Characterization of Toxoplasma gondii isolates in free-range chickens from Portugal.

ABSTRACT

The prevalence of Toxoplasma gondii in free-ranging chickens is a good indicator of the prevalence of T. gondii oocysts in the soil because chickens feed from the ground. The prevalence of T. gondii in 225 free-range chickens (Gallus domesticus) from Portugal was determined. Antibodies to T. gondii were assayed by the modified agglutination test (MAT) and found in 61 chickens with titers of 15 in 8, 110 in 6, 120 in 3, 140 in 23, 180 in 5, 1160 in 4, 1320 in 8, and 1640 or higher in 4. Hearts, leg muscles, and brains of 15 seropositive (MAT 110 or higher) chickens were bioassayed individually in mice. Tissue from 38 chickens with titers of 15 or less were pooled and fed to a T. gondii-free cat. Feces of the cat were examined for oocysts, but none was found. Toxoplasma gondii was isolated from 16 of 19 chickens with MAT titers of 110 or higher. Genotyping of 12 of these 16 isolates with polymorphisms at the SAG2 locus indicated that 4 were type III, and 8 were type II. None of the isolates was lethal for mice. Phenotypically, T. gondii isolates from chickens from Portugal were different from those of T. gondii isolates from chickens from Brazil.