Investigations of the vertical transmission of Erysipelothrix rhusiopathiae in laying hens

Erysipelas was diagnosed in a layer breeder flock in Sweden in 2002. Although vertical transmission of Erysipelothrix rhusiopathiae has not been previously described in chickens, the potential of erysipelas infection to adversely affect hatching eggs was of concern. To clarify the possible impact of erysipelas on hatching eggs and their progeny, an experiment was done using 200 hatching eggs collected from the infected flock. The eggs were incubated for 21 days, and the egg shells, infertile eggs, dead-in-shell embryos, and a sample of day-old hatched chicks and blood samples from 5-day-old chicks were cultured for E. rhusiopathiae. In addition, after 28 days of grow-out, the male chickens were euthanatized and cultured for the bacterium, and the remaining female chickens were placed as a backyard flock and observed over a 4-mo period. Bacteriological test results of the above-mentioned samples were negative for E. rhusiopathiae. Mortality rates were not excessive, and no clinical symptoms of erysipelas were observed during the period of observation. The result of the investigation suggests that in layer breeder chickens, E. rhusiopathiae is not vertically or egg transmitted and that the disease outbreak in the parent stock had no adverse impact on the quality of hatching eggs in terms of increased embryo mortality.