Psoroptes – a problem parasite

Ear mite infections in rabbits are relatively common, and may be seen at this time of year as a result of immunosuppression and stress following a long, cold, wet and windy winter.

Posted: 14 May 2018

Psoroptes – a problem parasite

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Psoroptes cuniculi

The Psoroptes cuniculi mite is a non-burrowing mite that feeds on blood and serum. It has a life cycle of around 21 days, with eggs hatching after just 4 days. Many thousands of ear mites can affect the external ear canal and pinna, creating hyperkeratosis and a thick, dry, red/brown crust. Intense erythema develops as a result of the inflammation caused by the mucus and faeces from the mite. This in turn causes pruritis and head shaking, which is both painful and debilitating. It’s more common for just one ear to be affected and may be seen as a rabbit with a ‘dropped ear’, but in severely immuno-compromised animals, the infection can become more widespread affecting both ears, the neck, thorax, abdomen and perianal region.

Don’t attempt to remove the crusts

Whilst it may be tempting to try and remove the thick crust, it’s generally not recommended as the procedure is very painful and will just expose a large area of bleeding, inflammed tissue.

Secondary bacterial and fungal infections are common if the problem is left untreated, so an early diagnosis and prompt action is recommended.

Middle ear disease secondary to a bacterial infection of the deep ear canal and rupture of the tympanic membrane can occur, in which case you’d normally expect to see a head tilt and loss of balance.

Diagnosis of ear mite infections

Clinical signs and visualisation of the mite with an otoscope will confirm your suspicions. It measures as much as 0.7mm in length and can even be seen with the naked eye. Skin scrapes and microscopic examination of the crusts will usually reveal the mite, larvae or eggs. KOH and liquid paraffin on the slide will help to break down the keratin and slow the mite movement down. If you get a chance show your client the mite under the microscope and it will convince that treatment is essential.

  • Otoscopic examination – this is useful in the consulting room and will help to visualise the mites
  • Microscopic examination - collect scales and debris, place in mineral oil and KOH on glass slide - examine under low magnification
  • Skin scrapings - useful if the lesions are generalised

6 ways to treat Psoroptes cuniculi

There are several reported effective treatments available in the UK, however we must stress you always follow the cascade to ensure compliance. The avermectins seem to be particularly effective, but are non-ovicidal and hence require repeated doses. Some examples of treatments used include;

  1. Ivermectin – given either orally or as an injection at a dose rate between 0.2 – 0.4 mg/kg every 2 weeks for 2 or 3 treatments. Injectable doses work better.
  2. Selamectin – this has been used at dose rates between 6 – 18mg/kg twice with an interval of 28 days between doses.
  3. Imidacloprid / moxidectin – applied as drops on 3 occasions with an interval of 30 days between doses
  4. Pain relief – the degree of inflammation of the pinna and ear canal can be dramatic, and the condition is indeed very painful and irritating. Any attempt to physically remove the scabs from a conscious rabbit will soon result in screams. Appropriate use of opiate and non-steroidal analgesia is important.
  5. Antibiotics – secondary bacterial infections of the ear and surrounding tissues can occur. In advanced cases, middle ear disease may be diagnosed (check for a head tilt and incoordination), which is usually bacterial in nature. Culture, isolation and sensitivity tests would be recommended, with antibiotics being prescribed.
  6. Hygiene – mites and eggs may easily fall of the crusts into the cage and surrounding environment. Thorough cleaning of the rabbit housing and bedding area is necessary to prevent reinfection

Don’t use Pyrethrins or Fipronil on rabbits

  • Pyrethrins – these have been known to cause serious side effects in rabbits including tremor, seizures, paralysis and death.
  • Fipronil – this is moderately toxic in rabbits and has caused some fatalities.

Psoroptes cuniculi – 7 fun facts

  1. Psoroptes mites feed by piercing and chewing the skin
  2. Some rabbits can develop a severe allergic reaction to the mite's faeces and saliva
  3. The life cycle of this mite is approximately 21 days
  4. The entire life cycle is spent on the rabbit
  5. Mites can remain infective off the host for 15 days
  6. Mite eggs can live up to a month
  7. Eggs hatch in four days

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