Risk factors for asthma in a helminth endemic area in bahia, Brazil.

Protective factors associated with atopy or asthma in rural areas include socioeconomic level, overcrowding, and helminth infection. However, little epidemiological information was originated from schistosomiasis areas. This study aimed to investigate factors associated with asthma in a schistosomiasis endemic area. A questionnaire was used to obtain information on demographics, socioeconomic, and environmental features. The ISAAC questionnaire was used to identify individuals with asthma. Parasitological exam was done in all participants and skin prick test to aeroallergens in all asthmatics. Prevalence of Schistosoma mansoni infection was 57.4% and Ascaris lumbricoides, 30.8%. Asthma was found in 13.1% of the population, and 35.1% of them had a positive SPT. Active and passive smoking was positively associated with asthma, whereas A. lumbricoides was negatively associated. In a schistosomiasis hyperendemic region, current infection with A. lumbricoides is protective against asthma. However, we cannot rule out the involvement of S. mansoni infection in this process.

The effect of antihelminthic treatment on subjects with asthma from an endemic area of schistosomiasis: a randomized, double-blinded, and placebo-controlled trial.

This is a prospective, double-blinded, and placebo-controlled trial evaluating the influence of antihelminthic treatments on asthma severity in individuals living in an endemic area of schistosomiasis. Patients from group 1 received placebo of Albendazole or of Praziquantel and from group 2 received Albendazole and Praziquantel. Asthma severity was assessed by clinical scores and by pulmonary function test. There was no significant difference in the asthma scores from D0 to D1-D7 after Albendazole or Praziquantel and from D0 to D30-90 after Albendazole or Praziquantel in both, group 1 and 2. It was observed, however, a clinical worsening of the overall studied population after 6 months and 12 months of antihelminthic treatments. Additionally, we observed increased frequency of forced expiratory volume in 1 second (FEV1) <80% on 12 and 18 months after treatment. The worsening of asthma severity after repeated antihelminthic treatments is consistent with the hypothesis of the protective role conferred by helminths in atopic diseases.

Factors associated with resistance to Schistosoma mansoni infection in an endemic area of Bahia, Brazil.

Detailed knowledge of factors associated with resistance to Schistosoma mansoni infection in endemic areas might facilitate more effective schistosomiasis control. We conducted a cross-sectional study of persons resistant to schistosomiasis and found no association between socioeconomic status and resistance to infection. Mononuclear cells of resistant subjects produced higher levels of interleukin-5 (IL-5), IL-13 and interferon-γ upon stimulation with soluble egg antigen (SEA) compared with infected persons. When stimulated with Sm21.6 or Sm22.6, levels of IL-10 were higher in cell culture of resistant persons. Levels of IgE against soluble adult worm antigen (SWAP) and against interleukin-4-inducing principle from S. mansoni eggs (IPSE) and levels of IgG4 against SWAP, SEA, and Sm22.6 were lower in the resistant group compared with the susceptible group. Our data suggest that socioeconomic status could not fully explain resistance to S. mansoni infection observed in the studied area. However, a mixture of Th1 and Th2 immune responses and low levels of specific IgG4 against parasite antigens could be mediating resistance to infection.