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A Genomic Approach To Developing A Tick Vaccine

10 October 2011

The Australian cattle industry incurs losses of A$175 million each year due to the impact of ticks and tick-borne diseases and costs of treatment to ensure compliance with regulatory protocols for interstate and international livestock movement.

The high costs associated with controlling cattle ticks in Australia and internationally, together with the impact of the use of chemicals to control ticks on food safety and the environment, have meant the cattle industry and governments worldwide have identified the development of a tick vaccine with 12 month's immunity duration and 90 per cent efficacy as a very high priority.

But the tick knows how to stick. "Cattle ticks have been living on cattle for a long period of time," says Professor Mike Goddard, Beef CRC's research leader who was recently elected as a Fellow of the Australian Academy of Science in recognition of his work with innovative use of genetic markers for agriculture.

"Brahman breeds have a natural immunity to ticks but British-based cattle breeds are very susceptible to ticks. The tick has evolved mechanisms for evading the host's immune response."

Professor Goddard says that, unlike bacteria and viruses which are relatively simple organisms the tick is a complex parasite, which makes it harder to develop a vaccine against.

"There has been a good deal of ongoing effort around the world to make malaria vaccines yet it has been extraordinarily difficult to get a vaccine that will protect people against malaria parasites - and malaria parasites aren't as complicated as ticks."

The Beef CRC and its partners are researching the efficacy of anti-tick antigens - which when introduced into the body trigger the production of an antibody in the cattle's immune system.

"We are a bit unique in targeting ticks," says Beef CRC Chief Executive, Dr Heather Burrow.

"Ticks are not one of the targets for human vaccines, yet they are a serious problem in the cattle industry."

The cattle tick was first introduced into Australia in 1872 on 12 Brahman cattle imported from Batavia.

Tick infestation can reduce beef and milk production, and if severe enough, can cause death. However the main damage is caused by transmitting tick-borne diseases to the cattle. These diseases are Babesia bovis ("red water" or babesiosis), Babesia bigemina, (red water) and Anaplasma marginale, (anaplasmosis).

The Beef CRC is undertaking animal trials to determine the efficacy of 14 anti-tick vaccine candidates singly and in combination with other antigens/ peptides.

"Very preliminary results of three antigens (two of which are cocktails of mixed antigens) of CRC candidates are encouraging," says Dr Ala Lew-Tabor, who heads the tick vaccine research project.

"Although the project is on track with all its milestones to date, the degree of difficulty in achieving viable vaccine candidate(s) is extremely high," says Beef CRC CEO Dr Burrow.

"If the Beef CRC does successfully identify effective vaccine targets through its animal trials, very significant additional funds and several more years research would be required to develop the vaccine into a fully registered commercial product available."

By way of example, Dr Burrow said that it took nine years for two Bovine Respiratory Disease (BRD) vaccines developed in CRCI to pass through all national registration requirements and become commercially available.

It is likely that a successful vaccine would as part of a management program using traditional acaricidal and chemical treatments to protect animals against ticks, and would not replace the use of these chemicals entirely.

October 2011

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