Laboratorio de Inmunoparasitología, Facultad de Ciencias Veterinarias, Universidad Nacional de La Plata, 60 y 118 (1900), La Plata, Argentina.
Vet Parasitol. 2012 Mar 23;184(2-4):116-21. doi: 10.1016/j.vetpar.2011.09.012. Epub 2011 Sep 12.
This study aimed at isolating and genotyping Toxoplasma gondii from serologically positive free-range chickens from Argentina, and to evaluate the use of sentinel animals during a short time period of exposure to determine environmental contamination with T. gondii oocysts. Two groups of chickens on six farms were compared in this study: (i) young, 2-3 month-old broiler-type chickens reared as sentinel animals on the farms and (ii) adult chickens reared on the same farms for more than one year. Seroconversion rates of 7.0% or 5.7% were observed in sentinel broiler chickens reared for a period of 74 days (January-April 2010) or 88 days (August-November 2010) respectively, as shown by a T. gondii specific immunofluorescent antibody test. Fifty-three percent (17 of 32) of adult chickens were positive and showed higher titres than sentinel animals. Isolation of T. gondii from tissues (brain and heart) of serologically positive chickens was achieved from six of seven free-range adult birds with IFAT titres of 200 and higher. The isolated parasites were analysed by multi-locus polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP). The isolated T. gondii showed three different genotypes: two genotypes consisted in atypical allele combinations, and the remaining genotype had exclusively clonal type II alleles. All isolates obtained at a single farm, corresponded to the same genotype. The T. gondii genotypes observed are identical to those described in cats, dogs, chickens and capybaras elsewhere in South America. Two isolates, which showed different allele combinations in PCR-RFLP, were characterized in a mouse virulence assay. While one isolate showed a low virulence a second isolate was of intermediate virulence to mice.
本研究旨在从阿根廷血清学阳性的自由放养鸡中分离和基因分型弓形虫，并评估在短时间暴露期间使用哨位动物来确定环境中是否存在弓形虫卵囊污染。在这项研究中，比较了六个农场的两组鸡：（i）在农场中饲养的 2-3 个月龄的年轻肉鸡型哨位动物，和（ii）在同一农场饲养超过一年的成年鸡。用弓形虫特异性免疫荧光抗体试验检测到，分别饲养 74 天（2010 年 1 月至 4 月）或 88 天（2010 年 8 月至 11 月）的哨兵肉鸡的血清转化率为 7.0%或 5.7%。结果显示，53%（32 只中的 17 只）的成年鸡呈阳性，且比哨位动物的滴度更高。从 7 只血清学阳性的自由放养成年鸡的组织（脑和心）中分离到弓形虫，这些鸡的间接免疫荧光抗体试验滴度为 200 及以上。用多基因座聚合酶链反应-限制性片段长度多态性（PCR-RFLP）分析分离的寄生虫。分离的弓形虫显示出三种不同的基因型：两种基因型由非典型等位基因组合组成，其余基因型则仅具有克隆型 II 等位基因。在单个农场获得的所有分离株均对应于相同的基因型。观察到的弓形虫基因型与在南美洲其他地区的猫、狗、鸡和水豚中描述的基因型相同。在 PCR-RFLP 中显示不同等位基因组合的两个分离株，在小鼠毒力试验中进行了特征描述。一个分离株显示出低毒力，而第二个分离株对小鼠的毒力为中等。
