Infection with new Seadornavirus could be misdiagnosed as Japanese encephalitis in China

[Stephane P. Rousseau (RCU)]

Infection with new Seadornavirus could be misdiagnosed as Japanese encephalitis in China

Three more species of mosquito have been found carrying banna virus (BAV) in China, widening the reach of a virus that was first identified in the late 1980s, report medical scientists this month in Emerging Infectious Diseases. Although the risks to human health remain unclear, the virus may be an undiagnosed cause of viral encephalitis in the region, they say.

 “Our results demonstrate that BAV strains are distributed from the tropics of Southeast Asia to the northern temperate regions of China,” write Hong Lui and colleagues from the Chinese Center for Disease Control and Prevention in Beijing. “These observations suggest that the distribution of BAV is wider than previously recognized and may be increasing.”

 BAV is a species of Seadornavirus that can cause febrile disease and encephalitis in people. It was first identified in 1987, when scientists isolated it from 27 people suffering from encephalitis and fever in Yunnan province in southwest China. Since then it has turned up in pigs, cattle, and ticks in the province, and in the blood sera of 98 febrile patients in Xinjiang province in the northwest of the country. It has also been spotted in mosquitoes in Indonesia and Vietnam. The authors say the virus may be an emerging pathogen.

 To better understand the geographical reach of the virus in China, Lui and colleagues collected mosquitoes from several sites in four provinces in the north of the country between July and September in 2006 and 2007. The researchers identified 10 new isolates of BAV in the mosquitoes collected in three of the four states, and analysed them alongside 28 other samples of the virus that had been collected from mosquitoes in China, Vietnam and Indonesia over the past seven years. Their findings showed that the reach of the virus now extends from the tropics to north temperate climates.

 They also identified the mosquito species carrying the viruses in China. Before now, BAV had been detected in seven species of mosquito, five belonging to the Culex family, and one to each of the Anopheles and Aedes families. “To this list we now add 3 species in the genus Aedes, which are widely distributed in China and elsewhere,” they write.

 The virus appears to circulate in areas where Japanese encephalitis virus is endemic, they explain. The main mosquito vector of the Japanese encephalitis virus, Culex tritaeniorhynchus, also appears to be a common vector of BAV. Symptoms of infection with BAV and the Japenese encephalitis virus appear to be similar, they note. “BAV cases may be undetected during a Japanese encephalitis outbreak.”  In 2002 Chinese scientists reported that immunological tests on 130 of more than 1100 patients diagnosed with Japanese encephalitis tested positive for antibodies against BAV.

 “Our observations suggest that the public health impact of BAV may be underestimated,” they write.

http://www.eht-forum.org/news.html?fileId=news100305063529&from=home&id=0

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