Chicken embryo lethality assay for determining the virulence of Riemerella anatipestifer isolates.

Chicken embryo lethality assay for determining the virulence of Riemerella anatipestifer isolates. Avian Pathol. 2013 Aug;42(4):387-92 Authors: Seo HS, Cha SY, Kang M, Jang HK Abstract Riemerella anatipestifer is the causative agent of polyserositis and septicaemia in waterfowl. Twenty-one serotypes have been reported, and there is a strong variation in virulence between strains according to serotype or strain. However, little information is available to assess virulence, such as virulence-associated genes; thus, it is difficult to estimate the risk from field strains. Hence, we established a chicken embryo lethality assay (ELA) model to determine the virulence of R. anatipestifer strains. Three virulent strains (RA T1, RA T7, and V-1) and three avirulent strains (Av-1, Av-2, and Av-3), which were confirmed by duck challenge, were used to perform the ELA. Inoculating 10(2) to 10(4) colony-forming units into the allantoic cavity of 10-day-old embryos discriminated between virulent and avirulent strains based on mortality. Differences in invasion rates into embryonic tissues were found between the RA T1 and Av-1 strains. The maximum colony-forming units of the RA T1 strain were about 1000 times higher than those of the Av-1 strain in the tissue invasion rate for 4 days. We found that the virulent strains killed embryos at mortality rates ≥50% during the first 3 days after inoculation and that the avirulent strains had death rates of ≤20% ove...
Source: Avian Pathology - Category: Pathology Authors: Tags: Avian Pathol Source Type: research