Safety and serologic response to a Haemonchus contortus vaccine in alpacas

Abstract

Haemonchosis in camelids remains a challenging disease to treat, and prevention has become increasingly problematic due to widespread anthelmintic resistance. Barbervaxis an adjuvanted vaccine containing natural H-11, H-gal-GP antigens obtained from Haemonchus contortus adults via a proprietary process and solubilized in Quil A. This vaccine is approved for use in Australia, after demonstrating its safety and efficacy in sheep and goats. There are no published studies evaluating Barbervax in other ruminants/pseudoruminants such as camelids which can be parasitized with H. contortus. The vaccine utilizes a mixture of the parasite gut mucosal membrane enzymes including H-gal-GP and H11, involved in digesting a blood meal from the host. This study monitored the safety profile of the Barbervax vaccine in a group of adolescent alpacas. Although designed into the original study of vaccine efficacy, the experimental infection with viable H. contortus third stage larvae could not be completed due to lack of detectable significant variation of infection following experimental challenge. Twelve alpacas (158 + 15 days) were randomized to vaccination with Barbervax or no treatment. Three doses of Barbervax were administered at 3 week intervals and investigators involved in animal monitoring and sample collection were blinded to the groupings. Clinical pathologic parameters were evaluated 7 days before vaccination, and 1 and 2 months post-vaccination. Daily clinical observations were made and specific observations regarding the injection site and rectal temperatures were monitored in each alpaca twice daily for 1 week following vaccination. Fecal egg counts, packed cell volume, and total protein were monitored following challenge with 1500 H. contortus larvae on days 42, 46, and 50. An increase in rectal temperature for a duration of 2 days (range 2-4 days) was observed post-vaccination. Vaccinated alpacas were lethargic for 2-3 days following vaccination; however, they maintained an appetite and no visible or palpable injection site reactions were observed. Following the first vaccination, all animals maintained normal clinical pathologic parameters throughout the study period. The vaccinated animals did develop titers to the H. contortus antigen as measured by ELISA. In conclusion, the Barbervax vaccine demonstrated safety in this small group of young, healthy alpacas, but additional studies are required to evaluate the efficacy of the vaccine under field conditions in protecting alpacas against infection with H. contortus.

The excretory–secretory antigen HcADRM1 to generate protective immunity against Haemonchus contortus

“…Administration of rHcADRM1 antigen elicited sufficient levels of immune protection in H. contortus-inoculated goats, resulting in 48.9 and 58.6% reductions in cumulative FEC and worm burden, respectively. As demonstrated by the protective mechanism of action for Barbervax (LeJambre et al, 2008;VanHoy et al, 2018), the levels of repeated immunizations-induced antigenspecific antibodies (mainly IgG) were well correlated with the protective efficacy of an anti-H. contortus vaccine. Hence, anti-rHcADRM1 IgG was employed in the parallel passive trial and was shown to confer encouraging levels of protection to inoculated goats by reducing cumulative FEC and worm burden by 46.7 and 56.2%, respectively.…”

Haemonchosis in Sheep and Goats, Control Strategies and Development of Vaccines against Haemonchus contortus

“…Both antigens may induce strong protective immunity in sheep and goats when used separately. Vaccine trials of Barbervax ® have confirmed elevated serum immunoglobulin levels and significant reductions of faecal egg count and worm burden in vaccinated animals [ 40 , 59 , 84 , 85 , 86 ]. Currently, native H11 and H-gal-GP antigens have to be isolated from H. contortus adults derived from the abomasa of donor sheep upon slaughter, since adult parasites cannot be obtained by in vitro cultivation.…”

Development and Advancement in Vaccines Against Haemonchus Contortus

“…A vaccine named Barbervax® has been recently licensed to be marketed in Australia which contain two native integral gut membrane protein H11 and H-gal-GP from H. controtus (Nisbet et al 2016). During evaluation of safety and serological outcome of this vaccine significant antibody titers have been detected in the vaccinated animals (Vanhoy et al 2018).…”