Abstract
BackgroundThe increasing trend of adult cases of Japanese encephalitis (JE) in China, particularly in northern China, has become an important public health issue. We conducted an epidemiological investigation in the south of Shanxi Province to examine the relationships between mosquitoes, Japanese encephalitis virus (JEV), and adult JE cases.MethodsMosquito specimens were collected from the courtyards of farmers’ households and pig farms in Shanxi Province. Mosquitoes were pooled, homogenized, and centrifuged. Reverse transcription-polymerase chain reaction (RT-PCR) was used to detect mosquito-borne arbovirus genes in homogenates. Specimens positive for these genes were inoculated into the baby hamster kidney cell line (BHK-21) to isolate virus. Minimum infection rate was calculated and phylogenetic analyses were performed.ResultsA total of 7 943 mosquitoes belonging to six species in four genera were collected; Culex tritaeniorhynchus accounted for 73.08% (5 805/7 943), C. pipiens pallens for 24.75% (1 966/7 943), and the remaining 3% (104/ 7943) consisted of Anopheles sinensis, Aedes vexans, Ae. dorsalis, and Armigeres subalbatus. Sixteen pools were positive for JEV based on RT-PCR using JEV pre-membrane gene nested primers. Phylogenetic analyses showed that all JEVs belonged to genotype I; two pools were positive using Getah Virus (GETV) gene primers. In addition, one JEV strain (SXYC1523) was isolated from C. pipiens pallens specimens. These results indicate that the minimum infection rate of JEV in mosquito specimens collected from the courtyards of farmers’ households with pigsties was 7.39/1 000; the rate for pig farms was 2.68/1 000; and the rate for farmers’ courtyards without pigsties was zero.ConclusionsThe high-prevalence regions of adult JE investigated in this study are still the natural epidemic focus of JEV. Having pigsties near dwellings is a potential risk factor contributing to the prevalence of adult JE. To prevent the occurrence of local adult JE cases, a recommendation was raised that, besides continuing to implement the Expanded Program on Immunization for children, the government should urge local farmers to cease raising pigs in their own courtyards to reduce the probability of infection with JEV.
Highlights
The increasing trend of adult cases of Japanese encephalitis (JE) in China, in northern China, has become an important public health issue
Japanese encephalitis (JE) is a central nervous system disease caused by Japanese encephalitis virus (JEV), which has severe symptoms and a fatality rate of 30%
17 to 22 August 2015, and consisted of six species from four genera (Table 3); Culex tritaeniorhynchus accounted for 73.08% (5 805/7 943), C. pipiens pallens for 24.75% (1 966/7 943), and Anopheles sinensis, Aedes vexans, Ae. dorsalis, and Armigers subalbatus for about 3% (104/7 943)
Summary
The increasing trend of adult cases of Japanese encephalitis (JE) in China, in northern China, has become an important public health issue. We conducted an epidemiological investigation in the south of Shanxi Province to examine the relationships between mosquitoes, Japanese encephalitis virus (JEV), and adult JE cases. JE is mainly epidemic in developing countries in Asia such as China, India, Thailand, Vietnam, Myanmar, Laos, and Indonesia. It is the most important form of viral encephalitis in these regions [3, 4]. In 2006, 66 cases of JE were reported with 22 deaths in Shanxi Province, China, among which only 1 patient was 4 years old and more than 86% were over 30 years old [5]. The epidemic of adult JE in local regions has become a new public health issue
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