Seroprevalence of Japanese Encephalitis Virus Infection in Wild Birds - Thailand, 2015-2016

  • Vector-borne
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Background:
Japanese encephalitis virus (JEV) is a mosquito-borne zoonotic disease causing encephalitis in human, with high case fatality rate in Southeast Asia. Wild birds constitute a part in maintenance community and potentially introduce the virus to new areas. The information about virus circulation in wild birds in Thailand is neglected. This study aims to estimate JEV seroprevalence in wild birds in Thailand.

Methods:
Serum samples were collected from birds captured in 13 provinces, where HPAI H5N1 outbreaks occurred during 2004-2008, in the Northern, Northeastern, and Central regions under HPAI surveillance during 2015-2016. Hemagglutination inhibition (HI) test was performed to quantify a titer of JEV antibody. Distribution of seroprevalence was described using descriptive statistics.

Results:
Three hundred and twenty-four samples from 32 species in 17 families were collected. The positive rate was 6.2% (20/324), predominantly from birds of the family Estrildidae 50.0% (2/4), Laniidae 50.0% (1/2), Sturnidae 12.5% (3/24), Pycnonotidae 10.0% (1/10), Columbidae 6.0% (3/50), Ciconiidae 5.6% (2/36), Scolopacidae 5.6% (2/36). The birds in the family Anatidae and Ardeidae are considered common reservoir host for JEV and their seroprevalences were. 4.0% and 5.1% in this study, respectively. Seropositive birds presented only in Northern 7.9% (10/127), and Central regions 8.5% (10/117). Forty-seven samples (47/324; 14.51%) were collected from migratory birds and showed seropositive 10.64% (5/47).

Conclusion:
This was the earliest reports of JEV infection in wild birds in Thailand. The results were consistent with human situation that was more prevalent in these regions. Some migrants were seropositive and study on virus activity in these birds should be focused. Waterfowl, main avian reservoir host, in Korea had as high as 86.4% seroprevalence considerably far from which in this study. Given positive samples from HPAI surveillance, the intentional study designed for JEV detection in this host, linking with prevalence in other species and human, will give more valid results.

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