Less Common Fur Mites in rabbits:
Trombicula autumnalis and Dermanyssus gallinae
Esther van Praag Ph.D.
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Both parasites infest other species of animals or birds, but have been observed on rabbits. Trombicula autumnalis, or harvest mite, is found in the fur of rabbits that have free access to a yard. The female mite lays eggs in the soil. The hatching larvae, which are barely visible with the naked eye, move into the grass and wait till a suitable host is found. Only larvae will attack a rabbit, cat, dog, or human; further developing stadia proceed in the soil. The parasite will suck body fluids up to 3 times its body size, after which it will fall down on the soil to complete its life cycle.
Dermanyssus gallinae, also called red mite, may accidentally be hosted by rabbits living in the presence of birds.
Larvae are usually found on the head of rabbits (ears, inner and outer corners of the eyes, chin), the neck and shoulder regions, under the front legs and between the toes, and in the perianal region.
Their presence of these uncommon parasites leads to intense pruritis and the formation of macules and pustules. Scratching will lead to self-mutilation, wounds, and the development of secondary bacterial infections.
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.
Treatment of Trombicula autumnalis may be difficult. While fipronil, permethrins, and organophosphates are used on other animals to treat these mites, all have been linked to serious adverse effects in rabbits and should be avoided. The manufacturer of fipronil (Frontline® - Merial) strongly advises against using it on rabbits. Serious adverse effects (depression, anorexia, seizures, death) have been observed in rabbits, especially young or small rabbits.
Dermanyssus gallinae is best treated with carbamates. The treated rabbit must be closely monitored, as this type of insecticide can trigger toxic reactions. The use of a powdered product should be favored, due to poor absorption of the insecticide through the skin.
If any mite problem is not solved, the presence of infested dogs and cats (both can be asymptomatic carriers) or survival of the parasite to treatment should be considered.
Fur mites (live on the surface of the skin) can fall off and contaminate the environment. While treating for mites, careful cleaning of the cage and environment is recommended.
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.
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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