Meningoencephalitis

Veterinarians have observed meningoencephalitis in animals infected with listeriosis, caused by the pathogenic bacteria L. monocytogenes. Meningitis and encephilitis already present in the brain or spinal cord of an animal may form simultaneously into meningeoencaphilitis.[6] The bacterium commonly targets the sensitive structures of the brain stem. L. monocytogenes meningoencephalitis has been documented to significantly increase the number of cytokines, such as IL-1β, IL-12, IL-15, leading to toxic effects on the brain.[7]

Meningoencephalitis may be one of the severe complications of diseases originating from several Rickettsia species, such as Rickettsia rickettsii (agent of Rocky Mountain spotted fever (RMSF)), Rickettsia conorii, and Rickettsia africae. It can cause impairments to the cranial nerves, paralysis to the eyes, and sudden hearing loss.[8][9] Meningoencephalitis is a rare, late-stage manifestation of tick-borne ricksettial diseases, such as RMSF and Human monocytotropic ehrlichiosis (HME), caused by Ehrlichia chaffeensis (a species of rickettsiales bacteria).[10]

Other bacteria that can cause it are Mycoplasma pneumoniae, Tuberculosis, Borrelia (Lyme disease) and Leptospirosis.

• Tick-borne encephalitis.
• West Nile virus.
• Measles.
• Epstein-Barr virus.
• Varicella-zoster virus.
• Enterovirus.
• Herpes simplex virus type 1.
• Herpes simplex virus type 2.
• Rabies virus.
• Mumps, a relatively common cause of meningoencephalitis. However, most cases are mild, and mumps meningoencephalitis generally does not result in death or neurologic sequelae.[11]
• HIV, a very small number of individuals exhibit meningoencephalitis at the primary stage of infection.[12][13]

• Antibodies targeting amyloid beta peptide proteins which have been used during research on Alzheimer's disease.[14]
• Anti-N-methyl-D-aspartate (anti-NMDA) receptor antibodies, which are also associated with seizures and a movement disorder, and related to Anti-NMDA receptor encephalitis
• NAIM or "Nonvasculitic autoimmune inflammatory meningoencephalitis" (NAIM).[15] They can be divided into GFAP- and GFAP+ cases. The second is related to the Autoimmune GFAP Astrocytopathy.

• Primary amoebic meningoencephalitis, e.g., Naegleria fowleri, Balamuthia mandrillaris, Sappinia diploidea
• Trypanosoma brucei
• Toxoplasma gondii (sporozoa)

Amoebic pathogens exist as free-living protozoans. Nevertheless, these pathogens cause rare and uncommon CNS infections. N. fowleri produces primary amoebic meningoencephalitis (PAM). The symptoms of PAM are indistinguishable from acute bacterial meningitis. Other amoebae cause granulomatous amoebic encephalitis (GAE), which is a more subacute and can even a non-symptomatic chronic infection. Amoebic meningoencephalitis can mimic a brain abscess, aseptic or chronic meningitis, or CNS malignancy.[16]

• Halicephalobus gingivalis

Animal pathogens exist as facultative parasites. They are an exceptionally rare cause of meningoencephalitis.[17]

• Granulomatous meningoencephalitis.
• The fungus, Cryptococcus neoformans, can be symptomatically manifested within the CNS as meningoencephalitis with hydrocephalus being a very characteristic finding due to the unique thick polysaccharide capsule of the organism.
• Vasculitis.