The stool examination reports amoeba cysts: should you treat in the face of over diagnosis and lack of specificity of light microscopy?

Amoebiasis is a common clinical diagnosis in tropical settings and clinicians continue to treat asymptomatic carriers diagnosed by light microscopy. A minority of carriers, however, are infected with Entamoeba histolytica and the remaining with the non-pathogenic Entamoeba dispar. We compared the diagnostic results of 298 asymptomatic residents of Aracaju, Brazil, obtained by different diagnostic methods, and ascertained their clinical symptoms, to highlight the implications for practitioners. Fifty-eight (19.4%) specimens were amoebae positive by microscopy. Of these, 38 (13%) were E. histolytica/E. dispar enzyme-linked immunosorbent assay (ELISA) positive and 4 (1%) E. histolytica ELISA positive. The frequent use of anti-amoebic treatment on the basis of non-specific symptoms and the findings of light microscopy tests is not justified. Methods for the specific diagnosis of E. histolytica infection for developing countries are urgently needed.

Anemia and intestinal parasitic infections in primary school students in Aracaju, Sergipe, Brazil.

Anemia is estimated to affect half the school-age children and adolescents in developing countries. The main causes are parasitic infections, malaria, and low iron intake. This study aimed to describe the prevalence of anemia, parasitic infections, and nutritional status of children attending public primary schools in Aracaju, Northeast Brazil. Of 360 students, 26.7% were anemic, and prevalence was higher in children under 8 and over 15 years of age. Overall prevalence of intestinal parasites was 42%, with Ascaris lumbricoides (28.7%), Trichuris trichiura (15.6%), and hookworm (1. 7%) most frequently found. There was an association between parasitic infections and poor sanitary conditions, but there was no association between anemia and presence of intestinal parasites. Height-for-age Z scores were lower than the NCHS standard, and prevalence of stunting was 5.4%. Although intestinal parasites were not associated with anemia, children with parasites had lower nutritional indices (weight- and height-for-age Z scores) than those without parasites.

Humoral responses in human strongyloidiasis: correlations with infection chronicity.

Strongyloides stercoralis L3-specific antibody isotype responses amongst individuals with known long-standing (28-46 years) infection were compared with those of 'young' (6-29 years of age) and 'old' (30-80 years of age) infected individuals from an endemic Jamaican population. Characterization of age-dependent isotype patterns in the endemic community showed that immunoglobulin (Ig) G1 responses were significantly inversely correlated with age. Additionally, a trend towards lower IgE levels in the older age group was observed. Comparison with responses amongst known chronically infected individuals showed that IgG1 and IgE levels were similar to those of the 'old' endemic group, but were significantly lower than those of the 'young' group. In contrast, IgA levels were similar in both endemic groups, but were elevated in chronically infected individuals. IgG4 levels were similar in all groups studied. These findings suggest that age correlates with infection chronicity in communities endemic for S. stercoralis, and that individuals acquire infection early in their lives and remain infected into adulthood. Early and sustained upregulation of IgG4 may facilitate the establishment of infection and, in combination with developing IgE hyporesponsiveness, may promote chronic asymptomatic strongyloidiasis. Conversely, upregulated IgA may be involved in controlling chronic infection levels which are reflected in reduced IgG1 production.

Serum IgG reactivity with 41-, 31- and 28-kDa larval proteins of Strongyloides stercoralis in individuals with strongyloidiasis

Proteins from a deoxycholate-soluble extract of Strongyloides stercoralis infective larvae were separated by SDS-PAGE, blotting onto nitrocellulose paper, and reacted with sera from individuals with confirmed S. stercoralis infections (n = 100), suspectedS. stercoralis infections in whom no larvae could be detected (n = 27), and other nematode infections (40 with Wuchereria bancrofti, 20 with Onchocerca volvulus, 20 with Necator americanus, and 20 with mixed Ascaris lumbricoides and Trichuris trichiura infections). Immunodominant proteins of approximately 41, 31, and 28 kDa were recongnized by IgG in 91 percent, 88 percent and 90 percent respectively, of sera from those with confirmed strongyloidiasis; in 100 percent, 100 percent, and 93 percent of sera from those with suspected strongyloidiasis; and in 9 percent, 12 percent and 14 percent of sera from those infected with other nematodes. IgG reactivity to each of these proteins was a more specific means of immunodiagnosis than the currently use indirect ELISA; the methods were equally sensitive.(AU)

Immunodiagnosis of Strongyloides stercoralis infection: a method for increasing the specificity of the indirect ELISA

Indirect enzyme-linked immunosorbent (ELISA) allows sensitive detection of serum immunoglobulin (Ig) G against a soluble extract of Strongyloides stercoralis infective larvae. In this study, 40/40 (100 percent) human strongyloidiasis sera had high levels of anti-S. stercoralis IgG, but 30/40 (75 percent) filariasis sera, and 12/40 (30 percent) necartoriasis sera also had higher levels than control sera from UK residents. In attempts to increase the assay specificity by absorption of cross-reactive IgG, the effectiveness of pre-incubation of sera with extracts of different parasitic nematodes was investigated. One hour of incubation with 20 æ/ml aqueous extract of Onchocerca gutturosa absorbed cross-reactive IgG in most filariasis and necatoriasis sera, reducing the proportion with IgG levels above the positivity threshold by more one-half. Preliminary results suggest that absorption with extracts of other filarial nematodes is equally effective, and that some cross-reactive IgG is directed against phosphorylcholine. Cross-reactive IgG in most necatoriasis sera was effectively absorbed with an extract of Ascaris lumbricoides. Absorption of cross-reactive IgG is an effective means of increasing the specificity of the indirect ELISA, for use in the immunodiagnosis and immuno-epidemiology of S. stercoralis infection.