Kenneth W Walls

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Six cows and 6 calves were each inoculated with 100 or 100,000 Toxoplasma gondii oocysts. Serum samples were analyzed, using the Sabin-Feldman dye test (DT), indirect hemagglutination test, latex agglutination test, and the modified direct agglutination test (MAT). Antibody titers in cows were lower than in calves. In the cows, DT titers increased briefly(More)
The Waorani Indians of eastern Ecuador provide a unique opportunity for studying exposure of an isolated human population to various infectious disease agents. Using serologic tests to determine antibody prevalence, skin test data, and stool examination for parasites, we have been able to construct a profile of infectious diseases which are endemic, and(More)
A simple algorithm is proposed by which multiple categorization of absorbance values from ELISA plates is performed under a microcomputer control. The printed output is a pictorial emulation of a 96-well plate with the color intensities represented for each reaction. Although the method is presented as a colorimeter computer interfaced system, a provision(More)
The enzyme-linked immunosorbent assay (ELISA) has proved to be a sensitive and specific quantitative procedure for the serodiagnosis of toxoplasmosis. Using the toxoplasma model, several parameters of the test were investigated. Day-to-day reproducibility was 90% within one twofold dilution and 98% specific when tested against batteries of sera from other(More)
To determine epidemiological and clinical associations with Toxocara canis seropositivity, we studied 333 (87%) children of a cohort of 383 five- to seven-year-olds. The prevalence of seropositivity (antibody titer to T canis, greater than or equal to 1:32) was 23.1%. Black children were more frequently seropositive than were white children, as were(More)
We studied a cohort of 333 children in kindergarten to determine the prevalence of seropositivity to Toxocara canis, and to detect and measure chronic health effects that might be attributable to past infection. We found that 23.1% of the children had serologic evidence of infection (antibody titer greater than or equal to 1:32), assayed by means of an(More)
A reverse enzyme immunoassay (R-EIA) is described, in which polystyrene muplates are sensitized with anti-immunoglobulin M (IgM) (mu chain) antibodies and then sequentially allowed to react with patient's serum, peroxidase-labeled Toxoplasma gondii soluble antigen, and substrate. Measurement of activity of the solid-phase bound enzyme conjugate was done by(More)