A Central Nervous System Disease of Unknown Cause That Occurred in the Minamata Region: Results of an Epidemiological Study

Abstract

Recently, a series of cases of a central nervous system disease of unknown cause with extrapyramidal tract abnormalities as the most prominent feature occurred, mainly in fishermen's communities, on the periphery of Minamata City. Because the symptoms of the disease were unique and severe, and its prognosis was extremely poor, the disease caught immediate attention. In response to the request from the local Minamata Strange Disease Countermeasures Committee to investigate this disease, we visited this area many times since September 1956 and conducted a detailed epidemiological study, including face-toface interviews of 40 households with patients and 68 adjacent households without patients as control households. The results of the study are described below.

Biochemical evidence on the potential role of methyl mercury in hepatic glucose metabolism through inflammatory signaling and free radical pathways

“…Many in vivo studies have been conducted previously to prove this notion. For instance, few evidence raised from epidemiological studies concluded that MeHg induce toxicity in motor neurons and affects human behavior . This study was further confirmed by animal modeling, which was performed by Ekino et al Moreover, other experimental studies in which animals were exposed to MeHg, it was concluded that visual (Visual sensitivity check was checked), emotional (ie, depression during the behavior evaluation in forced swimming) and cognitive functions effected leading towards movement disorder, loss of balance, and ataxia …”

Cellular and Molecular Mechanisms Mediating Methylmercury Neurotoxicity and Neuroinflammation

“…The pollutant was produced from mercury as a by-product of acetaldehyde and vinyl compounds manufacturing by Chisso Co. Ltd. in Minamata City and discharged into the Minamata Bay [ 7 , 28 , 30 ]. This way, the population of the Minamata area that largely depended on fish and shellfish consumption from the Minamata Bay was contaminated with MeHg [ 7 , 28 , 31 , 32 ]. The Minamata disaster was a stereotypical case of biomagnification of MeHg through trophic levels that ended up in human exposure [ 29 ].…”

Lessons From an Early-stage Epidemiological Study of Minamata Disease

“…In the descriptive study, following the principle of descriptive epidemiology (ie, time, place, and person), 9 they examined the time trend of patients correlating it with amount of fishing in the exposed area, plotted the locations of the patients, and examined the characteristics of the patients in a detailed manner. In particular, they plotted the time sequence of cases on a map ( Figure 4 in the article 1 ) and speculated that the disease was not contagious, which is a very remarkable discovery in the early phase of the incident.…”

“…Moreover, they examined an association between family occupation of the households and the disease in the analytical epidemiological study ( Table 8 in the article 1 ) and demonstrated that the households with the patients had higher odds of fishing occupation compared with the control households (odds ratio 21.6; 95% confidence interval, 6.8-68.7). They further focused on intake of fish caught in Minamata Bay (which is the bay where the effluent from the factory was discharged into) and demonstrated that the households with the patients had higher odds of eating fish caught in the bay compared with the control households (Table 17 in the article 1 ).…”