Submitted to: Veterinary Parasitology
Publication Type: Peer reviewed journal
Publication Acceptance Date: 3/15/2004
Publication Date: 3/31/2004
Citation: Dubey, J.P., Salant, H., Sreekumar, C., Dahl, E., Vianna, M.C., Shen, S.K., Kwok, O.C., Spira, D., Hamburger, J., Lehmann, T.V. 2004. High prevalence of Toxoplasma gondii in a commercial flock of chickens in Israel, and public health implications of free-range farming. Veterinary Parasitology. 121:317-322. Interpretive Summary: Infection by the single-celled parasite Toxoplasma gondii, is common in man and animals. Humans become infected by eating undercooked infected meat or ingesting the resistant stage of Toxoplasma (oocysts) in the environment. Infections in free range-range chickens is indicative of Toxoplasma infection in the environment because chickens feed from the ground. Scientists at the Beltsville Agricultural Research Center and Centers for Disease Control, Atlanta, Georgia, report isolation and molecular characterization of Toxoplasma gondii strains from free-range chickens from Israel. These results will be of interest to public health workers, parasitologists and veterinarians.
Technical Abstract: Little is known of the prevalence of Toxoplasma gondii in commercially raised chickens. In the present study, the prevalence of T. gondii in 96 free range chickens (Gallus domesticus) from a commercial farm in Israel was assessed. Blood, heart, and brain from each chicken were examined for T. gondii infection. Antibodies to T. gondii, assayed with the modified agglutination test (MAT ' 1:5) were found in 45 of the 96 chickens. Hearts and brains of seropositive (MAT ' 1:5) chickens were bioassayed in mice. Additionally, hearts and brains of 51 seronegative (MAT<1:5) chickens were bioassayed in two T. gondii-free cats. T. gondii was isolated from 19 of the 45 (42.2%) seropositive chickens by bioassay in mice. Both the cats fed tissues pooled from seronegative chickens shed T. gondii oocysts. Tachyzoites and tissue cysts of all 21 isolates of T. gondii from chickens were avirulent for mice. Seventeen of the 19 isolates genotyped were found to be type II, and 2 were type III. Understanding of the sources of infection on such farms is the key to the development of better prevention strategies.