Human leukocyte antigen-associated susceptibility to pulmonary tuberculosis: molecular analysis of class II alleles by DNA amplification and oligonucleotide hybridization in Mexican patients.

BACKGROUND: Pulmonary tuberculosis (PTB) develops by a complex combination of environmental factors with genetic susceptibility. In this context, an association between human leukocyte antigens (HLAs) and tuberculosis has been examined in several populations, but results have been controversial. DESIGN AND MEASUREMENTS: A prospective evaluation of class II HLA genotypes was completed by the polymerase chain reaction (PCR) sequence-specific primer technique and PCR sequence-specific oligonucleotide hybridization in a Mexican population. SETTING: This study was conducted at the Clinical Service of Tuberculosis and the Department of Immunology, National Institute of Respiratory Diseases, Mexico City, Mexico. PATIENTS: Four groups were examined: 95 healthy subjects; 50 nonimmunosuppressed PTB patients; 15 HIV-infected patients (stage IVc in the Centers for Disease Control and Prevention [CDC] classification system for AIDS) with PTB; and 37 HIV-infected patients in the asymptomatic stage (CDC stage II). RESULTS: The frequencies of alleles DQA1*0101 (odds ratio [OR], 6.18; 95% confidence interval [CI], 2.38 to 16.08), DQB1*0501 (OR, 6.16; 95% CI, 2.44 to 17.71), and DRB1*1501 (OR, 7.92; 95% CI, 2.71 to 23.14) were significantly increased in nonimmunosuppressed patients with PTB when compared with healthy subjects. By contrast, frequencies of allele DQB1*0402 and antigens DR4 and DR8 were significantly decreased in patients with PTB. Additionally, a significantly higher frequency of the DRB1*1101 allele was found in HIV-positive subjects (OR, 6.67; 95% CI, 2.13 to 20.83). CONCLUSION: The genetic influence associated with the HLA system appears to have an important role in the development of PTB, although this susceptibility may not be relevant in patients with severe immunodeficiency diseases such as AIDS.

[Intra-domiciliary low volume spraying of malathion and deltamethrin for controlling Anopheles sp]. / Aplicación intradomiciliar de malatión y deltametrina en bajo volumen para el control de Anopheles sp.

The effectiveness of low volume (LV) house-spraying of deltamethrin 0.027 per cent and malathion 20 per cent in the control of Anopheles sp was evaluated in two villages of Tabasco, México during the last semester of 1987. Two spray rounds were carried out at three-month intervals, using Fontan R-12 back-pack-space sprayers. Residual effect and cost-benefit were evaluated and compared to the standard DDT spraying technique using the Hudson X-pert sprayer. The entomological evaluation focused on mortality rates and density levels observed from intra and peridomicilliary man biting collections, indoor mosquito resting densities, curtain trap and the standard WHO wall bioassay. It was determined that when using the LV method these insecticides were highly effective. Malathion showed a residual effect of eight weeks whereas deltamethrin was found to have a residual activity of up to 12 weeks. Deltamethrin was more effective in reducing intra and peridomiciliary biting rates, and indoor resting mosquitoes. The cost-benefit ratio of deltamethrin and malathion LV house-spraying was 2.56 and 0.89, respectively, as compared to the standard DDT house-spraying. Considering its effectiveness in anopheline control and its cost-benefit, in addition to being a functional technique, intradomicile LV insecticide spraying should be considered as a practical alternative in malaria control programs.

Determinants and predictors of dengue infection in Mexico.

A national serosurvey was conducted in Mexico from March to October 1986 to identify predictors of dengue transmission and target areas at high risk of severe annual epidemics. A total of 3,408 households in 70 localities with populations less than 50,000 were randomly sampled, and serology was obtained from one subject under age 25 years in each household. When comparing exposure and infection frequencies across the 70 communities, the authors found that median temperature during the rainy season was the strongest predictor of dengue infection, with an adjusted fourfold risk in the comparison of 30 degrees C with 17 degrees C. High temperatures increase vector efficiency by reducing the period of viral replication in mosquitoes. The proportion of houses in a community with larva on the premises was significantly associated with the community proportion infected (odds ratio (OR)adj = 1.9; 95% confidence interval (CI) 1.4-2.5), as was the proportion of households with uncovered water containers present (ORadj = 1.9; 95% CI 1.4-2.7). Because these factors have effects beyond the individual household and subjects infected from them create a risk for other subjects, both analyses of effects and organization of control efforts must be at the community level. A predictive model was constructed using the community level risk factors to classify communities as being at high, medium, or low risk of experiencing an epidemic; 57% of these communities were correctly classified using this model.

Anopheles vestitipennis, the probable vector of Plasmodium vivax in the Lacandon forest of Chiapas, México.

Baseline studies to evaluate the role of different anopheline mosquitoes as probable vectors of malaria in the Lacandon rainforest region in Chiapas (México) were carried out in 3 rural villages between June and November 1988. Anopheles vestitipennis was the most abundant species in all the villages, followed by An. albimanus, An. punctimacula and An. darlingi. Human bait collections showed that An. vestitipennis and An. albimanus tended to bite man either indoors or outdoors, while An. punctimacula preferred to bite outdoors. Monthly man-biting rates of An. vestitipennis tended to follow the rainfall pattern. Plasmodium vivax was detected in An. vestitipennis only, with an estimated overall infection rate of 4.67 per 1000 mosquitoes (range 0-54.42, of 3500 mosquitoes assayed). This is the first incrimination of An. vestitipennis as a probable vector of P. vivax in México.