Abdominal abscess associated with Parascaris equorum infection in a foal.

The research article documents a case study of a 4.5-month-old male Quarter Horse foal infected with Parascaris equorum, causing an abdominal abscess and severe health complications that led to eventual euthanization.

Context and Symptoms

• The foal was presented to the University of Illinois Veterinary Medical Teaching Hospital after it showed signs of abdominal discomfort and failed to defecate after deworming with trichlorfon.
• The foal returned gastric contents containing Parascaris equorum en route to the hospital. On admission, the foal had symptoms such as a high temperature, high heart rate, respiratory distress, distended abdomen, and lethargy.
• A physical examination confirmed distended loops of small intestines and blood in the abdominal fluid.

Diagnosis and Treatment

• The foal was diagnosed with a blockage possibly due to P. equorum, and intussusception (telescoping of the intestines into themselves) of the small intestines.
• The foal was prepared for laparotomy, a surgical procedure to examine the abdominal organs. A large abscess filled with pus and adhered to multiple loops of small intestine was found in the abdominal cavity.
• Due to the severe peritonitis (inflammation of the abdominal lining), extensive adhesions (abnormal bands of fibrous tissue that cause organs to stick together), and a generally poor prognosis, the decision was taken to euthanize the foal.

Necropsy Findings and Understanding

• Necropsy (an autopsy for animals) revealed a large abscess located near the aorta and cranial mesenteric artery, consisting of numerous small cavities filled with pus.
• An adult P. equorum was found in the abscess and parts of the jejunum, ileum, and cecum were adhered to the abscess. Dead worms had also obstructed the small and large intestines.
• The P. equorum infection often occurs with few to no clinical signs, highlighting the potential severity of such overlooked infections.
• The report contextualizes this case by mentioning that P. equorum has similarly been reported to cause perforation of intestines, with adult worms escaping into the peritoneal cavity, leading to peritonitis.

Treatment Implications

• The article emphasizes that P. equorum infections often occur after deworming with anthelmintics like piperazine or organophosphates. These substances paralyze worms unlike benzimidazoles, which disrupt metabolic pathways to kill the worms.
• This observation pushes for caution when treating severe P. equorum infections with anthelmintics that only immobilize worms, as they can stay in the body and cause internal issues, as seen in this case.