Narong Nitatpattana

Change in Japanese Encephalitis Virus Distribution,Thailand

Japanese encephalitis virus (JEV) genotypes in Thailand were studied in pigs and mosquitoes collected near houses of confirmed human JEV cases in 2003–2005. Twelve JEV strains isolated belonged to genotype I, which shows a switch from genotype III incidence that started during the 1980s.

Detection of chikungunya virus antigen by a novel rapid immunochromatographic test.

ABSTRACT Chikungunya fever is a mosquito-borne disease of key public health importance in tropical and subtropical countries. Although severe joint pain is the most distinguishing feature of chikungunya fever, diagnosis remains difficult because the symptoms of chikungunya fever are shared by many pathogens, including dengue fever. The present study aimed to develop a new immunochromatographic diagnosis test for the detection of chikungunya virus antigen in serum. Mice were immunized with isolates from patients with Thai chikungunya fever, East/Central/South African genotype, to produce mouse monoclonal antibodies against chikungunya virus. Using these monoclonal antibodies, a new diagnostic test was developed and evaluated for the detection of chikungunya virus. The newly developed diagnostic test reacted with not only the East/Central/South African genotype but also with the Asian and West African genotypes of chikungunya virus. Testing of sera from patients suspected to have chikungunya fever in Thailand (n = 50), Laos (n = 54), Indonesia (n = 2), and Senegal (n = 6) revealed sensitivity, specificity, and real-time PCR (RT-PCR) agreement values of 89.4%, 94.4%, and 91.1%, respectively. In our study using serial samples, a new diagnostic test showed high agreement with the RT-PCR within the first 5 days after onset. A rapid diagnostic test was developed using mouse monoclonal antibodies that react with chikungunya virus envelope proteins. The diagnostic accuracy of our test is clinically acceptable for chikungunya fever in the acute phase.

Elevated Japanese encephalitis virus activity monitored by domestic sentinel piglets in Thailand.

Twenty-nine domestic piglets from pig farms located in three provinces of Thailand between 2003 and 2004 were used as sentinel animals for Japanese encephalitis virus (JEV) circulation. Piglets were used as sentinel to underline, on one hand, the role of domestic pigs as JEV amplifying host and, on another hand, to point out the interest of using sentinel animals for Japanese encephalitis surveillance. JEV activity was demonstrated through i/ antibody detection using a specific ELISA test for the identification of Immunoglobulins of class M and G, ii/ virus isolation on cell culture, after experimental mosquito inoculation for virus amplification. Almost 100% and 83% of the piglets, respectively, had specific IgG and IgM JEV antibodies and 35% yielded a virus isolate. Piglets of the growing farm industry act as virus amplifier increasing the risk of transmission for the human community. Conclusively, since piglets JEV infection appears early in life and is generally clinically unnoticed, it represents an exceptional sentinel model for human health threats, which has to be considered by health authorities.

Geographic dynamics of viral encephalitis in Thailand.

Viral encephalitis (VE) continues to be a major disease in Asia, causing serious illness which may result in death or have neurological sequelae. This study involves an ecological analysis of the climatic, geographic and seasonal patterns of clinically reported VE in Thailand from 1993 to 1998 to investigate regional and seasonal differences in disease incidence. Three thousand eight hundred and twenty nine cases of VE were clinically diagnosed nationwide during the study period by the Thai Ministry of Public Health. Spearman rank correlations of temporal, spatial and geographic variables with disease incidence were performed. The monthly incidence of VE correlated significantly with seasonal changes in temperature, relative humidity and rainfall in the north-northeast region of Thailand (P < 0.001), whereas incidence in the south-central region correlated only with relative humidity (P = 0.003). Spatial analysis revealed a positive correlation of disease with elevation (P < 0.001), and negative correlations with rice-field cover (P < 0.001), agricultural land-use (P < 0.001) and temperature (P = 0.004) in the north-northeast region. No significant spatial correlation was identified in the south-central region. The spatial distribution of VE suggests that etiologic variations may be responsible, in part, for the geographic patterns of disease. Active etiologic surveillance is necessary in a variety of geographic settings in order to provide physicians with information necessary for disease prevention and clinical management.

Hantaan virus antibody prevalence in rodent populations of several provinces of northeastern Thailand

We conducted a serological survey of 632 rodents from the northeast region of Thailand in order to assess the presence of Hantaan‐like viruses that may be a risk to the human population. Rodents were collected from rice fields, houses and domestic gardens in five northeastern provinces and tested for IgG reacting sera to Hantaan antigen using enzyme‐linked immunoassays. The overall prevalence of Hantavirus infection in rodents was 2.1% (13/632). Species that tested positive included Bandicota indica (4.3% positive within species), Rattus exulans (2.1%), R. losea (1.6%) and R. rattus (0.9%). Species such as R. exulans and R. losea are candidate hosts of unidentified Hantaan‐like viruses in Thailand.

Dengue, Japanese encephalitis and Chikungunya virus antibody prevalence among captive monkey (Macaca nemestrina) colonies of Northern Thailand.

The potential of macaque Macaca nemestrina leonina in Thailand to be infected by endemic arboviruses was assessed. The prevalence of antibodies of three arboviruses actively circulating in Thailand was determined by Plaque Reduction Neutralization assay procedures using samples from captive colonies in Northern Thailand. Out of 38 macaques, 9 (24%) presented reacting antibodies against dengue virus, 5 (13%) against Japanese encephalitis virus, and 4 (10%) against Chikungunya virus. Our results indicate that the northern pig‐tailed macaque in Thailand can be infected by these arboviruses, inferring therefore that their virus specific vectors have bitten them. Given that, northern pig‐tailed macaque represents an abundant population, living in close range to human or in peridomestic setting, they could play a role as potential reservoir host for arboviruses circulating in Thailand. Am. J. Primatol. 76:97–102, 2014.

Generation and preclinical evaluation of a DENV-1/2 prM+E chimeric live attenuated vaccine candidate with enhanced prM cleavage.

In the absence of a vaccine or sustainable vector control measures, illnesses caused by dengue virus infection remain an important public health problem in many tropical countries. During the export of dengue virus particles, furin-mediated cleavage of the prM envelope protein is usually incomplete, thus generating a mixture of immature, partially mature and mature extracellular particles. Variations in the arrangement and conformation of the envelope proteins among these particles may be associated with their different roles in shaping the antibody response. In an attempt to improve upon live, attenuated dengue vaccine approaches, a mutant chimeric virus, with enhanced prM cleavage, was generated by introducing a cleavage-enhancing substitution into a chimeric DENV-1/2 virus genome, encoding the prM+E sequence of a recent DENV-1 isolate under an attenuated DENV-2 genetic background. A modest increase in virus specific infectivity observed in the mutant chimeric virus affected neither the attenuation phenotype, when assessed in the suckling mouse neurovirulence model, nor multiplication in mosquitoes. The two chimeric viruses induced similar levels of anti-DENV-1 neutralizing antibody response in mice and rhesus macaques, but more efficient control of viremia during viral challenge was observed in macaques immunized with the mutant chimeric virus. These results indicate that the DENV-1/2 chimeric virus, with enhanced prM cleavage, could be useful as an alternative live, attenuated vaccine candidate for further tests in humans.

Correction for Okabayashi et al., Detection of Chikungunya Virus Antigen by a Novel Rapid Immunochromatographic Test

Volume 53, no. 2, p. [382–388][1], 2015. Page 384, Fig. 1: Incorrect images were mistakenly placed in the second (Thai), fourth (S27), and sixth (SV) columns in the row labeled “Alphavirus Antibody.” The figure should appear as shown below. ![Figure][2] Page 385, Table 2: Several