Development of a serologic assay for cysticercosis, using an antigen isolated from Taenia spp cyst fluid.

An ammonium sulfate-soluble fraction of Taenia hydatigena cyst fluid (ThFAS) was further evaluated for use in the immunodiagnosis of cysticercosis. Analysis of ThFAS by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and protein immunoblot analysis confirmed earlier reports of a highly specific, low molecular weight antigen in this preparation; in contrast, other components of ThFAS were shown to react nonspecifically. Antibodies against the less than 12-kD diagnostic antigen were detected in sera from 10 cattle and 4 swine inoculated with metacestodes of T saginata and T solium, respectively, but not in animals inoculated with Fasciola hepatica, Trichinella spiralis, Brucella abortus, or Toxoplasma gondii, or in noninoculated controls. Isolation and immobilization of the less than 12-kD antigen on a hydrophobic transfer membrane resulted in development of an unambiguous dipstick assay capable of correctly identifying fully developed (10-week) experimentally induced infections in cattle and swine. In addition, the dipstick assay was highly specific for diagnosis of the disease in human beings, and offers the potential of distinguishing between human clinical cases of cysticercosis and taeniasis. A similar reactive antigen of diagnostic potential was also identified and isolated from T crassiceps and T taeniaeformis cyst fluids.

Evaluation of a 'dipstick' immunoassay to detect cysticercosis in experimentally infected cattle.

A 'dipstick' immunoassay for bovine cysticercosis, using an antigen isolated from Taenia hydatigena cyst fluid, was evaluated in cattle experimentally infected with Taenia saginata. The assay correctly identified six out of seven infected cattle, including an animal in which only 12 living cysticerci were found. Cattle became seropositive as early as 3 weeks post-infection. A false-negative reaction was found for one very lightly infected animal, from which only four living cysticerci were recovered at necropsy. The assay was also used to detect circulating antibodies in experimentally infected cattle before and after therapeutic treatment with anthelminthics. The results suggest that praziquantel-treated animals gradually revert to being seronegative after the cysticerci are killed.

Prevalence of trichinosis in southern Louisiana swine.

After an outbreak of human trichinosis in Louisiana involving 45 cases and 1 death in 1979 and 1980, a survey of pigs killed in 21 selected small slaughterhouses in southwestern Louisiana was conducted from November 1980 to September 1981. The sera from 1,225 pigs were examined for trichinella antibodies using an enzyme-linked immunosorbent assay (ELISA); 1,223 diaphragms were subjected to peptic digestion and examined for the presence of Trichinella spiralis larvae. One diaphragm (0.08%) was found to contain T spiralis (26 larvae/g of muscle) and 4 of the slaughterhouse sera were positive (0.33% seroprevalence). Pigs in 52 herds throughout the state were also tested for ELISA antibodies. The ELISA-positive pigs were not found among the 267 pigs tested from the 52 herds.

Enzyme immunoassay for swine trichinellosis using antigens purified by immunoaffinity chromatography.

Various preparations of crude and a purified preparation of Trichinella spiralis antigens were compared in a rapid, micro-enzyme immunoassay (EIA) for detecting trichinellosis in swine. The crude antigen preparations (XM-300 or S3 fraction) were lipid-free, cell-free fractions of muscle larvae, and the purified antigen was prepared by immunoaffinity chromatography of the soluble fraction of stichocyte secretory granules from rat muscle larvae. The antigens were tested against normal and immune swine sera for sensitivity and specificity, and for their ability to detect seroconversions early in the immune response. At optimum concentrations, absorbance values from immune and nonimmune sera produced sample to noise (S/N) ratios three-fold higher for the column antigen than for XM-300. Tests of sequential sera from experimentally-infected pigs showed that the column antigen produced lower absorbances with pre-infection sera and, from 18 days post-infection, higher absorbances with positive sera. From 21-28 days post-infection, absorbances and S/N ratios with column antigen were nearly twice those with XM-300. Column antigen detected antibodies more often than XM-300 antigen in sera collected prior to the appearance of larvae. Crude antigen did not distinguish all true negatives from weakly positives in a study involving 100 sera from muscle digestion-negative pigs and 75 sera from experimentally infected pigs, whereas the column antigen distinguished all negatives from positives. In a larger scale test of the column antigen, 1,130 pigs from Puerto Rico were tested in the micro-EIA test. Puerto Rico has no endogenous trichinellosis, and all 1,130 pigs were shown to be muscle digestion negative. These same pigs were all negative using the column antigen. These results show that the column antigen out-performs the crude antigens in sensitivity, specificity, and early detection. The column antigen is therefore a major improvement in the EIA for swine trichinellosis.