Mário Sérgio Assayag Jr., MV, DSc

Mário Sérgio Assayag Jr., MV, DSc, the veterinarian in charge of animal health for Brasil Foods, Curitiba, explained that IB has been a problem for both broilers and broiler breeders and that the challenges are both seasonal and periodic.

In broilers, IB often leads to increased use of medication in the field and higher condemnations due to air-sacculitis and colibacillosis, the veterinarian reported.

In breeders, IB results in poor hatching, egg production and mortality. An added complication is frequent co-infection with avian metapneumovirus, which requires its own vaccination, he added.

In one field example cited by Dr Assayag, broiler flocks affected with IB had watery faeces, extremely wet litter and were depressed and rough-feathered; they also were severely dehydrated, which was indicated by dark muscles, and had kidney lesions, mild airsacculitis and contact dermatitis. Mortality was elevated by three per cent.

A field case involving breeders was characterized by watery feces, severe dehydration, kidney lesions, air-sacculitis, contact dermatitis and a 0.5 per cent increase in mortality, he said.

Economic Impact

The economic impact of IB has been significant: Over US$3 million annually for broilers and nearly US$4 million for breeders, Dr Assayag continued.

The company, which has its own facilities where IB viruses can be typed using polymerase chain reaction (PCR) and genetic sequencing, also conducts challenge trials in its lab as well as field trials. It has found that 58 per cent of IB viruses affecting its flocks are of the Massachusetts serotype and 42 per cent are IB variants, he said.

Brasil Foods uses testing results to adapt its vaccine programmes to the IB challenge as needed. In broilers, it has administered IB H120 or Ma5, both of the Massachusetts IB serotypes.

“The protection with an IB Ma5 vaccine is much higher, and it’s a better vaccine to use because you don’t have to vaccinate as many times,” Dr Assayag said.

In breeders, the vaccination programme used also varies depending on the IB challenge and is tailored to meet the needs of these longer-lived birds that need protection longer than broilers. The company may use a live IB Ma5, H120 or both vaccines to start, followed by killed IB vaccines such as Mass or the variant D274, and then revaccinates during production with two killed vaccines.

“We use those two inactivated vaccines with good results when there is a very high IB challenge,” Dr Assayag said.

The concept of Protectotype — using more than one IB vaccine from serotypes that have cross-protective ability — “is a very important way to look at infectious bronchitis if we want results in the field,” he added.

Further Reading

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