Detection of Anti-ZIKV NS1 IgA, IgM, and Combined IgA/IgM and Identification of IL-4 and IL-10 as Potential Biomarkers for Early ZIKV and DENV Infections in Hyperendemic Regions, Thailand.

The frequency of Zika virus (ZIKV)-specific IgA and IgM and the cytokine expression profile of ZIKV-infected patients in hyperendemic areas remain unclear. This study investigated the rates of ZIKV non-structural protein 1 (NS1)-specific IgA and IgM and evaluated serum cytokine levels of ZIKV and Dengue virus (DENV) cases in Thailand to identify potential diagnostic biomarkers, elucidate the immunity against ZIKV and DENV, and investigate the association between cytokine levels and ZIKV symptoms. Low rates of positivity for ZIKV NS1-specific IgA and IgM were detected in our study. ZIKV NS1 IgA/M (11%, 11/101) in combination was more frequently detected than ZIKV NS1 IgM (2%, 2/101) or ZIKV NS1 IgA (4%, 4/96) alone, especially in acute ZIKV cases with previous DENV exposure (14%, 10/72). Cytokine analysis showed that both ZIKV and DENV infections induced polyfunctional immunity, and the latter triggered more prolonged responses. The existence of significant differences in IL-4 and IL-10 levels between acute ZIKV and acute DENV cases suggested that IL-4 (p = 0.0176) and IL-10 (p = 0.0003) may represent biomarkers for acute ZIKV and acute DENV infections, respectively. Analysis of the association between increased cytokine levels and ZIKV symptoms indicated that CXCL10 (p = 0.0029) was associated with exanthema, while IL-5 (p = 0.0496) was linked to headache. The detection of ZIKV NS1 IgA and IgM in combination may enhance the diagnosis of early ZIKV infection, particularly when levels of IgM or IgA alone are low or undetectable. IL-4 and IL-10 may serve as targets for the development of diagnostic tools to detect ZIKV and DENV infections early, respectively, in flavivirus-endemic regions.

Love or conflict: A qualitative study of the human-long tailed macaque interface in Nakhon Sawan Province, Thailand.

A wide range of zoonotic pathogens can be transmitted during human-wildlife interactions. Few qualitative studies have been conducted on human-nonhuman primate interfaces in Thailand, notably direct and indirect contact. Since Long-tailed macaques (LTMs) are prevalent in Thailand's Banphot Phisai district, part of Nakhon Sawan province, this qualitative study was conducted in 2019 to determine in-depth contact characteristics between humans and LTMs in the communities. Key informant interviews (KIIs) and focus group discussions (FGDs) were conducted with 35 villagers who reported close contact with LTMs in this study location. The results showed that villagers had different levels of contact with LTMs, depending on their occupations, perceptions, beliefs, religions, previous experiences, and local regulations. Monks in temples and vendors selling food for LTMs were reported to have the closest contact with them. LTMs have been reported to destroy personal property, houses, buildings, and crops. However, the villagers do not hurt them due to their religious beliefs relating to a respected abbot (a man who headed an abbey of monks). Even community members have had extensive interaction with LTMs, but they lacked awareness and information regarding diseases transmitted to humans directly or indirectly by non-human primates. Therefore, individuals who have frequent and close contact with LTMs should be provided health education, and appropriate behavioral change communication interventions should be performed. Furthermore, the results could be used to develop future disease prevention strategies and public awareness campaigns in the area.

HIV and syphilis knowledge, perceptions, and practices among Myanmar migrant workers in Samut Sakhon Province, Thailand.

BACKGROUND: Thailand has been one of the largest migration hubs in Southeast Asia for the past four decades and keeps attracting migrants from neighboring countries. Due to difficulties associated with their status, migration can place individuals at a heightened risk for sexually transmitted diseases. This study aimed to examine factors influencing HIV and syphilis preventive behaviors among Myanmar migrants in Samut Sakhon, Thailand. METHODS: A cross-sectional mixed-method study was conducted among Myanmar migrants aged 18 years and above in Samut Sakhon Province, Thailand. To fulfill this study's aims, four hundred seventy-three respondents completed a survey to provide quantitative data, and eight participants completed in-depth qualitative interviews. The factors associated with protective sexual behaviors were identified with multiple logistic regression analysis of the quantitative study data and thematic analysis of the qualitative data. RESULTS: The respondents showed good knowledge of HIV and syphilis (50.1%), but over half (55.6%) exhibited the negative perception of sexually transmitted disease prevention; about 81.4% of male respondents never used a condom when they had sexual intercourse in the past year. Based on multivariate analysis, income expenses-balance (adjusted odds ratio (AOR) = 2.379, 95% confidence interval (CI): 1.002-5.731, p = 0.049), number of sex partners (AOR = 3.044, 95% CI: 1.339-6.924, p = 0.008), and having sex with a prostitute (AOR = 6.085, 95% CI: 1.28-28.918, p = 0.023) were all statistically associated with unprotected sex. In the qualitative analysis, knowledge, understanding, beliefs; the influence of culture, community, and environment; and condom perceptions were also important factors. CONCLUSION: Low use of condoms in sexual practice was identified, and the appropriate intervention or approach to improve the utilization of condoms in the community was provided.

Arbovirus Seroprevalence Study in Bangphae District, Ratchaburi Province, Thailand: Comparison between ELISA and a Multiplex Rapid Diagnostic Test (Chembio DPP® ZCD IgG).

Arboviruses, particularly dengue virus (DENV), Zika virus (ZIKV), and Chikungunya virus (CHIKV), pose a growing threat to global public health. For disease burden estimation and disease control, seroprevalence studies are paramount. This study was performed to determine the prevalence of DENV, ZIKV, and CHIKV on healthy individuals aged from 1-55 years old in Bangphae district, Ratchaburi province, Thailand. Enzyme-linked immunosorbent assays (ELISAs) and rapid diagnostic tests (RDTs) were performed on archived samples from a dengue serological survey conducted from 2012-2015. All 2012 samples had been previously tested using an anti-DENV immunoglobulin (Ig)G ELISA, and 400 randomly selected samples stratified by age, sex, and residential area were assessed by an in-house anti-ZIKV IgG ELISA and a commercial anti-CHIKV IgG ELISA to determine virus-specific antibody levels. An RDT (Chembio DPP® ZCD IgM/IgG System) was also used to investigate the presence of antibodies against DENV, ZIKV, or CHIKV. The ELISA results indicate that the seroprevalences of DENV, ZIKV, and CHIKV were 84.3%, 58.0%, and 22.5%, respectively. The youngest age group had the lowest seroprevalence for all three arboviruses, and the seroprevalences for these viruses were progressively higher with increasing participant age. The DPP® IgG sensitivities, as compared with ELISAs, for DENV, ZIKV, and CHIKV were relatively low, only 43.92%, 25.86%, and 37.78%, respectively. The ELISA results indicate that 16% of the study population was seropositive for all three viruses. DENV had the highest seroprevalence. ZIKV and CHIKV were also circulating in Bangphae district, Ratchaburi province, Thailand. The DPP® ZCD rapid test is not sensitive enough for use in seroprevalence studies.

Rodent-Human Interface: Behavioral Risk Factors and Leptospirosis in a Province in the Central Region of Thailand.

This sequential explanatory mixed-method study consisted of analytical, cross-sectional, and qualitative studies. The research was conducted in the Khao Nor and Khao Kaew areas of the Banphot Pisai districts of Nakhon Sawan Province in 2019. Here, we examined the rodent contact characteristics of villagers in these areas and determined the potential characteristics/risk factors associated with rodents using a semi-structured questionnaire, key informant interview (KII), and focus group discussion (FGD). Results of the quantitative study (N1 = 372) characterized participants that contacted rodents per gender, age, occupation, knowledge, attitude, and practice (KAP), including their cultural contexts, and beliefs. Ninety participants (24.2%) reported contact with rodents, and the reasons for their direct physical rodent contact were hunting (35, 9.4%), killing (41, 11.0%), preparing rodents as food (33, 8.9%), consuming cooked meats (12, 3.2%), feeding food (4, 1.1%), cleaning feces (17, 4.6%), and cleaning carcasses (33, 8.9%). Moreover, logistic regression results showed that males encountering rodents were statistically significant (Adjusted OR = 3.137, 95% CI 1.914-5.139, p < 0.001). Low monthly household income (

Helminth Infections in Cattle and Goats in Kanchanaburi, Thailand, with Focus on Strongyle Nematode Infections.

Gastrointestinal helminths are major enteric parasites affecting the health of important livestock ruminants, such as cattle and goats. It is important to routinely survey these animals for helminth infections to allow effective management and control programs to be implemented. A cross-sectional helminth survey carried out in Kanchanaburi Province, Thailand, revealed the infection rate of gastrointestinal helminths in cattle (n = 157) and goats (n = 117) to be 35.7% and 88%, respectively, by microscopic fecal examination, and a 100% herd prevalence was observed in goats. Eggs of strongyle nematodes, Strongyloides spp., Trichuris spp., Capillaria spp., Paramphistomum spp., and Moniezia spp. were detected, with a relatively high rate of strongyle nematode infection in both cattle (28.7%) and goats (86.3%). Mixed infections were observed in 14.3% and 35.9% of egg-positive samples from cattle and goats, respectively. Risk factor analysis showed that dairy cattle were 5.1 times more likely to be infected with strongyles than meat cattle. In contrast, meat goats were 9.3 times more likely to be infected with strongyles than dairy goats. The inverse findings in cattle and goats are discussed. Female gender was associated with a higher risk of strongyle infection in goats. DNA sequencing and in-house semi-nested PCR with primers specific to a region in the internal transcribed spacer 2 (ITS2) were successfully used to identify strongyle genera in randomly selected egg-positive cattle (n = 24) and goat (n = 24) samples. Four strongyle genera, i.e., Cooperia spp., Haemonchus spp., Oesophagostomum spp., and Trichostrongylus spp. were identified by DNA sequencing. By semi-nested PCR, Cooperia spp. were detected as a major parasite of cattle (70.8%), whereas Haemonchus spp. were abundant in goats (100%). The majority of samples from cattle (58.3%) and goats (95.8%) were found to coinfect with at least two strongyle genera, suggesting that coinfection with multiple strongyle genera was more common than single infection in these animals.

Molecular Epidemiological Study of Hand, Foot, and Mouth Disease in a Kindergarten-Based Setting in Bangkok, Thailand.

Hand, foot, and mouth disease (HFMD) is a contagious childhood illness and annually affects millions of children aged less than 5 years across the Asia-Pacific region. HFMD transmission mainly occurs through direct contact (person-to-person) and indirect contact with contaminated surfaces and objects. Therefore, public health measures to reduce the spread of HFMD in kindergartens and daycare centers are essential. Based on the guidelines by the Department of Disease Control, a school closure policy for HFMD outbreaks wherein every school in Thailand must close when several HFMD classrooms (more than two cases in each classroom) are encountered within a week, was implemented, although without strong supporting evidence. We therefore conducted a prospective cohort study of children attending five kindergartens during 2019 and 2020. We used molecular genetic techniques to investigate the characteristics of the spreading patterns of HFMD in a school-based setting in Bangkok, Thailand. These analyses identified 22 index cases of HFMD (symptomatic infections) and 25 cases of enterovirus-positive asymptomatic contacts (24 students and one teacher). Enterovirus (EV) A71 was the most common enterovirus detected, and most of the infected persons (8/12) developed symptoms. Other enteroviruses included coxsackieviruses (CVs) A4, CV-A6, CV-A9, and CV-A10 as well as echovirus. The pattern of the spread of HFMD showed that 45% of the subsequent enteroviruses detected in each outbreak possessed the same serotype as the first index case. Moreover, we found a phylogenetic relationship among enteroviruses detected among contact and index cases in the same kindergarten. These findings confirm the benefit of molecular genetic assays to acquire accurate data to support school closure policies designed to control HFMD infections.

Seasonal prevalence, risk factors, and One Health intervention for prevention of intestinal parasitic infection in underprivileged communities on the Thai-Myanmar border.

BACKGROUND: Tha Song Yang District, located on the Thai-Myanmar border, contributes to the second highest cases of amoebic dysentery due to intestinal parasitic infections (IPI). However, there were limited disease prevalence data, specific surveillance systems, and interventions available. OBJECTIVE: This study aimed to explore the epidemiological features of the IPIs and apply the One Health (OH) approach to solve IPI-related problems. METHODS: Prevalence of asymptomatic infections in human and animals, yearly symptomatic cases, and associated risk factors were investigated. The OH intervention included improving the knowledge, attitude, and practice (KAP) of the community, microscopic diagnosis training, and stakeholder engagement for IPI prevention designs. RESULTS: The prevalence of asymptomatic cases was much higher than that of the symptomatic cases. Infective stages of the intestinal parasites were discovered in animal stool and water samples, indicating possible transmission routes. One year after the intervention, there were significant declines in asymptomatic IPIs and symptomatic cases of amoebic dysentery. Significant improvements in KAP and awareness regarding water and manure-waste management of the community were observed. CONCLUSION: We reported the successful application of the OH intervention in reducing the IPI prevalence and mitigating disease-related risks. The intervention might be applied to address other infectious diseases in the future.

Perception and belief in oral health among Karen ethnic group living along Thai-Myanmar border, Thailand.

BACKGROUND: Utilization of oral health services has been low among rural populations in Thailand, especially for minority ethnicity populations living along the borders. The aim of this study was to increase understanding of the determinants of the underutilization of oral health services among these populations. METHODS: A qualitative study using in-depth interview and semi-structured interview was conducted among participants of Karen ethnicity living in Mae Tan Sub-district, Thasongyang District, Tak Province, Thailand. The interviews focused on exploring the participants' perceptions of oral health problems, oral health and hygiene, and oral health-seeking behaviors. The verbatim-transcribed interviews were analyzed using thematic analysis. RESULTS: A total of 101 participants (50 adults and 51 children) with a Karen ethnic background took part in the interviews. Most participants could not identify oral health problems and did not perceive dental disease as a problem unless there was severe pain that could not be relieved by painkillers. The Karen ethnic community worked as subsistence farmers, and their busy daily activities consisted of farming, going to the forest to hunt and gather, performing housework, and taking care of their children. Dental health was given a lower priority compared with general health. The perceived value of primary teeth was low, which was identified as an underlying factor resulting in delayed oral health care seeking among this population. The participants had relied on self-care throughout their lifetimes, using either traditional medicines or modern painkillers to relieve toothaches. Fear of dental procedures among children was also described as a barrier to seeking dental health care. CONCLUSIONS: This study found that the lifestyle and traditions of Karen people living in this area influence their oral health care and hygiene activities as well as their health-seeking behaviors. Further research should emphasize how to improve oral health promotion by providing necessary services and health education appropriately to Karen ethnic populations living along the Thai-Myanmar border.

Molecular Identification of Enteroviruses from Cattle and Goat Feces and Environment in Thailand.

The identification and characterization of viruses of the genus Enterovirus in healthy and infected livestock, including cattle and goats, have been increasing. Enterovirus E (EV-E) and Enterovirus F (EV-F) are commonly found in cattle, whereas Enterovirus G (EV-G) is found in goats. In this study, molecular and phylogenetic analyses were performed to determine the prevalence of EVs in cattle and goat feces from Kanchanaburi Province, Thailand. The presence of EVs in water samples and the feces of other animals collected from the areas surrounding cattle and goat farms was also investigated. By use of 5'-untranslated region (5' UTR) real-time reverse transcription-PCR (RT-PCR), EVs were detected in 39.5% of cattle samples, 47% of goat samples, 35.3% of water samples, and one pool of chicken feces. Phylogenetic analysis revealed the presence of EV-E and EV-F in cattle, EV-E and EV-G in goats, and EV-F in water samples and chicken feces. Analysis of enteroviral VP1 sequences from cattle revealed that the EV-E genotypes circulating in the study region were EV-E1, with a possible new genotype that is closely related to EV-E2. Analysis of enteroviral VP1 sequences from goats suggested the circulation of EV-G5 and a possible new genotype that is closely related to EV-G20. Sequence analyses also suggested that although the VP1 sequences from goats were closely related to those of EV-G, which were considered porcine enterovirus sequences, their 5' UTRs form a separated cluster with sequences of sheep and goat origin, suggesting a new classification of the ovine/caprine-specific enterovirus group.IMPORTANCE Possible new EV-E and EV-G genotypes were identified for EVs detected in this study. The EV-E viruses were also successfully isolated from MDBK cells. The goat EV sequence analysis suggested the presence of an ovine/caprine-specific EV group that is different from EV-G of porcine origin. The significance of our research is that it identifies and characterizes possible novel EVs, thereby indicating that enteroviruses in animals are continually evolving. The facts that enteroviruses can persist in the environment, contaminate it for long periods, and be transmitted between animals raise serious concerns regarding this group of viruses as emerging livestock pathogens.

Monitoring arbovirus in Thailand: Surveillance of dengue, chikungunya and zika virus, with a focus on coinfections.

Infections caused by arboviruses such as dengue virus (DENV), chikungunya virus (CHIKV), and Zika virus (ZIKV) frequently occur in tropical and subtropical regions. These three viruses are transmitted by Aedes (Ae.) aegypti and Ae. albopictus. In Thailand, the highest incidence of arbovirus infection and the high circulation of Aedes mosquito mainly occurs in the Southern provinces of the country. Few studies have focused on the incidence of co-infection of arboviruses in this region. In the present study, a cross-sectional study was conducted on a cohort of 182 febrile patients from three hospitals located in Southern Thailand. Surveillance of DENV, CHIKV and ZIKV was conducted from May to October 2016 during the rainy season. The serological analysis and molecular detection of arboviruses were performed by ELISA and multiplex RT-PCR respectively. The results demonstrated that 163 cases out of 182 patients (89.56%) were infected with DENV, with a predominance of DENV-2. Among these DENV positive cases, a co-infection with CHIKV for 6 patients (3.68%) and with ZIKV for 1 patient (0.61%) were found. 19 patients out of 182 were negative for arboviruses. This study provides evidence of co-infection of arboviruses in Southern Thailand and highlight the importance of testing DENV and other medically important arboviruses, such as CHIKV and ZIKV simultaneously.

Variation at position 350 in the Chikungunya virus 6K-E1 protein determines the sensitivity of detection in a rapid E1-antigen test.

Chikungunya virus (CHIKV), a mosquito-borne pathogen, consists of three genotypes: East/Central/South African (ECSA), West African (WA), and Asian. Although a current rapid immunochromatographic (IC) test detecting CHIKV E1-antigen showed high sensitivity to ECSA-genotype viruses, it showed poor performance against the Asian-genotype virus that is spreading in the American continents. To understand the basis for the low performance of this IC test against Asian-genotype virus, we re-examined the anti-CHIKV monoclonal antibodies (mAbs) used in the assay for their interaction with E1-antigen of the three CHIKV genotypes. We found that the reactivity of one mAb for Asian-genotype virus was lower than that for ECSA virus. Comparison of E1 amino acid sequences revealed that the ECSA virus used to generate these mAbs possesses glutamic acid (E) at position 350, in contrast to WA and Asian, which possess aspartic acid (D) at this position. Site-directed mutagenesis confirmed that the mutation altered mAb reactivity, since E-to-D substitution at position 350 in ECSA reduced recognition by the mAb, while D-to-E substitution at this position in Asian and WA increased affinity for the mAb. Taken together, these results indicate that residue 350 of the CHIKV 6K-E1 is a key element affecting the performance of this IC assay.

Obesity prevalence and contributing factors among adolescents in secondary schools in Pemagatshel district, Bhutan.

Background The prevalence of obesity has increased globally, with childhood and adolescent obesity being more common in developed countries. There has been no study on teenage obesity in Bhutan. In this study, we aimed to assess the prevalence of obesity in Bhutan for the first time in order to provide a baseline for future researchers. Methods The investigation, which included 392 adolescents, aimed to identify the prevalence of overweight and obesity and its contributing factors. Anthropometric measurements, food recall and knowledge, attitude, behaviour and environment questionnaires were administered. The body mass index (BMI) cut-off points for adolescents matched with those of the US Centers for Disease Control and Prevention. Results The prevalence of overweight and obesity among the participants were 7.1% and 1.5%, respectively. The prevalence of obesity was 1.0% in females and 0.5% in males (p < 0.001). There were significant (p < 0.001) correlations between BMI and other variables; however, Pearson's χ2 test uncovered no significant associations. BMI also had no significant associations with attitude, behaviour, environment and distance travelled to school. Food recall results revealed the following findings for average food consumption: total energy intake, 3522.6 kcal; fat, 47.6 g; carbohydrate, 690.2 g; protein, 90.5 g; fibre, 20.3 g; and sodium, 12.5 g. Conclusion The results of this study clarified the prevalence of obesity among adolescents in Bhutan, who require appropriate strategies for combating overweight and obesity.

Molecular genotyping of human papillomavirus l1 gene in low-risk and high-risk populations in Bangkok.

BACKGROUND: Human papillomavirus (HPV) infections in Thailand are a public health concern, but information on HPV infection in sex workers and men who have sex with men (MSM) is limited. The aim of this study was to measure the prevalence and genotype distribution of HPV among low- and high-risk, HIV-negative populations. METHODS: A total of 300 participants were categorized as general women, female sex workers, MSM, and MSM sex workers. Human papillomavirus infections were identified by the Papanicolaou test and nested polymerase chain reaction. A phylogenetic analysis of partial HPV L1 genes was performed. RESULTS: Abnormal cytology was found in 5% of general women, 10% of female sex workers, 24% of MSM, and 28% of MSM sex workers. Human papillomavirus was detected in 9% of general women, 13% of female sex workers, and 30% in both MSM and the MSM sex workers. The prevalence of HPV high-risk genotypes was significantly higher in female sex workers and MSM, whereas low-risk genotypes and genital warts were significantly higher in MSM sex workers. Significantly more patients with genital warts and cervical intraepithelial neoplasia I/anal intraepithelial neoplasia I harbored low-risk genotypes, whereas those with cervical intraepithelial neoplasia II/anal intraepithelial neoplasia II harbored high-risk genotypes. CONCLUSIONS: High- and low-risk HPV genotypes persist in high-risk groups in Bangkok. Some genotypes infecting at-risk populations are not vaccine preventable. These findings may help to elucidate the prevalence of HPV infections in Thailand and serve as the basis for additional investigations into risk factors for these populations.

Chikungunya virus was isolated in Thailand, 2010.

Chikungunya fever (CHIKF) is an acute febrile illness caused by a mosquito-borne alphavirus, chikungunya virus (CHIKV). This disease re-emerged in Kenya in 2004, and spread to the countries in and around the Indian Ocean. The re-emerging epidemics rapidly spread to regions like India and Southeast Asia, and it was subsequently identified in Europe in 2007, probably as a result of importation of chikungunya cases. On the one hand, chikungunya is one of the neglected diseases and has only attracted strong attention during large outbreaks. In 2008-2009, there was a major outbreak of chikungunya fever in Thailand, resulting in the highest number of infections in any country in the region. However, no update of CHIKV circulating in Thailand has been published since 2009. In this study, we examined the viral growth kinetics and sequences of the structural genes derived from CHIKV clinical isolates obtained from the serum specimens of CHIKF-suspected patients in Central Thailand in 2010. We identified the CHIKV harboring two mutations E1-A226V and E2-I211T, indicating that the East, Central, and South African lineage of CHIKV was continuously circulating as an indigenous population in Thailand.

Border malaria associated with multidrug resistance on Thailand-Myanmar and Thailand-Cambodia borders: transmission dynamic, vulnerability, and surveillance.

This systematic review elaborates the concepts and impacts of border malaria, particularly on the emergence and spread of Plasmodium falciparum and Plasmodium vivax multidrug resistance (MDR) malaria on Thailand-Myanmar and Thailand-Cambodia borders. Border malaria encompasses any complex epidemiological settings of forest-related and forest fringe-related malaria, both regularly occurring in certain transmission areas and manifesting a trend of increased incidence in transmission prone areas along these borders, as the result of interconnections of human settlements and movement activities, cross-border population migrations, ecological changes, vector population dynamics, and multidrug resistance. For regional and global perspectives, this review analyzes and synthesizes the rationales pertaining to transmission dynamics and the vulnerabilities of border malaria that constrain surveillance and control of the world's most MDR falciparum and vivax malaria on these chaotic borders.

T helper (Th) 1 and Th2 cytokine expression profile in dengue and malaria infection using magnetic bead-based bio-plex assay.

Dengue and malaria infections are two very common vector-borne diseases annually affecting millions of people around the world. Both diseases show a variety of clinical presentations, ranging from mild symptoms of dengue fever (DF) to severe dengue hemorrhagic fever (DHF) in dengue infection, and low and high parasitemia in malaria infection. T helper (Th)1 and Th2 cytokine expressions in mild and severe forms of dengue virus type-2 (DENV-2) and Plasmodium falciparum infection, were compared to normal human sera using high throughput magnetic bead-based Bio-Plex assay. A significant elevation of Th1 and Th2 cytokines expression [interleukin (IL)-2, IL-4, IL-5, IL-10, IL-13, granulocyte-macrophage colony-stimulating factor (GM-CSF), interferon (IFN)-gamma, and tumor necrosis factor (TNF)-alpha] was detected in DENV-2 and P. falciparum malaria infections compared with normal controls (p < 0.05). DENV-2 infection showed a slight higher expression of Th1 and Th2 cytokines in DHF than DF, except for IL-13. In P. falciparum infection, high parasitemia showed a significantly higher expression of IL-4, IL-10, GM-CSF, and TNF-alpha (p < 0.05). Both DENV-2 and P. falciparum malaria infections manifested high IL-10 expression, greatest among the cytokines examined, and in the severe forms of infection. The results of this study should lead to a better understanding of pathogenesis of dengue infection and P. falciparum malaria.

Malaria-associated rubber plantations in Thailand.

Rubber forestry is intentionally used as a land management strategy. The propagation of rubber plantations in tropic and subtropic regions appears to influence the economical, sociological and ecological aspects of sustainable development as well as human well-being and health. Thailand and other Southeast Asian countries are the world's largest producers of natural rubber products; interestingly, agricultural workers on rubber plantations are at risk for malaria and other vector-borne diseases. The idea of malaria-associated rubber plantations (MRPs) encompasses the complex epidemiological settings that result from interactions among human movements and activities, land cover/land use changes, agri-environmental and climatic conditions and vector population dynamics. This paper discusses apparent issues pertaining to the connections between rubber plantations and the populations at high risk for malaria. The following questions are addressed: (i) What are the current and future consequences of rubber plantations in Thailand and Southeast Asia relative to malaria epidemics or outbreaks of other vector-borne diseases? (ii) To what extent is malaria transmission in Thailand related to the forest versus rubber plantations? and (iii) What are the vulnerabilities of rubber agricultural workers to malaria, and how contagious is malaria in these areas?

Natural transovarial dengue virus infection rate in both sexes of dark and pale forms of Aedes aegypti from an urban area of Bangkok, Thailand.

Transovarial dengue virus infection status of two forms of adult Aedes aegypti (dark or Ae. aegypti type form and pale or form queenslandensis), reared from field-collected larval and pupal stages, was determined by one-step RT-PCR and dengue viral serotype by nested-PCR. Natural transovarial transmission (TOT) of dengue virus was detected in the two Ae. aegypti forms, and in both adult males and females. Male Ae. aegypti had a higher rate of TOT dengue virus infection than female. The overall minimum infection rate among the male and female populations was 19.5 and 12.3 per 1,000 mosquitoes, respectively. All four dengue serotypes were detected in mosquito samples, with DEN-4 being the predominant serotype. Thus, both male and female Ae. aegypti have influences on the epidemiology of dengue virus transmission.

Protein expression in the salivary glands of dengue-infected Aedes aegypti mosquitoes and blood-feeding success.

Mosquito salivary glands (SG) play an essential role in food digestion and pathogen transmission. The function of the salivary components during infection is poorly understood. In this study, female Aedes aegypti mosquitoes were infected with dengue virus serotype 2 (DENV-2) via an artificial membrane feeding apparatus. The mosquito SGs were examined for DENV-2 infection for 14 days post-infection (dpi). The amount of dengue virus increased throughout the 14 dpi. Three different meals were provided for the Ae. aegypti mosquitoes. SG protein expression was compared among sugar-fed (SF), blood-fed (BF), and dengue-infected blood-fed (DF) mosquitoes using SDS-PAGE coupled with densitometric analysis. The SG of SF mosquitoes had fewer protein bands than those of BF and DF mosquitoes. The major SG proteins seen among BF and DF mosquitoes had molecular weights of 12-15, 25-30, 35-40, 45-50, 55-60 kDa and 61-67 kDa. We compared the SG protein band expression profiles in BF and DF mosquitoes. Two bands (35-40 and 61-67 kDa) were expressed more by DF mosquitoes and 3 different bands (25-30, 45-50, and 55-60 kDa) were expressed more by BF mosquitoes. These SG proteins may have some role in facilitating blood-feeding and dengue infection. We speculate these specific SG proteins in dengue-infected mosquitoes may increase the chance of blood-feeding and virus transmission by infected mosquitoes. These results may be useful for designing additional tools to investigate the interaction between Ae. aegypti SG and the dengue virus.