Encephalitis Secondary to Parasitic Migration in Cats
Also known as encephalitis, brain inflammation may be due to a variety of factors. Parasites, for instance, can migrate into the cat's central nervous system (CNS), gain entry via blood or through adjacent tissues, including the middle ear, natural opening in the skull, nasal cavities and cribriform plate (part of the skull), or open fontanelles, also called “soft spots.”
These parasites may normally affect another organ system of the same host (e.g., Dirofilaria immitis, Taenia, Ancylostoma caninum, Angiostrongylus), or a different host species (e.g., raccoon roundworm, Baylisascaris procyonis; skunk roundworm, B. columnaris; Coenurus spp., or Cysticercus cellulosae). Dirofilaria immitis is most often seen in adult cats, while the other parasites generally infect younger kittens that are exposed to the outdoors.
Symptoms and Types
Symptoms associated with this type of encephalitis will vary depending on the portion of CNS affected. Cuterebriasis, for example, occurs mainly between July and October in the U.S. and is characterized by the sudden onset of behavior changes, seizures, and vision issues. In addition, parasite infections are often asymmetrical, affecting one side but not the other.
The most common way a cat acquires this type of encephalitis is by being housed in a cage that has been previously occupied by an infected host; e.g., raccoons, skunks.
You will need to give a thorough history of your cat’s health, including the onset and nature of the symptoms, to the veterinarian. He or she will then perform a complete physical examination as well a biochemistry profile, urinalysis, complete blood count (CBC) -- the results of which are typically normal unless the parasites have also migrated into other organs.
Computed tomography (CT) or magnetic resonance imaging (MRI) of the brain may reveal a focal lesion and/or cerebral tissue death from blockage of cerebral blood vessels, both of which are consistent with parasitic infections. A cerebrospinal fluid tap is another common diagnostic method used to confirm parasitic infection; however, the tap may yield normal results despite encephalitis.