A guide to E cuniculi in rabbits
Encephalitozoon cuniculi, or E cuniculi, is a microscopic parasite that causes the disease encephalitozoonosis. The parasite is intracellular – it replicates by invading the host’s cells. This causes the cells to burst, and infection is spread to other cells, causing massive inflammation. It mostly affects the nervous system (brain and spinal cord) and kidneys. Here in the UK, the parasite is common in pet rabbits and laboratory rabbits, but rare in the wild. A study revealed that 52% of healthy pet rabbits from across the UK had E cuniculi antibodies. Only a small proportion of infected rabbits ever show any illness, with some becoming very unwell.
The E cuniculi parasite is zoonotic (it can be transmitted to humans), but it seems only those with severely compromised immune systems are at risk (for these people, extra hygiene should be observed when in contact with rabbits). The pathogen can be carried by wild rabbits and other animals, but most are asymptomatic – few have been found to be affected.
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There’s always a
risk of E cuniculi when introducing a new rabbit, |
How do rabbits become infected?
E cuniculi can pass through the placenta from an infected mother to a kit before it’s born. It can also spread in infected rabbits’ urine (eg. rabbits may eat food contaminated by the urine or lick their paws which have stepped in it).
Rabbits are infectious for several months (from about a month after they’ve become infected), and some remain infectious throughout their life.
What are the symptoms?
The parasite is carried in the blood to the rabbit’s organs (eg. liver, kidney) and central nervous system (brain and spinal cord). This results in rupture of these cells, inflammation, and clinical signs, primarily in the brain, spinal cord, kidneys, and liver. Many infected rabbits never display symptoms of the disease. Older rabbits, or those suffering from some form of stress or illness, are more likely to develop symptoms – with their weakened immune system, the parasite can replicate more easily. Many of the signs are a result of the parasite causing inflammation in the brain, and some are related to inflammation in other organs. They might include:
· Head tilted to one side.
· Bag leg weakness (shuffling or paralysis).
· Loss of balance.
· Fitting or tremors.
· Spinning or rolling.
· Eyes tracking (side to side, or up and down).
· Sudden deafness.
· Kidney failure and bladder weakness (thirst and increased urination, decreased appetite, weight loss).
· Behavioural changes.
· Loss of appetite.
· Cataracts.
· Red, swollen eyes.
Many of these are also symptoms for other conditions/illnesses, so E cuniculi may not be diagnosed. E cuniculi can even result in gut stasis by affecting the contractions of the stomach.
E cuniculi is one of the main causes of head tilt, but there are other causes, such as middle ear infections, spinal trauma, and inherited congenital abnormalities (splay leg).
Kits’ eyes can be infected whilst still in their mother’s womb, and they will suffer eye problems later in life (often aged 6 months to 2 years), including cataracts, lens rupture, and uveitis (inflammation within the eye).
Prevention
More than half of all pet rabbits have been exposed to the E cuniculi parasite (and therefore have antibodies to it). This makes it almost impossible to prevent rabbits being exposed to E cuniculi – unless they’re kept alone for their entire life, which is not recommended, as we know that rabbits need companionship of other rabbits. It’s difficult to predict which rabbits will show signs of infection – of the rabbits exposed to E cuniculi, most show no signs of an infection at all, but others suffer acute and rapidly fatal infections.
Routine worming treatment to prevent E cuniculi is not recommended – it should only be used when necessary (see below under ‘Testing and treatment). However, there are some precautions that can be taken:
· Stress: Stress may be a factor causing infected rabbits who were previously showing no signs to suddenly become ill, so always try to protect rabbits from stress.
· Monitoring: Watch for any changes in eating or drinking, balance, or eyes problems, and consult a vet if there are signs which might indicate E cuniculi.
· Hygiene: E cuniculi can be killed with routine disinfectants, so it’s important to keep your rabbits’ area clean.
Testing
If an E cuniculi infection is suspected, rabbits should be tested. However, blood testing is not simple, as it measures antibodies that are produced from exposure to E cuniculi, and studies have revealed that over half of all pet rabbits have antibodies. They can be exposed to infection, and it can be lying dormant, without the rabbit having a current infection. Even a positive result in a rabbit showing signs may be inconclusive, as the signs may be symptoms of another condition, and the positive result simply a result of previous exposure to E cuniculi. To determine whether a positive result is because a rabbit has a current infection, rather than antibodies from exposure, a second blood test is often required, a month later – different antibodies are produced as infection progresses, and so if levels increase between tests, it’s likely to indicate a current infection.
Urine can be tested to check for e cuniculi – samples are usually collected for three days. Although most spores are shed in the first 3 months, rabbits may continue to shed spores for longer, so results are not definitive.
There is no specific treatment to reverse damage caused by E cuniculi. If the symptoms are advanced, the rabbit is likely to die.
Treatment aims to:
· Reduce inflammation (using anti-inflammatory medication such as steroids).
· Slow or stop the rate of multiplication of the parasite (using Fenbendazole – brand names Panacur and Lapizole, a medication used to treat a variety of parasites). Treatment is daily for 28 days, and success depends on how severe the infection is at that point. Fenbendazole should stop E cuniculi from causing further signs or damage. It does not protect a rabbit from any future exposure to the pathogen.
· Treat or manage the other signs, eg. urinary problems, eye symptoms.
Ideally, all new rabbits should have a blood test to check for E cuniculi, before introducing to any future companion(s), but this may require two tests, a month apart (as explained above), followed by treatment with Fenbendazole for 28 days if positive. Also, any rabbits suspected of infection should be tested and treated in the same way.
However, due to the time involved with testing, it’s often better just to administer Fenbendazole to new rabbits (and current rabbits before they are introduced to their new companion), and any rabbits suspected of infection. A new rabbit can be introduced after completing 14 days of the 28-day treatment. It’s particularly important to treat rabbits being introduced to a larger group, as the risk is greater. Treatment does not cause any side effects in rabbits, so there’s no harm in using it if a rabbit doesn’t have E cuniculi.
If a rabbit tests positive for E cuniculi, any bonded companions should be treated.
Always consult a vet before starting treatment.
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