Intestinal nematodes, Toxocara infection, and pyogenic liver abscess in children: a possible association

Eosinophilia and intestinal helminths are frequent in children with pyogenic liver abscess (PLA) diagnosed in Vitória (Brazil). For these reasons we hypothesized that nematode infection with larvae migrating through the tissues (Ascaris, Strongyloides, Ancylostoma, Necator and Toxocara) may be a predisposing factor for PLA in children. We compared the prevalence of intestinal helminth and Toxocara infection between children with PLA and a control group of children with no evidence of PLA at the Children's Hospital N.S. da Glória in Vitória. From October 1996 to February 1998, 13 children with PLA and 110 children with diseases other than PLA provided five stool samples (Hoffman, Baerman and Kato-Katz methods) and one blood sample for anti-Toxocara antibodies (ELISA IgG, with previous adsorption with Ascaris suum antigen). All PLA and comparison children belonged to a low socioeconomic class and lived in similar conditions. The frequency of intestinal nematodes and anti-Toxocara antibodies were significantly higher in PLA patients than in controls (intestinal helminths: 10/13 or 76.9 per cent in PLA cases and 31/110 or 28.1 per cent in controls; OR = 8.94; 95 per cent confidence interval (CI): 1.97 < OR < 50.06; anti-Toxocara antibodies: 9/13 or 69.2 per cent in PLA and 31/110 or 28.1 per cent in controls; OR = 6.59; 95 per cent CI: 1.65 < OR < 31.05). Moreover, the degree of eosinophilia was higher in PLA patients. Malnutrition was present in both groups. Hemoglobin was 9.5 g/dl in PLA patients and 9.7 g/dl in controls; p = 0.900. Serum levels of IgA and IgM were normal or above normal, with no difference between the two groups, but the levels of IgG and IgE were higher in PLA patients. Although there is some missing data in respect to some socioeconomic parameters in affected and comparison groups. these results support the hypothesis that helminth infection with larvae migrating through tissues may be a predisposing factor for PLA in children. Th2 cell activation and downregulation of Th1 cells, induced by helminths, thus reducing the microbicidal activity of phagocytes, as well as the granulomatous reaction around the larvae (mainly of Toxocara sp.) causing the trapping of bacteria in liver, may be possible explanations for the increased risk for PLA in children with intestinal nematodes and/or Toxocara infection.