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Papers by Chitti Chansang

On Ko Samui, Thailand there were two epidemics of dengue hemorrhagic fever (DHF) in 1966 and 1967... more On Ko Samui, Thailand there were two epidemics of dengue hemorrhagic fever (DHF) in 1966 and 1967, followed by endemics up to 1994. Aedes aegypti and Aedes albopictus were the vectors. From January to July 1995, 51 cases of DHF were reported, out of these were many foreigners who still suffer from dengue fever and return home with negative impression.

The American journal of tropical medicine and hygiene, 2007

Dengue hemorrhagic fever is a major public health problem in several countries around the world. ... more Dengue hemorrhagic fever is a major public health problem in several countries around the world. Dengue vector surveillance is an important methodology to determine when and where to take the control action. We used a combination of the Global Positioning System (GPS)/Geographic Information System (GIS) technology and the immature sampling count method to improve dengue vector surveillance. Both complete count and sampling count methods were used simultaneously to collect immature dengue vectors in all houses and all containers in one village in eastern Thailand to determine the efficiency of the sampling count technique. A hand-held GPS unit was used to record the location of surveyed houses. Linear regression indicated a high correlation between total immature populations resulting from the complete count and estimates from sampling count of immature stages. The immature survey data and the GPS coordinates of house location were combined into GIS maps showing distribution of immat...

Journal of vector ecology : journal of the Society for Vector Ecology, 2001

A 1995 outbreak of dengue haemorrhagic fever (DHF) occurred on Samui Island in Thailand with an i... more A 1995 outbreak of dengue haemorrhagic fever (DHF) occurred on Samui Island in Thailand with an incidence of almost 500 cases/100,000 population. To find and develop effective strategies to control this disease through cost-effective vector control programs, entomological studies were carried out on the island between 1996 and 1998. There were two species of DHF vectors, Aedes aegypti and Ae. albopictus prevailing on the island, and the population of Ae. aegypti remained relatively constant throughout the year while the abundance of Ae. albopictus increased substantially during the rainy season (May-December) and then declined drastically in the dry season (January-April). The ranges of the three Aedes larval indices, Breteau index (BI), house index (HI) and container index (CI) were 93-310, 43-89 and 16-50 respectively. The ceramic or earthen jars both inside and outside the dwellings and concrete water storage tanks (mostly in toilets and bathrooms) served as the main breeding pla...

The Southeast Asian journal of tropical medicine and public health, 2007

Tablet (40 mg a.i./tablet) and granular (2% a.i.) formulations of diflubenzuron, a chitin synthes... more Tablet (40 mg a.i./tablet) and granular (2% a.i.) formulations of diflubenzuron, a chitin synthesis inhibitor, insect growth regulator, were evaluated for larvicidal efficacy against the larvae of Aedes aegypti (L.) in water-storage containers under field conditions in Thailand. Each formulation was applied to 200-1 clay jars at 5 different dosages (0.02, 0.05, 0.1, 0.5 and 1 mg/l a.i.). The jars were covered with solid celocrete sheets and placed in the shade under a roof. Another experiment was also carried out using 3 different dosages (0.1, 0.5 and 1 mg/l) where half the water in each treated jar and the control was removed and refilled weekly. Each treatment was replicated four times. The treatments were challenged by adding 25 3rd instar larvae/jar weekly. Assessments were made of each treatment through emergence inhibition (%EI) by removing and counting pupal skins one week after larval addition. Using these assessment techniques, a high degree of larvicidal efficacy (96-100%...

International Journal of Environmental Research and Public Health, 2014

Dengue and malaria are vector-borne diseases and major public health problems worldwide. Changes ... more Dengue and malaria are vector-borne diseases and major public health problems worldwide. Changes in climatic factors influence incidences of these diseases. The objective of this study was to investigate the relationship between vector-borne disease incidences and meteorological data, and hence to predict disease risk in a global outreach tourist setting. The retrospective data of dengue and malaria incidences together with local meteorological factors (temperature, rainfall, humidity) registered from 2001 to 2011 on Koh Chang, Thailand were used in this study. Seasonal distribution of disease incidences and its correlation with local climatic factors were analyzed. Seasonal patterns in disease transmission differed between dengue and malaria. Monthly meteorological data and reported disease incidences showed good predictive ability of disease transmission patterns. These findings provide a rational basis for identifying the predictive ability of local meteorological factors on disease incidence that may be useful for the implementation OPEN ACCESS of disease prevention and vector control programs on the tourism island, where climatic factors fluctuate.

PLoS Neglected Tropical Diseases, 2013

Background: The genetic population structure of Aedes (Stegomyia) aegypti (L.), the main vector o... more Background: The genetic population structure of Aedes (Stegomyia) aegypti (L.), the main vector of dengue virus, is being investigated in areas where a novel dengue suppression program is to be implemented. The aim of the program is to release and establish mosquito populations with impaired virus transmission capabilities. To model effects of the release and devise protocols for its implementation, information about the genetic structure of populations at a range of spatial scales is required.

Tropical Medicine and International Health, 2003

An intense epidemic of dengue haemorrhagic fever in 1998 prompted the Thai government to investig... more An intense epidemic of dengue haemorrhagic fever in 1998 prompted the Thai government to investigate the feasibility of focalized vector (Aedes aegypti) control programmes. We tested for correlations of three indices of Aedes larval abundance (housing index, container index and Breteau index) against 38 socio-economic and four climatic variables. Availability of public water wells, existence of transport services and proportion of tin houses were positively associated with larval indices. Private water wells, health education, health insurance coverage, thatched houses and use of firewood for cooking were negatively associated. These probably represent both direct effects on breeding sites (private vs. public wells decrease necessity to store water, and health education may encourage breeding site removal), and more general effects of health-related attitude, housing quality and remoteness from urban areas. Indices were positively associated with daily minimum temperature, an increase in precipitation from the previous month (reflecting the onset of the rainy season) and daily maximum temperatures of approximately 33-34 °C.

Journal of the American Mosquito Control Association, 2006

Studies of blood-feeding behavior of mosquito vectors of Dengue Haemorrhagic Fever (DHF) and mala... more Studies of blood-feeding behavior of mosquito vectors of Dengue Haemorrhagic Fever (DHF) and malaria have been continuously carried out in Thailand, whereas those of encephalitis and filariasis are scanty because of difficulty methodology and high risk of infection. To get more information for disease control, we then studied on blood sources, biting time and behavior of mosquito vectors in an endemic area of encephalitis and filariasis. Animal-baited

Frequencies of blood meals and survival rates of vector mosquitoes are important parameters influ... more Frequencies of blood meals and survival rates of vector mosquitoes are important parameters influencing transmission efficiency of pathogens. We applied the time series analysis proposed by Holmes and Birley (1987) for estimation of gonotrophic cycle lengths and survival rates of Culex tritaenio- rhynchus and Cx. gelidus, Japanese encephalitis (JE) vectors in Thailand. Females of these species were collected at a