Time series analysis of mycobacteriosis in California slaughter swine

Records of a California abattoir were reviewed for the 46-month period August 1977 through May 1981, and data were collected for 23 ranches which only marketed hogs born and raised in California. Passed for cooking (PFC) rates (per 100 000 animals slaughtered) due to lymph node lesions listed as TB (mycobacteriosis) by inspectors were roasters (32–50 kg) 0, market hogs (82–105 kg) 243, and sows (> 145 kg) 125. Effective exposure to disease-causing factors seemed to have taken place at 2–3 months of age or earlier. Time series analysis of hog PFC rates for the 23 California ranches combined demonstrated statistically significant, regular cycles of 6 and 24 months duration with seasonal peaks of PFC rates in June and December. Based on an estimated incubation period of 4–6 months, animals were at greatest risk of effective exposure to factors associated with lymph node lesions during the periods December–February and June–August.