Submitted to: American Association of Veterinary Laboratory Diagnosticians
Publication Type: Abstract Only
Publication Acceptance Date: 10/21/2000
Publication Date: N/A
Technical Abstract: These studies suggest that fecal culture severely underestimates the true Salmonella prevalence. They also demonstrate the confounding effects that transport and holding have on Salmonella prevalence estimation. In a study of market pigs from one commercial producer, fecal (1 g) samples collected 24 h before slaughter revealed an average herd prevalence of 3.5% (10/290). However, after slaughter 71.8% of these same pigs were Salmonella positive on at least one abattoir collected tissue (cecal contents, ileocecal lymph nodes [lnn], colon contents). Based on the Danish serum ELISA, 1.7% (5/293) of pigs showed evidence of historical Salmonella infection (OD% >/= 40). In another study, using six herds depopulated during the Accelerated Pseudorabies Eradication Program (APEP), we tested and necropsied almost 600 market pigs. On the day of depopulation, one-half of the group was sent to slaughter at a commercial abattoir. After 2-3 h holding, these pigs were stunned, exsanguinated, and necropsied. The remaining 50 pigs were necropsied on the farm, the next day. The same tissues were collected at the abattoir and on the farm (ileocecal lnn, cecal contents, fecal loops, superficial inguinal lnn). The following results are based on presumptive biochemical tests for Salmonella and serogrouping. The estimates from on-farm collected ileocecal lnn and cecal contents were 3.9% and 2.8%, respectively. The average herd prevalence estimate was 8.5%, when combining cecal contents, ileocecal lnn, and postmortem fecal samples. For pigs necropsied at the abattoir, the estimated average herd prevalence was 40.8% (117/287).