The association between environmental factors and tuberculosis infection among household contacts.

A cross-sectional study was conducted to determine the association between environmental factors and tuberculosis infection among household contacts aged less than 15 years in Bangkok, Thailand, between May and December 2003. During the study period, 480 household contacts aged under 15 years were identified. The prevalence of tuberculosis infection among household contacts was 47.08% (95% CI = 42.60-51.56). A generalized estimating equation (GEE) indicated that the risk of positive tuberculin skin testing in household contacst was found to increase with household crowding. Children living in a crowded household were five times more likely to have tuberculosis infection (OR = 5.19, 95% CI = 2.65-8.69). The association between environmental factors and tuberculosis infection assists community tuberculosis staff in understanding the risks for tuberculosis infection in the community and planning appropriate preventive actions based on this risk.

Determination of lead toxicity in Culex quinquefasciatus mosquitoes in the laboratory.

Laboratory investigations were carried out to study the effects of lead toxicity and lead uptake on Culex quinquefasciatus mosquitoes. Three different concentrations of lead nitrate were used in laboratory tests (0.05, 0.1, and 0.2 mg/l). An atomic absorption spectrometer (AAS) was used to the determine lead concentrations. The results showed that lead significantly reduced hatching, egg-production, and emergence rates, compared with the unexposed group (p < 0.05). The ratio of female to male offspring was 3.64:1, which was observed in the second generation, after the parents were exposed to 0.2 mg/l lead. No effects were observed on oviposition preference, larval weight, or larval deformation. The LC50 of lead against Cx. quinquefasciatus larvae within 24 hours was 0.18 mg/l. There was a significant increase in lead uptake related to increased lead exposure in mosquito larvae (p < 0.05). The bioconcentration factor (BCF) showed that the lead concentration in the larvae was 62 times greater than in the water. The lead concentration from parents to offspring reduced in the first and second generations (p < 0.05). There was no significant difference between female and male mosquitoes in lead concentration (p > 0.05).

Factors associated with the household contact screening adherence of tuberculosis patients.

A cross-sectional study was conducted to explore factors associated with the adherence of tuberculosis patients in bringing their household contacts to a TB clinic in Bangkok, Thailand. During the study period, May to December 2003, 325 sputum-smear-positive tuberculosis patients were recruited into the study. Of the 325 eligible tuberculosis patients, 169 (52.00%, 95% Cl = 47.00-57.00) brought their household contacts to the TB clinic. Psychosocial and cues to action factors were examined as indicators of the household contact screening adherence of tuberculosis patients. The results reveal that the household contact screening adherence of tuberculosis patients was significantly associated with a higher perceived susceptibility (Adjusted OR = 2.90, 95% Cl = 1.18-7.16), lower perceived barriers (Adjusted OR = 4.60, 95% CI = 1.99-10.60), a higher intention to bring the contacts to the TB clinic (Adjusted OR = 3.35, 95% Cl = 1.44-7.76), and a short distance from home to the TB clinic (Adjusted OR = 11.47, 95% Cl = 4.57-28.79). The results from this study provide information for TB clinic staff for developing an appropriate intervention program. Through effective intervention and active policy enforcement, a higher percentage of household contact screening adherences can be achieved.

Risk factors for tuberculosis infection among household contacts in Bangkok, Thailand.

A cross-sectional study was conducted to determine the prevalence of tuberculosis infection and risk factors for tuberculosis infection among household contacts aged less than 15 years in Bangkok, Thailand, between August 2002 and September 2003. During the study period, 342 index cases with sputum smear positive pulmonary tuberculosis patients were recruited into the study and their 500 household contacts aged under 15 years were identified. The prevalence of tuberculosis infection among household contacts was found to be 47.80% (95%CI = 43.41-52.19). In multivariate analysis, a generalized estimating equation (GEE) was used to determine the risk factors for tuberculosis infection among household contacts. The results indicated that the risk of tuberculosis infection was significantly associated with close contact (adjusted OR = 3.31, 95%CI = 1.46-7.45), exposure to female index case (adjusted OR = 2.75, 95%CI = 1.25-6.08), exposure to mother with tuberculosis (adjusted OR = 3.82, 95%CI = 1.44-10.14), exposure to father with tuberculosis (adjusted OR = 2.55, 95%CI = 1.19-5.46), exposure to index case with cavitation on chest radiograph (adjusted OR = 4.43, 95%CI = 2.43-8.05), exposure to index case with 3+ sputum smear grade (adjusted OR = 3.85, 95%CI = 1.92-7.70), and living in crowded household (adjusted OR = 2.63, 95%CI = 1.18-5.85). The distribution of tuberculosis infection and risk factors among contact cases are significant for health care staff in strengthening and implementing tuberculosis control programs in Thailand.

Cigarette smoking and its relation to pulmonary tuberculosis in adults.

The purpose of this hospital-based case-control study is to determine the effect of passive and active smoking on pulmonary TB in adults. The study subjects were 100 new pulmonary TB cases diagnosed at TB Division, and age-sex matched 100 non-TB cases from patients admitted to Taksin Hospital and healthy subjects who came for annual physical check-up at either the outpatient clinic of the TB division or Taksin Hospital, during May 2001 to October 2001. All subjects had blood tests and only persons who were HIV-negative, DM-negative and free of other lung diseases were included. Data were collected by direct interview using questionnaires. Multivariate analysis of cigarette smoking related to pulmonary TB in adults was performed. The factors related to pulmonary TB in adults were current active smoking regardless of passive smoking exposure. There was a significant association between early age at initiation of smoking and TB. Active (current + ex-active) smokers who started smoking at age 15-20 years had a higher risk of pulmonary TB compared to others (OR = 3.18, 95% CI = 1.15-8.77); as well as the long duration of smoking: persons who had smoked >10 years had a higher risk of pulmonary TB (OR = 2.96, 95% CI = 1.06-8.22). There was a relationship between pulmonary TB and the amount of smoking exposure. Those who smoked >10 cigarettes/day (OR = 3.98, 95% CI = 1.26-12.60) or >3 days/week (OR = 2.68, 95% CI = 1.01-7.09) had higher risk of pulmonary TB compared to non-smokers. Passive smokers who were exposed to tobacco smoke >3 times/week outside the home had a higher risk of pulmonary TB than those with exposure < or =3 times/week (OR = 3.13, 95% CI = 1.07-9.17). It was also found that the effects of passive smoking in the office and/or neighborhood were strong. Persons with such exposures had a higher risk of pulmonary TB than no exposure or exposure < or =3 times/week from either or both places (OR = 4.62, 95% CI = 1.68-14.98). Therefore, an effective anti-smoking campaign is expected to have a positive repercussion on TB incidence. Smoking cessation must be considered and promoted by all levels of health care providers.