Download Furry Facts 18 – EC Series Part 1

Furry Facts: Veterinary Articles No 18: August 2015 Encephalitozoon Cuniculi (EC) Part 1 of 3 *references available on request EC is an obligate intracellular microsporidium that commonly infects rabbits. Rabbits are infected with EC through ingesting or inhaling the EC spores or transplacental transmission. EC invades the cells of the reticuloendothelial system which distribute the parasite around the body. The vacuole becomes distended and cells rupture releasing spores that invade new cells. The rupture of the cells is associated with an inflammatory response and chronic infection results in the development of granulomatous lesions in target organs. EC spores excreted in urine into environment inhalation Dependant on the host/parasite relationship and immune status EC Infection in pet rabbits Ingestion Travel in the circulation to target organs (brain, kidneys, lungs, heart, and liver) Transplacental transmission Also travels to lens Acute infection (primarily affects kidneys and lungs) Chronic infection (primarily affects CNS) Asymptomatic Latent carrier (could relapse at a later stage due to stress) cataracts, phacoclastic uveitis (later on in life) Flowchart of E. cuniculi infection in rabbits The rabbit’s humoral immune response is not thought to be protective; cell-­‐mediated immunity is essential to eliminate the parasite. Whether or not the rabbit goes on to display signs of encephalitozoonosis is dependent on the host/parasite relationship: parasite species and strains, route of infection, age of the rabbit and its immune status. Research shows that there is an infectious dose-­‐dependent increase in the severity of lesions, which can be another reason for the variable response seen in each infected rabbit. Vets are constantly learning more about EC and rabbits and updating protocols. Table 1. Types of disease state: Clinical infection: About 40-­‐50% of EC positive rabbits show clinical signs of disease. encephalitozoonosis -­‐ Acute infections can result in respiratory disease and renal disease. -­‐ Chronic infections can manifest as vestibular disease, seizures, tremors, head swaying at rest (granulomatous meningoencephalitis), paresis/paralysis, collapse, urinary incontinence, subclinical renal failure (interstitial fibrosis/nephritis). -­‐ These rabbits intermittently shed EC spores in urine. -­‐ Transplacental transmission can lead to cataract formation (often bilateral) later in life and lens rupture-­‐induced phacoclastic uveitis/hypopyon (usually unilateral). Subclinical infection: EC multiplication and the rabbit’s immune response are in equilibrium. These rabbits don’t Latent carrier show any clinical signs but are carriers of EC. Approximately 25% of healthy rabbits can (asymptomatic) suffer from active infection and shed infective EC spores in urine. * Stress or another suppressive factor (eg another medical condition) may act as a trigger for reactivation of the infection and clinical disease may develop. Resolved infection: These rabbits mounted an adequate antibody response that does not persist. Their immune system overcame EC and they are no longer infected with EC.