Hookworm

Hookworm

The hookworm is a parasitic nematode worm that lives in the small intestine of its host, which may be a mammal such as a dog, cat, or human. Two species of hookworms commonly infect humans, Ancylostoma duodenale and Necator americanus. Necator americanus predominates in the Americas, Sub-Saharan Africa, Southeast Asia, China, and Indonesia, while A. duodenale predominates in the Middle East, North Africa, India and (formerly) in southern Europe. Hookworms are thought to infect more than 600 million people worldwide. The A. braziliense and A. tubaeforme species infect cats, while A. caninum infects dogs. Uncinaria stenocephala infects both dogs and cats.

Hookworms are much smaller than the large roundworm, Ascaris lumbricoides, and the complications of tissue migration and mechanical obstruction so frequently observed with roundworm infestation are less frequent in hookworm infestation. The most significant risk of hookworm infection is anemia, secondary to loss of iron (and protein) in the gut. The worms suck blood voraciously and damage the mucosa. However, the blood loss in the stools is not visibly apparent.

Ankylostomiasis, alternatively spelled anchylostomiasis and also called helminthiasis, "miners\' anaemia", "tunnel disease", "brickmaker\'s anaemia" and "Egyptian chlorosis", is the disease caused by hookworms. It is caused when hookworms, present in large numbers, produce an iron deficiency anemia by voraciously sucking blood from the host\'s intestinal walls. The name is derived from Greek ancylos αγκυλος "crooked, bent" and stoma στομα "mouth."

Hookworm is a leading cause of maternal and child morbidity in the developing countries of the tropics and subtropics. In susceptible children hookworms cause intellectual, cognitive and growth retardation, intrauterine growth retardation, prematurity, and low birth weight among newborns born to infected mothers. Hookworm infection is rarely fatal, but anemia can be significant in the heavily infected individual.

Signs and symptoms
There are no specific symptoms or signs of hookworm infection. As mentioned above, they arise from a combination of intestinal inflammation and progressive iron/protein-deficiency anaemia. Larval invasion of the skin might give rise to intense, local itching, usually on the foot or lower leg, which can be followed by lesions that look like insect bites, can blister ("ground itch"), and last for a week or more. Animal hookworm larvae on penetrating humans may produce a creeping eruption called cutaneous larva migrans. The larvae migrate in tortuous tunnels in between stratum germinativum and stratum corneum of the skin, causing serpigenous vesicular lesions. With advancing movement of the larvae, the rear portions of the lesions become dry and crusty. The lesions are typically intensely pruritic. Coughing, chest pain, wheezing, and fever will sometimes be experienced by people who have been exposed to very large numbers of larvae. Epigastric pains, indigestion, nausea vomiting, constipation, and diarrhea can occur early or in later stages as well, although gastrointestinal symptoms tend to improve with time. Signs of advanced severe infection are those of anemia and protein deficiency, including emaciation, cardiac failure and abdominal distension with ascites.