Toxocara (the cause of
visceral larva migrans in humans) and
allergy have in common both elevated
immunoglobulin E (
IgE) levels and
eosinophilia. In the present study, we investigated: 1) associations between Toxocara seropositivity and allergic manifestations; 2) risk factors for Toxocara
infection; and 3) differences in Toxocara seroprevalence, allergic manifestations and the associations between these two, in children from urban and rural environments. Blood samples from 1,379 Dutch urban and rural elementary schoolchildren, were examined for Toxocara
antibodies, eosinophil numbers, total
IgE concentrations, and the occurrence of inhaled
allergen-specific
IgE. Questionnaires investigating respiratory health and putative risk factors for
infection were completed. It was found that 8% of the children had Toxocara
antibodies, occurring significantly less often in females than in males. The means of total serum
IgE levels and blood eosinophils were significantly higher in the Toxocara-seropositive than in the seronegative group. Allergic
asthma/recurrent
bronchitis was found in 7% of the children,
allergic reaction on animal contact in 4%, and
IgE to at least one inhaled
allergen in 16%. These variables were associated with Toxocara seroprevalence. Inhaled
allergen-specific
IgE and
asthma/recurrent
bronchitis occurred significantly less often in rural than in urban areas, and significantly less often among girls than among boys. Furthermore, occurrence of
allergen-specific
IgE increased significantly with age. No association existed between Toxocara seroprevalence and assumed risks, i.e. contact with pet animals and public playgrounds. In conclusion, our results indicate that allergic manifestations occur more often in Toxocara-seropositive children. A relationship with an already existing allergic condition is plausible.