Salpingitis and peritonitis are common pathological manifestations observed in egg-laying hens. To improve methods to study these important pathological manifestations of laying hens, a surgical model has recently been developed (Pors et al., 2014). The surgical approach includes laparotomy under inhalation anesthesia using isoflurane with subsequent inoculation of the selected pathogen into the oviduct. Following recovery the birds are monitored for a certain time period before euthanization and subsequent post mortem and bacteriological investigations are performed. By the use of this model a clinical isolate belonging to the sequence type 95 was shown to cause severe clinical signs, epithelial necrosis of the oviduct and purulent salpingitis.
In the current study, the isolates investigated for the virulence properties in the oviduct were obtained from typical cases of septicemia, swollen head syndrome (SHS), and chronic salpingitis in addition to a commensal isolate. In all the birds, appr. 5x104 CFU of the isolates under investigation were injected into the oviduct of twenty-five week old brown leghorns, between five and seven cm cranial to the isthmus. The birds were sacrificed after 7 days and investigated as indicated above. Major variation in virulence was observed between the isolates used in relation to, gross lesions and bacteriology. In brief, the commensal isolate was neither able to colonize the oviduct or other tissues nor to cause gross lesions whereas the isolate from chronic salpingitis was capable of inducing salpingitis and consistently to colonize the oviduct. The SHS- and sepsis isolate were of intermediate virulence. The results will be discussed in relation to previous investigations.
Susanne Elisabeth Pors, Rikke Heidemann Olsen and Jens Peter Christensen (2014). Variations in virulence of avian pathogenic Escherichia coli demonstrated by the use of a new
in vivo infection model. Veterinary Microbiology.