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Vaccine for "Crook Chooks"

New Zealand vaccine distributor PacificVet NZ, researcher Dr Rob McFarlane and PhD candidate Ramneek from the Animal and Food Sciences Division at Lincoln University have joined forces to find out more about a common viral infection in poultry.

The research team has identified the different strains of the infectious bronchitis virus present in poultry in New Zealand and checked how effective current vaccines were in protecting against this disease.

Poultry are commonly infected with the infectious bronchitis virus but usually they show no signs of the disease and so it is not a problem. However, the disease can be triggered when the hens are stressed or exposed to a sudden fall in temperature. The virus can spread rapidly from hen to hen by coughing. Infected birds typically do not grow as efficiently, develop kidney lesions and can die.

A vaccine developed in New Zealand has been available for the last 20 years but there has not been any recent research into the pattern of this viral disease. The numbers of animals raised for human consumption have increased significantly, so more animals are at risk from infection as they are concentrated in large production units.

"We developed a new detection system that uses the latest gene technology to identify the particular strain of the infectious bronchitis virus present. The test targets the genetic material of the virus," says McFarlane.

The virus contains genetic material known as ribonucleic acid (RNA) which is closely related to the more commonly known DNA.

"We multiply the genetic material from field samples in the laboratory, cut it into short lengths with special enzymes before placing it on a tray of a jelly-like substance (gel) and passing an electric current through it. Different lengths of RNA move different distances along the gel and the characteristic pattern of each length gives each virus strain its "fingerprint".

"The test is fast and sensitive, results are obtained within a few hours rather than the days required for virus isolation, and the results are comparable with previous methods of identification."

Four different strains of the virus have been identified and tests showed that when compared with the overseas strains the New Zealand strains were more closely related to Australian than European or American strains (98% similarity with the Australian vaccine). This hints at the original source of our New Zealand isolates.

"It is important for the vaccine supplier, PacificVet, to know if their vaccine is still effective against the viral strains found in New Zealand," said McFarlane, "and it's satisfying to find out that this is true."

Further research will be needed to find our how cold stress triggers the disease and to investigate the feasibility of developing an improved vaccine.