Submitted to: International Symposium on the Epidemiology and Control of Foodborne Pathogens in Pork
Publication Type: Proceedings
Publication Acceptance Date: 10/1/2003
Publication Date: 10/1/2003
Citation: ROSTAGNO, M.H., HURD, H.S., GAILEY, J.K., MCKEAN, J.D. SAMPLING CECAL CONTENTS OR ILEOCECAL LYMPH NODES: IS IT DIFFERENT?. Proceedings of the International Symposium on the Epidemiology and Control of Foodborne Pathogens in Pork. 2003. p. 103-104.
Technical Abstract: The objective of this study was to compare the prevalence of Salmonella enterica in swine populations by testing cecal contents versus ileocecal lymph nodes. In each of two abattoirs, four groups of pigs were studied. From each studied group, 30 animals were randomly selected. Cecal contents (10 g) and ileocecal lymph nodes were individually collected and processed by standard bacteriological methods for isolation and identification of S. enterica. Overall, the S. enterica prevalence in abattoir A, determined by cecal contents and ileocecal lymph nodes was 36.7% and 27.5% (p<0.05), respectively. In abattoir B, the prevalence found was 43.3% and 18.3% (p<0.05), respectively. Combining results from both samples, the prevalence found was 47.5% for abattoir A and 53.3% for abattoir B (p>0.05). A total of 13 different S. enterica serovars was isolated (11 from cecal content and 9 from ileocecal lymph node samples). Four serovars were isolated only from cecal content samples (Montivideo, Ohio, Mbandaka and Bovis-morbificans), whereas 2 serovars were only isolated from ileocecal lymph nodes (Choleraesuis var. kunzendorf and 4,12:autoaglutinable). S. enterica serovars isolated from both samples included: Typhimurium var. Copenhagen, Typhimurium, Derby, Anatum, Agona, Newport and Heidelberg. The relative sensitivity of cecal content sampling was 79.3%, whereas for ileocecal lymph node sampling it was only 45.5%. The agreement (Kappa statistic) between both sample types was 13.1%, indicating that both sample types are complementary. The invasiveness of a serovar, as well as the period of time elapsed between exposure and sample collection constitute determinant factors to the prevalence and serovar diversity found in each sample. Probably, ileocecal lymph node samples reflect on-farm infections and rapid infections acquired from pre-slaughter contaminated environments (transport trailers and abattoir holding pens) by more invasive serovars, whereas cecal content samples reflect (not exclusively) rapid infections or contaminations of the gastrointestinal tract after pigs leave the farm. This study demonstrates that sampling either cecal contents or ileocecal lymph nodes affects quantitative (prevalence), as well as qualitative (serovar diversity) results of S. enterica epidemiological studies. It is recommended that both samples be simultaneously used to get a better epidemiological picture of S. enterica in swine populations.