The cat is host to several species of worms that are members of the Ancylostomatoidea. The disease most typically associated with hookworm infection is anemia due to blood loss in the intestine that is caused by the adult worms. These nematodes are found as adults in the small intestine and are characterized by the possession of a copulatory bursa, a large dorsally flexed buccal cavity that is armed on its anterior edge with either teeth or cutting plates, and which tend to be one to three centimeters long. Although cats are probably often infected by the penetration of the skin by the infective third-stage larvae of this worm, the lrvae are also capable of utilizing small vertebrates as paratenic hosts. It is not known to what extent the hookworms of the cat utilize transmammary infection which is a very common mode of transmission for the canine hookworm, Ancylostomacaninum.
The two genera of worms present in the cat are Ancylostoma and Uncinaria. The genus Ancylostoma is characterized by the possession of large teeth on the front of the buccal capsule, while the genus Uncinaria is characterized by the possession of cutting plates on the front of the buccal capsule. The most common hookworm of the cat is probably Ancylostomatubaeforme. In coastal areas of Africa and the Americas, another hookworm of the cat, Ancylostomabraziliense is found that is a parasite that cats share with dogs. A similar worm, Ancylostomaceylanicum, is found in cats, dogs, and humans in Asia. Another worm, Ancylostomapleuridentatum (Alessandrini, 1905) Schwartz, 1927 is very similar to Ancylostoma braziliense, but has only been reported from members of the Felidae other than the domestic cat. This species differs from Ancylostomabraziliense in that there are three small tooth-like projections on each size of the buccal capsule opposite to the large teeth present on front of the buccal capsule. Uncinariastenocephala has only rarely been reported from the cat.