Acute small intestinal obstruction associated with Parascaris equorum infection in young horses: 25 cases (1985-2004).

The study explores the effect of Parascaris equorum, a type of parasite, on young horses, particularly its association with acute small intestinal obstructions. The research covers a period of almost two decades and aims to assess treatment outcomes and describe the related gastrointestinal conditions.

Study Design and Methodology

• The study evaluated medical and surgical records of 25 horses with acute small intestinal obstructions caused by P. equorum infection from 1985 to 2004. It collected information on the animals’ backgrounds, health history, physical examination findings, surgical or autopsy outcomes, and treatment results.
• All but one horse were less than a year old, and Standardbreds, a common horse breed, were found more than expected, indicating a potential vulnerability in this breed.
• Detailed data were gathered and analyzed regarding anthelmintic (anti-parasitic) treatment administration, the type of intestinal obstruction present, and survival rates.

Results of the Study

• Of the 25 horses, 16 had simple obstructive ascarid impactions (SOAIs), and nine had complicated obstructive ascarid impaction (COAI), including volvulus (twisting of the intestine) or intussusception (inversion of one portion of the intestine within another).
• Findings revealed that most horses had been treated with anthelmintics, including pyrantel, ivermectin, and trichlorphon, before the onset of colic symptoms. This treatment incidence (72%) was significantly higher than previously reported.
• The short-term survival rate (discharge from hospital) was 79% for horses treated for SOAI, with an overall survival rate of 64%. Long-term survival (>1 year) was noted in 33% of horses with SOAI and 27% overall.
• The leading cause of death was the formation of adhesions – abnormal tissue that can develop after surgery. This was most common in horses that did not survive long-term.

Conclusion

• The study concluded that the higher than expected presence of anthelmintic treatment before the onset of colic symptoms might be associated with increased ascarid burdens, potentially predisposing horses to ascarid impaction.
• The resistance of P. equorum to ivermectin, as reported in Ontario, is also hinted to play a role in increased ascarid burdens.
• Despite these challenges, the study suggests that the long-term survival rate of horses suffering from this condition has improved from past data.