What is the symbiotic relationship between a hookworm and puppies?

Hookworm infection can be looked at as a natural check in the canine population as it is frequently lethal to young puppies. A young puppy is growing and that includes making enough new blood to serve not only its needs but the needs of its growth. Growing requires a tremendous red blood cell production from the puppy's bone marrow, yet in the hookworm infected puppy this process is being sabotaged by numerous tiny vampires within. The puppy may be effectively bled to death.

This form of symbiotic relationship is parasitism; a relationship in which one organism - the host - is the source of food and/or shelter for another organism, the parasite. In this relationship, all of the benefits go to the parasite; the host is harmed by the relationship.