Encephalitozoonosis in Rabbits
Encephalitozoonosis is an infection caused by the parasite Encephalitozoon cuniculi. It is well known in the rabbit community, and is also known to occasionally infect mice, guinea pigs, hamsters, dogs, cats, primates, and even immune compromised humans (e.g., those with HIV or cancer). In rabbits as well, most infections occur when the rabbit has an impaired immune system.
Infection typically occurs when the rabbit ingests the spores of the parasitic organism through contaminated food, after which the spores spread to all of the body organs, resulting in infection once the spores have grown to maturation. The spores may also be transferred from the pregnant female to the developing offspring. The disease process can affect various systems, and symptoms will depend on the areas that are affected. In most cases there will be no clinical symptoms of the parasite's presence, and the infected rabbit will remain disease free until the immune system fails for some reason. Stress, old age, or illness may be causes for a weakened immune system, allowing the parasite to take on a stronger role. The liver, heart, kidneys, spleen, and spinal nerves may all be affected. A certain strain of this infection is seen more often in young rabbits and Dwarf breeds, and the nervous system is affected more in older rabbits.
Symptoms and Types
Symptoms are determined mainly by the location and extent of tissue damage; signs related to eye disease and nervous system are most commonly reported. In addition, most infections are asymptomatic (without symptoms). Some common symptoms to look out for include:
- Abscess, cataract, and hypersensitivity to light if the eyes are involved)
- Head tilt, rolling of eyeballs, tremors, loss of balance, rolling, seizures if the neurological system is affected
- Paresis/paralysis (partial or complete motor loss) if the vestibular system is affected
- Lethargy, depression, anorexia, and weight loss if kidneys are affected
Historically, encephalitozoonosis is a difficult disease to diagnose. It is often not diagnosed at all and is found incidentally after death during a necropsy. You will need to begin by providing a thorough history of your rabbit's health leading up to the onset of symptoms. A complete blood profile will be conducted, including a chemical blood profile, a complete blood count, and a urinalysis. Your veterinarian will check levels of antibodies in the blood and make a detailed analysis of the serum to check for possible levels of infection.
Because there are several possible causes for this condition, a differential diagnosis may be the best method for diagnosis. This process is guided by deeper inspection of the apparent outward symptoms, ruling out each of the more common causes until the correct disorder is settled upon and can be treated appropriately. In this way, your veterinarian will be able to differentiate form other causes of nervous system and eye diseases. A detailed eye examination will be performed to rule out disease processes there. Visual diagnostics will include X-rays of skull to rule out ear infection, and computed tomography (CT) and magnetic resonance imaging (MRI) can be used to localize and identify lesions in the brain and spinal cord.