Knowledge and use of preventive measures against malaria in endemic and non-endemic villages in northern Thailand.

The objective of this study was to determine the frequency and determinants of knowledge of malaria in four sites in northern Thailand, and to compare the use of prevention measures between people with and without a knowledge of malaria. An epidemiological survey was conducted in January 2002 among 857 persons living in four sites in northern Thailand. Of the 857 persons, 53% had a knowledge of malaria, ranging from 38% and 51% in non-endemic to 76% and 77% in endemic sites. Headache (89%), shivering (83%) and fever (79%) were the most frequently mentioned symptoms. Younger persons had more knowledge of malaria than older persons; adjusted Odds Ratio (aOR): 3.91 [95% confidence interval (CI): 2.32-6.56] for the 15-29 age group compared to persons 60 years and older. In comparison to men, knowledge of malaria was significantly lower among women (aOR: 2.00, 95%-CI: 1.47-2.70). Persons with knowledge reported a significantly higher use of prevention measures than persons without knowledge of malaria.

Multi-level analyses of spatial and temporal determinants for dengue infection.

BACKGROUND: Dengue is a mosquito-borne viral infection that is now endemic in most tropical countries. In Thailand, dengue fever/dengue hemorrhagic fever is a leading cause of hospitalization and death among children. A longitudinal study among 1750 people in two rural and one urban sites in northern Thailand from 2001 to 2003 studied spatial and temporal determinants for recent dengue infection at three levels (time, individual and household). METHOD: Determinants for dengue infection were measured by questionnaire, land-cover maps and GIS. IgM antibodies against dengue were detected by ELISA. Three-level multi-level analysis was used to study the risk determinants of recent dengue infection. RESULTS: Rates of recent dengue infection varied substantially in time from 4 to 30%, peaking in 2002. Determinants for recent dengue infection differed per site. Spatial clustering was observed, demonstrating variation in local infection patterns. Most of the variation in recent dengue infection was explained at the time-period level. Location of a person and the environment around the house (including irrigated fields and orchards) were important determinants for recent dengue infection. CONCLUSION: We showed the focal nature of asymptomatic dengue infections. The great variation of determinants for recent dengue infection in space and time should be taken into account when designing local dengue control programs.

Spatial patterns of and risk factors for seropositivity for dengue infection.

Spatial patterns of and risk factors for seropositivity of dengue infection were studied in three sites in northern Thailand. A survey was conducted in 2001 among 1,750 persons. Potential risk factors for dengue infection were measured by questionnaire and IgM antibodies against dengue were detected by an enzyme-linked immunosorbent assay. The role of landscape as a risk factor was studied using land cover maps and a geographic information system. Logistic regression identified risk factors for dengue seropositivity. Spatial patterns of seropositive cases were determined by cluster analyses. Six percent of the study population was seropositive. Risk factors for dengue seropositivity differed per site, demonstrating variation in local infection patterns. In the periurban site, seropositivity depended on human behavior and factors related to housing quality rather than environmental factors. In both rural sites, older persons had a higher risk of seropositivity and persons living in houses surrounded by natural and agricultural land covers had a lower risk of seropositivity.