Submitted to: Veterinary Parasitology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/15/2006
Publication Date: 10/1/2006
Citation: Dubey, J.P., Su, C., Pineda, N., Kyvsgaard, N.C., Sundar, N., Luna, L.A., Rimbaud, E., Oliveira, J.B., Qi, Y., Kwok, O.C. 2006. Biologic and genetic characteristics of Toxoplasma gondii in free-range chickens from Nicaragua, Central America. Veterinary Parasitology. 142:47-53. Interpretive Summary: Toxoplasma gondii is a single-celled parasite of all warm-blooded hosts worldwide. It causes mental retardation and loss of vision in children, and abortion in livestock. Cats are the main reservoir of T. gondii because they are the only hosts that can excrete the resistant stage (oocyst) of the parasite in the feces. Humans become infected by eating undercooked meat from infected animals and food and water contaminated with oocysts. Scientists at the Beltsville Agricultural Research Center and a Diagnostic Center in Nicaragua have found a very high prevalence of T. gondii in chickens from Nicaragua.The results will be of interest to biologists, parasitologists, public health workers, and veterinarians.
Technical 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 98 free-range chickens (Gallus domesticus) from Nicragua was determined. Antibodies to T. gondii were assayed by the modified agglutination test (MAT), and found in 84 (85.7%) of 98 chickens with titers of 1:5 in 10, 1:10 in eight, 1:20 in seven, 1: 40 in nine , 1: 80 in 11, 1:160 in one, 1:200 in 27, 1:400 in six, 1:800 four, and 1: 3200 in one bird. Hearts and brains of 32 chickens with titers of 1:10 or less were pooled and fed to three T. gondii-free cats. Hearts and brains of 66 chickens with titers of 1:20 or higher were bioassayed in mice. Feces of cats were examined for oocysts. The cat fed tissues from eight chickens with titers of 1:10 shed T. gondii oocysts. The two cats fed tissues of 24 chickens with titers of 1:5 or less did not shed oocysts. T. gondii was isolated by bioassay in mice from 47 chickens with MAT titers of 1:20 or higher. All infected mice from six isolates died of toxoplasmosis. Overall, 41 of 170 (24.1%) mice that became infected after inoculation with chicken tissues died of toxoplasmosis. Genotyping of these 48 isolates using polymorphisms at the loci SAG1, SAG2, SAG3, BTUB and GRA6 revealed eight genotypes. Seven isolates had type I alleles, three isolate had type II at all loci, and seven had Type III alleles at all loci. Two isolates have a unique allele at SAG1 locus and combination of I and III alleles at other loci. The rest 29 isolates contained the combination of type I and III alleles and were divided into four genotypes. This is the first report of genetic characterization of T. gondii isolates from Nicragua, Central America.