I apologize in advance if this has been asked many times. What if a dhamma-practitioner or his or her children is infected by pinworms or other intestinal parasites? In the US, about 20% of children are infected by pinworms at any given time, and it causes an intense itch. While the infection rarely causes serious problems, it is a source of suffering for the host and it is also highly contagious. Other forms of parasites can seriously harm their host. I have seen no such cases in the suttas when they address killing, and so I wonder what standard practice is, particularly in monastic communities.
I once lived in a forest hermitage and saw monks using vermifuge. I don’t think they use it unless they believe it is affecting their health and wellbeing.
Intention is the cure, not the killing.
There are some restrictions for monks using medicine.