Psoroptes cuniculi Ear Mite Infection in Lagomorphs 

Disease Summary

• Psoroptes cuniculi is a cause of ear mite infection in several different host species particularly rabbits, horses, goats, antelopes, sheep and cattle. (J477.3.w1)
• Psoroptes ovis can be found in cattle and sheep. Rabbits may also be susceptible to this mite. (B608.21.w21)

• Psoroptes cuniculi is a large, obligate, non-burrowing mite which may be seen infesting in the ears of rabbits. (B601.13.w13, B602.19.w19, B609.2.w2, B610.23.w23)
  • This mite "is the most common ectoparasite of the rabbit, and all rabbits should be considered infected unless proven otherwise". (B608.21.w21)
  • There are two clinical pictures of this disease: 
    1. The characteristic ear mite infection with crusts in the ear and significant pruritus.
    2. Extra-auricular mange where ectopic Psoroptes cuniculi infections cause lesions elsewhere on the body. (J477.3.w1)
  • Infestation is usually intensely pruritic and painful for the affected rabbit although early infestations are often asymptomatic or only mildly pruritic. (B601.13.w13, B609.2.w2)

Alternative Names (Synonyms)

• Ear canker (B10.45.w47, B608.21.w21)
• Otoacariasis (B608.21.w21)
• Ear mange (B10.45.w47)
• Psoroptic mange (J213.4.w4)
• Psoroptic scabies (B614.11.w11)

Old names for Psoroptes cuniculi:

• Dermatodectes cuniculi
• Psoroptes longirostris var. cuniculi
• Psoroptes communis var. cuniculi
• Psoroptes equi var. cuniculi

(B614.11.w11)

See also other mite infections in lagomorphs:

• Cheyletiellosis
• Chiggers (Trombiculiasis) (In Waterfowl, Hedgehogs and Bears and Lagomorphs)
• Demodicosis (with special reference to Hedgehogs, Bears and Lagomorphs)
• Leporacarus gibbus Fur Mite Infection in Lagomorphs
• Miscellaneous Mite Infections of Wild Lagomorphs
• Notoedres Mange in Hedgehogs and Lagomorphs
• Psorobia lagomorphae Mite Infection in Lagomorphs
• Red Fowl Mite Infection in Lagomorphs
• Sarcoptic Mange

Disease Type

Infectious/Non-Infectious Agent associated with the Disease

"Morphological and behavioral similarities of the rabbit Psoroptes sp. are found in the ears of horses, mules, goats, and sheep, as well as the ears and / or bodies of white-tailed dear, muledeer, and black buck antelope. This suggests that cross-infections of these mites to rabbits is possible". (J213.4.w4)

• Psoroptes cuniculi is oval, 400 - 750 um long by 325 - 500 um wide, with four easily-identified pairs of legs. On the first two pairs there is a short-segmented stalk on the distal end of the limb, with a single bell-shaped structure on the end of this (i.e. terminal suckers on a segmented stock). The mite's mouth parts are pointed but lack claws. (J495.41.w5)

Infective "Taxa"

• Psoroptidae

Non-infective agents

Physical agents

References

Disease Author

Referees

Major References / Reviews

Code and Title List

J15.29.w1, J29.5.w1, J32.137.w2, J213.4.w4, J213.7.w1

P600.1.w1, P601.1.w1

Other References

Code and Title List

Detailed Clinical and Pathological Characteristics

Clinical Characteristics

Clinical findings

• Pruritis, erythema, and debris in the ears. (J29.5.w1)
• Mild to moderate pruritus of the ears in mildly affected rabbits or those with a subclinical infestation. This may go on for years. (B602.19.w19, B606.4.w4, B609.2.w2)
• Intense pruritus with head shaking and scratching which exacerbates the lesions. (B600.9.w9, B601.13.w13, B602.19.w19, B604.5.w5, B608.21.w21, B609.2.w2, B610.23.w23, B615.6.w6)
• Hyperaemia of the lining of the ears occurs and then production of exudates begins. (B601.13.w13, B610.23.w23)
• Exudate
  • In the early stages, there may be a dry whitish-grey to tan, crusty exudate in the vertical canal of the ear. (B608.21.w21)
  • Occasionally, only one ear may be affected. (B600.9.w9)
  • Brown to beige, thick, crusty exudate that originates in the ear canal and may eventually spread to cover the pinna. (B600.9.w9, B601.13.w13, B602.19.w19, B609.2.w2, B610.23.w23)
    • In severe infestations, this crust layer may take on a foliated appearance. This is pathognomonic for ear mite infestation in rabbits. (B608.21.w21, B609.2.w2)
  • This crust is composed of exfoliated cells, inflammatory cells, serum, mites and detritus. (J213.4.w4)
  • The crusty material can thicken to 2 cm or more. (B614.11.w11)
  • The crusty exudate can spread to the head and neck and then also to other parts of the body during grooming. (B600.9.w9, B610.23.w23)
  • Underneath the crusts, the skin is moist, hairless and raw. (B604.5.w5)
• Ear drooping due to the weight of the debris. (B64.22.w8, B602.19.w19)
• Alopecia around the pinnae. (B608.21.w21, B609.2.w2)
• Excoriations and loss of fur around the pinnae and neck due to the rabbit scratching itself. (B10.45.w47, B608.21.w21, B609.2.w2)
• Secondary bacterial infection which may contribute to the pain and the foul smell of the parasitic otitis externa (B608.21.w21, J29.5.w1)
• Signs of bacterial otitis media or interna (e.g. head tilt and vestibular signs) can occur with chronic disease and secondary infections. (B602.19.w19, B604.5.w5, B609.2.w2, J29.5.w1)
  • Rupture of the ear drum can occur and then a purulent otitis media and meningitis may result from a secondary bacterial infection. (B601.13.w13, B610.23.w23)

The inflammation and crusting of the ears may spread (particularly in debilitated rabbits) to almost any other part of the body. Psoroptes mites have been reported to occur in the following areas:

• Face 
• Head 
• Neck (especially in the folds of the dewlap)
• Perineal region (especially in skin folds)
• Abdomen 
• Back (especially in the folds of skin dorsal to the tail head)
• Ventral abdomen 
• Limbs 
• Feet 

(B600.9.w9, B602.19.w19, B604.5.w5, B606.4.w4, B608.21.w21, B609.2.w2, B610.23.w23, B615.6.w6, J477.3.w1, J495.41.w5, P600.1.w1)

Pathophysiology

• Psoroptes mites feed by piercing the skin and it may be that a hypersensitivity to mite-related antigens plays an important role in the pathogenesis of the pruritus and dermatitis. (B600.9.w9, B608.21.w21)
• These mites feed on loose epidermal debris particularly lipid material. Antigenic material found in the mite's faeces and saliva can invoke an inflammatory reaction that is quite intense. (B610.23.w23)
• "mites chew and pierce epidermal layers of of the pinnae of the ear causing an inflammatory response and accumulations of multiple layers of thin, tan, flaky, crust in the external ear canal". (B604.5.w5)

Incubation

• The life cycle of this mite is approximately 21 days. (B601.13.w13, B602.19.w19, B604.5.w5, B610.23.w23, B615.6.w6)
• The entire life cycle is spent on the animal. (B64.22.w8)
• Females can survive off the host for many weeks. (B615.6.w6)
• These mites can maintain viability and infectivity off the host for approximately 15 days. (J32.137.w2)

Eggs

• Mite eggs may live up to thirty days. (B10.45.w47)
• Normally the eggs hatch in four days. (J32.137.w2)

Mortality / Morbidity

• One study of natural infections reported a mite count of 40 to 100000 mites per rabbit. (B608.21.w21)
• Psoroptes cuniculi infection can potentially cause great economic loss if it is not treated and controlled. (B604.5.w5)
• The infection rate of Psoroptes cuniculi in rabbits has been reported as between 7.98 and 15.7 in China. (J32.137.w2)
• This condition is common in captive rabbits (particularly the laboratory colonies and the commercial breeding establishments) but virtually unknown in wild lagomorphs of Lepus spp. and Sylvilagus spp.in the USA and wild Oryctolagus cuniculus - European rabbit in Great Britain and New Zealand. (B614.11.w11)

Pathology

• "A chronic inflammation with hypertrophy of the Malpighian layer, parakeratosis of the horny layer, and epithelial sloughing. The corneum is infiltrated with small round cells". (B614.11.w11)

Human Health Considerations

• Low zoonotic potential. (J15.29.w1)
• Psoroptes mites do not affect humans. (B604.5.w5)

Disease has been reported in either the wild or in captivity in:

Further information on Host species has only been incorporated for species groups for which a full Wildpro "Health and Management" module has been completed (i.e. for which a comprehensive literature review has been undertaken). Host species with further information available are listed below:

Host Species List

• Rabbits (Oryctolagus - (Genus))
• Oryctolagus cuniculus domesticus - Domestic rabbit

(List does not contain all other species groups affected by this disease)

Disease has been specifically reported in Free-ranging populations of:

• --

Further information on Host species has only been incorporated for species groups for which a full Wildpro "Health and Management" module has been completed (i.e. for which a comprehensive literature review has been undertaken). Host species with further information available are listed below:

Host Species List

• --

(List does not contain all other species groups affected by this disease)

General Information on Environmental Factors/Events and Seasonality

• Psoroptes cuniculi can survive off the host for four to twenty one days at temperatures between 5ºC and 31ºC and relative humidities between 20% and 99%. (J213.4.w4, J477.3.w1)
• Survival of this mite is greatest at low temperatures and a high humidity. Temperatures greater than 40ºC and a humidity less than 75 % are lethal to the mite within two days. (B614.11.w11)

Regions / Countries where the Infectious Agent or Disease has been recorded

• UK
• USA
• China (J32.137.w2)
• Every continent (B614.11.w11)

Regions / Countries where the Infectious Agent or Disease has been recorded in Free-ranging populations

• --

General Information on Investigation / Diagnosis

• Otoscopic examination is useful to visualise mites although they are also visible to the naked eye. (B600.16.w16, B601.13.w13, B602.19.w19, B604.5.w5, B609.2.w2, B610.23.w23, J29.5.w1)
• Microscopic examination: 
  • Collect scales and debris by ear swab and place in mineral oil on a glass slide, and examine under low magnification. It is usually easy to visualise Psoroptes cuniculi. (B600.16.w16, B601.13.w13, B602.19.w19, B604.5.w5, B608.21.w21, B609.2.w2, B610.23.w23, J29.5.w1)
    • Large oval-shaped mites with a terminal anus and long pointed chelicerae. (B614.11.w11)
      • The legs are jointed and end either in bell-shaped suckers (the first three pairs of legs in males and the first two pairs of legs in females) or in setae. (B614.11.w11)
      • The legs extend beyond the margin of the mite's body. (J213.4.w4)
    • The mite may reach up to 0.7mm in size and it has pointed mouthparts. (B606.4.w4)
    • The mites will usually be present in large numbers. (B606.4.w4)
    • Eggs, desquamated epithelial cells, inflammatory cells and serum may also be seen. (B602.19.w19)
• Skin scrapings can be useful if the lesions have a generalised distribution. (B608.21.w21, B609.2.w2)
• See: Clinical Pathology of Lagomorphs - Skin Testing

• Environmental Assessment
• History & Documentation
• Physical Examination of Mammals
• Necropsy of Mammals
• Imaging in Lagomorph Diagnosis and Treatment
• Clinical Pathology of Lagomorphs
• Chapter 2 - B36 Field Manual of Wildlife Diseases - Specimen Collection and Preservation
• Chapter 3 - B36 Field Manual of Wildlife Diseases - Specimen shipment
• Appendix A - B36 Field Manual of Wildlife Diseases - Sample specimen history form

Similar Diseases (Differential Diagnosis)

Exudate in the ear canal

• Normal wax
  • Light yellow to beige waxy exudate is often found in the ear canal of normal rabbits. This exudate does not usually extend onto the pinnae as in ear mite infestation. 
• Bacterial or mycotic otitis externa
  • This is a more common problem than ear mites in pet rabbits. 
  • Thick, white and creamy exudate limited to the ear canal. 
  • Differentiation from ear mites is by examination of the exudate with microscopy. 

Pruritus or Alopecia

• Fur mites: 
  
  • Cheyletiellosis or the less commonly reported Leporacarus gibbus Fur Mite Infection in Lagomorphs.
  • They may be concurrent with an ear mite infestation.
  • Distribution: Lesions around the tail base or intrascapular region.
  • Clinical signs: Profuse amounts of large, white scale.
  • Diagnosis: Skin scrapes or acetate tape preparations- easy to see mites under low magnification.
  • Differentiation from ear mites: no exudate in the ear canals.
    
• Flea hypersensitivity dermatitis: (Flea Infection in Mammals).
  
  • Clinical signs: patchy alopecia and pruritus usually in other areas of the body in addition to the head. Sometimes see a secondary pyoderma.
  • Diagnosis: fleas or flea dirt found in coat.
    
• Other ecto parasites:
  
  • Sarcoptes scabiei (Sarcoptic Mange) and Notoedres cati (Notoedres Mange)
    • Both are rare in the rabbit
    • Distribution: head and neck.
    • Clinical signs: very pruritic lesions.
    • Differentiation from ear mites: no exudate in the ear canals.

(B609.2.w2)

• Psoroptes cuniculi is oval, 400 - 750 um long by 325 - 500 um wide, with four easily-identified pairs of legs. On the first two pairs there is a short-segmented stalk on the distal end of the limb, with a single bell-shaped structure on the end of this (i.e. terminal suckers on a segmented stock). The mite's mouth parts are pointed but lack claws. In contrast, Sarcoptes scabei and Notoedres cati are spherical, have short stubby legs, no terminal suckers, and blunt mouth parts, while Cheyletiella parasitivorax has mouth parts with a single pair of associated claws. (J495.41.w5)

Crusty lesions around the vent

• These lesions needs to be differentiated from Treponematosis (Bacterial Disease). (B606.4.w4)

Specific Medical Treatment

Notes:

• Ear mite infection is contagious so all in-contact rabbits must be treated even if they are not showing any clinical signs. (B601.13.w13, B606.4.w4, B609.2.w2, B610.23.w23, B615.6.w6, J213.7.w1)
• Do not try to clean the ear canal: 
  • This does not enhance the treatment and may traumatise the ear canal. Instead, treat first with one of the medications below. (B600.9.w9, B608.21.w21, B609.2.w2)
  • Most crusts will resolve rapidly after medication, without the need to manually remove them. (B601.13.w13, B602.19.w19 B609.2.w2)
  • If necessary, the crusts may be removed by softening first with mineral oil but care must be taken to avoid damage of the ear canal lining. (B601.13.w13, B610.23.w23)
  • Residual debris may be removed when the ulceration and inflammation have subsided after the use of the ivermectin regime. (B600.9.w9, J213.7.w1)

Medications:

• Ivermectin
  • Treatment of choice. (B608.21.w21, J29.5.w1)
  • 0.4 mg/kg by subcutaneous injection every ten to fourteen days for two to three doses. (B336.42.w42, B606.4.w4, B609.2.w2, J495.41.w5, J213.4.w4)
    • "at this dose, the maximum plasma concentration of about 42 ng/ml was achieved approximately 2 days postinjection; however the biological half-life in rabbits is not known". (B604.5.w5)
    • 0.4 mg/kg produced faster regression of ear lesions than 0.2 mg/kg. (J35.145.w2)
    • Two injections at 0.4 - 0.44 mg/kg subcutaneously, 18 days apart, appeared to be safe and effective. (J4.196.w1)
    • Two treatments 14 days apart were effective (99.61% reduction in mites) with 0.2 mg/kg or 0.4 mg/kg, but with less than 78% efficacy with 0.1 mg/kg. (J13.53.w2)
    • Two treatments of 0.4 mg/kg, 15 - 17 days apart were effective. (J495.40.w5)
    • Use 0.4 mg/kg for three treatments. (B601.13.w13, B602.19.w19, B610.23.w23, B615.6.w6)
  • This mite is particularly sensitive to this drug although lower dosages of 0.2 mg/kg were reported to be inadequate in eliminating the mite. (B600.4.w4, J477.3.w1)
    • This drug does not kill the eggs of this mite but its persistence in the tissues is long enough to eliminate the new generation of hatching mites. Eggs hatch after four days. (B600.4.w4)
  • Contraindications:
    • This should not be used in pregnant animals. (B609.2.w2)
    • Do not use parenteral and topical ivermectin concurrently. (B609.2.w2)
• Selamectin
  • A very effective treatment for this condition; a single dose seems to last long enough to eliminate all stages of the life cycle. Routine administration is recommended for rabbits that cannot groom themselves properly. (P601.1.w1)
  • Appears to be effective and safe at 6-12 mg/kg applied topically every 30 days. (B609.2.w2, J477.3.w1)
  • Studies have shown that this drug may be used effectively and safely at 6 mg/kg or the higher dosage of 18 mg/kg every 28 days for two doses. (B600.9.w9, B602.19.w19)
  • In one study conducted on New Zealand rabbits (Oryctolagus cuniculus domesticus), a single application of 30 mg of selamectin topical spot-on solution (0.25 mL of a 120 mg/mL solution) was completely effective in the treatment of natural infestations of this mite. Recovery was complete by the 28th day of the study. No live mites were found at the end of the trial on day 56 and there was no reoccurrence of clinical signs within three months of the trial. Depending on their weight (range of 1.6 kg to 5.0 kg), the rabbits received doses that ranged from 6 to 18 mg/kg. (J476.18.w1)
• Eprinomectin
  • A single dose at 0.2 mg/kg (or at the higher dose of 0.3 mg/kg) by subcutaneous injection has been reported as being effective in eliminating Psoroptes cuniculi mites from naturally infected rabbits. (J32.137.w2)
    • In this particular study, there were no mites after the seventh day of treatment and the rabbits remained mite free until the end of the study (day 35). All rabbits clinically recovered by the fourteenth day after treatment. Like other avermectins, this drug has no ovicidal effect on the Psoroptes mite eggs. However the absence of mites from day 7 to day 35 after treatment suggests that sufficient concentration of this drug was able to prevent re-infection of mites off the host and kill any larvae hatching from eggs. (J32.137.w2)
    • A lower dose of 0.1 mg/kg significantly reduced the number of mites but did not eliminate the infection. (J32.137.w2)
    • "Higher potency of eprinomectin than ivermectin has been demonstrated". (J32.137.w2)
  • Topical administration of eprinomectin at a dose of 0.5 mg/kg applied to the skin at the back of the neck, twice, at 14 day intervals, was reported as being only partially effective in the treatment of rabbits with natural infestations of Psoroptes cuniculi. Although clinical improvement was seen in the rabbits from three days after the first administration of eprinomectin, only one out of six Psoroptes infested rabbits was free of clinical signs and live mites by the end of the trial on day 42. (J476.16.w1)
• Moxidectin
  • 0.2 mg/kg by subcutaneous injection every ten days for two treatments. (B601.13.w13, B610.23.w23, J477.3.w1)
• Imidacloprid and moxidectin
  • "a practical and well-tolerated means of treatment for ear mite infestation in rabbits". (J477.3.w1)
  • Imidacloprid plus moxidectin at a dosage of 10 mg/kg and 1 mg/kg respectively, percutaneously every four weeks for three treatments. (J477.3.w1, P600.1.w1)
• NSAIDs
  • Non steroidal anti inflammatory drugs (NSAIDs) may be used to reduce the pain and intense irritation, e.g. Meloxicam or Carprofen. (B601.13.w13)
• Acaricidal ear drops
  • These may be used to treat a mild infection. (B601.13.w13, B610.23.w23)
  • Less effective than ivermectin. (B602.19.w19)
• Topical otic antibiotic or antifungal medications
  • These are usually not required. (B609.2.w2)
  • Secondary yeast and / or bacterial otitis may occur due to overzealous cleaning of the ear canals and / or pinnae.
  • Topical treatment with mineral oils and acaricides used to be the main method of treating this condition but this is uncomfortable for the rabbit and systemic therapy has now become more widely used. (B615.6.w6)
  • Thiabendazole, Dexamethasone and Neomycin sulfate (Tresaderm, MSD-AGVET, Rahway, NJ) 
    • This can be used during the time between ivermectin treatments to reduce inflammation and loosen crusts. Note: there is no need to remove crusts. (B602.19.w19, J213.4.w4)
    • However, the use of topical corticosteroids in rabbits is controversial- see precautions below.

Contraindications:

• Avoid overzealously cleaning the ear canals. 
• Do not try to manually remove the crusts as it can be very painful and it may traumatise the ear canal. 
• Do not use on rabbits: Fipronil (due to adverse fatal reactions), flea collars, products containing Organophosphates, or straight Permethrin sprays or spot-ons. 

(B609.2.w2)

Precautions:

• Off-label use of medication: products discussed above are not licensed for use in rabbits and therefore their efficacy and safety have not been evaluated in this species. Use with caution particularly in debilitated or young animals. (B609.2.w2)
• Licking of topical spot-on products: must prevent the animal or its cage mate from doing this before the product has had chance to dry. (B609.2.w2)
• Topical otic medication containing corticosteroids: these should be avoided in the rabbit. (B609.2.w2)
• Insecticide baths or dips: e.g. pyrethrin, carbaryl (Carbamates) and lime sulfur-based products, must be used cautiously in rabbits as shock and death have been reported in association with these products. 
  • Also, the act of dipping or bathing rabbits can induce stress that is made worse by chilling, overheating or an underlying hepatic dysfunction. (B602.19.w19)
  • See: Bathing Rabbits (Techniques)
• Toxicity of topical drugs in rabbits: although a drug may be safely used in dogs and cats, the same may not be true in rabbits due to the following possible reasons:
  • thinness of rabbit skin;
  • ingestion of the topical medication due to excessive grooming;
  • hypersensitivity to the drug's vehicle;
  • absolute overdosage.

  (B602.19.w19)

Follow up:

• Clinical examination and an ear swab should be performed one month after the therapy started. 

(B609.2.w2)

• Bathing Rabbits
• Treatment and Care
• Subcutaneous Injection of Mammals

General Nursing and Surgical Techniques

• Treatment and Care

Preventative Measures

--

• Monthly treatment with Ivermectin. (J29.5.w1)
• Fipronil spray
  • This has been ued in rabbits at 3 mL/kg every two months to prevent reinfestation in cases of poor environmental disinfection. However, administration of fipronil in rabbits has been associated with death of rabbits and the manufacturer of this product does not recommend its use in this species. (B602.19.w19) See: Fipronil Toxicity in Rabbits

• New arrivals, unless they are known to be free of mites, should ideally be quarantined and treated twice with Ivermectin with a 14 day interval before entering an established clean colony. (B604.5.w5)

• Preventative Medicine for Mammals

Environmental and Population Control Measures

Lagomorphs

• Mites can live for up to 21 days on exfoliated crusts found in the environment. (B600.9.w9, B601.13.w13, B602.19.w19, B608.21.w21, B609.2.w2, B610.23.w23)
  • This occurs if the temperature range is within 5 to 30ºC and the relative humidity range is within 20 to 75 %. (B608.21.w21)
  • Survival is greatest at high humidity and low temperatures. (B600.9.w9)
• It is extremely important to thoroughly clean and treat the rabbit's environment if elimination of the infestation is to be achieved. (B602.19.w19, B606.4.w4, B609.2.w2, B615.6.w6)
  • Remove and discard all the organic material from the cage (paper or wood products, bedding). (B609.2.w2)
  • Replace the bedding with shredded paper bedding and discard this daily along with thoroughly daily cleaning of the cage during the treatment period. (B609.2.w2)
  • Discard or thoroughly disinfect any grooming utensils before reuse. (B609.2.w2)
  • Treat contaminated areas with flea products. (B602.19.w19)
• "The cage and the environment should be sanitized, and reducing the relative humidity to less than 20% while increasing the temperature to 40ºC (104ºF) is of benefit in this regard". (B608.21.w21)
• Cleaning the loose hair out of the rabbit's accommodation is useful in preventing infestation. (B10.45.w47)

• Quarantine and treat all new rabbits. (B10.45.w47)
• If infection is noted in one individual of a colony, all the other rabbits need to be checked for the mites and treated. (J495.41.w5)

• Ear mite infection is contagious so all in-contact rabbits must be treated. (B601.13.w13, B609.2.w2, B610.23.w23)
• A case of an in-contact guinea pig that developed psoroptic mange has been reported. (B608.21.w21)

• Environmental and Population Management - General