Dubey J P, Gennari Solange M, Labruna Marcelo B, Camargo Luis M A, Vianna M C B, Marcet Paula L, Lehmann T
United States Department of Agriculture, Agricultural Research Service, Animal and Natural Resources Institute, Animal Parasitic Diseases Laboratory, Building 1001, Beltsville, Maryland 20705-2350, USA.
J Parasitol. 2006 Feb;92(1):36-40. doi: 10.1645/GE-655R.1.
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, 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. Tissues 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 by 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.
由于鸡在地面觅食，散养鸡中弓形虫的流行情况是土壤中弓形虫卵囊流行情况的一个良好指标。测定了来自巴西亚马逊地区的50只散养鸡（家鸡）中弓形虫的流行情况。通过改良凝集试验（MAT）检测弓形虫抗体，在33只（66%）鸡中检测到抗体，其滴度分别为：3只鸡为1:5，2只鸡为1:10，1只鸡为1:20，1只鸡为1:40，2只鸡为1:80，5只鸡为1:160，9只鸡为1:200，5只鸡为1:400，2只鸡为1:800，2只鸡为1:1600，1只鸡为1:3200或更高。对33只血清阳性鸡的心脏和大脑分别在小鼠中进行生物测定。将17只血清阴性鸡的组织混合后喂给2只无弓形虫的猫。检查猫的粪便中是否有卵囊，但未发现。从MAT滴度为1:5或更高的24只鸡中分离出弓形虫。通过SAG2位点的多态性对这24株弓形虫分离株进行基因分型，结果表明14株为I型，10株为III型；证实巴西不存在II型菌株。无论基因型如何，50%的感染小鼠死于弓形虫病。
