Hookworms are parasites that get their name from the hook-like mouthparts they use to attach to the intestinal wall. There are 3 common types that affect dogs and cats are Ancylostoma caninum, Uncinaria stenocephaia, and Ancylostoma tubaeforma. They are so small that it is very difficult to see them with the naked eye, and most times the adult worms are not found by pet owners in the feces. Despite their small size, they ingest large amounts of blood from the tiny vessels in the intestinal wall. A large number of hookworms can cause anemia. This problem is most common in puppies and kittens, but can occur in adult dogs and cats as well. The eggs are periodically shed in the feces where other dogs can become infected by sniffing or licking the ground. Infected mothers can also pass the worms on to the unborn offspring through their placenta and then after birth through their milk. Thirdly, the hookworm larvae may penetrate the skin and migrate through the body causing an inflammatory reaction (cutaneous larval migrans). Hookworm eggs and larvae can also infect humans, either by ingestion or penetration of the skin. Pale gums, diarrhea, or weakness are common signs of anemia (low red blood cell count) caused by hookworm infection. Some animals also experience significant weight loss, bloody diarrhea, or failure to grow properly with hookworm infection. Routine fecal checks should be performed to detect the parasite and monthly heartworm preventatives should be used which also prevent against roundworm infection.