Abstract：
Anthelmintic resistance to Haemonchus contortus creates increasing management challenges with small ruminants and camelids. The commercial vaccine, Barbervax®, contains H11 and H-gal-GP antigens, derived from gut mucosal membrane enzymes of H. contortus involved in digesting blood. Antibody neutralization of these antigens causes failure of H. contortus to digest blood, resulting in parasite death. H11 and H-gal-GP are considered \"hidden\" antigens, meaning the host immune system does not encounter these proteins under natural infection. Therefore, repeat immunization is required to maintain protective humoral responses. One previous study evaluated the safety of Barbervax® in camelids but the efficacy could not be assessed due to lack of successful infection in the controls. The objective of the current study was to evaluate clinical parameters of anemia, fecal egg counts (FECs), and humoral immune responses of healthy alpacas after immunizing with Barbervax® compared to non-vaccinated controls, all under natural environmental exposure on parasite-laden pastures. A crossover-like study was performed where twenty alpacas (298 ± 66 days of age) were assigned to be initially vaccinated with Barbervax® (n=10) or receive no treatment (n=10). Three doses of Barbervax® were administered at three-week intervals. Feces and blood were collected on Day -10, 0, 21, 43, 64, 85, 106, and 135 to evaluate FECs, packed cell volume (PCV), and antibody titers. Each group was kept on separate adjacent pastures. Tracer sheep (n=2 per study group) were introduced on Day 43 for a three-week period to ensure parasite acquisition. For the crossover-like component on Day 85, the initial non-vaccinated group was administered Barbervax® with dosing repeated on Day 106 and 135. Results indicated all initially vaccinated alpacas produced antibody titers to vaccine antigen that corresponded to lower mean FECs compared to the initially non-vaccinated group. A reduced mean FEC in the vaccinate group was observed 21 days after peak antibody titers. Similarly, when pooled vaccinate antibody titers were noted to wane on Day 106, an increase in FEC was observed at the following time point (Day 135). Conclusions from our study support the use of Barbervax® to reduce H. contortus burdens in alpacas. Furthermore, a less than 30-day lag time between antibody titer and resultant effect in FECs was observed. Additional studies assessing the ability of Barbervax® to reduce H. contortus burdens during subsequent grazing seasons would provide even greater information regarding the use of Barbervax® within alpaca herds to modulate H. contortus infections, refugia, and anthelmintic use.
摘要：
对小反刍动物和骆驼科动物的驱虫抗药性给管理带来了越来越多的挑战。商业疫苗，Barbervax®,含有H11和H-gal-GP抗原，来自H.contortus的肠粘膜酶参与消化血液。这些抗原的抗体中和导致扭曲H.导致寄生虫死亡。H11和H-gal-GP被认为是“隐藏”抗原，这意味着宿主免疫系统在自然感染下不会遇到这些蛋白质。因此,重复免疫是维持保护性体液应答所必需的。先前的一项研究评估了Barbervax®在骆驼中的安全性，但由于对照组中缺乏成功的感染，因此无法评估疗效。本研究的目的是评估贫血的临床参数，粪便卵数（FECs），与未接种疫苗的对照组相比，健康羊驼在用Barbervax®免疫后的体液免疫反应，所有这些都暴露在充满寄生虫的牧场上的自然环境下。进行交叉样研究,其中二十只羊驼(298±66日龄)被指定为最初接种Barbervax®(n=10)或不接受治疗(n=10)。以三周的间隔施用三个剂量的Barbervax®。在第-10、0、21、43、64、85、106和135天收集粪便和血液以评估FECs。细胞体积（PCV），和抗体滴度。每个小组都保持在单独的相邻牧场上。在第43天引入示踪绵羊(每个研究组n=2)持续三周时间以确保获得寄生虫。对于在第85天的交叉样组分,在第106天和第135天重复给药的情况下,向初始未接种组施用Barbervax®。结果表明,与最初未接种的组相比,所有最初接种的羊驼产生的针对疫苗抗原的抗体滴度对应于较低的平均FECs。在峰值抗体滴度后21天观察到疫苗组中平均FEC降低。同样，当在第106天注意到汇集的疫苗接种抗体滴度减弱时,在随后的时间点(第135天)观察到FEC增加.我们研究的结论支持使用Barbervax®来减少羊驼中的H.contrortus负担。此外，在FECs中观察到抗体滴度与最终效应之间的滞后时间少于30天.其他研究评估Barbervax®在随后的放牧季节中减少H.contrortus负担的能力，将提供有关在羊驼群中使用Barbervax®调节H.contrortus感染的更多信息，避难所,和驱虫药的使用。
