A Critical Review on Vaccine Development Against Helminths of Ruminants

Abstract

Helminthes have harmful impacts on livestock productivity by affecting growth rate, fertility, meat quality, and wool and milk production. The financial costs associated with these worms are significant. The global increase in anthelmintic-resistant nematodes of ruminants, together with consumer concerns about chemicals in food, necessitates the development of alternative methods of control for these pathogens. Vaccines are considered a favorable alternative because of the long-lasting protection they can provide and the absence of chemical residues in animal products and the environment. The process of vaccine development against parasites is complicated and faces several challenges. The safety and efficacy of the vaccine, detecting the protective antigens, identifying the protective mechanism, difficulty in obtaining enough quantities of parasite material, and decisions from policymakers are the main challenges for the production of effective hel-minth vaccines. Very few helminth vaccines are on the livestock market, currently for nematodes. These comprise only the cattle lungworm (Dictyocaulus viviparous) vaccine and a vaccine against the barber's pole worm (Haemonchus contortus) in sheep, and the only recombinant helminth vaccine against the cestodes (Echinococcus granulosus) in ruminants. The ongoing development of experimental vaccines against several other hel-minth species in livestock holds promise for a wider range of helminth vaccines in the future.