Colibacillosis in caged layer hens: characteristics of the disease and the aetiological agent

Abstract

In Europe, outbreaks of acute mortality in layer flocks due to colisepticaemia have frequently been observed since the mid-1990s. The aims of this study were to describe the disease, to identify the serotypes of the avian pathogenic Escherichia coli (APEC) present in these outbreaks, and to detect the presence of F11 fimbriae and flagella in the isolates. For this purpose, 20 flocks with APEC-associated increased mortality and 20 control flocks matched for age were examined. Weekly mortality rates in the colibacillosis-affected flocks reached 1.71%, versus 0.30% in the control flocks. The maximum cumulative mortality over an entire colibacillosis outbreak reached 9.19%. The disease was often flock and hen house associated, with recurrent outbreaks within one round and in successive rounds in the same house. Disease was usually acute without clinical symptoms. Peritonitis with yolk material deposited in the peritoneal cavity and polyserositis were the main lesions at necropsy. O78 strains were isolated in 15 of the 20 colibacillosis flocks, and in only one of the control flocks. The majority of strains from the control flocks could not be serotyped by the 28 O-antisera used. In general, F11 fimbriae and flagella were present in the majority of the strains. F11 fimbriae were significantly more often found in O78 isolates than in the other serotypes, and are thus more often present in isolates from colibacillosis flocks. Strains positive for F11, and for F11 and flagella, were more frequently present in heart and liver of the colibacillosis-affected flocks.

Risk factors associated with colibacillosis outbreaks in caged layer flocks

“…Traditionally, it was mostly associated with losses in broilers, but in Europe from the mid-1990s onwards it has been increasingly observed in layer hens (Zanella et al, 2000;Vandekerchove et al, 2004a). In our recent field study, we described a distinct syndrome associated with colibacillosis in laying hens, characterized by acute mortality without prior clinical signs of disease and without a significant impact on egg production or quality.…”

“…A decrease in egg quality (percentage of second-grade eggs exceeding 1.5%) was seen in three affected flocks. In only one affected flock was a decrease in both egg production and egg quality seen (Vandekerchove et al ., 2004a). No significant associations were seen between the colibacillosis outbreaks and antibodies against IBV, NDV, APV, M. gallisepticum , M. synoviae or O. rhinotracheale (Vandekerchove et al ., 2004b).…”

“…(2004a): (1) a 'farmer-reported' increase in mortality, as compared with the normal baseline mortality in the flock; (2) detection of lesions compatible with colibacillosis after necropsy of five hens; and (3) E. coli isolated from heart and/or liver in pure or abundant cultures according to the criteria of Vandekerchove et al (2004a). A control flock was defined as a flock in the house of which no increased mortality, compared with the standards of the breeding organization, had been observed during the current and the previous batch(es).…”

“…The study was based on voluntary participation. Flocks suffering from an outbreak of colibacillosis were visited within 2 weeks of the onset of the increased mortality to collect diseased or dead hens for necropsy (Vandekerchove et al ., 2004a). This was followed by collection of four sets of blood samples at 2-week intervals to examine the flocks for possible seroconversions against IBV, NDV, APV, M. gallisepticum , M. synoviae or O. rhinotracheale (Vandekerchove et al ., 2004b).…”

“…In the majority of the flocks, most of the E. coli isolated belonged to the O78 serotype, although other serotypes, including O2 and O18, were also detected. The strains usually possessed F11 fimbriae and flagella ( Vandekerchove et al, 2004a). Infection with other pathogens is reported to make chickens more susceptible to colibacillosis (Barnes & Gross, 1997).…”