OBJECTIVETo investigate the abundance and seasonal dynamics of mosquitoes, and to detect Japanese encephalitis virus (JEV) in these mosquitoes at the nesting colony of ardeid birds.

METHODSMosquitoes were collected bimonthly from July 2009 to May 2010 by Centers for Disease Control. Light traps and dry ice, as a source of CO2, were employed to attract mosquitoes. Mosquitoes were first identified, pooled into groups of upto 50 mosquitoes by species, and tested for JEV infection by viral isolation and reverse transcriptase polymerase chain reaction.

RESULTSA total of 20 370 mosquitoes comprising 14 species in five genera were collected. The five most abundant mosquito species collected were Culex tritaeniorhynchus (95.46%), Culex vishnui (2.68%), Culex gelidus (0.72%), Anopheles peditaeniatus (0.58%) and Culex quinquefasciatus (0.22%). Mosquito peak densities were observed in July. All of 416 mosquito pools were negative for JEV.

CONCLUSIONSThis study provides new information about mosquito species and status of JEV infection in mosquitoes in Thailand. Further study should be done to continue a close survey for the presence of this virus in the ardeid birds.

Animals ; Bird Diseases ; epidemiology ; virology ; Birds ; Culicidae ; physiology ; virology ; Encephalitis Virus, Japanese ; isolation & purification ; Encephalitis, Japanese ; epidemiology ; veterinary ; virology ; Population Dynamics ; Reverse Transcriptase Polymerase Chain Reaction ; veterinary ; Seasons ; Thailand ; epidemiology ; Virus Cultivation ; veterinary

Japanese encephalitis virus (JEV) causes a mosquitoborne viral zoonosis that is becoming increasingly important to public health in east and south Asia. Although JEV is primarily associated with reproductive failure in swine, JEV infection can cause fever and headache in humans and is associated with aseptic meningitis and encephalitis. The exact mode of transmission, including host range and possible source of viral amplification within livestock, is still not completely clear. This study consisted of a serological survey of JEV infection in goats. A total of 804 goat serum samples were collected from 144 farms in Korea between May 2005 and May 2006. The incidence of positive cases was 12.1% (97 out of 804 goats). The seroprevalence of JEV infection in the 144 farms screened was 31.3% (45/144), indicating that JEV infection is frequent in goat farms in Korea. In addition, three districts of Korea (mainly in the southern region) had a higher seroprevalence of JEV compared to other areas. The results suggest that goats could be monitored epidemiologically as a sentinel animal for JEV transmission in Korea.
Age Factors ; Animals ; Antibodies, Viral/blood ; Encephalitis Virus, Japanese/*isolation & purification ; Encephalitis, Japanese/epidemiology/*veterinary/virology ; Goat Diseases/*epidemiology/*virology ; Goats ; Hemagglutination Inhibition Tests/veterinary ; Korea/epidemiology ; Seroepidemiologic Studies

Climate change induced by recent global warming may have a significant impact on vector-borne and zoonotic diseases. For example, the distribution of Japanese encephalitis virus (JEV) has expanded into new regions. We surveyed the levels of hemagglutination-inhibition (HI) antibodies against JEV (Family Flaviviridae, genus Flavivirus) in wild birds captured in Korea. Blood samples were collected from 1,316 wild birds including the following migratory birds: Oceanodroma castro (n = 4), Anas formosa (n = 7), Anas penelope (n = 20), Fulica atra (n = 30), Anas acuta (n = 89), Anas crecca (n = 154), Anas platyrhynchos (n = 214), Aix galericulata (n = 310), and Anas poecilorhyncha (n = 488). All were captured in 16 locations in several Korea provinces between April 2007 and December 2009. Out of the 1,316 serum samples tested, 1,141 (86.7%) were positive for JEV. Wild birds captured in 2009 had a higher seroprevalence of ant-JEV antibodies than those captured in 2007. Wild birds with an HI antibody titer of 1 : 1,280 or higher accounted for 21.2% (280/1,316) of the animals tested. These findings indicated that wild birds from the region examined in our study have been exposed to JEV and may pose a high risk for introducing a new JEV genotype into Korea.
Animal Migration ; Animals ; Animals, Wild ; Bird Diseases/*epidemiology/virology ; Birds ; Encephalitis Virus, Japanese/genetics/*isolation & purification ; Encephalitis, Japanese/blood/epidemiology/*veterinary/virology ; Genotype ; Hemagglutination Inhibition Tests ; Population Surveillance ; Republic of Korea/epidemiology ; Seroepidemiologic Studies

Japanese encephalitis virus (JEV) is the leading cause of viral encephalitis in Asia and domestic pigs serve as the amplifying hosts. In the present study, the full genomic sequences of two JEV strains (HEN0701 and SH0601) isolated from pigs in China were determined and compared with other 12 JEV strains deposited in GenBank. These two strains had an 88.8% nucleotide sequence similarity and 97.9% deduced amino acid sequence homology. HEN0701 had high nucleotide sequence and high amino acid sequence identity with genotype I (GI) strains, while SH0601 had high nucleotide sequence and high amino acid sequence identity with GIII strains at both the gene and full genome levels. Further phylogenetic analysis showed that HEN0701 belonged to the JEV GI group and SH0601 was classified as a GIII strain. Analysis of codon usage showed there were a few differences between the GI and GIII strains in nucleotide composition and codon usage for the open reading frames.
Animals ; Cell Line ; Cricetinae ; Encephalitis Virus, Japanese/classification/*genetics ; Encephalitis, Japanese/epidemiology/*veterinary/virology ; Gene Expression Regulation, Viral/physiology ; Genome, Viral ; Molecular Epidemiology ; Phylogeny ; Swine ; Swine Diseases/epidemiology/*virology

Japanese encephalitis virus (JEV) is the leading cause of viral encephalitis in Asia and domestic pigs serve as the amplifying hosts. In the present study, the full genomic sequences of two JEV strains (HEN0701 and SH0601) isolated from pigs in China were determined and compared with other 12 JEV strains deposited in GenBank. These two strains had an 88.8% nucleotide sequence similarity and 97.9% deduced amino acid sequence homology. HEN0701 had high nucleotide sequence and high amino acid sequence identity with genotype I (GI) strains, while SH0601 had high nucleotide sequence and high amino acid sequence identity with GIII strains at both the gene and full genome levels. Further phylogenetic analysis showed that HEN0701 belonged to the JEV GI group and SH0601 was classified as a GIII strain. Analysis of codon usage showed there were a few differences between the GI and GIII strains in nucleotide composition and codon usage for the open reading frames.
Animals ; Cell Line ; Cricetinae ; Encephalitis Virus, Japanese/classification/*genetics ; Encephalitis, Japanese/epidemiology/*veterinary/virology ; Gene Expression Regulation, Viral/physiology ; Genome, Viral ; Molecular Epidemiology ; Phylogeny ; Swine ; Swine Diseases/epidemiology/*virology

Japanese encephalitis (JE) is an important vector-borne viral disease of humans and horses in Asia. JE outbreaks occur regularly amongst humans in certain parts of India and sporadic cases occur among horses. In this study, JE seroprevalence and evidence of JE virus (JEV) infection among horses in Haryana (India) is described. Antibodies against JEV were detected in 67 out of 637 (10.5%) horses screened between 2006 and 2010. Two foals exhibiting neurological signs were positive for JEV RNA by RT-PCR; JEV was isolated from the serum of one of the foals collected on the second day of illness. This is the first report of JEV isolation from a horse in India. Furthermore, a pool of mosquitoes collected from the premises housing these foals was positive for JEV RNA by RT-PCR. Three structural genes, capsid (C), premembrane (prM), and envelope (E) of the isolated virus (JE/eq/India/H225/2009) spanning 2,500 nucleotides (from 134 to 2,633) were cloned and sequenced. BLAST results showed that these genes had a greater than 97% nucleotide sequence identity with different human JEV isolates from India. Phylogenetic analysis based on E- and C/prM genes indicated that the equine JEV isolate belonged to genotype III and was closely related to the Vellore group of JEV isolates from India.
Animals ; Antibodies, Monoclonal ; Cloning, Molecular ; Culex/virology ; Encephalitis Virus, Japanese/*genetics/*isolation & purification ; Encephalitis, Japanese/epidemiology/*veterinary/virology ; Enzyme-Linked Immunosorbent Assay/methods/veterinary ; Female ; Genes, Viral ; Genotype ; Horse Diseases/epidemiology/*virology ; Horses ; India/epidemiology ; RNA, Viral/genetics/isolation & purification ; Reverse Transcriptase Polymerase Chain Reaction/veterinary ; Seroepidemiologic Studies

Vector-borne arboviruses produce mild to severe symptoms in domestic animals. Bovine ephemeral fever (BEF), Akabane, Aino, and Chuzan virus have been primarily attributed to reproductive disorders or febrile diseases in cattle, and Japanese encephalitis virus (JEV) is mainly associated with reproductive failures in swine. We investigated antibody titers from domestic swine against four bovine arboviruses (BEF, Akabane, Aino, and Chuzan virus) and from cattle against JEV in Korea. While the positive rates for Akabane and BEF were 37.4% and 15.7%, the positive incidence of Chuzan and Aino were relatively low, with positive rates of 3.04% and 0.4%, respectively, based on a virus neutralization assay. Antibody titers against more than one virus were also frequently detected in domestic swine. The incidence of JEV was 51.3% among domestic cattle. In addition, one positive case was detected in the thoracic fluids from 35 aborted calves, based on the hemagglutination inhibition test. Our results indicate that swine are susceptible hosts of bovine arboviruses without showing clinical symptoms in a natural environment. Moreover, we confirmed that JEV could be associated with reproductive failure in pregnant cattle, as were other vector-borne bovine arboviruses assessed in this study.
Animals ; Antibodies, Viral/blood ; Cattle ; Cattle Diseases/*epidemiology/*virology ; Encephalitis Virus, Japanese/*immunology ; Encephalitis, Japanese/blood/epidemiology/*veterinary/virology ; Ephemeral Fever/blood/*epidemiology/virology ; Ephemeral Fever Virus, Bovine/*immunology ; Hemagglutination Tests ; Incidence ; Korea/epidemiology ; Neutralization Tests ; Swine ; Swine Diseases/*epidemiology/*virology