Institute for Integrative and Comparative Biology, Faculty of Biological Sciences, University of Leeds, Clarendon Way, Leeds LS2 9JT, UK.
Vet Parasitol. 2010 May 11;169(3-4):258-63. doi: 10.1016/j.vetpar.2010.01.021. Epub 2010 Jan 25.
Toxoplasma gondii in sheep is important as a cause of lambing losses and as a food hazard. We aimed to assess the prevalence of infection in lambs via development of a standardised PCR technique applied to neonates together with follow-up serology at age 4 months. We measured the sensitivity of PCR targeting the T. gondii sequences B1, SAG1, 5'SAG2, 3'SAG2 and SAG3 in the presence of abundant sheep DNA. B1-PCR was the most sensitive protocol, achieving 50% positivity when 0.02 parasite genome copies were present in an assay testing 10 ng of template. Standardised B1-PCR, and serological follow-up using the modified agglutination test (MAT), were used to estimate infection prevalence in lambs from two flocks in Northern England. Neonatal prevalence detected by PCR on umbilical cord did not differ significantly between viable Charollais (16/243 (6.6%)) and viable Swaledale (30/264 (11.4%)). In contrast, at age 4 months seroprevalence was higher (P<0.001, OR=4.42) in Charollais (50/411 (12.2%)) than in Swaledale (10/335 (3.0%)). There was no evidence of a relationship between the results of PCR and those of serology. In addition, prenatal exposure was not associated with mortality: among non-viable lambs, 3/54 Charollais but 0/16 Swaledale were PCR positive, and 1/26 Charollais and 1/14 Swaledale were seropositive. These results indicate that both standardised B1-PCR, and serology, can be used to detect T. gondii in lambs. Frequent prenatal exposure was detected without mortality and sometimes without an IgG response. Some lambs, without PCR evidence of prenatal exposure, seroconverted early.
弓形虫在绵羊中很重要，它是导致羔羊损失的原因之一，也是食物中的健康隐患。我们旨在通过开发一种标准化的 PCR 技术应用于新生儿，并在 4 个月大时进行后续血清学检测，来评估羔羊的感染率。我们测量了针对 T. gondii 序列 B1、SAG1、5'SAG2、3'SAG2 和 SAG3 的 PCR 技术的灵敏度，该技术在存在大量绵羊 DNA 的情况下进行检测。B1-PCR 是最敏感的方案，当在检测 10ng 模板的试验中存在 0.02 个寄生虫基因组拷贝时，其阳性率达到 50%。标准化的 B1-PCR 和使用改良凝集试验（MAT）进行的血清学随访，用于估计英格兰北部两个羊群中羔羊的感染率。通过对脐带血进行 PCR 检测，在有活力的夏洛莱羊（16/243（6.6%））和有活力的斯瓦莱羊（30/264（11.4%））之间，新生儿的流行率没有显著差异。相比之下，在 4 个月大时，夏洛莱羊（50/411（12.2%））的血清阳性率显著高于斯瓦莱羊（10/335（3.0%））（P<0.001，OR=4.42）。PCR 结果和血清学结果之间没有证据表明存在相关性。此外，产前暴露与死亡率无关：在非有活力的羔羊中，54 只夏洛莱羊中有 3 只是 PCR 阳性，但 16 只斯瓦莱羊中没有；26 只夏洛莱羊和 14 只斯瓦莱羊中有 1 只是血清阳性。这些结果表明，标准化的 B1-PCR 和血清学都可以用于检测羔羊中的 T. gondii。虽然没有死亡率，但检测到频繁的产前暴露，有时也没有 IgG 反应。一些没有产前暴露 PCR 证据的羔羊很早就发生了血清转化。
