Granulomatous meningoencephalitis (GME) is an inflammatory disease of the central nervous system (CNS) of dogs and, rarely, cats. It is a form of meningoencephalitis. GME is likely second only to encephalitis caused by canine distemper virus as the most common cause of inflammatory disease of the canine CNS. The disease is more common in female dogs of young and middle age. It has a rapid onset. The lesions of GME exist mainly in the white matter of the cerebrum, brainstem, cerebellum, and spinal cord. The cause is only known to be noninfectious and is considered at this time to be idiopathic. Because lesions resemble those seen in allergic meningoencephalitis, GME is thought to have an immune-mediated cause, but it is also thought that the disease may be based on an abnormal response to an infectious agent. One study searched for viral DNA from canine herpesvirus, canine adenovirus, and canine parvovirus in brain tissue from dogs with GME, necrotizing meningoencephalitis, and necrotizing leukoencephalitis (see below for the latter two conditions), but failed to find any. Types of GME
Disseminated – This is a diffuse disease throughout the CNS. It was previously known as inflammatory reticulosis. There is an accumulation of mononuclear cells and neutrophils around the blood vessels (perivascular) of the CNS. Meningitis is seen with this form of GME and causes fever and neck pain. It has an acute progression over a few weeks. Symptoms include incoordination, nystagmus, head tilt, seizures, and depression. Focal – The disease presents as a granuloma, which mimics a tumor.
Organisms, including humans, fish-eating birds, and fish-eating mammals such as otters and cetaceans (i.e. whales and dolphins) that consume fish from the top of the aquatic food chain receive the methylmercury that has accumulated through this process, plus the toxins in their habitat. Fish and other aquatic species are the main source of human methylmercury exposure.The concentration of mercury in any given fish depends on the species of fish, the age and size of the fish and the type of water body in which it is found. In general, fish-eating fish such as shark, swordfish, marlin, larger species of tuna, walleye, largemouth bass, and northern pike, have higher levels of methylmercury than herbivorous fish or smaller fish such as tilapia and herring. Within a given species of fish, older and larger fish have higher levels of methylmercury than smaller fish. Fish that develop in water bodies that are more acidic also tend to have higher levels of methylmercury. Biological impact
Human health effects
Ingested methylmercury is readily and completely absorbed by the gastrointestinal tract. It is mostly found complexed with free cysteine and with proteins and peptides containing that amino acid. The methylmercuric-cysteinyl complex is recognized by amino acids transporting proteins in the body as methionine, another essential amino acid. Because of this mimicry, it is transported freely throughout the body including across the blood–brain barrier and across the placenta, where it is absorbed by the developing fetus. Also for this reason as well as its strong binding to proteins, methylmercury is not readily eliminated.