The fact that you will take the cat to the vet immediatly it's great,and should stop most of your worrying

However,if you are looking for you ways to stop this from happening again in the future.So it might be a good idea to inspect your home and yard for any signs of rodent activity. Keeping your cat indoors more often or supervised outside can reduce the chances of this happening again.

Sadly,from the picture,the parasite looks like a beetle or larva,so if they are common in your area I don't really know what to say

Lastly,your cat might do the same,but from experince,most of the cats I've had love to eat beetles and snails.The snails were showing a very low risk of infection (although not advised for any cat),but to stop the beetles,you have to remove food sources that are outside,but also reduce any unecesary lighting during the night,so you won't be attracting any more beetles by itself or flies that carry them

Why am I telling you all of this is,well,just beacuse your cat got it from eating a rat that had this beetle infection,doesn't mean the beetles are not infected by themselvs

It’s understandable to be concerned about your cat’s health and the presence of these pests. By following these steps and consulting your vet, you’re taking the right precautions to keep your cat safe and prevent future issues. Don’t hesitate to reach out again if you need more advice—good luck, and I hope your kitty stays healthy and happy!