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.
Unless your rabbit is severely affected by the encephalitozoonosis, it is normal for outpatient treatment to be provided. Inpatient treatment will be given if your rabbit is in a state of severe disease or if it cannot maintain adequate nutrition or hydration on its own. Dehydration will be treated with intravenous fluids or subcutaneous fluids, and mild sedatives, anti-epileptics (for seizures), and anti-parasitic drugs may be prescribed. Many rabbits with otherwise healthy immune systems improve with supportive care alone.
Living and Management
Restrict or confine your rabbit to a cage if it is showing neurological signs, like severe tremors, seizures, or rolling. A padded cages should be set up in a quiet spot in the home so that your rabbit will not be startled and will have the opportunity to rest and recover.
It is imperative that the rabbit continue to eat during and following treatment. Encourage oral fluid intake by offering fresh water, wetting leafy vegetables, or flavoring water with vegetable juice, and offer a large selection of fresh, moistened greens such as cilantro, romaine lettuce, parsley, carrot tops, dandelion greens, spinach, collard greens, and good-quality grass hay. You should also offer the rabbit its usual pelleted diet, as the initial goal is to get the rabbit to eat and maintain a healthy weight and fluid balance. If your rabbit either cannot or will not eat solid foods, you will need to use a feeding syringe to feed your rabbit a gruel mixture. Do not feed anything new to your rabbit during this time unless it has been directly advised by your veterinarian. Particularly, high-carbohydrate, high-fat nutritional supplements are not indicated for this disorder.
There is no prescription medication that has been found to successfully treat this infection, it is mainly treated with supportive care, as described here. Response to therapy is inconsistent, and long-term care for disabled rabbits may be necessary