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.

Investigations on the pathogenicity of Erysipelothrix rhusiopathiae in laying hens.

Erysipelas was diagnosed in 1998 from 34-wk-old laying hens in a free range flock in Germany. Erysipelothrix rhusiopathiae of serotype 1 was cultured from internal organs of the affected birds. This article describes the pathogenicity of the field isolate of E. rhusiopathiae in experimentally infected specific pathogen-free (SPF) laying hens. Three experiments were performed with SPF chickens inoculated at 17, 27, and 37 wk of age by either intramuscular (IM) or oral route. Inoculated birds were observed for 14 days. The highest mortality rates occurred in older birds, with 100% mortality observed in the 37-wk-old birds inoculated IM, 60% mortality reported in the younger 27-wk-old birds, and no mortality in the 17-wk-old age group. In the orally infected 27-wk-old birds, 40% mortality was detected, whereas no mortality was observed in the oldest birds by the same route. The results of the experiments support the contention that older birds are more sensitive to infection than younger birds and that mortality in laying hens is age related and dependent on the route of infection.