Sager H, Fischer I, Furrer K, Strasser M, Waldvogel A, Boerlin P, Audigé L, Gottstein B
Institute of Parasitology, University of Berne, Länggass-Strasse 122, CH-3001 Berne, Switzerland.
Vet Parasitol. 2001 Dec 3;102(1-2):1-15. doi: 10.1016/s0304-4017(01)00524-6.
Neospora caninum is one of the most frequent infectious organisms causing abortion in cattle worldwide. The present case-control study was designed to assess the importance of bovine neosporosis for causing abortion in Swiss cattle and to identify selected risk factors. Infection was primarily diagnosed by a N. caninum-specific PCR and serology, complemented with histopathology and immunohistochemistry. A total of 113 case and 113 corresponding control-farms were studied for 1.5 year. During this time period, 242 abortions were reported and referred for bacteriological, virological, parasitological and pathohistological examinations. N. caninum was detected by PCR in the brains of 21% of all aborted fetuses. Microscopic lesions indicative for cerebral protozoa infection were detected in 84% of PCR-positive fetal brains. Bovine viral diarrhea virus (BVDV) was demonstrated in 7% of the cases, and bacterial infections were detected in 4% of the abortions. One or more N. caninum-abortions occurred in 20% of the herds (41 case-farms and 3 control-farms). Serological examination of aborting mother cows revealed a significantly higher percentage of N. caninum-seropositive animals (44%) in comparison to the prevalence in a randomly selected population (12%). However, in eight cases (4% of all investigated abortions) seronegative cows aborted N. caninum PCR-positive fetuses, and in 50 cases the fetus remained negative although the respective mother cow was N. caninum-seropositive. Repetitive serological investigations (at a 3-12 months interval) of 3551 cows from case- and control-farms showed a decrease of the overall N. caninum-seroprevalence from 17 to 12%. Ninety out of 3008 seronegative animals were converted to N. caninum-seropositivity. Conversely, 212 out of 543 initially seropositive animals became seronegative for their second serum sample. The obtained data underlined the importance of N. caninum as a causative agent for abortion in Swiss cattle. Furthermore, PCR was confirmed to be a valuable diagnostic tool for the primary diagnosis of N. caninum in aborted fetuses. On the other hand, the value of serology appears to be hampered by the temporal instability of N. caninum antibody concentrations in adult cattle, including especially seronegativity of some individual animals. Thus, seronegativity in a mother cow or heifer does not exclude N. caninum-associated abortions.
犬新孢子虫是全球范围内引起牛流产的最常见感染性生物之一。本病例对照研究旨在评估牛新孢子虫病在瑞士牛流产中的重要性，并确定某些风险因素。感染主要通过犬新孢子虫特异性聚合酶链反应（PCR）和血清学诊断，并辅以组织病理学和免疫组织化学检查。共对113个病例农场和113个相应的对照农场进行了1.5年的研究。在此期间，报告了242例流产病例，并进行了细菌学、病毒学、寄生虫学和病理组织学检查。通过PCR在所有流产胎儿的21%的大脑中检测到犬新孢子虫。在84%的PCR阳性胎儿大脑中检测到指示脑原虫感染的微观病变。在7%的病例中检测到牛病毒性腹泻病毒（BVDV），在4%的流产病例中检测到细菌感染。20%的牛群（41个病例农场和3个对照农场）发生了一次或多次由犬新孢子虫引起的流产。对流产母牛的血清学检查显示，与随机选择的群体中的患病率（12%）相比，犬新孢子虫血清阳性动物的百分比显著更高（44%）。然而，在8例（占所有调查流产病例的4%）中，血清阴性的母牛产下了犬新孢子虫PCR阳性的胎儿，在50例中，尽管相应的母牛血清学呈犬新孢子虫阳性，但胎儿检测仍为阴性。对病例农场和对照农场的3551头母牛进行重复血清学调查（间隔3 - 12个月）显示，犬新孢子虫的总体血清阳性率从17%降至12%。3008头血清阴性动物中有90头转为犬新孢子虫血清阳性。相反，543头最初血清阳性的动物中有212头在第二次血清样本检测时变为血清阴性。所获得的数据强调了犬新孢子虫作为瑞士牛流产病原体的重要性。此外，PCR被确认为流产胎儿中犬新孢子虫初步诊断的有价值诊断工具。另一方面，血清学的价值似乎受到成年牛中犬新孢子虫抗体浓度的时间不稳定性的影响，特别是包括一些个体动物的血清阴性情况。因此，母牛或小母牛的血清阴性并不排除与犬新孢子虫相关的流产。
