Aetiology
CLM is caused by infestation with the larval stages of the dog hookworm Ancylostoma caninum or the cat hookworm Ancylostoma braziliense. Other animal hookworms, such as Uncinaria stenocephala (dog hookworm found in Europe) and Bunostomum phlebotomum (cattle hookworm), are less common causes.[20][21] Adult hookworms live in the animal intestinal tract, and their eggs contaminate the environment during defecation. Eggs then hatch and release larvae that survive in the moist soil and sand of the tropics and subtropics. Human infestation occurs when exposed skin comes into contact with soil or sand contaminated with animal hookworm larvae. Therefore, tourists on holiday in tropical or sandy subtropical regions of the world (especially the Caribbean, Brazil, Mexico, Southeast Asia, and Africa), particularly if walking barefoot or sunbathing on the beach, are at risk.[3][4][11] People living in these endemic areas, especially children of low socioeconomic status and those who frequently walk barefoot, are also at risk.[10]
Zoonotic hookworms cannot complete their life cycles in humans, hence adult worms are not found in the gastrointestinal tract nor eggs in the faeces, making person-to-person transmission impossible.
Pathophysiology
Upon contact, the hookworm larvae penetrate unbroken skin and then migrate into the deeper layers of the epidermis; however, they are unable to penetrate the basal membrane of human skin and remain confined to the epidermis.[1] As humans are not their normal hosts, the larvae are unable to complete their natural life cycle but instead migrate laterally in the deeper layers of the epidermis before they die, usually after 2 to 8 weeks.[4] [22]The appearance of dermatological findings typically occur within 1 to 5 days of skin penetration, and consist of an intense inflammatory reaction that is probably provoked by hydrolytic enzymes secreted by the larvae to facilitate tissue migration.[23]
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