Background Toxocara canis and T. cati are parasites of dogs and cats, respectively, that infect humans and cause human toxocariasis. Infection may cause asthma-like symptoms but is often asymptomatic and is associated with a marked eosinophilia. Previous epidemiological studies indicate that T. canis infection may be associated with the development of atopy and asthma.ObjectivesTo investigate possible associations between Toxocara spp. seropositivity and atopy and childhood wheezing in a population of children living in non-affluent areas of a large Latin American city.MethodsThe study was conducted in the city of Salvador, Brazil. Data on wheezing symptoms were collected by questionnaire, and atopy was measured by the presence of aeroallergen-specific IgE (sIgE). Skin prick test (SPT), total IgE and peripheral eosinophilia were measured. Toxocara seropositivity was determined by the presence of anti-Toxocara IgG antibodies, and intestinal helminth infections were determined by stool microscopy.FindingsChildren aged 4 to 11 years were studied, of whom 47% were seropositive for anti-Toxocara IgG; eosinophilia >4% occurred in 74.2% and >10% in 25.4%; 59.6% had elevated levels of total IgE; 36.8% had sIgE≥0.70 kU/L and 30.4% had SPT for at least one aeroallergen; 22.4% had current wheezing symptoms. Anti-Toxocara IgG was positively associated with elevated eosinophils counts, total IgE and the presence of specific IgE to aeroallergens but was inversely associated with skin prick test reactivity.ConclusionThe prevalence of Toxocara seropositivity was high in the studied population of children living in conditions of poverty in urban Brazil. Toxocara infection, although associated with total IgE, sIgE and eosinophilia, may prevent the development of skin hypersensitivity to aeroallergens, possibly through increased polyclonal IgE and the induction of a modified Th2 immune reaction.

BackgroundEnvironmental factors are likely to have profound effects on the development of host immune responses, with serious implications for infectious diseases and inflammatory disorders such as asthma.ObjectiveThis study was designed to investigate the effects of environmental exposures on the cytokine profile of children.MethodsThe study involved measurement of T helper (Th) 1 (interferon-gamma), 2 [interleukin (IL)-5 and IL-13], and the regulatory cytokine IL-10 in unstimulated peripheral blood leukocytes from 1,376 children 4–11 years of age living in a poor urban area of the tropics. We also assessed the impact of environmental exposures in addition to biological characteristics recorded at the time of blood collection and earlier in childhood (0–3 years before blood collection).ResultsThe proportion of children producing IL-10 was greater among those without access to drinking water [p < 0.05, chi-square test, odds ratio (OR) = 1.67]. The proportion of children producing IL-5 and IL-10 (OR = 10.76) was significantly greater in households that had never had a sewage system (p < 0.05, trend test).ConclusionsThese data provide evidence for the profound effects of environmental exposures in early life as well as immune homeostasis in later childhood. Decreased hygiene (lack of access to clean drinking water and sanitation) in the first 3 years of life is associated with higher spontaneous IL-10 production up to 8 years later in life.

The seroprevalence of Toxocara infection is high among children living in a poor urban setting of Brazil. The association of low maternal education with higher Toxocara infection supports studies showing that low socioeconomic status is a risk factor for the acquisition of this infection as a reflection of hygiene habits of the family. And both infected-dogs and cats may be involved in this parasite transmission in this children population.

Summaryobjective To investigate the association between Toxocara canis infection and total IgE levels and eosinophilia in blood donors from a large Brazilian city.methods Two hundred and sixty-eight blood donors from a government blood bank were tested. No helminth infection was diagnosed by parasitological stool examination. Total IgE levels and T. canis infection status were determined by ELISA. Eosinophil levels were determined using an automatic blood cell counter.results Toxocara canis IgG antibodies were found in 124 (46.3%); 102 (38.0%) had eosinophilia ‡4% and 29 (10.8%) had eosinophilia ‡10%, respectively; 140 (52.2%) individuals had total IgE antibodies above the cut-off levels. Both total IgE and eosinophil levels ‡10% were positively associated with the infection.conclusion This study revealed a high prevalence of T. canis infection in blood donors, highlighting the need for screening for this infection. It also demonstrated that this population otherwise healthy has higher levels of blood eosinophils and total IgE and that both parameters are associated with T. canis infection.

Prevalência e fatores de risco da infecção humana por ABSTRACTIntroduction: Larva migrans visceral is caused by Toxocara sp and has never been studied in Bahia. This work investigated the prevalence and risk factors for infection by Toxocara canis in individuals from Salvador, State of Bahia. Methods: Three hundred and thirty-eight individuals were investigated for the presence of serum IgG anti-T. canis. Results: IgG anti-T. canis was higher in individuals from lower social classes who had more contact with dogs and cats, indicating that these variables are factors risk for this infection. Conclusions: The prevalence of T. canis infection was high. The risk factors for this infection identified are in agreement with in the literature.