Avian influenza A (H5N1) virus antibodies in pigs and residents of swine farms, southern China.
BACKGROUND
Since 1997, the H5 avian influenza viruses (AIVs) circulating in China have become an international concern. Clade 2.3.2 of H5N1 AIVs is genetically distinct from the viruses isolated before 2007 and antigenically different from the vaccine strains widely used in China. Swine farms in rural China are thought to play an important role in AIVs ecology.


OBJECTIVE
A seroepidemiological study was undertaken among swine farm residents and pigs to understand the prevalence of antibodies against H5N1 AIVs in southern China.


METHODS
During the period March 24, 2008 to December 25, 2012,serum samples were collected from 1606 swine farm residents on 40 swine farms in southern China. A total of 1980 pigs' serum samples were collected in the same swine farms where swine workers' serum samples were collected from March 2009 to March 2013. For a control group, 104 serum samples were collected from healthy city residents in Nanchang. All the serum samples were collected to perform hemagglutination inhibition (HI) and (neutralization) NT assays to investigate the prevalence of H5N1 AIV infections in southern China.


RESULTS
Sixteen human samples were positive by HI assay and 10 of these were also positive by NT assay against H5N1. No serum samples from human control and pigs were HI positive for H5N1 AIV.


CONCLUSIONS
Our results demonstrate minimal transmission H5N1 AIV from birds to pigs in the swine farms studied and the risk of poultry-to-human and poultry-to-pig transmission for at least clades 2.3.2 seemed very low. This study provides the first data regarding antibodies against H5N1 AIV in humans and pigs on swine farms in China. The findings of this study can serve as a baseline for additional serologic studies to assess transmission of H5N1 viruses between avian species, pigs and swine workers.
Key Laboratory of Animal Disease Control and Prevention of the Ministry of Agriculture, South China Agricultural University, 483 Wushan Road, Tianhe District, Guangzhou 510642, China.
Nan
N
Cao
Wanjun
W
Zhu
Ye
Y
Chen
Likai
L
Tan
Pei
P
Zhou
Zhenpeng
Z
Cao
Changwen
C
Ke
Yugu
Y
Li
Jie
J
Wu
Wenbao
W
Qi
Peirong
P
Jiao
Guihong
G
Zhang
D000328:Adult; D000818:Animals; D000914:Antibodies, Viral / Q000097:blood*; D002681:China / Q000453:epidemiology; D005260:Female; D006801:Humans; D053124:Influenza A Virus, H5N1 Subtype / Q000145:classification / Q000235:genetics / Q000302:isolation & purification*; D007251:Influenza, Human / Q000453:epidemiology / Q000821:virology*; D008297:Male; D008875:Middle Aged; D009976:Orthomyxoviridae Infections / Q000453:epidemiology / Q000662:veterinary*; D015995:Prevalence; D034421:Sus scrofa; D013552:Swine; D013553:Swine Diseases / Q000453:epidemiology / Q000821:virology*; D055815:Young Adult
D000914:Antibodies, Viral
H5N1; Pigs; Swine farm residents