Pathology of <i>Clostridium colinum</i> infection in quail

<i>Clostridium colinum</i> causes ulcerative enteritis in several avian species. The disease is particularly prevalent in quail, and it is therefore colloquially known as quail disease. The pathogenesis of the infection is poorly understood. A retrospective study of <i>C. colinum</i> infection in quail submitted for necropsy and diagnostic work up to the California Animal Health and Food Safety Laboratory System between 1992 and 2022 was performed. The necropsy reports were reviewed, and polymerase chain reaction (PCR) for <i>C. colinum</i> (<i>16S rRNA</i>) was performed on formalin-fixed, paraffin-embedded tissues. <i>C. colinum</i> was isolated in 17% (4/24) and detected by PCR in 96% (23/24) of cases. Bobwhite quail (<i>Colinus virginianus</i>) were overrepresented, and the most affected quail were juveniles. Clinical history and signs were increased mortality (92%), lethargy (29%), depression (25%), diarrhea (21%), loss of nutritional condition (8%), and seizures (8%). Grossly, intestinal ulceration (100%) affecting the duodenum (79%), jejunum (100%), ileum (29%), and/or ceca (21%). Fibrinous celomitis (13%), hepatic necrosis (46%), and pectoral muscle atrophy (92%) were observed. Histologically, all quail showed multifocal ulcerative jejunitis, duodenitis, ileitis, and/or typhlitis with intralesional bacilli. Ulcerative enteritis was transmural in 92% of cases, associated with intestinal perforation in 38%, and causing celomitis in 50% of cases. Hepatic necrosis was confirmed in 63% of cases, and neuronal changes suggesting a combination of hypoxia-ischemia and hypoglycemia were found in 63% of cases. These results suggest that a diagnosis of <i>C. colinum</i> infection should be made based on gross and microscopic lesions, coupled with PCR.