Introduction

Classification

Taxonomy

• Family: Psoroptidae.
• Genus: Otodectes.

Active Forms

Resting Forms

Clinical Effects

Epidemiology

Habitat

• Deep in the ear canal of dogs, cats, foxes, other Canidae and Felidae, and ferrets.
• May spread to the pinna, neck, head, rump, paws, tail tip.

Lifecycle

• O. cynotis lifecycle  :
  • Adult male  and female .
  • Egg .
  • Larva .
  • Nymph.

Transmission

• Permanent parasite of the ear, therefore transmission by close, direct contact, particularly mother to young while suckling, but also in kennels, etc.
• O. cynotis seems not to be host-specific so transmission occurs between different host species, especially the cat and dog.
• O. cynotis can be maintained in vitro on ear debris and survives in the environment, but the importance in transmission of environmental contamination with mites remains unsubstantiated.

Pathological effects

• Infection induces a pruritic, hypersensitivity reaction.
• This has been studied only in cats and consisted of an immediate (Type I) and Arthus (Type III) hypersensitivity reaction.

• Marked infiltration of wall of ear canal with plasma cells and lymphocytes.
• Severe pruritus, head shaking and scratching.
• Excess cerumen production exuding as a dark brown colored, waxy discharge that can crust. Mites live beneath the crust next to the skin.
• May lead to purulent otitis with invasion of neutrophils and a brown, purulent, fetid discharge.

Other Host Effects

• Surface parasites feeding on epidermal debris and excess cerumen.

Control

Control via animal

• Treatment of dog and all in-contact animals.
• Remove wax and cleanse ear canal.
• Most acaricidal ear drops or ointments have little or no residual activity so many treatments are given daily, and treatment should be repeated at least once at 10-14 days to kill mites hatched from eggs present at the time of treatment.

Control via chemotherapies

• a) Amethocaine hydrochloride/neomycin sulfate/thiabendazole (ear drops).
• b) Diethanolamine fusidate/framycetin/nystatin/prednisolone (ear drops).
• c) Piperonyl butoxide/pyrethrins (ear drops).
• d) Amethocaine hydrochloride/neomycin sulfate/permethrin (ear drops).
• e) Chlorbutol/phenoxyethanol (Otodex ear drops).
• f) Thiabendazone/dexamethasone/neomycin sulfate.

• a) Amitraz Amitraz (0.025% in mineral oil), by topical application and used at least twice, is effective (unlicensed use in dogs).
• b) Ivermectin Ivermectin (200-400 ug/kg) by injection used at least twice, is effective in kennel situations (not licensed for use in dogs).
  Toxic in Collies and Collie crosses.
• Fipronil Fipronil (topical application in ears once) - unlicensed use in dogs.
• Selamectin Selamectin , 1x month, is an effective treatment for ear mites - unlicensed use in dogs.

Control via environment

• The relevant importance of mites in the environment is unknown. Repeated treatment of the dog at about 10-day intervals should eliminate any reinfestation from the environment.

• In persistent cases, remove and boil bedding and clean or treat the area where the dog sleeps with acaricide.

Other countermeasures

• In persistent cases it may be useful to treat the whole body with amitraz bath or lime sulfur dip.

Diagnosis

Further Reading

Publications

Refereed papers

• Recent references from PubMed and VetMedResource.
• Chickering W R (1988) Cytologic evaluation of otic exudates. Vet Clin North Am Small Anim Pract 18 (4), 773-782 PubMed.
• Pott J M, Riley C J (1979) The efficacy of a topical ear preparation against Otodectes cynotis infection in dogs and cats. Vet Rec 104 (25), 579 PubMed.