(E Cunicili) in Rabbits, Information for Owners

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ENCEPHALITOZOON CUNICULI (E CUNICULI)
ELISABETTA MANCINELLI, DVM, MRCVS, CERTZOOMED
ECZM RESIDENT IN SMALL COMPANION EXOTIC MAMMAL MEDICINE AND SURGERY
Great Western Exotic Vets
Unit 10 Berkshire House, County Park,
Shrivenham Road, Swindon, SN1 2NR
www.gwexotics.com
It’s a tiny organism called protozoon that primarily infects rabbits but may also be found
in other mammals, in birds and snakes. It is possible for the organism to be transmitted
to humans, however human infection usually only occurs in immunocompromised
patients. It is frequently encountered in laboratory rabbits but it is thought to be rare in
the wild rabbit population. A recent study (Keeble and Shaw; 2006) demonstrated
evidence of current or recent infection with 52% incidence of exposure in normal
healthy pet rabbits. Other reports have described 6-22% of all rabbits developing
disease caused by the organism. As the main target organs are the brain and kidney,
disease is serious, such that some rabbits either do not survive or are left with lifelong
signs.
The parasite is spread as spores (resistant eggs) that are shed in the URINE of
infected rabbits. Unborn kits may be infected from their mothers, via the placenta
during pregnancy whereas young rabbits may contract it from an infected mother or
from a cage mate by eating the spores in urine contaminated food or water.
When a rabbit is first infected the parasite is absorbed from the intestines and it is
carried into the blood circulation to target organs (LIVER, KIDNEY, CENTRAL
NERVOUS SYSTEM, HEART, EYE) where it causes inflammation and small lesions
that are called MICRO-GRANULOMAS. This eventually results in clinical signs.
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drinking excessively
loss of litter training
reduced appetite
weakness
depression
weight loss
are some of the most common clinical signs showed by infected rabbits.
Depending on which structure, between the brain and the spinal cord, is affected
neurological disease may manifest as
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changes in behaviour
seizures
paralysis of one or both hind legs
neck spasm
head tilt
urinary incontinence
loss of balance
It is important, though, to rule out other possible diseases that may cause the same
clinical signs. Therefore other causes of head tilt and neurological disease in rabbits
should be considered such as SPINAL TRAUMA, INHERITED CONGENITAL
ABNORMALITIES, ABSCESSES, MIDDLE EAR INFECTIONS, PARASITES and
LEAD TOXICITY. If the foetus becomes infected whilst in-utero the parasite infects the
eye and, as a result, cataracts (clouding of the crystalline lens in the eye), uveitis
(inflammation involving the interior of the eye), hypopion (white patches visible in the
eye) and blindness may develop.
DIAGNOSING an active infection in the live rabbit can be challenging.
A blood test can be performed to detect ANTIBODIES to E. cuniculi in the blood. The
test is called ELISA and a positive result is referred to as a “positive titer”. In some
cases it is necessary to carry out two separate blood tests at least 4 weeks apart to
check for a RISING ANTIBODY TITRE. We need to consider though that antibody
levels can persist for years in rabbits without any clinical signs and that there is
considerable individual variation in immune response in each case (some rabbits have
persistently high titers for long time, others become negative after 8 weeks). If there are
other in-contact rabbits, these can be screened to identify infected animals before the
parasite is excreted, in an outbreak. These animals may be isolated and treatment
started.
More recently a test called PCR (Polymerase Chain Reaction) has been developed for
detection of spores in samples of lens content from eyes with uveitis (very sensitive
and specific test) or from tissue samples (especially kidney) collected during
laparoscopy.
Unfortunately post mortem examination is often the only reliable way of testing for this
parasite which causes typical lesions in the brain and kidneys.
Treatment is aimed at reducing inflammation using ANTIINFLAMMATORY DRUGS and
stopping spore formation using BENZIMIDAZOLE DRUGS (such as fenbendazole). A
study has shown that a 28 days course of fenbendazole can eradicate E. cuniculi.
Killing the parasite, though, does not reverse the chronic changes that have already
taken place in many organs. Many rabbits, despite treatment, may not get any better
because the brain inflammation caused by the parasite has already induced irreversible
damage. Animals seem to have less difficulty adjusting to loss of mobility than humans
do. Rabbits which manifest the clinical disease may stabilise and live comfortably for a
prolonged period of time. Broad spectrum antibiotics are usually prescribed to cover
against risk of other infections mostly when using anti-inflammatory that can depress
the immune system. Supportive care is necessary and sometimes with severe
neurological signs sedation might be required. Eye disease may be initially cured with
eye drops. In particular cases, cataract surgery might be performed but if the disease is
severe the eye may need to be removed.
There are an estimated 1.3-3 million pet rabbits in UK and over 50% are likely to have
been exposed to E.cuniculi. Increased awareness is important so that clinical cases
may be identified and treated at an early age. Hopefully over the next few years more
definitive recommendations will emerge. In the meantime if your bunny shows
suspicious clinical signs DO HAVE HIM/HER BLOOD TESTED. Radiographs and urine
test aid ruling out other diseases that might cause the same symptoms.
CAN DISEASE BE PREVENTED? Whilst this remains an area of active debate and
research, it is now believed that in the vast majority of rabbits this is possible. Some
feasible measures to reduce the likelihood of infection, in a group situation, apply:
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prophylactic fenbendazole in feed
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disinfection of environment, food bowls and water containers
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lifting the food bowls off the floor to reduce the risk of urine contamination
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water bottle instead of bowl to reduce the risk of urine splash
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housing rabbits in separate hutches to reduce the risk of urine dropping onto
lower cages
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avoid contact with wild rabbits and rodents that might be a potential source of
infection
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during shows/studs observe rigid hygiene rules and avoid urine contact between
rabbits
The aim is to set up ‘E cuniculi free’ colonies or households of rabbits. This is done by
treating all rabbits in the household with 28 days fenbendazole (being careful not to
over dose). Simultaneously, the accommodation is well cleaned and disinfected at 21
and 28 days. Any subsequent new rabbits joining the group, would be treated prior to
mixing. Whilst theoretically rabbits could become reinfected from rodents, foxes etc.
the current view is that this is unlikely. So this method of infection is controlled and
eliminated prior to clinical disease. This protocol has been ongoing at Great Western
Exotic Vets for 18 months, to date no member of a treated colony has subsequently
suffered from clinical disease and no treated rabbit has demonstrated any side effects
from treatment.
If you should suffer the sadness of losing a rabbit under these circumstances, please
consider having a POST MORTEM EXAMINATION performed so that we take more
steps in the quest to unravel exactly what impact this parasite may be having on the
welfare of our rabbits!
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