Testing and verification of a single-dose cattle tick vaccine

Summary

Of all parasites, cattle ticks have the most devastating impact to Australia's cattle industry and cause an estimated $161 million in losses a year. In the north, where cattle are only mustered once or twice a year, the current multiple-dose vaccines are not always practical.

Given the value of a vaccine that gives season-long cover from the time of injection, this project evaluated the efficiency of an experimental single-dose vaccine to protect herds from cattle ticks and cattle-tick larvae.

The results of the single-dose cattle-tick vaccine are promising, but further work is required to improve the safety of the injection.

Objectives

This project's primary objective was to determine the capacity and functionality of a new single-dose cattle tick vaccine to protect cattle from tick infestations for at least six months after they receive the injection.

Key findings

• A single injection of the experimental vaccine stimulated an immune response that was 76.9% effective when the cattle were purposely infested with ticks 56 days after the injection.
• The immune response peaked 28 days after the vaccine was injected and persisted for more than one year. This suggests a single dose of the vaccine might be possible for future tick control.
• Optimal control of cattle-ticks is estimated to return $61 million in lost productivity to northern Australian cattle producers. This single-dose cattle tick vaccine could be a crucial component of an integrated pest management system to achieve this return.
• When the vaccine was given to the cattle for a second time 12 months after the first injection, there were some tissue reactions at the injection site, which means that more work is needed to improve the vaccine's safety.

Benefits to industry

A single-dose cattle tick vaccine would overcome the challenge of providing effective immunisation to cattle that are not frequently mustered. An effective and practical cattle tick vaccine would also reduce industry reliance on chemical tick control and reduce the risk of chemical contamination of beef.

MLA action

MLA is currently collaborating with the researchers to determine how the vaccine formulations can be improved to increase safety and effectiveness of the injections.

Other avenues of research funded by MLA include a continuation of the search for a new tick-derived immune response and the investigation of a completely novel vaccine that would have efficacy against a variety of different ticks.

Future research

The results of this project clearly demonstrate the feasibility of a single-dose cattle vaccine, however, there are several areas where further research is required before the vaccine is ready for commercialisation and adoption. These include:

• determining the level of protection provided by the vaccine at different times after immunisation
• identifying the relationship between immune response and protective efficacy
• addressing the variation in immune responses between animals
• improving the safety of the vaccine in terms of its injection site reactions.