Multifocal Avian Influenza (H5N1) Outbreak

During March 2006, an outbreak of highly pathogenic avian influenza (H5N1) occurred in multiple poultry farms in Israel. The epidemiologic investigation and review of outbreak mitigation efforts uncovered gaps in planning for and containing the outbreak, thus affording valuable lessons applicable to other countries in similar settings

Herd immunity to Newcastle disease virus in broiler flocks in Israel

<p>Due to the ongoing need to protect poultry from virulent Newcastle disease virus, all commercial poultry flocks in Israel are vaccinated according to a defined programme using a combination of live and inactivated vaccines. The vaccination protocol for broilers during the years of the study comprised a live vaccine administered by spray on the day of hatching, inactivated vaccine by subcutaneous injection at 10–12 days of age, and another live vaccine given by aerosol at 17–21 days of age. A cross-sectional study was designed in order to examine the influence of herd immunity on the risk of Newcastle disease outbreak in broiler flocks. The study was based on the extensive field data kept in the Poultry Health Laboratories database. The results of serology tests employing haemagglutination inhibition for Newcastle disease virus were analysed and crossed with the list of flocks that had been diagnosed with ND in the years 2007–2014. At the peak of induced immunization (fifth week of growth), 87.5% of the tested flocks had achieved herd immunity (≥85% of birds in the flock with an HI titre ≥4). Based on a logistic regression model, the odds ratio for ND in flocks without herd immunity was 3.7 (95% CI 1.8–7.3, <i>P</i>-value < 0.001). The higher the percentage of birds with low HI titres the higher the risk of ND outbreak. Under field conditions, herd immunity is an important indicator for the risk of ND outbreak.</p