What you’re describing almost certainly isn’t parasites.
Those “white stringy worm-like things” in slow-cooked beef are usually one of these completely normal things:
In a beef roast cooked in a slow cooker, connective tissue (collagen, sinew, and silverskin) breaks down and can turn into pale, thread-like strands. As the meat becomes tender, these fibers loosen and sometimes stick out in a way that looks very “wormy,” especially when you pull the meat apart.
Another common culprit is rendered fat and muscle fibers. Fat melts and then re-solidifies slightly as pale, stringy or waxy-looking strands. Muscle fibers can also separate into thin, white threads once the meat is fully cooked and falling apart.
Parasites in beef that look like visible worms are extremely unlikely in properly sourced and cooked meat. The main parasite people worry about in meat (like Trichinella) is associated with pork or wild game, not beef, and it doesn’t show up as visible white strings in cooked roast anyway—it’s microscopic and would be killed by proper cooking temperatures.
So what you’re seeing is almost certainly just normal breakdown of connective tissue from slow cooking.
If the meat:
- smells normal
- was cooked thoroughly (fall-apart tender is a good sign in a slow cooker)
- and looks like shredded fibers rather than distinct moving organisms
…it’s safe to eat.
If you want, you can describe what it looked like more closely (length, whether it was attached throughout the meat, etc.), and I can help you confirm it further.
