Submitted to: Veterinary Parasitology
Publication Type: Peer reviewed journal
Publication Acceptance Date: 6/2/2005
Publication Date: 7/1/2006
Citation: Smith, W.D., Zarlenga, D.S. 2006. Development and hurdles in generation vaccines for controlling helminth parasites of grazing ruminants. Veterinary Parasitology. 139(4):347-359. Interpretive Summary: Currently, no recombinant vaccines are commercially available for the control of helminth parasites. Unfortunately, this failure extends across the entire spectrum of human and animal parasites as well. Gastrointestinal nematodes are nearly always controlled by joint use of anthelmintics and pasture management; however the onset of drug resistance and decades of failures to produce viable vaccines, has left the industry in a quandary as to future approaches to vaccine development. Herein, an evaluation was performed of past and current technologies used to produce vaccines, bringing to light those which deviate from conventional approaches and those which show promise for future research. It was concluded that science has demonstrated a lack of appreciation for the roles that evolution, host parasite adaptation, genetic diversity, poor modeling, and parasite evasion tactics have played in the elusive search for vaccine candidates. Furthermore, it was concluded that future research in designing recombinant vaccines should focus on understanding the effects of incomplete vaccination, vaccinating against the disease rather than the organism, and testing models to appraise the relationship between virulence and resistance. This paper is among the first that evaluates obstacles to vaccine development rather than touting failed approaches of the past.
Technical Abstract: As a direct consequence of rising drug resistance among common nematodes of grazing animals, efforts toward state-of-the-art vaccine development have clearly intensified in recent years, fuelled primarily by the advent of newer technologies in gene discovery, and by advancements in antigen indentification, characteriation and production. In this regard, it is appropriate to review progress that has been made in generating helminth vaccines and in particular, vaccines against common nematodes of food animals. In like manner, it is prudent to evaluate barriers that have hindered progress in the past and continue to present obstacles that must be bridged when utilizing and depending on host immunity to attenuate parasitic infections.