They are very small, thin worms that fasten to the wall of the small intestine and suck blood. Dogs get hookworms from larval migration in the uterus, from contact with the larvae in stool-contaminated soil, or from ingesting the eggs after birth. As with roundworms, the hookworm larvae can also be transferred to the nursing pup from the mother's milk. Chronic hookworm infestation is a common cause of older dogs not performing optimally, having poor feed efficiency and weight maintenance, and having poor stamina. Often the signs include bloody diarrhea, weight loss, anemia, and progressive weakness.
Diagnosis is made by examining the feces for eggs under a microscope.
Whipworms This parasite is more often seen in dogs than cats. Adult whipworms, although seldom seen in the stool, look like tiny pieces of thread with one end enlarged. They live in the cecum, the first section of the dog's large intestine. Repeat wormings may be necessary especially if there is a probability that the dog will become reinfested. Although they seldom cause a dog's death, whipworms are a real nuisance for the dog and can be a problem for the veterinarian to diagnose.