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Infectious disease immunology

31 Oct 2007   Developing vaccines for diseases

Developing vaccines for diseases

Using vaccines to prevent  infectious animal diseases and to increase productivity is a driving force behind work being done by the Hopkirk's team of Infectious Diseases Immunology scientists.

Bovine TB, or Mycobacterium bovis, is one of the group's priorities as scientists work to beat the 2013 deadline for virtually TB-free stocks of cattle and deer in New Zealand. The levels of TB in New Zealand livestock prevent any exports of live animals to Australia and North America, and limit live export trade to other countries.

Some areas in New Zealand have high infection rates - particularly where there are large numbers of Australian brush tailed possums. These pests are the main wildlife reservoir of TB but Professor of Infectious Disease and head of the Immunology team, Dr Bryce Buddle, says it is difficult to eradicate bovine TB from wildlife reservoirs simply by relying on existing culling procedures.

Searching for an alternative, the Immunology group is testing responses to a new vaccine in the hope of stopping the spread of the disease in possums. Field trials are proving positive where the vaccines are used in oral bait formulations to stimulate a response that makes the possums immune to infection from M. bovis.

Other research involves identifying novel vaccines to protect cattle from bovine TB, as well as identifying and characterising novel drug-enhancing agents for vaccine technologies in possums and cattle. Work in this area is funded by MAF, Animal Health Board and the Department for Environment, Food and Rural Affairs (DEFRA), UK.

The Infectious Disease Immunology team has also been involved in isolating and characterising viruses from possums to be used in a possum biological management programme.

"We are currently evaluating two enteroviruses, isolated from wild possums, to see if they could be used as vaccine delivery vehicles for possum biocontrol," says virologist Dr Tao Zheng. The research is carried out under the umbrella of the National Research Centre for Possum Biocontrol.

With the spectre of the bird flu threat ever present, studying the ecology of avian influenza viruses in domestic poultry is another key project for the group. The avian influenza project is a joint research project between Biosecurity New Zealand, Environmental Science and Research Ltd and AgResearch, under the name of the newly established National Centre for Biosecurity and Infectious Disease (NCBID)-Wallaceville at Upper Hutt.

Other work being done in tandem with dairy research company, Dexcel, and funded by the Foundation for Research, Science and Technology (FRST), is the search for a vaccine to combat mastitis in dairy cows. The focus is on the main mastitis pathogen in New Zealand - Streptococcus uberis. An opportunistic bacterium, it can exist in the dairy environment without any ill effect except when it enters the mammary glands, causing an infection that reduces milk yield and quality. Treatment is usually with antibiotics but this is becoming problematic because of concerns about drug residues in milk.

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