Monday, 18 August 2014

Resisting the Japanese invader: the China success story against Japanese encephalitis

by Michael Woodhead
 As China cranks up its media hate campaign against its former enemy Japan, the country can actually celebrate victory in its war against another 'Japanese' invader from the 1940s: Japanese encephalitis. 

This mosquito borne viral disease used to cause about 200,000 cases of severe neurological illness in China every year at its peak in the 1960s and 70s - with about 30% patients dying and many of the survivors  left with lasting neurological disability as a result of the infection.

The name is misleading - the disease did not originate in Japan, but was first identified there in the 19th century. The infection was first recorded in China in the 1940s and became widespread in the 1960s - partly because of the breakdown in public health preventive activities during the chaos of Mao Zedong's Cultural Revolution.

A vaccine against the virus was developed in Japan in 1965, and China started manufacturing its own vaccine a few years later.  Writing in the journal PLOS Neglected Tropical Diseases, Dr Gao Xiaoyan and colleagues at the Chinese Centre for Disease Control and Prevention, Beijing, describe how Japanese encephalitis was brought under control in China.

The initial Chinese vaccine was only available in limited quantities and required many doses. It was expensive and was only available to privileged cadres and Party members, not to the peasants who were most at risk of the disease. With more than half the cases of Japanese encephalitis in the world, China continued to work on improving the vaccine and eventually developed one in 1988 that was more convenient and could be mass produced at relatively low cost, to make it affordable for public health use.

This vaccine was gradually made available at a cost of 1 yuan to rural residents, and was fully subsidised as a free vaccine after the year 2005. Since it was included in the "Expanded Program of Immunisation" this cheap and effective vaccine had reduced the incidence of Japanese encephalitis in China from 21/100,000 people to just a fraction of 1 per 100,000 - a remarkable achievement.

But the vaccine is not the only reason for the drastic reduction in Japanese encephalitis in China. Other public health measures were implemented by local health authorities to reduce mosquito breeding and transmission:  pig farms were moved away from villages,  sewage disposal was improved to reduce mosquito breeding, and mosquito breeding grounds in areas of static water were eliminated.

The threat from Japanese encephalitis has now been markedly reduced in the more prosperous eastern provinces of China but it remains a problem in the poorer parts of southwest China. Nevertheless, Chinese researchers say other developing countries can copy the Chinese model for eliminating Japanese encephalitis: low cost programs using inexpensive vaccine and anti-mosquito measures.

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