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Myxomatosis – a timely reminder

In this refresher article, we take a look at the essentials of Myxomatosis in rabbits. With the UK slowly coming out of lockdown, and everyone’s desire to enjoy a happier spring and summer, there will undoubtedly be plenty of rabbit owners keen to get their pet outside into the garden. The risks of disease are still there, so perhaps you could use this content as a timely reminder to ensure their rabbits are protected from the threat.


What is Myxomatosis?

Myxomatosis is a fatal disease of the rabbit caused by the Myxoma virus, which is a poxvirus and a member of the genus Leporipoxvirus. It affects both wild and domestic rabbits, causing subcutaneous swellings around body orifices and the face. It’s spread mainly by blood sucking insects such as,

  • Fleas – the rabbit flea, Spilopsyllus cuniculi, which is the main vector.
  • Midges – the Culicoides
  • Cheyletiella parasitovorax
  • Cat and dog fleas (Ctenocephalides spp.)
  • Any other insect that penetrates the skin – for example some mosquitos.

Virus variation

There are different strains of the myxoma virus, each showing a slightly different virulence and end result. For example, strains with a high virulence often have such a devastating effect on the wild population of rabbits that there isn’t enough exposure to transmit the infection easily. However less virulent strains tend to be more infectious since an infected individual can survive long enough to transmit the virus. Other features of the virus and disease worthy of a mention include.

  • Low temperature risk – the disease is more lethal at colder temperatures.
  • Waxing and waning – in the event of an outbreak, we can often find the disease within a population going up and down in relation to virulence and the immune status of the rabbit population.
  • Reservoir of infection - fleas infected with myxomatosis virus can maintain infectivity throughout the winter and act as a reservoir of infection for the following year
  • Close contact – the virus can also be spread between rabbits by close contact or inhalation.

Risk to pet rabbits

Owners need to be reminded that whatever the lifestyle of their rabbit, there is always a risk of infection, usually resulting in a long-drawn-out distressing and often fatal decline.

The risk depends largely on the amount of contact they have with wild rabbits. They need to be in close proximity to each other, as this facilitates the movement of the rabbit flea from one to the other. It’s also significantly affected by the season and weather conditions. For example, mosquitoes and midges can transmit infection when the weather conditions are right, especially in the warmer months of summer and autumn.

In cases where the disease has already occurred, there is still a risk that the virus persists in the housing and enclosures, which can then go on to infect unvaccinated individuals that are brought in.

Clinical signs

The presence or absence of clinical signs can vary tremendously with the individual and viral strain, but typically we would see;

  • Localised swellings – these are usually found around the head, face, base of the ears, lips, anus and genitalia. Initially, there is hyperaemia followed by soft swellings that enlarge, harden and become crusty. These swelling are painful and will cause difficulty with feeding and drinking.
  • Skin lesions – these tend to appear around 4-5 days after the initial infection. They grow to around 2-3cm in diameter within 7 to 10 days.
  • Swollen eyelids – the lids can become inflamed and thickened. Often the eyes are completely closed after about one week.
  • Conjunctivitis – a yellow purulent ocular discharge is frequently produced.
  • Dyspnoea and tachypnoea - secondary bacterial respiratory infections often complicate the disease resulting in a fatal pneumonia. Lesions around the nose block the nares causing respiratory distress.
  • Infertility - male rabbits can become infertile for up to 12 months.
  • Death – it’s not always easy to know in the early stages, which rabbits will survive, and which ones will die. Although it is possible for some rabbits to recover, the disease tends to follow a long-drawn-out process, causing considerable distress. Euthanasia should always be considered.

Making a diagnosis

In most cases the condition is diagnosed from the clinical signs alone. It can also be confirmed by post-mortem examination and with PCR tests of the lesions.

Treating a case of myxomatosis

Before making unrealistic promises to the client, it’s wise to be open and honest about the extent of suffering that will occur. Many owners would choose not to attempt treatment and agree to euthanasia, especially if the rabbit has stopped eating or has developed pneumonia. Remind them that it can take up to 8 weeks to recover. However, if you feel the patient warrants a chance, then the essentials of treatment include.

  • Nursing – provide a clean, quiet, stress free environment. Use supportive feeding and cleaning of lesions around the eyes, nose, mouth and anus etc.
  • Antibiotics – these are generally used to treat secondary bacterial infections.
  • Analgesia - non-steroidal analgesics are frequently used, though they should be used with caution if the patient is dehydrated.
  • Warm environment – a high environmental temperature increasing the chances of recovery.
  • Topical ointments – these can help to soften and protect skin lesions.
  • Avoid hay as bedding – instead, use bedding material that won’t stick to and contaminate the lesions.
  • Handfeeding – this may be necessary in those with painful lesions around the mouth, lips and nose.
  • Avoid corticosteroids - the use of corticosteroids is contraindicated due to their immunosuppressive effects.

Vaccination

The Nobivac Myxo-RHD PLUS vaccine provides broad cover against the myxoma virus and both RHD-1 and RHD-2 infections from a single dose. Find out more here and see below.

The key Benefits of the Nobivac Myxo-RHD plus vaccine are;

  • Rapid onset - a single vaccination provides immunity within 3 weeks.
  • Effective - the vaccine has a one-year duration of immunity against both myxomatosis and RHD.
  • Protect the young - it can be given from 5 weeks of age onwards.
  • Practical - it’s available in single dose vials.
  • Easy to use - unlike previous myxomatosis vaccines, it’s fully effective when given as a subcutaneous injection. There is no need to vaccinate by the intradermal route.

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