Hookworms: how are they transmitted to children?
Hookworms are round and unsegmented worms that belong to the group of nematodes. In New Zealand, the most common species observed in pets are: Ancylostoma caninum (in dogs), and Uncinaria stenocephala (in dogs and sometimes in cats).
Adult hookworms are found attached to the wall of the small intestine. They have teeth around their “mouth” and they pump their host’s blood. An anemia can develop in infected animals.
During the cycle of hookworms, eggs are passed by adult females in dog or cat faeces and hatch as larvae on the ground where they become infective within 1 to 3 weeks. These larvae are found in shady, moist, sandy soil. The larvae infect the animal either by being ingested or by penetrating the host’s skin.
Larvae that enter the host through the skin migrate to the lungs. Once there, they crawl up to the wind pipe, where they cause an irritation that makes the animal cough. Coughing brings the larvae to the mouth, where they are swallowed and travel to the small intestine, and mature to adulthood.
If the larvae are ingested, they travel directly to the small intestine. Some burrow through the intestinal wall and travel to the lungs through tissues. Once in the lungs, they follow the same path as larvae that penetrated the skin.
Some of the larvae stay in the tissues, and when the host is a female and becomes pregnant, these encysted larvae become active at the end of the pregnancy; they travel to the mammary glands, where they can pass in the milk to the newborn kittens and puppies.
Immature hookworm larvae may accidentally penetrate the skin of human people. Adults and children can be infected by walking barefoot on beaches or sand pits, where dogs and cats have been allowed to roam freely and contaminate the sand with infected feces.
Fortunately, when the larvae of these parasites penetrate the human skin, they cannot go any further. For the hookworms, human species is an atypical host and larvae cannot penetrate into blood vessels and travel to the lung. However, a disease called cutaneous larva migrans or creeping eruption develops on the skin. The infection can be detected through papules or even pustules (reddish bumps containing pus) that develop in areas where the skin is very thin: on the abdomen, between toes… Since people are a dead-end host, the lesions can usually disappear spontaneously within a few weeks or a few months.
Hookworm contamination is rather common in hunting dogs, when there is often poor hygiene in the kennel. Regular deworming treatments in dogs and cats will help to prevent hookworm infestation.
