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United States Department of Agriculture

Agricultural Research Service


item Dubey, Jitender
item Gennari, Solange
item Laabruna, Marcelo
item Camargo, Luis M A
item Vianna, M C B
item Marcet, Paula
item Lehmann, T

Submitted to: Journal of Parasitology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/1/2005
Publication Date: 2/10/2006
Citation: Dubey, J.P., Gennari, S.M., Laabruna, M.B., Camargo, L., Vianna, M., Marcet, P.L., Lehmann, T. 2006. Characterization of toxoplasma gondii isolates in free-range chickens from Amazon, Brazil. Journal of Parasitology. 92:36-40.

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 Univ. of Sao Paulo, Brazil have found a very high prevalence of T. gondii in chickens from Amazon, Brazil. 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 50 free-range chickens (Gallus domesticus) from Amazon, Brazil was determined. Antibodies to T. gondii were assayed by the modified agglutination test (MAT), and found in 33 (66 %) chickens with titers of 1:5 in 3, 1:10 in 2, 1:20 in 1, 1: 40 in 1, 1: 80 in 2, 1: 160 in 5, 1:200 in 9, 1: 400 in 5, and 1:800 in 2, 1:1,600 in 2, and 1:3,200 or higher in 1. Hearts and brains of 33 seropositive chickens were bioassayed individually in mice. Tissue from 17 seronegative chickens were pooled and fed to 2, T. gondii-free cats. Feces of cats were examined for oocysts, but none was found. Toxoplasma gondii was isolated from 24 chickens with MAT titers of 1:5 or higher. Genotyping of these 24 T. gondii isolates using polymorphisms at the SAG2 locus indicated that 14 were Type I, and 10 were Type III; the absence of Type II strains from Brazil was confirmed. Fifty percent of the infected mice died of toxoplasmosis, irrespective of the genotype Toxoplasma gondii infections are widely prevalent in human beings and animals worldwide (Dubey and Beattie, 1988). Humans become infected post-natally by ingesting tissue cysts from undercooked meat, consuming food or drink contaminated with oocysts, or by accidentally ingesting oocysts from the environment. However, only a small percentage of exposed adult humans develop clinical signs. It is unknown whether the severity of toxoplasmosis in immunocompetent persons is due to the parasite strain, host variability, or to other factors.

Last Modified: 10/18/2017
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