There is good geographic evidence that an environmental factor is implicated in the aetiology of multiple sclerosis (MS). Controversy surrounds the interpretation of many studies supporting notions on whether the disease has greater prevalence in urban or rural communities. Rather than focus on residence at birth, in teenage years or at the time of study, analyses of MS mortality by occupation and a case control study to define exposure to animal farm products is thought to shed light in this controversy. The conclusion reached from the results of these studies is that exposure to farm animals or raw products is a common denominator in the aetiology of MS. A literature search for references of zoonotic disease with neurological symptoms produced a range of papers on brucellosis. A study of the literature on neurobrucellosis supports the hypothesis on clinical grounds. Finally, blood serum studies of Brucella exposure in a series of MS subjects and controls is described. These epidemiological studies support the hypothesis, that central nervous system involvement from exposure to brucellosis, may present with the features of multiple sclerosis.