Summaryobjective To determine the frequency and determinants of knowledge of dengue infection in three sites in northern Thailand, and to compare prevention measures of people with and without knowledge of dengue.methods In May 2001 we conducted an epidemiological survey among 1650 persons living in three areas in northern Thailand. Knowledge of dengue and the use of prevention measures were measured by means of a structured questionnaire. Differences in knowledge of dengue and the use of prevention measures between risk groups were calculated by chi-square test. Logistic regression was used to identify determinants of knowledge.results Of the 1650 persons, 67% had knowledge of dengue. Fever (81%) and rash (77%) were the most frequently mentioned symptoms. Persons with knowledge of dengue reported a significantly higher use of prevention measures than persons without knowledge of dengue. In multivariate analyses, knowledge of dengue significantly differed by age, sex, occupation and site (P < 0.05). Younger people knew more about dengue than older persons: adjusted odds ratio (aOR) of 6.75 [95% confidence interval (CI): 4.32-10.6] for the 15-29 age group compared with people aged 60 and older. In comparison with farmers (reference group), knowledge of dengue was significantly higher among students (aOR: 10.6, 95% CI: 4.27-26.4), but lower among housewives or unemployed persons (aOR: 0.44, 95% CI: 0.31-0.64).conclusion The overall knowledge of dengue was high, but housewives, unemployed and old persons had relatively little knowledge of dengue. Therefore, these groups may need special attention in future dengue education programmes. Persons with knowledge of the disease more frequently reported the use of preventive measures, indicating the value of education programmes as a tool in dengue prevention.

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.

SummaryThe prevalence of the four human malaria parasites was investigated among malaria patients at northern, central and southern towns in Thailand along the border with Myanmar between September 1995 and May 1996. Thin smears obtained from 548 Thai and Burmese patients were reviewed by an acridine orange staining method, and many mixed infections with two to four species, including P. malariae and P. ovale, were detected. These diagnostic results were compared with those by two PCR-based diagnoses, microtitre plate hybridization (MPH) and a nested PCR method, both of which targets the same, species-specific regions in the 18S rRNA genes. In both PCR diagnoses, many P. malariae and P. ovale infections were also detected. Detection sensitivity of P. malariae infection was higher in nested PCR than MPH, and a total prevalence of P. malariae infection estimated by nested PCR reached 24.3% (133/548). In 16 of them, the size of PCR products amplified by the P. malariae-specific primer was about 20-bp shorter than the expected size of 115-bp. Four of 16 possessed two different bands with normal and shorter sizes, suggesting that P. malariae isolates may be separated into two types, and that those with shorter products may be new variant form (s) with a nucleotide deletion in the target region. On the other hand, 21 P. ovale infections (3.8%) were detected by nested PCR, but four of them were MPH-negative because of the sequence variation at the probe region. These results indicated that the prevalence of P. malariae and P. ovale along the ThaiMyanmar border may be substantially higher than previously reported.keywords Plasmodium malariae, Plasmodium ovale, Thailand, Myanmar, acridine orange staining, PCR diagnosis correspondence Dr F. Kawamoto,

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).

Comparative morphometric and morphological studies of microfilariae and infective stages were undertaken in nocturnally periodic and subperiodic Wuchereria bancrofti. For microfilariae, the body dimensions of nocturnally periodic (NP) were significantly smaller than nocturnally subperiodic (NSP), i.e. body length 268.03 ± 14.75 μm (NP), 307.61 ± 11.52 μm (NSP); cephalic space length 4.21 ± 0.62 μm (NP), 5.32 ± 0.79 μm (NSP); head to nerve ring 49.39 ± 5.43 μm (NP), 57.40 ± 4.46 μm (NSP); innenkörper length 33.05 ± 5.89 μm (NP), 44.02 ± 8.71 μm (NSP); cephalic space width 4.28 ± 0.59 μm (NP), 6.04 ± 0.68 μm (NSP); body width at nerve ring 5.01 ± 0.57 μm (NP), 7.45 ± 0.75 μm (NSP). The number of nuclei between the cephalic space and nerve ring of NP (66.67 ± 5.19) was also significantly less than in NSP (94.74 ± 6.95). For infective stages, the body dimensions of NP were significantly smaller than NSP, i.e. body length 1632.50 ± 131.48 μm (NP), 2002.63 ± 222.60 μm (NSP); head to nerve ring 103.09 ± 7.47 μm (NP), 122.44 ± 9.62 μm (NSP); head to oesophago-intestinal junction 567.69 ± 94.84 μm (NP), 666.75 ± 110.08 μm (NSP); body width at oesophago-intestinal junction 23.15 ± 1.55 μm (NP), 26.78 ± 1.62 μm (NSP). It is too early to infer the NP type as an additional sibling species of W. bancrofti but it is reasonable to treat it as a new variety and additional work is needed to clarify its status.