ANTIBODIES LEVELS AGAINST Neospora caninum DURING PREGNANCY IN NATURALLY INFECTED DAIRY COWS

Abstract Neosporosis is one of the major causes of reproductive failure in bovine around the world. The period of gestation, in which the infection or the recrudescence of bradzoites forms occurs and reflects in the antibodies levels, is one of the factors that define pregnancy future. Therefore, this study aimed to determine the serological profile during pregnancy of naturally infected females. To do that, serological samples of 25 Holstain Friesian cows were collected from artificial insemination day until parturition, in monthly intervals. These samples were tested by indirect immunofluorescence for IgG anti-Neospora caninum. Of the 25 animals, only 13 were used in the analysis, because they were seropositive since the beginning or seroconverted during pregnancy. The results showed a gradual increase in antibody levels along pregnancy, more visible at the end of the period. We observed a significant difference in antibodies title between initial and final periods of pregnancy, which suggests the reactivation of bradzoite forms present in tissues during pregnancy. These results reinforce the knowledge of antibodies fluctuation along pregnancy, affected by N. caninum reinfection or reactivation. This serological knowledge is important to Neosporosis pathogeny, epidemiology and diagnostic.

摘要：新孢子虫病（Neosporosis）是全球范围内导致牛繁殖失败的主要病因之一。妊娠期是犬新孢子虫（Neospora caninum）缓殖子感染或复发形成，并反映为抗体水平变化的关键时期，亦是决定妊娠结局的核心影响因素之一。因此，本研究旨在明确自然感染犬新孢子虫的孕牛妊娠期的血清学特征。

为达成上述研究目标，研究人员于25头荷斯坦弗里生奶牛的人工授精当日至分娩期间，按月采集血清样本，并采用间接免疫荧光法（indirect immunofluorescence）检测样本中的抗犬新孢子虫免疫球蛋白G（IgG）抗体。25头受试牛中仅13头自妊娠初始即呈血清学阳性，或在妊娠期间发生血清转换，因此最终仅纳入该13头进行数据分析。

结果显示，妊娠期间抗体水平呈渐进式升高趋势，于妊娠末期尤为显著。研究观察到妊娠初始阶段与末期的抗体滴度存在显著差异，这提示妊娠期间组织内潜伏的缓殖子发生了活化。上述结果进一步证实了犬新孢子虫感染或复发可导致妊娠期间抗体水平波动的学术认知。该血清学研究结果对于新孢子虫病的发病机制、流行病学及诊断具有重要意义。