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Causal Agents:

Many hookworms infecting animals can invade and parasitize humans (A. ceylanicum) or can penetrate the human skin (causing cutaneous larva migrans), but do not develop any further (A. braziliense, A. caninum, Uncinaria stenocephala). Occasionally A. caninum larvae may migrate to the human intestine, causing eosinophilic enteritis. Ancylostoma caninum larvae have also been implicated as a cause of diffuse unilateral subacute neuroretinitis.

Life Cycle:

Life Cycle of non-human hookworm species.

Cutaneous larval migrans (also known as creeping eruption) is a zoonotic infection with hookworm species that do not use humans as a definitive host, the most common being A. braziliense and A. caninum. The normal definitive hosts for these species are dogs and cats. The cycle in the definitive host is very similar to the cycle for the human species. Eggs are passed in the stool The number 1, and under favorable conditions (moisture, warmth, shade), larvae hatch in 1 to 2 days. The released rhabditiform larvae grow in the feces and/or the soil The number 2, and after 5 to 10 days (and two molts) they become filariform (third-stage) larvae that are infective The number 3. These infective larvae can survive 3 to 4 weeks in favorable environmental conditions. On contact with the animal host The number 4, the larvae penetrate the skin and are carried through the blood vessels to the heart and then to the lungs. They penetrate into the pulmonary alveoli, ascend the bronchial tree to the pharynx, and are swallowed. The larvae reach the small intestine, where they reside and mature into adults. Adult worms live in the lumen of the small intestine, where they attach to the intestinal wall. Some larvae become arrested in the tissues, and serve as source of infection for pups via transmammary (and possibly transplacental) routes The number 5. Humans may also become infected when filariform larvae penetrate the skin The number 6. With most species, the larvae cannot mature further in the human host, and migrate aimlessly within the epidermis, sometimes as much as several centimeters a day. Some larvae may persist in deeper tissue after finishing their skin migration.

Life cycle image and information courtesy of DPDx.

 
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