be present asymptomatically in small numbers on healthy rabbits. The development from egg to adult mite takes place on the same rabbit host. The female lay eggs and stick them to the hair about 3 to 4 mm above the skin. The life cycle takes about 5 weeks under optimal conditions.
Cheyletiella parasitovorax has a zoonotic potential, causing a transient itching dermatitis in humans.
Fur mites appear associated with spring when weather becomes milder, with a lack of vitamin C due to e.g., stress, or due to an underlying disease, which suppresses the immune system.
The presence of fur mites is not always easy to determine. When present, Cheyletiella parasitovorax is most likely to be found on the dorsum and neck of the rabbit, where it causes dandruff, seborrheic lesions (lesions from abnormally increased secretion of fatty matter), and a pruritic (itching) condition. Leporacarus gibbus is found mainly on the dorsum and abdomen. The presence of fur mites can lead to skin hypersensitivity reactions.
Irritation and prurit caused by the presence of mites can lead to excessive scratching and mutilation of the skin.
Diagnosis can be difficult and visual examination is not always sufficient to confirm the presence of ear mites. Detection methods include the tape method, skin scraping (shallow if fur mites are suspected, deep if burrowing mites are suspected), or the vacuum aspiration method on a filter paper. Samples from scraping or aspiration should be spread on a microscope glass, dissolved in KOH, and examined under a microscope. Great is the chance to see at least one mite or a larva or eggs. Fur can also be sampled, dissolved in KOH, and examined under the microscope for the presence of eggs. If no mite is present in the first sample, other places on the body should be checked. If the presence of burrowing mites is suspected, but none found after a deep skin scraping, a biopsy on the area suspected of mite infestation is advisable.
Fur mites are eliminated by ivermectin: 0.2-0.4 mg/kg, PO (oral) or SC (subcutaneous injection), 3 times at intervals of 10-14 days. Ivermectin can also be used topically (directly on the skin). Dips (Aludex® - Hoechst; Seleen® - Sanofi; LymDyp® - DVM) can be used to treat the seborrhea (excessive secretion of fat by the skin) and remove the keratin layer on which the mites feed; they will not kill the parasite.
Although fipronil (Frontline® - Merial) is effective in eliminating Cheyletiella sp., the manufacturer forbids the use of Frontline® on rabbits. Serious adverse effects (depression, anorexia, seizures, death) have been observed in rabbits, especially young or small rabbits.
Imidacloprid (Advantage® - Bayer) is ineffective against Cheyletiella sp. mites.
Treatment of the environment is important (boric acid such as Fleabusters®; Vet-Kem Acclaim Plus® - Sanofi; Staykil® - Novartis; Indorex® - Virbac; acaricide spray). When treating a carpet, vacuum first in order to further penetration of the spray or powder. Shampooing and steam cleaning are not ideal; their residual humidity can increase the mite problem. During treatment of the environment, rabbits should be kept in another part of the home to avoid the danger of contact with the products.
Thanks are due to Ron Davies, BVSc., CertZooMed., MRCVS (UK), Michel Gruaz (Switzerland), Bruno Feirrera (Switzerland), Ils Vanderstay (Belgium), Pamela Alley (USA) and Akira Yamanouchi, (Veterinary Exotic Information Network, Japan, http://vein.ne.jp/), for the permission to use their illustrative material.
For detailed information on fur mite infestation in rabbits,
see: “Skin Diseases of Rabbits”, by E. van Praag, A. Maurer and T. Saarony,
408 pages, 2010.
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