· Most dangerous roundworm as maximum people is infected by Ancylostoma.
· Sexes are separate.
· No secondary host, humans are the hosts.
· They differ from roundworms like Ascaris having copulatory bursa.
· Monogenetic, found in the small intestine of the human and feed upon tissues and blood (Sanguivorous)
· The anterior end is curved. Its tip has a large buccal capsule with two pairs of sharp lancets for tearing intestinal mucosa in order to feed over it. The posterior end of the female is tapering and contains a caudal spine. In males, it is straight, broad, and bears a copulatory bursa.
· Adults mate in the host’s intestine. Fertilized eggs pass out with the host’s faeces. Under favourable environmental conditions, the embryo of hookworm develops into the 1st stage juvenile or rhabditiform larva which hatches out within 1 or 2 days. It moults twice to form a 3rd stage filariform larva.
It infects man by chance contact with his bare hands, barefoot (skin) i.e., percutaneous infection by its anterior end.
Infection is direct from soil contaminated with infective larvae.
It remains alive and infective for several weeks under favourable conditions. Infection is also possible through the ingestion of contaminated food and water. Within 24 hours of infection, larvae reach blood vessels and follow the same migratory course described for the larvae of Ascaris.

RV of heart- lungs- alveoli- trachea- pharynx-oesophagus-small intestine (ileum) - moult 2 times in 5-6 weeks and become adult.

Male and females copulate and female starts laying eggs, which pass out in the faecal matter of the human host.

· Wearing shoes prevents infection

· Symptoms: vomiting, loss of appetite, loss of body weight, mild diarrhoea, dermatitis (inflammation at entry), itching (at entry), Causes abdominal pain, anaemia, laziness, and mental weakness (ancylostomiasis)

· The total number of moults in the life cycle of the Ancylostoma duodenale is 4.

Why is Hookworm classified as New World and Old World Hookworms? 

It is classified based on the places of discovery and prevalence.

1. Old world Hookworm:
Ancylostoma duodenale: tropical, subtropical, and temperate regions of Asia, Africa, Europe, and two Americas, discovered by Dubini in 1838 AD.

2. New world Hookworm:
Necator americanus: tropical, subtropical, and temperate regions of Asia, Africa, Sri Lanka, tropical America, discovered by Stiles in 1902 AD.

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