It is clear that leukotrienes mediate inflammatory response; new aspects of leukotriene function have recently been described. In this study, we demonstrate that leukotrienes are key chemical mediators in the control of parasite burdens in mice infected with Strongyloides venezuelensis. High leukotriene levels were detected in the lungs and small intestines of Swiss mice. In infected Swiss mice treated with MK886, a leukotriene synthesis inhibitor, numbers of adult worms, and eggs/g/feces were greater than in infected-only animals. The MK886 treatment inhibited leukotriene B4 production in the lungs and small intestines, albeit on different postinfection days. Similarly, parasite burdens and eggs/g/feces were greater in 5-lipoxygenase−/− mice than in wild-type animals. These observation were confirmed by histopathological study of the duodena. We subsequently observed significant lower numbers of eosinophils and mononuclear cells in the blood, peritoneal cavity fluid, and bronchoalveolar lavage fluid of Swiss mice treated with MK886. In the lung parenchyma of infected animals, MK886 significantly inhibited synthesis of IL-5 at the beginning of infection, whereas levels of IL-12 increased progressively throughout the postinfection period. However, levels of leukotriene C4, PGE2, TNF-α, IL-3, IL-4, IFN-γ, and IL-10 were comparable between the treated and untreated groups. Nevertheless, IgE and IgG1 (but not IgG2a) synthesis was also significantly inhibited by MK886 administration. Therefore, in S. venezuelensis-infected mice, adult worm and egg burdens are leukotriene dependent. These findings indicate potential immunostimulatory strategies involving leukotriene administration, and may serve as an alert to physicians treating Strongyloides stercoralis-infected patients presenting asthma-like symptoms because use of 5-lipoxygenase inhibitors may worsen the infection.

The present study was conducted to detected IgG antibodies using Strongyloides venezuelensis alkaline extract for the diagnosis of human strongyloidiasis by the enzyme-linked immunosorbent assay (ELISA). (Siddiqui & Berk 2001). Due to the fluctuations on the larvae shedding in subjects infected with S. stercoralis, the parasitological methods have shown low sensitivity, being necessary repeated stool exams (Dreyer et al. 1996, Uparanukraw et al. 1999. Complementary tests for the diagnosis and the monitoring of the immune response in this parasitosis have been developed. However, the major limitation for the standardization of immunological methods is the difficulty in obtaining large amount of S. stercoralis larvae (Sato et al. 1995, Costa-Cruz et al. 1997.The aim of this study was to diagnose human strongyloidiasis by enzyme-linked immunosorbent assay (ELISA) using alkaline extract of S. venezuelensis filariform larvae. The study received approval from the Ethical Committee of the Federal University of Uberlândia.Strain of S. venezuelensis was isolated from feces of the wild rodent Nectomys squamips in August 1988 and maintained by experimental infection in Rattus norvergicus-Wistar. Infective larvae of S. venezuelensis were obtained from the feces of rats experimentally infected and cultured in mineral charcoal for two days at room temperature. Larvae were recovered by the Rugai et al. (1954) method and washed five times in 0.01 M phosphatebuffered saline (PBS) pH 7.2 containing 400 IU/ml of benzyl penicilin and 2 mg/ml of streptomycin sulfate and then stored at -70 o C in PBS until the antigen preparation. Alkaline extract of 100,000 larvae of S. venezuelensis was prepared by adding 1 ml of 0.15 M NaOH (Merck, Germany) during 6 h under slow agitation at 4 o C. Subsequently, 0.5 ml of 0.3 M HCl (Merck) was added until reaching the pH 7.0, and this preparation was centrifuged at 10,000 g for 30 min at 4 o C. Protein determination of the supernatant was 240 µg/ml as detected by the Lowry et al. (1951) method.ELISA was carried out using polystyrene microplates (Difco, São Paulo, Brazil) and the reagents were assayed in 50 µl/well. The plates were coated with alkaline extract at 10 µg/ml in 0.06 M carbonate-bicarbonate buffer, pH 9.6 and incubated overnight at 4 o C. The plates were washed three times for 5 min with PBS containing 0.05% Tween 20 (PBS-T) and incubated with the serum samples, including positive and negative control sera, diluted at 1:80 in PBS-T for 45 min at 37 o C. After new washing as previously described, the conjugate rabbit anti-human IgG (Fc chain specific) labeled with peroxidase (Sigma, US) diluted at 1:2,000 in PBS-T was added and incubated for 45 min at 37 o C. After washing, the enzymatic substrate consisting of H 2 O 2 (Merck) plus o-phenylenediamine (OPD) diluted in 0.1 M citrate-Na 2 HPO 4 buffer pH 5.5 was added. The reaction was stopped after 15 min with 20 µl/well of 1 M H 2 SO 4 and the absorbance values were determined in an

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Helminths can be transmitted to human beings in several ways, but little attention has been given to vector or mechanical transmission of infective forms by insects. The present study surveys the helminth species present in three orders of insects that coexist in proximity with the human environment. A total of 700 insects (54 Blattodea, 275 Diptera, and 371 Hymenoptera) were collected and examined externally and individually. In the Blattodea order, only specimens of Periplaneta americana were collected, and 58.3% were carrying the following helminth forms: Oxyuridae eggs (36.4%), Ascaridae eggs (28.04%), Nematoda larvae (4.8%), Cestoda eggs (3.5%), other Nematoda (0.08%), and Toxocaridae eggs (0.08%). No Diptera and Hymenoptera were found to contain parasitic forms. This study evaluates the importance and role of insects as mechanical vectors of helminth parasites, correlated with social and environmental conditions, and suggests the use of these data for preventive purposes.

The aim of this study was to detect levels of IgG and IgA by enzyme-linked immunosorbent assay (ELISA) using alkaline extracts of larvae, adult female worms, and eggs of Strongyloides venezuelensis as antigen. One hundred twenty serum samples divided into 3 groups were analysed: group I (40 strongyloidiasis patients), group II (40 patients with other parasitic infections), and group III (40 healthy subjects). Statistical variations were analyzed using analysis of variance. There was a significant statistical difference (P < 0.001) in the detection of antibodies in group I between larvae and female antigens and between larvae and egg antigens, with higher positivity using larvae antigen. The larvae antigen showed the highest values for sensitivity, specificity, and diagnostic efficiency in ELISA. This study is the first that examines the use of adult female worm and egg antigens to detect antibodies for human strongyloidiasis diagnosis compared with the larval extract. By comparing all 3 extracts, larval antigens demonstrated better diagnostic parameters.

IgG avidity assays have been developed for several parasitic diseases although there are no researches focused in strongyloidiasis diagnosis. Definitive diagnosis of strongyloidiasis is based on the presence of Strongyloides larvae in stool, but majority of cases involve low and irregular larval output. While limitations of serological assays for strongyloidiasis are well known, characteristics of persons who are misdiagnosed based on negative coproparasitological tests have been little explored. The aim of the present study was to evaluate the use of IgG avidity to detect patients with active strongyloidiasis and to characterize sources of disagreement between serology and coproparasitology. A total of 80 serum samples was analyzed, 40 from patients with Strongyloides larvae in stool (G1) and 40 from individuals with negative coproparasitology, but positive serology (G2). Serum samples were analyzed in an indirect IgG avidity ELISA using urea 6M in serial double dilutions from 1:80 to 1:2560. Avidity index (AI) was calculated to each serum dilution and analyzed as screening AI (serum dilution of 1:160) or mean AI of different serum dilutions that had a positive result. Statistical analyzes were performed by Mann-Whitney's (U) and Fisher's exact tests. At screening dilution, median of AI was 68% in G1 and 88% in G2 (P<0.0001), whereas median of mean AI in G1 was 72% and in G2 94% (P<0.0001), but there was no significant differences between both AI in each patient group. A cut off value established at AI of 75% demonstrated a significant difference between groups, with G1 sera showing AI<75% and G2 sera with AI>75% (P<0.0001). In conclusion, IgG avidity assays may distinguish active infection with Strongyloides stercoralis from suspect or serologically false positive cases.