A comparative analysis of coprologic diagnostic methods for detection of Toxoplama gondii in cats.

The relative role of transmission of Toxoplasma gondii infection from cats to humans appears to have recently increased in certain areas. Large-scale screening of oocyst shedding in cats cannot rely on microscopy because oocyst identification lacks sensitivity and specificity, or on bioassays, which require test animals and weeks before examination. We compared a sensitive and species-specific coprologic-polymerase chain reaction (copro-PCR) for detection of T. gondii infected cats with microscopy and a bioassay. In experimentally infected cats followed over time, microscopy was positive occasionally, and positive copro-PCR and bioassay results were obtained continuously from days 2 to 24 post-infection. The copro-PCR is at least as sensitive and specific as the bioassay and is capable of detecting infective oocysts during cat infection. Therefore, this procedure can be used as the new gold standard for determining potential cat infectivity. Its technologic advantages over the bioassay make it superior for large-scale screening of cats.

The development of a molecular approach for coprodiagnosis of Toxoplasma gondii.

Copro-diagnostic methods for Toxoplasma gondii infected cats have been traditionally based on the identification of oocysts by light microscopy or by bioassays. The first method is not sensitive and also unable to differentiate between Toxoplasma oocysts from other coccidian parasites in cats, and the second is cumbersome, time consuming and expensive. We have adapted a polymerase chain reaction (PCR) method to detect T. gondii oocyst DNA in fecal samples. Oocysts were successfully disrupted by freeze thawing coupled with mechanical means, and DNA extraction was subsequently accomplished. The test, based on amplifying a 529 bp repeated sequence, proved sensitive for detecting 1-2 oocysts in 200 microg of stool sample. The test specificity was established by showing that DNA from other cat coccidia tested negative. Specificity was reconfirmed by Southern hybridization of the PCR products with a specific probe. Of 122 stool samples from Jerusalem cats surveyed for the presence of Toxoplasma oocysts, 11 were found positive by PCR while none was detected by microscopy.

A cross-sectional survey of anti-Toxoplasma gondii antibodies in Jerusalem cats.

A cross-sectional seroprevalence study of anti-Toxoplasma gondii IgG antibodies was performed in Jerusalem domestic and stray cats. An enzyme linked immunosorbent assay (ELISA) immunodiagnostic technique was used and results analyzed according to specific variables. The overall seroprevalence was 16.8%. After an initial high seroprevalence of 29.7% in kittens after 1-10 days of age, average positive titers dropped to a low of 7.0% at ages 11-60 days. Thereafter, average positivity increased continuously and was observed in 50% of cats more than 5 years of age (P = 0.0081). Toxoplasma seroprevalence was highest in the month of summer (25.1%, P < 0.0001); domestic indoor cats had a higher seropositivity (39.0%) than stray cats (14.2%, P = 0.0004). On average, cats from the mainly Arab inhabited areas of Jerusalem showed a higher positive seroprevalence to Toxoplasma than Jewish inhabited areas (34.1% and 16.0%, respectively, P = 0.0032). There were no significant differences in positivity rates between sexes, and between rates of those with the presence/absence of clinical symptoms similar to those of the disease.