100% Mortality in Commercial Slow-Growing Broiler Chickens with Acute Fowl Cholera.

This case report details a severe outbreak of acute fowl cholera (FC) in commercial, slow-growing broiler chickens. Three necropsy cases of slow-growing broilers were submitted for postmortem examination at the California Animal Health Food Safety (CAHFS) Laboratory System at three different time points in their production cycle following an acute elevation in mortality on the farm. Broilers were submitted at 5 wk, 11 wk, and 14 wk of age. The birds were submitted from a flock of 25,000 broilers on a 262,500-broiler ranch that experienced 100% mortality by the time of processing at 14 wk of age. Gross findings included petechia, mottled livers and spleens, and congested and edematous lungs. On histology, major findings included hepatic necrosis, splenic necrosis, pulmonary edema, and bacterial colonies proliferation in multiple organs. A definitive diagnosis of FC was made with qPCR detection and aerobic culture and isolation of Pasteurella multocida. The P. multocida isolate was classified as serovar 1, fingerprint profile HhaI 0001 with serotyping and restriction enzyme analysis, respectively. A review of all FC cases detected in avian species submitted to the CAHFS laboratory in the last 11 yr revealed 10 cases of FC in slow-growing broilers and no cases in traditional broilers. This case underscores the need for enhanced biosecurity and potential vaccination strategies in slow-growing poultry systems to mitigate future risks of FC outbreaks.