Final answer:
The significant disadvantage of using an over-the-needle catheter for equine venipuncture is the elevated risk of bloodstream infections, which are serious complications that can lead to increased morbidity and mortality.
Step-by-step explanation:
A significant disadvantage of using an over-the-needle catheter for equine venipuncture is the increased risk of bloodstream infections. While over-the-needle catheters are popular due to their ease of insertion, the design can be less secure and more prone to contamination compared to other types of catheters. With reported estimates suggesting up to 80,000 catheter-related bloodstream infections annually in the US, resulting in approximately 20,000 deaths, the risks associated with these devices are non-trivial. Furthermore, specific patient populations, such as those with compromised immune systems, may be at an even higher risk of adverse outcomes if an infection occurs.