Peer-reviewed veterinary case report
Fatal pulmonary hemorrhage associated with RTX toxin producing Actinobacillus equuli subspecies haemolyticus infection in an adult horse.
- Journal:
- Journal of veterinary diagnostic investigation : official publication of the American Association of Veterinary Laboratory Diagnosticians, Inc
- Year:
- 2008
- Authors:
- Pusterla, Nicola et al.
- Affiliation:
- Department of Medicine and Epidemiology · United States
- Species:
- horse
Plain-English summary
A 6-year-old American Paint mare developed serious health issues over two weeks, including coughing, fever, and nosebleeds. Sadly, she passed away, and a postmortem examination revealed severe bleeding in her lungs along with a type of pneumonia caused by a bacterial infection. Tests showed that the bacteria responsible was Actinobacillus equuli subspecies haemolyticus, which produces a toxin that likely damaged the blood vessels in her lungs. The findings suggest that the mare's condition was linked to this bacterial toxin, which contributed to her fatal illness. Unfortunately, despite the investigation and testing, the treatment options available were not effective in saving her.
Abstract
A case of fatal pulmonary hemorrhage in a 6-year-old American Paint mare with a 2-week history of intermittent coughing, fever, and epistaxis is described. Significant macroscopic abnormalities at postmortem examination were restricted to the respiratory system, and microscopically, severe pulmonary hemorrhage with suppurative bronchopneumonia was found. Actinobacillus equuli subsp. haemolyticus was cultured from a transtracheal wash performed antemortem as well as from the lungs at necropsy. The presence of airway-associated hemorrhage in conjunction with bacterial bronchopneumonia suggested endothelial damage caused by a locally elaborated bacterial toxin, possibly produced by the A. equuli strain isolated from the lungs. The objective of this report was to indirectly document the presence of hemolysin repeat in structural toxin (RTX) in the lungs of the reported mare. A real-time polymerase chain reaction (PCR) assay targeting the recently described aqx gene of A. equuli subsp. haemolyticus was established and validated. Transcriptional activity of the aqx gene was used as a surrogate method to document toxin production. Real-time PCR analysis of the transtracheal fluid and lung tissue of the affected mare confirmed the presence and the transcriptional activity of the aqx gene at the genomic (gDNA) and complementary DNA (cDNA) levels, respectively. The presence of pneumonia associated with hemorrhagic pulmonary fluid and the culture of large numbers of hemolytic A. equuli should prompt the clinician to consider endothelial damage caused by bacterial toxins.
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Search related cases →Original publication: https://pubmed.ncbi.nlm.nih.gov/18182526/