Genetic and household determinants of predisposition to human hookworm infection in a Brazilian community.

BACKGROUND: Predisposition to heavy or light human hookworm infection is consistently reported in treatment-reinfection studies. A significant role for host genetics in determining hookworm infection intensity has also been shown, but the relationship between host genetics and predisposition has not been investigated. METHODS: A treatment-reinfection study was conducted among 1302 individuals in Brazil. Bivariate variance components analysis was used to estimate heritability for pretreatment and reinfection intensity and to estimate the contribution of genetic and household correlations between phenotypes to the overall phenotypic correlation (ie, predisposition). RESULTS: Heritability for hookworm egg count was 17% before treatment and 25% after reinfection. Predisposition to heavy or light hookworm infection was observed, with a phenotypic correlation of 0.34 between pretreatment and reinfection intensity. This correlation was reduced to 0.23 after including household and environmental covariates. Genetic and household correlations were 0.41 and 1, respectively, and explained 88% of the adjusted phenotypic correlation. CONCLUSIONS: Predisposition to human hookworm infection in this area results from a combination of host genetics and consistent differences in exposure, with the latter explained by household and environmental factors. Unmeasured individual-specific differences in exposure did not contribute to predisposition.

Older smokers' motivation and attempts to quit smoking: epidemiological insight into the question of lifestyle versus addiction.

BACKGROUND: Much media attention currently focuses on demands from the organized medical profession in Germany for an altered legal framework regarding remuneration for smoking-cessation interventions. With this development, the question whether smoking is an autonomously chosen lifestyle or, alternatively, an addiction constituting a disease in its own right has once again come to the fore of public debate. METHODS: In a population-based study in the German state of Saarland, 10,000 persons aged 50 to 74 were questioned about their health-related behavior and medical history. The frequency of attempts to quit smoking, and of the motivation to do so, was analyzed in relation to the total number of smokers in the survey and was stratified with respect to existing illnesses whose cardiovascular risk potential is exacerbated by smoking. RESULTS: Among 1528 persons who were smokers at the beginning of the study, 76% (95% confidence interval [CI]: 73.7%-78.0%) reported having tried to quit at least once. Among smokers with existing high-risk conditions, this figure was higher, reaching 89% (CI: 83.1%-93.0%) in smokers with known cardiovascular disease. Only 11% of the smokers were content with their smoking behavior; 30% said they wanted to cut down, and 59% said they wanted to quit smoking entirely. CONCLUSIONS: Most older smokers in Germany would like to quit smoking and have tried to do so repeatedly without success. In particular, high-risk patients with comorbidities, whose number will further increase as the population ages, are highly motivated to quit smoking and would derive major benefit from effective assistance with smoking cessation. The description of smoking as an autonomously chosen lifestyle appears cynical and deserves to be vigorously rejected.

Microscopic and sub-microscopic Plasmodium falciparum infection, but not inflammation caused by infection, is associated with low birth weight.

Pregnancy-associated malaria is one of the leading causes of low birth weight in malaria endemic areas. In this study, 145 parturient women residing in areas endemic for Plasmodium falciparum in Lambaréné, Gabon, were recruited into the study after delivery, and the association of maternal P. falciparum infection, inflammatory response, and birth weight was studied. At delivery, 10% (15) of the mothers (12 were positive in both peripheral and placental blood smears, 1 was positive in peripheral blood only, and 2 were positive in placenta blood only) were positive for P. falciparum by microscopy and 23% (30) by real-time polymerase chain reaction (PCR). The level of C-reactive protein (CRP) was significantly elevated in microscopically P. falciparum-positive pregnant women (34 mg/L; 95% CI: 3-458) but not in those with sub-microscopic infections (6 mg/L; 95% CI: 1-40) compared with those free of P. falciparum infection (7 mg/L; 95% CI: 1-43). In a multivariate analysis, the presence of microscopic (adjusted OR = 28.6, 95% CI = 4.8-169.0) or sub-microscopic (adjusted OR = 13.2, 95% CI = 2.4-73.0) P. falciparum infection in pregnant women and age of mothers < 21 years (adjusted OR = 9.7 CI = 1.0-89.7), but not CRP levels, were independent predictors for low birth weight. This finding may have important operational implications and emphasizes the need for appropriate diagnostic methods in studies evaluating the outcome of pregnancy-associated malaria.

Effectiveness of quinine monotherapy for the treatment of Plasmodium falciparum infection in pregnant women in Lambaréné, Gabon.

Pregnant women participating in a longitudinal immuno-epidemiologic survey in Lambaréné, Gabon, and presenting with Plasmodium falciparum parasitemia at monthly blood smear examinations were offered treatment with oral 7-day quinine monotherapy according to national health guidelines. A total of 50 pregnant women were offered 7-day oral quinine sulfate 10 mg/kg thrice daily. Clinical examinations and laboratory tests were performed on Days 28 and 56 to assess the effectiveness of this standard regimen. By Day 28, the effectiveness of the 7-day quinine regimen was 60% (95% confidence interval: 46-72%). We conclude that a 7-day course of quinine has a poor effectiveness and that alternative treatment regimens for malaria in pregnant women should be assessed.

Incidence of blindness during the Onchocerciasis control programme in western Africa, 1971-2002.

BACKGROUND: Infection with Onchocerca volvulus is associated with the prevalence of severe visual impairment and blindness. However, longitudinal studies of the incidence of blindness caused by onchocerciasis are scarce. METHODS: The relationship, at the individual level, between infection with O. volvulus microfilariae and bilateral blindness was examined, by use of data collected, during the Onchocerciasis Control Programme in western Africa (OCP), from 2315 villages in 11 countries. The data were analyzed by Poisson maximum-likelihood techniques with adjustment for overdispersion. RESULTS: A total of 297,756 persons were eligible for follow-up in the cohort, and, during 1971-2001, these persons accumulated 367,788 person-years of follow-up without blindness. A total of 673 bilateral cases of blindness occurred during this period; 29.7% were caused by onchocerciasis. After ivermectin therapy was introduced (during 1988-2001), only 19.6% of cases were caused by onchocerciasis. The incidence of blindness was significantly and positively associated with increasing microfilarial burden (P<.001). Overall, female subjects had an ~40% lower risk of becoming blind than did male subjects (P<.001). After an initially high incidence of blindness at the beginning of the OCP, the rate of blindness from causes other than onchocerciasis remained approximately constant during follow-up. CONCLUSIONS: We demonstrate, in a comprehensive data set and in both sexes, a direct relationship between microfilarial load and the incidence of blindness.