Submitted to: Parasitology
Publication Type: Peer reviewed journal
Publication Acceptance Date: 6/16/2007
Publication Date: 10/1/2007
Citation: Dubey, J.P., Applewhaite, L., Sundar, N., Velmurugan, G.V., Bandini, A., Kwok, O.C., Hill, R., Su, C. 2007. Molecular and biological characterisation of Toxoplasma gondii isolates from free-range chickens from Guyana, South America identified several unique and common parasite genotypes. Parasitology. 134:1559-1566. 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.Toxoplasmosis causes mortality in many species of animals in the zoos, especially primates. Scientists at the Beltsville Agricultural Research Center and a scientist in Guyana, South America report genetic characterization of Toxoplasma from chickens from Guyana. The results will be of interest to biologists, parasitologists, and veterinarians.
Technical Abstract: The prevalence of Toxoplasma gondii in free-ranging chickens (Gallus domesticus) 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 76 free-range chickens from Guyana, South America was determined. Antibodies to T. gondii were assayed by the modified agglutination test (MAT), and found in 50 (65.8%) of 76 chickens with titers of 1:5 in four, 1:10 in one, 1:20 in five, 1: 40 in seven, 1: 80 in six, 1:160 in eight, 1:320 in four, 1:640 or higher in 15. Hearts and brains of 26 chickens with titers of < 1:5 were pooled in five batches and bioassayed in mice. Hearts and brains of 39 chickens with titers of 1:5 or higher were bioassayed in mice. Toxoplasma gondii was isolated by bioassay in mice from 35 chickens with MAT titers of 1:20 or higher. All mice inoculated with tissues of 30 infected chickens remained asymptomatic. Toxoplasma gondii isolates from 35 chickens were genotyped using 11 genetic markers including SAG1, SAG2, SAG3, BTUB, GRA6, c22-8, c29-2, L358, PK1, a new SAG2 and Apico. A total of nine genotypes were identified, with five genotypes (#1, #4, #5, #6 and #7) unique to Guyana, two genotypes (#2 and #3) previously identified in chickens from Brazil, one genotype (#8) previously identified in chickens from Brazil, Costa Rica and Nicaragua, and one genotype (#9) belonging to the clonal type III lineage that exists globally. Infection with two genotypes was found from one chicken. This is the first report of genetic characterization of T. gondii isolates from any host from Guyana.