Final answer:
Bloody diarrhea and pale mucous membranes in very young puppies may be signs of a parasitic infection such as Ancylostoma caninum or Cryptosporidium.
Step-by-step explanation:
The signs of bloody diarrhea and pale mucous membranes in very young puppies are indicative of a parasitic infection. One possible parasite that can cause these symptoms is Ancylostoma caninum, also known as canine hookworm. This parasite attaches to the intestinal wall, causing blood loss and resulting in bloody diarrhea. Another potential parasite is Cryptosporidium, a protozoan parasite that can cause severe diarrhea when ingested.