[Escherichia coli salpingitis and peritonitis in layer chickens: an overview]

Escherichia coli can induce salpingitis and/or peritonitis, a major cause of mortality in layer hens, but also other localized and systemic infections. E. coli infections have also been described in turkeys, geese, and ducks and are thought to be the cause of significant economic losses. However little is known about the real economic impact of the disease in layer chickens. The pathogenesis of E. coli salpingitis and peritonitis has not been elucidated yet. Three routes of infection have been discussed in the literature: ascending faecal contamination from the cloaca, bacterial translocation from the respiratory tract (air sac and lungs) and bacterial translocation from the intestinal lumen. Only one study has reported the occurrence of ascending faecal contamination from the cloaca to the oviduct and subsequently to the peritoneum. Regarding bacterial translocation, the only models available are for mammals, and these have not been applied to chickens so far Animal models could prove valuable to elucidate the pathogenesis of E. coli-induced salpingitis and peritonitis, and for assessing the value of preventive and curative intervention strategies. Little is known about risk factors for E. coli salpingitis and peritonitis. In contrast to colibacillosis in broilers, recent research has failed to demonstrate an association between several pathogens of the respiratory tract and the occurrence of E. coli pathology in layer chickens. The distance between poultry farms and the hen density in the cages were recently proposed as important risk factors for outbreaks ofcolibacillosis in flocks of layer hens, while in the past hormonal factors were implicated. The latter is an area of research that deserves more attention. Several methods for the molecular typing of E. coli have been described and might prove useful to study the epidemiology ofE. coli outbreaks in poultry, about which little is known. The presumptive diagnosis E. coli salpingitis and peritonitis is rather simple to establish, based on the anamnesis, clinical symptoms, and macroscopic findings at post-mortem. However; bacteriological analysis is required to establish a definite diagnosis because other pathogens can also cause salpingitis and peritonitis in layer hens. Antibiotics, chosen on the basis of sensitivity testing and their pharmacokinetic properties can be used as therapy; however residues in eggs may occur. Autovaccines are often used as prevention because in practice effective protection is only achieved against homologous E. coli serotypes.