Phlebotomine Sand Flies in Southern Thailand: Entomological Survey, Identification of Blood Meals and Molecular Detection of Trypanosoma spp.

An entomological survey at rural and cavernicolous localities in four provinces in southern Thailand provided 155 blood-fed females of sand flies (Diptera: Psychodidae) that were identified based on morphological characters as Idiophlebotomus asperulus (n = 19), Phlebotomus stantoni (n = 4), P. argentipes (n = 3), Sergentomyia anodontis (n = 20), S. barraudi (n = 9), S. hamidi (n = 23), S. hodgsoni (n = 4), S. hodgsoni hodgsoni (n = 32), S. indica (n = 5), S. iyengari (n = 2), S. khawi (n = 17), S. silvatica (n = 11) and Sergentomyia sp. (n = 6). The dominant species in this study was S. hodgsoni hodgsoni, which was collected specifically in a Buddha cave. Screening for DNA of parasitic protozoans revealed eight specimens (5.16%) of four species (S. barraudi, S. indica, S. khawi and Id. asperulus) positive for Trypanosoma sp., while no Leishmania spp. DNA was detected. Blood meals of engorged females were identified by PCR-Restriction Fragment Length Polymorphism (PCR-RFLP) assay on a fragment of cytochrome b (cyt b) gene with a success rate 36%, humans, dogs, and rats being determined as sources of blood. Bloodmeal analysis of two Trypanopsoma-positive females (S. barraudi and Sergentomyia sp.) identified blood from dogs and humans, respectively. Our findings indicate that S. barraudi, S. indica, S. khawi and Id. asperulus may be incriminated in circulation of detected Trypanosoma spp.

Thailand momentum on policy and practice in local legislation on dengue vector control.

Over a past decade, an administrative decentralization model, adopted for local administration development in Thailand, is replacing the prior centralized (top-down) command system. The change offers challenges to local governmental agencies and other public health agencies at all the ministerial, regional, and provincial levels. A public health regulatory and legislative framework for dengue vector control by local governmental agencies is a national topic of interest because dengue control program has been integrated into healthcare services at the provincial level and also has been given priority in health plans of local governmental agencies. The enabling environments of local administrations are unique, so this critical review focuses on the authority of local governmental agencies responsible for disease prevention and control and on the functioning of local legislation with respect to dengue vector control and practices.

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.

Ecologic and sociodemographic risk determinants for dengue transmission in urban areas in Thailand.

This study analyzed the association between household-level ecologic and individual-level sociodemographic determinants and dengue transmission in urban areas of Chachoengsao province, Thailand. The ecologic and sociodemographic variables were examined by univariate analysis and multivariate logistic regression. In the ecologic model, dengue risk was related to households situated in the ecotope of residential mixed with commercial and densely populated urban residential areas (RCDENPURA) (aOR = 2.23, P = 0.009), high historical dengue risk area (aOR = 2.06, P < 0.001), and presence of household window screens (aOR = 1.62, P = 0.023). In the sociodemographic model, the dengue risk was related to householders aged >45 years (aOR = 3.24, P = 0.003), secondary and higher educational degrees (aOR = 2.33, P = 0.013), household members >4 persons (aOR = 2.01, P = 0.02), and community effort in environmental management by clean-up campaign (aOR = 1.91, P = 0.035). It is possible that the preventive measures were positively correlated with dengue risk because these activities were generally carried out in particular households or communities following dengue experiences or dengue outbreaks. Interestingly, the ecotope of RCDENPURA and high historical dengue risk area appeared to be very good predictors of dengue incidences.

Estimating dengue vector abundance in the wet and dry season: implications for targeted vector control in urban and peri-urban Asia.

BACKGROUND: Research has shown that the classical Stegomyia indices (or "larval indices") of the dengue vector Aedes aegypti reflect the absence or presence of the vector but do not provide accurate measures of adult mosquito density. In contrast, pupal indices as collected in pupal productivity surveys are a much better proxy indicator for adult vector abundance. However, it is unknown when it is most optimal to conduct pupal productivity surveys, in the wet or in the dry season or in both, to inform control services about the most productive water container types and if this pattern varies among different ecological settings. METHODS: A multi-country study in randomly selected twelve to twenty urban and peri-urban neighborhoods ("clusters") of six Asian countries, in which all water holding containers were examined for larvae and pupae of Aedes aegypti during the dry season and the wet season and their productivity was characterized by water container types. In addition, meteorological data and information on reported dengue cases were collected. FINDINGS: The study reconfirmed the association between rainfall and dengue cases ("dengue season") and underlined the importance of determining through pupal productivity surveys the "most productive containers types", responsible for the majority (>70%) of adult dengue vectors. The variety of productive container types was greater during the wet than during the dry season, but included practically all container types productive in the dry season. Container types producing pupae were usually different from those infested by larvae indicating that containers with larval infestations do not necessarily foster pupal development and thus the production of adult Aedes mosquitoes. CONCLUSION: Pupal productivity surveys conducted during the wet season will identify almost all of the most productive container types for both the dry and wet seasons and will therefore facilitate cost-effective targeted interventions.

Application of eco-friendly tools and eco-bio-social strategies to control dengue vectors in urban and peri-urban settings in Thailand.

BACKGROUND: Dengue is considered one of the most important vector-borne diseases in Thailand. Its incidence is increasing despite routine implementation of national dengue control programmes. This study, conducted during 2010, aimed to demonstrate an application of integrated, community-based, eco-bio-social strategies in combination with locally-produced eco-friendly vector control tools in the dengue control programme, emphasizing urban and peri-urban settings in eastern Thailand. METHODOLOGY: Three different community settings were selected and were randomly assigned to intervention and control clusters. Key community leaders and relevant governmental authorities were approached to participate in this intervention programme. Ecohealth volunteers were identified and trained in each study community. They were selected among active community health volunteers and were trained by public health experts to conduct vector control activities in their own communities using environmental management in combination with eco-friendly vector control tools. These trained ecohealth volunteers carried out outreach health education and vector control during household visits. Management of public spaces and public properties, especially solid waste management, was efficiently carried out by local municipalities. Significant reduction in the pupae per person index in the intervention clusters when compared to the control ones was used as a proxy to determine the impact of this programme. RESULTS: Our community-based dengue vector control programme demonstrated a significant reduction in the pupae per person index during entomological surveys which were conducted at two-month intervals from May 2010 for the total of six months in the intervention and control clusters. The programme also raised awareness in applying eco-friendly vector control approaches and increased intersectoral and household participation in dengue control activities. CONCLUSION: An eco-friendly dengue vector control programme was successfully implemented in urban and peri-urban settings in Thailand, through intersectoral collaboration and practical action at household level, with a significant reduction in vector densities.

Adverse reactions of 300 MG diethylcarbamazine, and in a combination of 400 MG albendazole, for a mass annual single dose treatment, in migrant workers in Phang Nga province.

BACKGROUND: Foreign migrant workers with work permits in Thailand are given once a year 300 mg diethyl-carbamazine (DEC) for bancroftian filariasis, and 400 mg albendazole (ABZ) for helminthiasis. Treatment effectiveness, tolerability, and safety of two treatment arms, DEC + ABZ and DEC alone, had never been fully documented. OBJECTIVE: Evaluate the tolerability of the two treatment arms and analyze the effects of adverse reaction, prevalence, and intensity of both common and uncommon adverse drug reactions (ADR) in relation to the reaction time (2 hours = acute, > 2 to 24 hours = subacute, and > 24 to 72 hours = latent). MATERIAL AND METHOD: A hospital-based clinical study of on-hour-2 treatment with both treatment arms in 280 Myanmar male migrant volunteers (DEC + ABZ = 150, DEC = 130) was conducted in Phang Nga province, southern Thailand Of these, ADR evaluation at three reaction times was performed using antigenemic (WbAg+) and non-antigenemic (WbAg-) volunteer groups (DEC + ABZ/WbAg+ = 14, DEC/WbAg+ = 12, DEC + ABZ/ WbAg- = 8, andDEC/WbAg- = 16). RESULTS: Both drug groups had similarly overall ADR prevalence [5.2%for DEC + ABZ and 5. 1% for DEC (p > 0. 05)], as well as mean ADRacute scores (p > 0. 05) on hour 2 post-treatment. The four groups had maximum overall prevalence (10% to 40%for ADRsubacute). It was more likely to show no relationship between treatment arms and WbAg (neither WbAg+ nor WbAg-) with adverse reaction intensity for ADRacute, ADRsubacute, Or ADRlatent Three major specific ADR were fatigue, dizziness, and headache. CONCLUSION: Adverse reaction prevalence and intensity were independent for WbAg and treatment arm. The DEC + ABZ have no greater effects on ADR development as the DEC does. The common ADR after treatment are not required for symptomatic treatment. The study confirms DEC + ABZ regime can be safe and not toxic for use in mass treatment of those migrants in Thailand and, its value, in a mass annual single dose treatment, is beneficial for the Global Alliance to Eliminate of Lymphatic Filariasis (GAELF).

Efficacy of a single-dose treatment with 300 mg diethylcarbamazine and a combination of 400 mg albendazole in reduction of Wuchereria bancrofti antigenemia and concomitant geohelminths in Myanmar migrants in Southern Thailand.

BACKGROUND: There seems to be a large magnitude of parasitic worm loads caused by nocturnally periodic Wuchereria bancrofti and geohelminths, in cross-border Myanmar migrant workers in Thailand. We are therefore considering an effective Mass Drug Administration (MDA) with Diethylcarbamazine (DEC) and Albendazole (ABZ). Due to short periods of their residency and current situation of W. bancrofti antigenemics and concomitant geohelminths, treatment effects on the containment of the infections need to be analyzed. OBJECTIVES: Analyze short-term effects on reduction of W. bancrofti antigen (WbAg) and geohelminths' egg (GhE) loads. The efficacy of a single-dose combined treatment with 300 mg DEC (for filariasis) and 400 mg ABZ (for helminthiasis) was evaluated and compared with a single-dose treatment arm with 300 mg DEC alone. MATERIAL AND METHOD: A randomized clinical trial of two treatment choices in 28 Myanmar male workers (DEC/ABZ or group I = 15, DEC or group II = 13) was conducted in Phang Nga province, Southern Thailand. Because of the withdrawal of three subjects of the DEC group, all the 10 DEC subjects were follow-up monitored at post treatment 2, 4, 8 and 12 weeks. Their mean age was 26.4 years; worm loads (mean +/- SD x 10(3)) of W. bancrofti, Ascaris and Trichuris was 103.9 +/- 44.1 antigen units (AU)/ml, 47.3 +/- 38.7 eggs per gram (EPG) and 16.6 +/- 22.2 EPG respectively. The data on the 15 DEC/ABZ subjects showed a mean age of 25.7 years; corresponding worm loads = 96.1 +/- 54.6 AU/ml, 397.0 +/- 117.3 EPG and 54.5 +/- 42.8 EPG respectively. The Antigen Reduction Rates (ARR) and Egg Reduction Rates (ERR) were presented. RESULTS: At the 12-week post treatment, WbAg loads (mean +/- SD x 10(3) AU/ml) were 61.5 +/- 58.4 for group I and 76.8 +/- 40.7 for group II. A significant WbAg reduction was noted for both groups at weeks 8 and 12 (p < 0.05). Also, the significant reduction of GhE loads was more pronounced for both groups after week 2 (p < 0.05). When comparing efficacy of the treatment choices by the treatment retention time, it was more likely to show both groups had similar adulticidal effects on either WbAg, denoted as the ARR (F = 0. 064, p = 0.806) or GhE, denoted as the ERR (F = 0.196, p = 0.669). CONCLUSION: The single-dose 300 mg DEC plus 400 mg ABZ, or 300 mg DEC alone, can be effectively used for treating infections with W. bancrofti and concomitant geohelminths commonly observed in the area. But treatment rounds are required to clear the infections. The reduction of the parasitic worm loads in the legal Myanmar migrants provide values in monitoring and evaluating an effective MDA program with the DEC/ABZ at the provincial level.

Surveillance of imported bancroftian filariasis after two-year multiple-dose diethylcarbamazine treatment.

Myanmar migrants are at increased risk for nocturnally periodic Wuchereria bancrofti causing imported bancroftian filariasis. They have a significant influence on the effectiveness of diethylcarbamazine (DEC) mass treatment at the provincial level in the National Program to Eliminate Lymphatic Filariasis (PELF) during the fiscal years (FY) 2002-2006, in Thailand. Two oral doses of DEC 6 mg/kg are given twice a year to the eligible Myanmar migrants (> or = 2 years old). A 300 mg DEC provocation test is given once a year to all Myanmar migrants with work permits. Effectiveness evaluation parameters, such as cumulative index (CI) and the effectiveness ratio (ER), were obtained after 2 years of the multiple-dose DEC treatment program in Ranong Province, Southern Thailand. By cross-sectional night blood surveys at the end of FY 2003 in two districts of Ranong Province, the microfilarial positive rates (MPR) were 0.8% and 1.2% for Mueang Ranong and Kra Buri, respectively. The MPR in the agricultural (1.5%) and industrial (0.4%) occupations were not significantly different from each other. Our findings suggest that most untreated microfilaremics working in agriculture, with short-term residency in Thailand, may have delayed multiple-dose DEC treatment.

Short-term effects of treatment with 300 mg oral-dose diethylcarbamazine on nocturnally periodic Wuchereria bancrofti microfilaremia and antigenemia.

Seven microfilaremic Myanmar patients were treated with a single 300 mg dose of diethylcarbamazine (DEC) orally, as part of a case-finding survey in Ranong Province, Southern Thailand. This was conducted in order to evaluate the short-term effects of single-dose DEC on Wuchereria bancrofti microfilaremia and antigenemia during a 12-week course of treatment. Analysis of microfilarial periodicity on initial treatment revealed the microfilarial peak density (k) was at 52 minutes after midnight (0052). The periodicity index was then 103.26%. Single-dose DEC treatment did not affect the k values. A linear model of W. bancrofti microfilarial density reduction predicts a sharp decrease in the mean microfilarial density 2 weeks after DEC intake (Z = -2.197, p = 0.028). Over a longer period, a non-linear model predicts an increase in the mean microfilarial density to pre-treatment levels, having little or no macrofilaricidal effects. We reconfirmed the existence of nocturnally periodic W. bancrofti infection in Myanmar migrants in Ranong Province, and the short-term microfilaricidal activity of 300 mg single-dose DEC treatment used for biannual mass treatment and the DEC provocative test. Without an adequate DEC treatment dose, recrudescence can occur. A rational approach to the management of introduced nocturnally periodic W. bancrofti in Myanmar migrants, who came for short periods of stay in transmission-prone areas, is needed.

Border and imported bancroftian filariases: baseline seroprevalence in sentinel populations exposed to infections with Wuchereria bancrofti and concomitant HIV at the start of diethylcarbamazine mass treatment in Thailand.

Border bancroftian filariasis caused by Wuchereria bancrofti nocturnally subperiodic mainly exists in Karens residing alongside the Thailand-Myanmar border. Imported bancroftian filariasis caused by W. bancrofti nocturnally periodic mainly exists in cross-border Myanmar migrants. We analyzed seroprevalence data based on W. bancrofti adult worm antigen (Ag) loads and human immunodeficiency virus (HIV) immunoglobulins in the sentinel population samples which were studied prior to the start of the diethylcarbamazine (DEC) mass treatment phase in the PELF during fiscal years 2002-2006. In the Karens, the cumulative infection prevalence (36.8% serological antigen positivity or SAP) was specific for age (p < 0.001) but universal for gender (p = 0.77). The infection intensity (median Ag load = 60,827 antigen units or AU/ml) was specific for age (p = 0.031) and for males (p = 0.016). In the Myanmars, infection prevalence (24.0% SAP) was universal for age (p = 0.961) and for gender (p = 0.676). The infection intensity (median Ag load = 19,068 AU/ml) was universal for age (p = 0.433) but specific for females (p = 0.027). Overall, the Ag loads between the groups were significantly different (p = 0.014). In analysis of concomitant HIV and W. bancrofti infections, 7 (3.2%) Myanmars infected with HIV 1 and 3 (5.7%) with concomitant infections, subjected to biannual DEC treatment with 300 mg oral-dose FILADEC, were prevalent. The antigenemia clearance in the concomitant infections (r = -0.732, p = 0.039) as well as in the single W. bancrofti infection (r = -0.781, p = 0.022) was correlated with time required to clear antigenemias. We reemphasize that W. bancrofti adult worm Ag loads in the sentinel population samples would be beneficial for the PELF's implementers at the provincial level to probe the disease burdens in target areas and to evaluate and monitor the DEC treatment efficacy and effectiveness in those sentinel populations, including those with concomitant HIV eligible for the DEC mass treatment phase in the PELF.

Evaluation of a single oral dose of diethylcarbamazine 300 mg as provocative test and simultaneous treatment in Myanmar migrant workers with Wuchereria bancrofti infection in Thailand.

We assessed the efficiency of oral diethylcarbamazine (DEC) 300 mg as a provocative test on blood examination 30 minutes after administration, while gauging the overall infection rate in Myanmar migrant workers with Wuchereria bancrofti infection who enrolled for work permits in Thailand in 2002, using circulating filarial antigens (CFA) assays, the NOW ICT Filariasis card test and the Og4C3 ELISA as reference. Overall infection rates of 0.3% (95% CI=0-0.7%), 4.2% (95% CI=1.8-6.5%) and 5.9% (95% CI=3.2-8.7%) by three diagnostic tests, respectively, were observed. Among three different location groups of Myanmar population sample tested, there were no statistically significant differences in the overall infection detection rates. When either the ICT card test or the Og4C3 ELISA was used as a reference, the specificity and positive predictive value of the DEC-provocative day test was the same, 100%. The sensitivities were 25.0% (95% CI = 0.5-49.5%) and 17.6% (95% CI = 0-35.8%) on the ICT and ELISA tests, respectively. The negative predictive values were 96.8% (95% CI = 94.8-98.9%) and 95.1% (95% CI = 92.6-97.6%), respectively. In three microfilaremic persons followed-up monitored at 8-weeks DEC post-provocation, there were 6 x 10(-1) and 7 x 10(-1) decreases in microfilaremia and antigenemia. These findings suggested that, unlike the CFA assays, the DEC-provocative day test is unsuitable for the diagnosis of active W. bancrofti infection in the population tested, and for gauging current infection prevalence. The treatment would likely be beneficial to reduce microfilaremia and antigenemia.

Wuchereria bancrofti antigenemia clearance among Myanmar migrants after biannual mass treatments with diethylcarbamazine, 300 mg oral-dose FILADEC tablet, in Southern Thailand.

Using qualitative ICT Filariasis and quantitative Og4C3 ELISA, we assessed a long-term macrofilaricidal effect of two-year biannual mass treatments with a 300 mg oral-dose FILADEC tablet, a reformulation of 6 mg/kg diethylcarbamazine (DEC), on clearance of the Wuchereria bancrofti adult worm circulating filarial antigens (CFA) in Myanmar migrants, at risk of emergence of imported bancroftian filariasis in Southern Thailand. Of the 34 antigenemic Myanmar index cases of varying initial CFA levels, who were initially screened out with the ICT Filariasis, 13 index cases were follow-up treated and monitored at the DEC post treatments, 6, 12, and 18 months. At the 18-month post treatment, residual antigenemias (%) in 4 of 5 index cases (group 1) with high antigen titers (99.7-181.6 x 10(3) AU/ml) were 54.44%, 33.58%, 27.43%, and 9.97%. Significant decreases of the CFA levels in only 3 out of 5 index cases were affected by the response to DEC treatments (p < 0.007). The treatment effects on clearance of the CFA in 8 index cases (group II) with low antigen titers (15.4-37.2 x 10(3) AU/ml) were shown for at least 6 months post DEC treatment and hence had 100% efficacy in the first 6 months of the first year of year round treatment. Group I, was more likely to show an increase of the DEC efficacy after the first 6 months of the second year round treatment, but there was no statistically significant difference (p = 0.063). We reemphasized that, for use in the national program to eliminate lymphatic filariasis (PELF) in Thailand, such a DEC regimen had a macrofilaricidal effect on antigenemia clearance, and confirmed its value in evaluating response to the treatment and monitoring the long-term efficacy of the DEC regimen in W. bancrofti adult worm burden reductions in Myanmar migrants on a wide scale.

Relationship between male hydrocele and infection prevalences in clustered communities with uncertain transmission of Wuchereria bancrofti on the Thailand-Myanmar border.

A cross-sectional community-based study was conducted in three clustered communities, belonging to a single small village in Mae Chan subdistrict, Umphang district, Tak Province, close to the Thailand-Myanmar border, where regular night blood survey have been discontinued since 1997 and no epidemiological study had been conducted. In order to understand prevalences of distribution of male hydrocele and infection in clinically diagnostic and epidemiologic implications in uncertain transmission of Wuchereria bancrofti, we analyzed the relationship between male hydrocele and community infection prevalences in 219 (90.5% coverage) subjects aged > or =1 year old, including 54.8% migratory and 45.2% local Karen inhabitants. Migratory inhabitants tended to have high prevalence of antigenemia (p < 0.05) and hydrocele. Overall rates of 23.7% antigenemia, 3.7% microfilaremia, and 4.6% male hydrocele were observed. Male hydrocele prevalence was significantly correlated (r = 0.348, p < 0.0001) with antigenemia prevalence, but not with microfilaremia prevalence (r = 0.065, p = 0.493). However, high antigenemia prevalence in local inhabitants was evident, particularly antigenemia prevalence in children suggesting that transmission in the village may have occurred in recent years.