Novel animal parasite vaccines

Livestock production efficiency is impaired by worm infections that cause debilitating respiratory, intestinal and hepatic dysfunctions. Disease management relies in many cases almost exclusively on the use of drugs, now threatened by the emergence of drug resistance. Vaccination constitutes a viable alternative but previous to the latest EU research, there were no commercial vaccines available.

The EU-funded PARAVAC (Vaccines against helminth infections) consortium brought together experts from all over the world for this ambitious initiative. Altogether, six parasites came under the PARAVAC microscope – H. contortus, Ostertagia ostertagi, Cooperia oncophora a roundworm infecting cattle, Fasciola hepatica (liver fluke), the lungworm Dictyocaulus viviparous and the dog tapeworm, Echinococcus granulosus.

Understanding how a vaccine establishes immunity, the avidity of the generated antibodies and what effector cells get triggered is central for maximising vaccine performance. Considerable effort was devoted to delineating the immune responses induced by each vaccine under trial.

Vaccine efficacy was tested on animals and the assessed parameters include parasite numbers and growth rate as well as body condition and welfare of recipient animals. The prototype vaccines against helminths such as C. oncophora, H. contortus and F. hepatica proved highly effective in housed trials.

Field trials were conducted all around the world to further validate the effectiveness of the PARAVAC vaccines. The Haemonchus and Cooperia vaccines are both highly effective under field conditions, the former also shown to be effective in Brazil, not only against H. contortus in sheep, but also H. placei and H. similis in cattle.

The Haemonchus and Fasciola vaccines have been produced in quantity with the required quality control. The researchers also used mathematical models to appraise the usefulness and cost-effectiveness of the vaccines prior to introduction. Additional models simulated the required performance characteristics of vaccines against certain parasites.

Launch of the Haemonchus vaccine in Australia in 2014 was followed by excellent uptake by producers. Moreover, a dossier has been submitted for production approval of the vaccine in South Africa. PARAVAC have made significant contributions towards the development of safe and efficacious vaccines for the control, reduction and management of important helminth infections in a range of livestock. A commercial evaluation has been made for all parasitic targets addressed by the project paving the way for further research.