PREVALENCE OF MOTILE SALMONELLAE IN EGG-L AYING HENS AT THE END OF THE LAYING PERIOD

A total of 3504 hens of the layer-type from 122 flocks (belonging to 8 9 farms), each with more than 10,000 animals, were culturally examined at the time of slaughter. Of these hens, 2112 (60.3%) from 74 flocks (60.7%) were obtained from 21.3% of the laying-hen farms in a selected region of lower Saxony in Germany. The other hens came from the remai ning part of Lower Saxony and seven other German states (Brandenburg, Mecklenburg Vorpommern, North Rhine Westphalia, Schleswig Holstein, Sa xony, Saxony Anhalt, and Thuringia). After arrival at the slaughter ho use, a random sample of 29 layers was collected from each of the flock s, and liver and spleen, as well as cecal samples, were separately cul tured for each bird. Motile salmonellae could be proved in 365 (10.4%) layers from 67 flocks (54.9%). In the selected region, 48 out of 74 f locks (64.9%) and 289 out of 2112 layers (13.7%) were Salmonella-posit ive. However, the isolation frequency of salmonellae did not differ si gnificantly between flocks of brown and white layers. These Salmonella (S) isolates could be serologically assigned to 6 different serovars, namely S-enteritidis (SE), S-infantis (SI), S-livingstone (SL), S-typ himurium (ST), S-indiana (SID) and S-cerro; only one isolate of serogr oup D1 was incompletely serotyped. SE was detected in 5.8% of the hens from 47.5% of the tested flocks, of which 4.6% of the animals and 32. 8% of the flocks came from the selected region in Lower Saxony. The SE isolates were classified into 12 different lysotypes. In 41 out of 58 SE-positive flocks (70.7%), the isolates belonged to lysotype (lt)4, in 12 flocks (20.7%) to lt8, in 5 flocks (8.6%) to lt7, and in 3 flock s (5.2%) to lt11. A total of 190 (93.1%) out of 204 isolates of the se rovar SE carried plasmids. All the plasmid-positive SE-strains harbour ed the serovarspecific 37MD virulence-plasmid, nine of them (4.4%) in conjunction with a second and eight strains (3.9%) with a second and a third smaller plasmid.