Hi Jackson,
Suppose, a certain bull which is going to be slaughtered is infected with several diseases. Before cooking meat is thoroughly washed. Though blood is the main carrier of pathogens, it is still not certain all the blood has been washed away.
This whole paragraph is not well-written. Rather than answer your questions about it, let me try to improve it.
Suppose a bull which is slaughtered is infected with several diseases. Before cooking, the meat must be thoroughly washed, because blood is the main carrier of pathogens. However, you still cannot be certain that all the blood has been washed away.
Best wishes, Clive