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）是全球范围内引发牛繁殖障碍的主要病因之一。妊娠期内发生的新孢子虫感染或缓殖子（bradzoites）复激活，可通过宿主抗体水平反映，该过程是决定妊娠预后的关键因素之一。因此，本研究旨在明确自然感染新孢子虫的孕牛在妊娠期间的血清学动态特征。为此，研究人员从25头荷斯坦弗里生奶牛（Holstain Friesian）的人工授精当日起，直至分娩，按月采集血清样本，并采用间接免疫荧光法（indirect immunofluorescence）检测所有样本的抗犬新孢子虫（Neospora caninum）IgG抗体水平。25头受试奶牛中仅13头纳入后续分析，原因是这些个体在妊娠起始时即呈血清学阳性，或在妊娠期间发生了血清转换。结果显示，孕牛体内抗体水平随妊娠进程逐步升高，该趋势在妊娠末期尤为显著。研究观察到妊娠初期与末期的抗体效价存在显著差异，这提示妊娠期间宿主体内组织中潜伏的缓殖子发生了复激活。上述结果进一步证实了犬新孢子虫（N. caninum）感染或复激活可导致妊娠期间抗体水平波动这一认知。该血清学研究结果对于新孢子虫病的发病机制、流行病学及诊断学均具有重要参考价值。