Haerdi Corinne, Haessig Michael, Sager Heinz, Greif Gisela, Staubli Daniela, Gottstein Bruno
Herd Health, Department of Farm Animals, Vetsuisse Faculty, University of Zurich, Winterthurerstr. 260, CH-8057 Zurich, Switzerland.
Parasitol Res. 2006 Oct;99(5):534-40. doi: 10.1007/s00436-006-0199-7. Epub 2006 Apr 21.
Neospora caninum is widely recognized as one of the most important infectious organisms causing abortion and stillbirth in cattle. This parasite causes severe economical losses worldwide. Infection is mostly passed vertically from mother to calf during pregnancy. Under certain circumstances, an infection can lead to abortion, but in most cases it results in a chronically infected calf, which itself will represent the next endogenously infectious generation. So far, no reliable therapeutic or metaphylactic tool has been developed. One possibility to control the problem may consist of treating newborn calves that became vertically infected by a persistently infected mother. This may allow parasite-free offspring. The aim of the present study was to address the questions: (1) can serology be used to assess efficiency of treatment in toltrazuril-medicated animals? and (2) is a strategic prevention measure possible by means of producing N. caninum-free calves from positive cows? Calves from Neospora-seropositive cows and heifers were randomly split into two different medication groups: 36 calves were medicated with toltrazuril and 36 calves obtained a placebo. Medication (20 mg toltrazuril per kg bw) was administered three times, every second day, within the 7 days post natum. Three months after medication, there was no difference in antibody reactivity between the two groups. At later time points (4-6 months), however, significant differences were found, as explained by a strong humoral immunity after chemotherapeutical affection of parasites, while the placebo-treated animals only responded weakly to the persistent infection. In summary, we concluded that (1) serology was not an entirely appropriate tool to answer our initial question and (2) toltrazuril has the potential to eliminate N. caninum in newborn calves. As a consequence, we plan to follow up toltrazuril-medicated calves clinically and serologically over a longer period and investigate if they give birth to Neospora-free calves.
犬新孢子虫被广泛认为是导致牛流产和死产的最重要的感染性生物之一。这种寄生虫在全球范围内造成了严重的经济损失。感染大多在怀孕期间从母体垂直传播给犊牛。在某些情况下，感染会导致流产，但在大多数情况下会导致犊牛慢性感染，而这头犊牛本身将成为下一个内源性感染源。到目前为止，尚未开发出可靠的治疗或预防工具。控制该问题的一种可能性可能是对因持续感染的母体而垂直感染的新生犊牛进行治疗。这可能会产生无寄生虫的后代。本研究的目的是解决以下问题：（1）血清学能否用于评估经托曲珠利治疗的动物的治疗效果？（2）通过从阳性母牛生产无犬新孢子虫的犊牛是否可以采取一种战略性预防措施？来自犬新孢子虫血清阳性母牛和小母牛的犊牛被随机分为两个不同的给药组：36头犊牛接受托曲珠利治疗，36头犊牛接受安慰剂。在出生后7天内，每隔一天给药一次（每千克体重20毫克托曲珠利），共给药三次。给药三个月后，两组之间的抗体反应性没有差异。然而，在随后的时间点（4 - 6个月），发现了显著差异，这是由于寄生虫化疗后产生了强烈的体液免疫，而接受安慰剂治疗的动物对持续感染的反应较弱。总之，我们得出结论：（1）血清学不是回答我们最初问题的完全合适的工具；（2）托曲珠利有潜力消除新生犊牛体内的犬新孢子虫。因此，我们计划对接受托曲珠利治疗的犊牛进行更长时间的临床和血清学随访，并调查它们是否能产下无犬新孢子虫的犊牛。
