Encephalitozoonosis is a common disease in rabbits that can also affect people
with weakened immune systems, with cases reported in children, older people and people with AIDS. The organism that causes it is Encephalitozoon cuniculi, an obligate intracellular parasite of the phylum Microsporidia.
Rabbits can become infected by ingesting or inhaling infectious spores, or while in their mother’s uterus. These spores can survive in the environment for up to four weeks. When active, the organism replicates in the lungs, liver and kidneys. It may also be found in the heart, central nervous system and eyes.
Signs in affected rabbits can range from mild, with subclinical kidney or central nervous system involvement, to severe kidney damage and serious neurological changes that may prevent a rabbit from living normally.
Neurological signs are the most frequent manifestation of active encephalitozoonosis and can occur at any age. Vestibular syndrome (head tilt) is characteristic, although not exclusive to this infection, so other diseases must be considered in the differential diagnosis. The rabbit may be unable to hold its head normally, tilting it to one side or even rolling over.
A complete blood count, biochemistry, radiographs of the tympanic bullae and serology can be useful. Traditionally, serology was difficult to interpret because a positive result did not distinguish a previous infection from an active one. We therefore could not tell whether the parasite or another cause explained the signs.
To understand this, when a rabbit becomes infected, whether or not it develops disease, it produces initial defence antibodies that disappear over time (immunoglobulin M), followed by memory antibodies that maintain immunity for much longer (immunoglobulin G). Earlier tests measured only IgG, so their presence did not establish that the parasite was responsible for the rabbit’s problems.
Laboratories can now also assess IgM, which this article describes as helping identify an active infection when the result is positive.
Here is an example:
This would be the typical result for a rabbit infected in the past but showing no signs, or for a rabbit with compatible signs whose sample may have been taken at a very early stage of disease.
In the interpretation described in this article, a positive IgM result would support the parasite as the cause of the current disease. Otherwise, we would only know that the rabbit was infected, without establishing a link to the signs at that time.
Consider a rabbit infected in the past that now begins to show compatible signs. If the parasite were responsible, serology could show positive IgM; otherwise, another cause might explain the signs, or the sample might have been taken before IgM began to rise. The following graph illustrates this situation.
As a preventive measure, if your rabbit is IgG-negative, the advice in this article is to avoid contact with positive rabbits or rabbits that have not undergone serological testing, to reduce the risk of infection and future illness.
[bctt tweet=”Si tu conejo es negativo a E. cuniculi, evita su contacto con otros conejos positivos o sin analítica realizada” username=”CV_ARACAVIA”]
