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Two IB Vaccines of different serotypes help producers implement 'Protectotype' strategy

Field experience and studies demonstrate that infectious bronchitis (IB) variants can be controlled by using two vaccines of different serotypes, or what many specialists now call a Protectotype strategy.

Research has demonstrated that some IB vaccine viruses can induce effective crossprotection against strains from serotypes other than those of the vaccines used, explains Aris Malo, DVM, global technical director for Intervet/Schering-Plough Animal Health.

A combination that is proving to be effective in the field is Nobilis IB Ma5 and Nobilis IB 4/91, an approach that Malo calls “a Protectotype protocol.” Nobilis IB Ma5 is based on the Massachusetts serotype, while Nobilis IB 4/91 is built on the IB-variant 4/91 serotype — one of the most common IB virus variants in Europe, the Middle East, Asia and Africa.

Extensive field monitoring

Evidence that the Protectotype concept works when these vaccines are utilized comes from x-OvO, a diagnostic services company headquartered in the UK. Richard Currie, DVM, president of x-OvO, says his company’s extensive field monitoring of Nobilis IB Ma5 and Nobilis IB 4/91 shows that “the combination of these two vaccines provides extremely broad protection against a wide variety of IB-variant viruses.”

Any vaccine coverage, he explains, will favor the selection of immunological escape mutants that will naturally “escape” the protective response of that vaccine.

“By using a vaccine, you are encouraging the variation that will lead to the generation of a new variant,” he explains. “However, because the Ma5 and 4/91 combination gives the broadest protection, it is less likely than other vaccine combinations to select immunological escapes since it is more likely to completely neutralize any challenge.”

Monitoring of the vaccines by x-OvO has also involved confirming the exact genetic sequence of the vaccine strain circulating on farms and has demonstrated that both vaccines are stable. “We have shown that the viral sequences of these two vaccines remain consistent, despite widespread cycling through the chicken population on farms,” he says.

Long track record

Malo says that Nobilis IB Ma5 has been available worldwide for over 20 years and Nobilis IB 4/91 for more than a decade. Both vaccines, which are manufactured by Intervet/Schering-Plough Animal Health, can be administered by coarse spray, eye drop or in drinking water, although the eye-drop and coarse-spray methods are preferable because they better stimulate local immunity.

In one study, administration of the Ma5 vaccine alone at 1 day of age provided excellent protection against the Arkansas IB isolate from the US and IB isolates from Brazil and Japan. The IB 4/91 vaccine used alone at 14 days of age protected against the same three isolates plus an IB isolate from Italy. Cross-protection was best, however, when birds received both vaccines, Malo says.

In a study published in the October 2008 issue of Avian Pathology, Italian investigators concluded that the use of Nobilis IB Ma5 and Nobilis IB 4/91 “may be instrumental in reducing the economic impact of QX IB virus infections” on layer and broiler farms.

Strategic combinations

The Ma5 vaccine can also be used with the live Newcastle disease vaccines such as Nobilis Clone 30. In layers, the Ma5 and IB 4/91 vaccines have been shown to be effective “primers” for an inactivated-IB Massachusetts booster before the onset of lay, he says.

Recent experience on two poultry farms in the Middle East demonstrated that after using IB vaccine protocols for broilers that featured three vaccines — Nobilis IB Ma5, Nobilis IB Ma5 + Clone 30 and Nobilis IB 4/91 — bodyweight increased and mortality from IB virus and days until slaughter decreased, Malo adds.

Currie sees one other advantage to the use of Nobilis IB Ma5 and Nobilis IB 4/91: flexibility. Having two individual vaccines with different serotypes enables veterinarians to time administration of each so that vaccine-strain replication is optimal when the challenge is highest. In contrast, bivalent products administered at a single time point rely on an extended duration of immunity, which can be “very variable” in a field situation, he says.

A practical example of this would be concern among veterinarians that hatchery administration of a bivalent vaccine may not give adequate protection toward the end of the commercial broiler’s lifespan, particularly in birds grown for 6 weeks or longer. Administration of the Nobilis combination program, with IB 4/91 administered at day 14 of age, will often relieve concerns about maintaining adequate protection during this critical economic period of the broiler’s life, Currie says.

For more information about the Protectotype strategy with Nobilis IB Ma5 and Nobilis IB 4/91, contact your Intervet/Schering-Plough Animal Health representative or go to www.infectious-bronchitis.com.

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More Information

www.infectious-bronchitis.com www.innovax-vaccines.com www.broilerhealth.com www.layerhealth.com www.ih-magazine.com

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