Hookworm

Hookworms are intestinal, blood-feeding, parasitic roundworms that cause types of infection known as helminthiases. Hookworm infection is found in many parts of the world, and is common in areas with poor access to adequate water, sanitation, and hygiene. In humans, infections are caused by two main species of roundworm, belonging to the genera Ancylostoma and Necator. In other animals the main parasites are species of Ancylostoma. The two most common types of hookworm that infect humans are Ancylostoma duodenale and Necator americanus. Hookworm species that are known to infect domestic cats are Ancylostoma braziliense and Ancylostoma tubaeforme. Wild cats are infected by Ancylostoma pluridentatum. Dogs are commonly infected by Ancylostoma caninum, but may also be infected by Uncinaria stenocephala and Ancylostoma braziliense. In Asia, Ancylostoma ceylanicum is endemic among dogs and cats and infects humans. Cattle are infected by Bunostomum phlebotomum. At least 68 species have been described in wild mammals. The two species that commonly infect humans have a similar morphology. A. duodenale worms are pale grey or slightly pink. The head is bent a little in relation to the rest of the body, forming a hook shape – hence the name. The hook is at the front end of the body. They have well-developed mouths with two pairs of teeth. Males measure approximately 10 by 0.5 mm, and females are often longer and stouter. Males also have a prominent copulatory bursa posteriorly. N. americanus is generally smaller than A. duodenale, with males usually being 5 to 9 mm long and females about 10 mm long. Instead of the two pairs of teeth in A. duodenale, N. americanus has a pair of cutting plates in the buccal capsule. Also, the hook is much more defined in Necator americanus. The host is infected by the larvae, not by the eggs, and the usual route is through the skin. Hookworm larvae need warm, moist soil, above 18 °C, in order to hatch. They will die if exposed to direct sunlight or if they become dried out.