Population biology and population genetics of the vectors and their relationship with the pathogens
The study will provide the baseline data for the future application of control technologies to the field population of vectors. Research along this line involves the study on biodiversity and coevolution of vectors, pathogens and symbiotic microbes that have the potential to be used for future genetic control. Other baseline data on vectors and vector-borne pathogens such as insecticide resistance will be studied.

Vector control methodologies
This area ranges from appropriate technologies that could be applied at the community level to the molecular-based technologies for future vector control approaches. The goal of research for short-termed vector control is to improve the practical community-based vector control technologies such as insecticide-coated bed nets for malaria control or insecticide-coated resting boxes for dengue control whereas for the long term is to find cost-effective and practical vector control methodologies as well as to search for the future promising vector control approaches.

Molecular ecology of the malaria parasite population and their vector specificity in Thailand
This project aims at studying molecular ecology, population structure and epidemiology of malaria parasites and their Anopheles mosquito vectors in different areas of Thailand bordering Cambodia and Myanmar. Cloning and sequencing of ten microsatellite loci and antigen loci of Plasmodium falciparum and Plasmodium vivax, including microsatellite markers developed for Anopheles dirus will be conducted. Data will be used to determine population structure and coevolution of these parasites and their main host.

Monitoring of insecticide resistance and mapping of malaria vectors in Southeast Asia: A prerequisite for sustainable malaria vector control.
New tools for improving sustainable control of malaria vectors in Southeast Asia will be developed. An adapted monitoring system to detect early development of insecticide resistance will be set up. We will develop molecular and biochemical tests to explore the resistance mechanism involved. At the end of the project, the insecticide resistance status will be available for at least 120 sites and a decision tree for the management of operational implications will be available. A Geographic Information System (GIS) on vector distribution and insecticide resistance will be developed. We will develop a model to predict vector distribution and associations of species by environmental factors. This will be a practical tool to delineate malaria risk areas to improve the targeting of vector control and assessing the resistance status of vectors.

Suppression of dengue transmission by focal vector control
This project aims to develop a cost-effective dengue vector control model for rural communities. We hypothesize, based on our previous serological data, that suppression of dengue vectors at foci within a village and in schools will effectively reduce dengue transmission throughout the community. The identification of foci will involve an integration of serosurvey and spatial GIS mapping of the study area. Our study design should also determine whether vector control efforts in villages or in schools or both are necessary to suppress transmission. The vector control methodologies will be an environmental-friendly, integrated, community-based approach using locally-made screen covers and the combination of local BTI toxin and local predaceous crustacean for controlling mosquito larvae. Lethal ovitraps will be added to control adult vector populations.

Densoviruses as transducing vector
Our project carried out in Thailand with the aim to Survey for novel strains of densoviruses in different mosquito species, mainly in genera Aedes, Anopheles and Culex in Thailand. The densoviruses found in different species of mosquitoes will be isolated and characterized. Complete genome sequencing of these viruses will be carried out. Studying infectivity and vertical transmission of these densoviruses and also the chimeric densoviruses constructed from the Colorado State University in the mosquito vectors in order to map the genes responsible for vilurence, infectivity, vertical transmission or other viral properties. The ultimate goal of this project is to develop densovirus as the tranducing vectors to express genes in the mosquito vector in an attempt to genetically control them.

Crustacean Wolbachia: strain diversity and host effect
This project aims at studying strain diversity and distribution of Wolbachia bacteria in crustacean hosts inhabiting fresh water and intertidal zone including the mangrove forests. This group of Wolbachia bacteria is poorly known in the tropics. The crustacean Wolbachia are known to cause feminization of genetic male hosts and this property may be useful for cost-effective mass-culturing of commercial or beneficial crustaceans. In this project, the effect of crustacean Wolbachia on different hosts will be investigated. The use of feminizing property of certain Wolbachia strain in mass-rearing of crustacean copepods, a mosquito larval predator used for biological control of mosquito vectors, will be studied. The use of these feminizing strains of Wolbachia for mass-rearing of fairly shrimps for commercial purpose will also be investigated.
Molecular ecology and vector capacity of tick and mite
This project aims to survey on distribution and variation of vectors and their related pathogens and to study epidemiology and prevalence of the diseases in Thailand.

RESEARCH PROJECTS

1. Control of Disease Vectors – STEP I.U
2001-2003
Description: Continued efforts on mosquito midgut extractions. Protein fractions were used in a bioassay to detect their effect on ookinete movement. Purified fractions by gel electrophoresis and characterized by amino acid sequencing.
Status: Data Collection
Collaborators: University of North Dakota (NIH R01)

2. GIS mapping of epidemiological, entomological, and environmental data
2002-2003
Description: Initiated a study to evaluate the correlation between malaria distribution and incidence and the distribution of larval and adult vectors. GIS was used to map epidemiological, entomological, and environmental data from 1999. This data will be analyzed to determine how changes in malaria were correlated with mosquito habitat.
Status: Initiated

3. Mosquito Surveillance
2000-2003
Description: Set up further studies at the malaria study site in the vicinity of Sanghlaburi, western Thailand, established in 1999. Monthly mosquito data was obtained, GPS was used to map the village, a human database (containing name, age, sex, occupation, and house number) was established in preparation of a malaria vaccine field site.
Status: Ongoing
Collaborators: AFRIMS-GEIS

4. Lab evaluations of arthropod Repellents
2000-2003
Description: Lab evaluations of the arthropod repellents deet, AI3-37220, and CIC4 were against the mosquitoes An. minimus and An. dirus.
Status: Ongoing
Collaborators: WRAIR

5. Dengue Virus Detection Assay
2000-2003
Description: Developed primers for use in a polymerase chain reaction to detect dengue virus. These primers were developed using information derived from GENBANK and computer software. These primers were used to develop a PCR assay that can detect all four strains of dengue virus in Aedes mosquitoes. The assay did not detect any non-dengue flaviviruses that we evaluated.

6. Vector Control Studies
2000-2003
Description: Advanced evaluation lab and field site, of a lethal ovitrap, to include identification and selection of compounds that will attract mosquitoes to the ovitrap. The lethal ovitrap attracts egg-laying Aedes mosquitoes (the vectors of dengue) into a container where they are exposed to a lethal dose of an insecticide. Evidence obtained in this study indicated that the lethal ovitrap provided significant control of Aedes aegypti.
Status: Collecting data

7. Malaria Sporozoite Detect Assay
2000-2003
Description: Research advances on a malaria sporozoite dipstick assay. Results indicated that the sensitivity/specificity of initial lots were below that achieved with CS-ELISA. Evaluation of subsequent lots found that sensitivity/specificity was comparable with that of the CS-ELISA.

8. Rickettsial Diseases Ecological and Epidemiological Studies
2000-2003
Description: Determine new associations between chiggers, rodents, and Orientia tsutsugamushi in active rice agricultural areas, a ecological habitat not previously known to support scrub typhus, continued to be researched and validated.

9. Scrub Typhus Detection Research
2000-2003
Description: Continued assessment and evaluation of recombinant Antigen (r56) of scrub typhus
Status: Initiated

10. Scrub Typhus Disease Prevalence
2001-2003
Description: Continued evaluation of the current risk of scrub typhus at Thai hospitals.
Status: Data collection