Diarrhea and hyperammonemia in a horse with progressive neurologic signs.

The research article discusses a case where a two-year old horse experienced severe diarrhea and abnormal neurological symptoms, attributed to a drastic increase in ammonia levels in its body due to an imbalance in gut bacteria. The horse was eventually euthanized due to rapid clinical deterioration.

Horse’s Symptoms and Laboratory Findings

• The horse, a two-year-old quarter horse filly, had originally presented symptoms of depression and partial anorexia, and these later progressed to severe diarrhea and neurologic abnormalities such as repetitive muscle fasciculations, muscle stiffening, and collapse.
• Laboratory findings revealed severe polycythemia, neutropenia, metabolic acidosis, alongside electrolyte and fluid loss consistent with severe diarrhea and endotoxic shock. There were increased creatine kinase and aspartate transaminase activities, which were consistent with the historical account of recent transport and the observed muscle abnormalities.
• Importantly, the horse was found to have extremely high levels of ammonia in its body (hyperammonemia) without any other significant laboratory signs of liver dysfunction, which is usually associated with such a condition.

Euthanasia and Postmortem Results

• Due to the severe symptoms and rapid deterioration of the horse’s condition, euthanasia was carried out. A necropsy, an autopsy for animals, subsequently performed did not provide significant findings, except for severe diffuse colitis.
• Culture of the contents from the horse’s colon, however, revealed more than 1000 colony-forming units of a bacterium known as Clostridium perfringens. This was considered as an unusual and significant finding.

Link between Intestinal Bacteria and Hyperammonemia

• The researchers concluded that the hyperammonemia in the horse was most likely a result of changes in the colonic (intestinal) flora. This change had led to increased bacteria-induced production of ammonia which was then absorbed through the inflamed bowel wall.
• This condition exceeded the liver’s capacity for deamination, the process of removing an amino group from a molecule, causing the ammonia to build up in the body, resulting in hyperammonemia. This connection was rare but the researchers attributed it to positive culture results for clostridial organisms.