Rezende-Gondim Mariana M, da Silva Aristeu V, Schares Gereon, Gondim Luís F P
Universidade Federal da Bahia, Escola de Medicina Veterinaria e Zootecnia, Departamento de Anatomia, Patologia e Clinicas, Av. Adhemar de Barros 500, 40170-110, Salvador, Bahia, Brazil.
Departamento de Biologia, Universidade Estadual de Feira de Santana, 44036-900, Feira de antana, Bahia, Brazil.
Vet Parasitol. 2017 Jan 30;234:19-24. doi: 10.1016/j.vetpar.2016.12.013. Epub 2016 Dec 21.
Neospora caninum and Toxoplasma gondii are coccidian parasites that infect a wide range of mammalian and avian species. While viable T. gondii has been in vitro isolated in natural infections from wild and domestic birds, attempts to isolate N. caninum from naturally-infected birds were unsuccessful. We speculate that body temperatures of birds, which are usually higher than those of mammals, may impair the multiplication of N. caninum. In contrast to N. caninum, T. gondii can grow in vitro at temperatures higher than 37°C. To test the hypothesis that N. caninum tachyzoites are impaired to grow in vitro at high temperatures, three strains of N. caninum (NC-1, NC-Liverpool, and NC-Bahia) and three of T. gondii (RH, ME-49 and NED) were cultivated at gradually increasing temperatures starting at 37°C up to 41.5°C. A permanent chicken cell line was chosen for the study. Parasites were observed microscopically and their presence in culture was evaluated by species-specific conventional PCRs. In a second experiment, growth rates of T. gondii (RH strain) and N. caninum (NC-1 strain) were evaluated after direct passage of tachyzoites from 37°C to 41.5°C, and quantified by real-time PCR. In addition to comparisons between N. caninum and T. gondii, growth rates of three T. gondii strains were compared at high temperatures. Neospora caninum tachyzoites could not sustain multiplication at temperatures between 39°C and 41.5°C. Toxoplasma gondii tachyzoites continued to multiply at the same experimental conditions. Direct passage of N. caninum tachyzoites from 37°C to 41.5°C caused a significant decrease in the number of parasites during 96h of observation, while T. gondii had a significant increase in the number of stages after the same period of time. T. gondii RH strain (clonal type I) presented a different growth rate at 41.5°C when compared with type II and type III strains. In conclusion, multiplication of N. caninum tachyzoites in vitro was inhibited at temperatures similar to those of chickens, what may be one of the reasons that isolation of the parasite is difficult in avian species. In contrast to N. caninum, T. gondii continued to grow at 41.5°C.
犬新孢子虫和刚地弓形虫是球虫寄生虫，可感染多种哺乳动物和鸟类。虽然在自然感染的野生和家养鸟类中已在体外分离出活的刚地弓形虫，但从自然感染的鸟类中分离犬新孢子虫的尝试均未成功。我们推测，鸟类的体温通常高于哺乳动物，这可能会损害犬新孢子虫的增殖。与犬新孢子虫不同，刚地弓形虫可以在高于37°C的温度下在体外生长。为了验证犬新孢子虫速殖子在高温下体外生长受损的假设，将三株犬新孢子虫（NC-1、NC-利物浦和NC-巴伊亚）和三株刚地弓形虫（RH、ME-49和NED）在从37°C逐渐升高至41.5°C的温度下培养。选择了一种永久性鸡细胞系进行研究。通过显微镜观察寄生虫，并通过物种特异性常规PCR评估其在培养物中的存在情况。在第二个实验中，将速殖子从37°C直接传代至41.5°C后，评估刚地弓形虫（RH株）和犬新孢子虫（NC-1株）的生长速率，并通过实时PCR进行定量。除了比较犬新孢子虫和刚地弓形虫外，还比较了三种刚地弓形虫菌株在高温下的生长速率。犬新孢子虫速殖子在39°C至41.5°C之间的温度下无法维持增殖。在相同的实验条件下，刚地弓形虫速殖子继续增殖。犬新孢子虫速殖子从37°C直接传代至41.5°C后，在96小时的观察期内寄生虫数量显著减少，而刚地弓形虫在相同时间段后虫体数量显著增加。与II型和III型菌株相比，刚地弓形虫RH株（克隆I型）在41.5°C时呈现出不同的生长速率。总之，犬新孢子虫速殖子在体外的增殖在与鸡体温相似的温度下受到抑制，这可能是该寄生虫在鸟类中难以分离的原因之一。与犬新孢子虫不同，刚地弓形虫在41.5°C时继续生长。
