Submitted to: Avian Diseases
Publication Type: Peer reviewed journal
Publication Acceptance Date: 2/26/2012
Publication Date: 2/27/2012
Citation: Edwards, I.C., Miller, P.J., Afonso, C.L. 2012. Characterization of the live LaSota-vaccine strain-induced protection in chickens upon early challenge with a virulent Newcastle disease virus of heterologous genotype. Avian Diseases. 56:464-470. Interpretive Summary: Newcastle disease virus (NDV) causes a serious disease in avian species and is especially important due to the economic damages it causes to the international poultry industry. Recently highly virulent isolates have emerged in Asia, African and South America and there is significant concern that the current vaccine may not be sufficient protective against clinical disease. Here we have tested the protective capacity of the most commonly used NDV vaccine (LaSota) under different conditions and demonstrated that the vaccine is fully protective against a strong challenge with the strain ZJ1 (also called goose paramyxovirus).
Technical Abstract: Newcastle disease (ND) is a major threat to the international poultry industry, causing bird mortality, reduction in growth and egg production and trade restrictions. The primary strategy available to the poultry industry to control Newcastle disease virus (NDV), the causative agent of ND, is vaccination. LaSota and other commonly used live-virus NDV vaccine strains were developed in the 1950s and 1960s and show a great degree of genetic divergence from currently circulating NDV strains. In order to characterize protective immunity induced by LaSota, we vaccinated groups of specific-pathogen-free (SPF) chickens with LaSota (virus titers ranging from 102-108 EID50 in ten-fold increments) and challenged the birds 14 days later with ZJ1 strain, which is a genetically divergent relatively recent NDV isolate from geese in China. We monitored multiple parameters of immunity and determined that specific-pathogen-free birds vaccinated with an adequate titer of LaSota strain live vaccine are fully protected from morbidity and mortality due to challenge with ZJ1 strain NDV, and we concluded that in the absence of interfering maternal antibody, protection due to vaccination increases with vaccine titer until a threshold titer is reached, beyond which, little or no further benefit can be elucidated.