Nielsen Martin K, Lyons Eugene T
M.H. Gluck Equine Research Center, Department of Veterinary Science, University of Kentucky, Lexington, KY, USA.
M.H. Gluck Equine Research Center, Department of Veterinary Science, University of Kentucky, Lexington, KY, USA.
Vet Parasitol. 2017 Mar 15;236:108-112. doi: 10.1016/j.vetpar.2017.02.013. Epub 2017 Feb 20.
Cyathostomins (small strongyles) are ubiquitous in grazing horses and are known pathogens as cause of larval cyathostominosis. As part of their life cycle, cyathostomin larvae invade the mucosal walls of the large intestines and undergo encystment. Newly ingested third stage larvae are known to undergo arrested development and this can lead to an accumulation of encysted burdens over the course of a grazing season. It is believed that the host immune system plays a significant role in triggering this arrestment. Little is known about the development and progression of larval stages in foals that are not expected to mount a pronounced immune response to ingested cyathostomin larvae. This study evaluated counts of encysted larvae measured in 37 foals. The foals were born in 2013, 2014, and 2015 into a parasitology research herd kept without anthelmintic intervention and were humanely euthanatized between 50 and 293days of age as part of an ongoing parasite transmission study. A mucosal digestion technique was performed to enumerate encysted early third stage (EL3) and late third stage/fourth stage (LL3/L4) larvae in the cecum, ventral colon and dorsal colon. Counts were analyzed statistically to evaluate the influence of foal age, sex, and seasonality on the counts. Total counts as well as LL3/L4 counts were significantly higher during the grazing season (March-November). Three defined age groups (>100, 100-200, >200days) did not have statistically different counts. Male foals had significantly higher total counts compared to females, and this has not been reported before. The study found that 41% of the recovered larvae were EL3s, but no indication of arrested development of these was observed. This indicates that cyathostomin infection in foals progresses in a manner substantially different from mature horses.
杯环线虫（小型圆线虫）在放牧马匹中普遍存在，是已知的引起幼虫杯环线虫病的病原体。作为其生命周期的一部分，杯环线虫幼虫侵入大肠黏膜壁并进行包囊化。已知新摄入的第三期幼虫会经历发育停滞，这可能导致在放牧季节中包囊负担的积累。据信宿主免疫系统在触发这种停滞中起重要作用。对于预计不会对摄入的杯环线虫幼虫产生明显免疫反应的幼驹，其幼虫阶段的发育和进展知之甚少。本研究评估了37匹幼驹中包囊幼虫的数量。这些幼驹于2013年、2014年和2015年出生在一个未经驱虫干预的寄生虫学研究马群中，并作为一项正在进行的寄生虫传播研究的一部分，在50至293日龄时被人道安乐死。采用黏膜消化技术对盲肠、腹侧结肠和背侧结肠中的早期第三期（EL3）和晚期第三期/第四期（LL3/L4）包囊幼虫进行计数。对计数进行统计分析，以评估幼驹年龄、性别和季节性对计数的影响。在放牧季节（3月至11月），总数以及LL3/L4计数显著更高。三个定义的年龄组（>100、100 - 200、>200天）的计数没有统计学差异。雄性幼驹的总数显著高于雌性，这在以前尚未有过报道。研究发现，回收的幼虫中有41%为EL3，但未观察到这些幼虫发育停滞的迹象。这表明幼驹中的杯环线虫感染进展方式与成年马有很大不同。
