Department of Veterinary Clinical Sciences, College of Veterinary Medicine, Ohio State University, Columbus, OH 43210, USA.
Department of Veterinary Preventive Medicine, College of Veterinary Medicine, Ohio State University, Columbus, OH 43210, USA.
Vet Parasitol. 2024 Oct;331:110242. doi: 10.1016/j.vetpar.2024.110242. Epub 2024 Jun 28.
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.
抗旋毛虫疫苗 Barbervax®在绵羊和骆驼中引起的抗药性，给小反刍动物和骆驼带来了越来越多的管理挑战。该商业疫苗含有 H11 和 H-gal-GP 抗原，来源于旋毛虫肠道黏膜消化血液的酶。这些抗原的抗体中和作用会导致旋毛虫无法消化血液，从而导致寄生虫死亡。H11 和 H-gal-GP 被认为是“隐藏”抗原，这意味着在自然感染下，宿主免疫系统不会遇到这些蛋白质。因此，需要重复免疫来维持保护性体液反应。先前的一项研究评估了 Barbervax®在骆驼中的安全性，但由于对照组未能成功感染，因此无法评估其疗效。本研究的目的是评估在受寄生虫污染的牧场中，健康羊驼在自然环境暴露下，接种 Barbervax®与未接种疫苗的对照组相比，其贫血、粪便卵计数（FEC）和体液免疫反应的临床参数。采用交叉样研究，将 20 只（298±66 日龄）羊驼分配为初始接种 Barbervax®（n=10）或不接受治疗（n=10）。 Barbervax®每三周接种三次。在第-10、0、21、43、64、85、106 和 135 天采集粪便和血液，以评估 FEC、红细胞压积（PCV）和抗体滴度。每组都放在相邻的不同牧场上。在第 43 天引入示踪羊（每组 2 只），为期 3 周，以确保寄生虫的获得。在第 85 天的交叉样部分，最初未接种疫苗的组接种 Barbervax®，并在第 106 和 135 天重复接种。结果表明，所有初始接种疫苗的羊驼均产生了针对疫苗抗原的抗体滴度，与初始未接种疫苗的组相比，这对应较低的平均 FEC。在抗体滴度达到峰值后的 21 天，接种组的平均 FEC 降低。同样，当接种抗体滴度在第 106 天下降时，随后的时间点（第 135 天）观察到 FEC 增加。我们的研究结果支持使用 Barbervax®来降低羊驼的旋毛虫负担。此外，在 FEC 中观察到抗体滴度和相应效果之间的滞后时间不到 30 天。评估 Barbervax®在随后的放牧季节降低旋毛虫负担能力的进一步研究将提供有关在羊驼群中使用 Barbervax®来调节旋毛虫感染、避难所和驱虫剂使用的更多信息。
