Detection of Toxoplasma Gondii in Feline and Canine Biological Samples by Use of the Polymerase Chain Reaction

Objective: To develop a polymerase chain reaction (PCR) technique to identify Toxoplasma gondii DNA in biological samples from cats and dogs.

Design: To artificially create samples that would mimic those acquired in a clinical setting from animals with naturally acquired toxoplasmosis. Using these samples, a PCR test to identify T gondii DNA was developed.

Sample Population: Feline and canine aqueous humor, CSF, serum, and blood samples.

Procedure: Tachyzoites of several strains of T gondii grown in cell culture were added to feline and canine aqueous humor, CSF, serum, and blood samples. Protocols for identifying T gondii DNA by use of the PCR were developed.

Results: The DNA from as few as 10 tachyzoites of T gondii could be identified in feline and canine aqueous humor, CSF, and serum samples. One hundred tachyzoites could be identified in blood samples.

Conclusions: Toxoplasma gondii can be identified in feline and canine biological samples by use of the PCR.

Clinical Relevance: Correlation of clinical disease to T gondii serum antibodies provides only a presumptive diagnosis of toxoplasmosis. Use of PCR to detect T gondii DNA in biological samples from cats and dogs may provide a sensitive tool for the antemortem diagnosis of toxoplasmosis and may be most beneficial when used in conjunction with serum antibody titers.