Roadmap for nematode control strategies

How long should a vaccine protect livestock and what levels of protection would be sufficient to prevent disease and production losses?
Do all animals in a group need to be vaccinated?
Is there a benefit to female vaccination for protection of the offspring?
What are the consequences of a mono-valent vaccine on the species composition and structure of worm populations?

Levels of efficacy required may vary among nematode species, the class of livestock targeted and between regions, depending on climatic context and local farm management practices.
Vaccine efficacy may vary between breeds depending on mechanisms of defence; also depending on the nutritional status of the vaccinated hosts; and in offspring co-grazing with dams.

For logistical, financial and animal welfare reasons, it will be practically impossible to test all possible scenarios by vaccine trials in the field. Evaluating vaccine efficacy requirements through mathematical modelling could be a valuable tool to help define useful levels of protection and to model integrated use of vaccines with other parasite control measures.

At present, regulatory authorities are not familiar with registration of nematode vaccines.
Modelling of the required efficacy of a vaccine for any given environment to provide a meaningful epidemiological benefit.

A hidden antigen vaccine (Barbervax©) has been developed and tested in different parts of the world against H. contortus with excellent levels of protection under natural conditions. This vaccine might not be sufficient where other parasites are more relevant.
A model simulating the effect of vaccines against larval stages or adult H. contortus in sheep has been developed, but a threshold for protection needed to protect animals from acquiring harmful burdens during the entire grazing season has not been determined.
A live attenuated vaccine against lungworm (Dictyocaulus viviparus) in cattle has been in use for some decades.