This study aimed to evaluate the dynamics of Haemonchus contortus and Haemonchus placei infections and hybridization between these species in grazing sheep without contact with cattle. On January 14, 2014, sixteen young sheep were infected with 4000 infective H. placei third-stage larvae L3; 11 days later, another group n = 16 was infected with 4000 H. contortus L3. The establishment rates of H. contortus and H. placei L3 were, on average, 61.6 % and 56.8 %, respectively, in the permanent sheep. After the establishment of patent infections, all permanent sheep were allocated together in the same clean pasture where they grazed for the next 12 months. Euthanasia of a sample of the permanent sheep was performed every three months: in May, August, November and February. Two weeks before the sheep were removed for euthanasia, 2 worm-free tracer sheep were introduced to the pasture to evaluate the larval population in the field. The tracer sheep grazed alongside the permanent sheep for 2 weeks. Then, they were housed indoors for 20 days; at the end of this period, they were euthanized. Parasites were recovered from the permanent and tracer sheep and identified using morphological and molecular techniques. A total of 432 worms (from permanent and tracer animals) were analyzed by PCR using species-specific primer pairs. Of these specimens, only two (0.46 %) male worms were identified as hybrids: one was recovered from a permanent animal euthanized in August and the other from a tracer sheep that grazed in May. The last detection of adult H. placei worms occurred in sheep euthanized in May (approximately 3.5 months after the beginning of the grazing period). The morphological evaluation of the L3 produced in fecal cultures showed that H. placei were progressively replaced by H. contortus populations starting in March. The last trace of H. placei L3 was found in August, when a small percentage (0.5 %) of infective larvae with H. placei morphology was identified in a fecal culture. In conclusion, hybridization between H. contortus and H. placei can occur in the field during coinfection. It was demonstrated that H. placei established successfully in artificially infected worm-free sheep; however, with concomitant natural reinfection with H. contortus, the H. placei population showed a rapid decrease and was eliminated within a few months in an environment without cattle.

中文翻译：

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在只绵羊放牧的牧场中，海龟（Haemonchus contortus）和海龟（haemonchus placei）之间存在竞争吗？

本研究旨在评估在不与牛接触的情况下，放牧绵羊的弯曲变形杆菌和胎盘变形杆菌感染的动态以及这些物种之间的杂交。2014年1月14日，十六只小绵羊感染了4000株感染性Placeh的第三阶段幼虫L3；11天后，另一组n ＝ 16感染4000 H.Contortus L3。永久绵羊中，Contortus和H. placei L3的建立率平均分别为61.6％和56.8％。建立专利感染后，所有永久性绵羊都被分配到同一干净的牧场中，在接下来的12个月里放牧。每三个月进行一次永久性绵羊样品的安乐死：五月，八月，十一月和二月。在为安乐死移走绵羊的两周前，将2只无蠕虫的示踪羊引入牧场，以评估田间幼虫的数量。追踪绵羊和永久绵羊放牧了两个星期。然后，他们被安置在室内20天。在此期间结束时，他们被安乐死。从永久羊和示踪羊中回收寄生虫，并使用形态学和分子技术对其进行鉴定。使用物种特异性引物对通过PCR分析了总共432种蠕虫（来自永久性动物和示踪动物）。在这些标本中，仅鉴定出两种（0.46％）雄性蠕虫为杂种：一种是从8月实施安乐死的永久动物中回收的，另一种是从5月放牧的示踪绵羊中回收的。最后一次检测到成年的H. placei蠕虫是在5月安乐死的绵羊中（放牧期开始后约3.5个月）。粪便培养物中产生的L3的形态学评估表明，从3月开始，胎盘螺旋藻逐渐被扭曲螺旋藻种群所取代。在八月份发现了粪便嗜血杆菌L3的最后痕迹，当时在粪便培养物中鉴定出一小部分（0.5％）具有嗜血杆菌形态的感染性幼虫。总之，在合并感染过程中，野外嗜血杆菌和胎盘菌之间可能发生杂交。结果表明，在人工感染的无蠕虫的绵羊中成功地建立了H. placei。然而，伴随着Con。contortus的自然再感染，在没有牛的环境中，H。Placei种群迅速减少并在几个月内被淘汰。从3月开始的contortus种群。在八月份发现了粪便嗜血杆菌L3的最后痕迹，当时在粪便培养物中鉴定出一小部分（0.5％）具有嗜血杆菌形态的感染性幼虫。总之，在合并感染过程中，野外嗜血杆菌和胎盘嗜血菌之间可能发生杂交。结果表明，在人工感染的无蠕虫的绵羊中成功地建立了H. placei。然而，伴随着Con。contortus的自然再感染，在没有牛的环境中，H。Placei种群迅速减少并在几个月内被淘汰。从3月开始的contortus种群。在八月份发现了粪便嗜血杆菌L3的最后痕迹，当时在粪便培养物中鉴定出一小部分（0.5％）具有嗜血杆菌形态的感染性幼虫。总之，在合并感染过程中，野外嗜血杆菌和胎盘菌之间可能发生杂交。结果表明，在人工感染的无蠕虫的绵羊中成功地建立了H. placei。然而，伴随着Con。contortus的自然再感染，在没有牛的环境中，H。Placei种群迅速减少并在几个月内被淘汰。合并感染期间在现场可能会发生胎盘。结果表明，在人工感染的无蠕虫的绵羊中成功地建立了H. placei。然而，伴随着Con。contortus的自然再感染，在没有牛的环境中，H。Placei种群迅速减少并在几个月内被淘汰。合并感染期间在现场可能会发生胎盘。结果表明，在人工感染的无蠕虫的绵羊中成功地建立了H. placei。然而，伴随着Con。contortus的自然再感染，在没有牛的环境中，H。Placei种群迅速减少并在几个月内被淘汰。