Fatal pulmonary hemorrhage associated with RTX toxin producing Actinobacillus equuli subspecies haemolyticus infection in an adult horse.

The paper describes a fatal case of pulmonary hemorrhage in a horse due to an infection from a toxin producing bacteria, Actinobacillus equuli subspecies haemolyticus. The paper presents successful identification and validation of a method to detect the presence of the toxin in the animal’s lungs using a real-time polymerase chain reaction (PCR) assay.

About the Disease

• The research examines a case of a 6-year-old horse that died due to a fatal pulmonary hemorrhage.
• These symptoms were accompanied by intermittent coughing, fever, and nosebleeds for two weeks before the horse’s death.
• The horse was infected with a bacteria called Actinobacillus equuli subsp. haemolyticus, which produces a toxin that can cause damage to the cells that line the interior surface of blood vessels.
• This bacterial infection was diagnosed at postmortem examination, with the disease primarily affecting the respiratory system and causing severe pulmonary hemorrhage and suppurative bronchopneumonia.

The Research Method

• The researchers used a technique known as real-time polymerase chain reaction (PCR) to test for the presence of the toxin produced by the bacteria in the lungs of the horse.
• The real-time PCR test was targeted towards the aqx gene of the Actinobacillus equuli subsp. haemolyticus, the gene responsible for toxin production.
• Once the PCR technique was successfully established and validated, it was used to detect the presence and activity of the aqx gene in the lung tissue and transtracheal fluid of the affected horse.
• The results confirmed that the toxin production gene was present and active at the genomic (gDNA) and complementary DNA (cDNA) levels.

Reflection and Implications

• The researchers concluded that the presence of pneumonia associated with hemorrhagic pulmonary fluid and the culture of large numbers of hemolytic A. equuli should prompt clinicians to consider endothelial damage, as occurred in this particular case, caused by bacterial toxins.
• The study highlights the importance of conducting robust diagnostic tests for horses displaying such symptoms, including real-time PCR assays, to detect the presence and activity of bacterial toxins.
• This portrays the necessity for early detection and treatment to boost chances of survival.