(E Cunicili) in Rabbits, Information for Owners

April 9, 2018 | Author: Anonymous | Category: Science, Biology, Zoology, Parasitology
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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.      

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

      

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: 

prophylactic fenbendazole in feed



disinfection of environment, food bowls and water containers



lifting the food bowls off the floor to reduce the risk of urine contamination



water bottle instead of bowl to reduce the risk of urine splash



housing rabbits in separate hutches to reduce the risk of urine dropping onto lower cages



avoid contact with wild rabbits and rodents that might be a potential source of infection



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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