About E.Cuniculi in Rabbits (Part 1) What Every Rabbit Owner Should Know
Encephalitozoon cuniculi infection, commonly known as E. cuniculi, is one of the most common infectious diseases veterinarians encounter in rabbits. In fact, studies have shown that 40–85% of rabbits worldwide have been exposed to it.
The good news is that most rabbits carrying E. cuniculi never become sick. However, in some rabbits, the parasite can cause inflammation affecting the brain, kidneys, or eyes, leading to serious health problems if left untreated.
Knowing what to watch for and seeking veterinary care early can make a significant difference in your rabbit's recovery.
What is E. cuniculi?
E. cuniculi is a microscopic parasite that lives inside the body's cells. Once a rabbit is infected, it invades cells and forms spores that allow it to survive and spread.
The parasite most commonly spreads through infected urine. Rabbits become infected by accidentally ingesting spores from contaminated food, water, bedding, or surfaces. Less commonly, spores may also be present in respiratory secretions or faeces. Pregnant rabbits can pass the infection to their unborn kits, which may lead to eye disease later in life.
After entering the body, the parasite travels through the bloodstream before settling primarily in the brain and kidneys. It can also affect the eyes.
Why don't all infected rabbits become ill?
One of the challenging aspects of E. cuniculi is that exposure does not equal disease.
Many rabbits develop antibodies against the parasite and remain perfectly healthy throughout their lives. Others may only develop clinical disease if the parasite causes enough inflammation to damage the nervous system, kidneys, or eyes.
Because E. cuniculi is so common, a positive blood test alone does not necessarily explain why a rabbit is unwell. Your veterinarian will always interpret test results together with your rabbit's history, physical examination, and any additional diagnostic tests.
Signs of E. cuniculi infection
The symptoms depend on which organs are affected.
Neurological disease
The nervous system is the area most commonly affected. Rabbits may develop:
- Head tilt
- Loss of balance
- Circling
- Rolling
- Difficulty walking
- Falling to one side
- Rapid flickering eye movements (nystagmus)
Some rabbits show only a mild head tilt, while others become unable to stand and roll continuously.
Rabbits may have difficulty eating or appear to have a reduced appetite because of poor balance and an abnormal body position make it challenging to reach, hold, or chew their food.
Kidney disease
The kidneys are another common site of infection. Most rabbits never develop noticeable kidney disease, but in some cases chronic inflammation may eventually lead to kidney failure.
Possible signs include:
- Drinking more than usual
- Passing larger amounts of urine
- Weight loss
- Reduced energy
- Poor appetite
Because these signs can be caused by a variety of illnesses—not just E. cuniculi—blood and urine tests are often needed to assess kidney function and identify the underlying cause of your rabbit's symptoms.
Eye disease
The parasite can also infect the eyes, resulting in:
- Cataracts
- Cloudiness of the eye
- Red, painful eyes
- Inflammation inside the eye (uveitis)
- Excessive tearing
- Squinting
Diagnosing E. cuniculi
Unfortunately, there is no single test that can definitively diagnose active E. cuniculi disease.
Diagnosis is based on a combination of:
- A thorough physical examination
- Neurological assessment
- Blood tests
- Antibody (serology) testing
- Urine testing where appropriate
- Imaging such as radiographs or advanced imaging in selected cases
Blood tests measure antibodies produced against the parasite. A positive result tells us that a rabbit has been exposed to E. cuniculi, but because exposure is so common, it does not automatically mean the parasite is responsible for the current illness.
One of the most important conditions that can mimic E. cuniculi is middle or inner ear infection (otitis media/interna). Both diseases can cause head tilt, loss of balance, and circling, and occasionally they occur together. Additional diagnostic tests may therefore be recommended to identify the underlying cause and guide treatment.
Read on for E. Cuniculi (Part 2) Treatment for E. Cuniculi