The man is the only natural host. Freshly passed eggs in faeces are not infective to man when deposited in the soil. The embryo develops inside the egg and its development takes place
optimally in a sandy loamy soil, with delaying vegetation under a moist warm shady environment. In about 2 days a Rhabdiform larva about 250µm long hatches out of the egg.
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It feeds on bacteria and other organic matter in the soil, grows in size and mount twice on the third and fourth-day hatching to become the third stage infective filariform larvae.
When a person walks barefooted on the soil containing the filariform larvae, they penetrate the skin and enter the subcutaneous tissue. During the migration cycle following infection, various systematic manifestations including bronchospasm occur.
The optimum temperature for Hookworm is about 21-27C. The larvae are most numerous in the upper layer 2.5cm of soil but can ascent from deeper layer protected from desiccation. They can live in the warm damp soil for years.
After penetrating the skin, it enters the blood stream reading lungs on the third day via the heart where it mouths within 24 hours breaking through the alveoli enter the bronchioles, moves up the trachea down the oesophagus to the stomach and small intestine.
Adult worm matures in the duodenum and jejunum and by causing local trauma (with hooks or teeth) produce blood loss between 0.05ml-0.2ml. However because the small intestine has a substantial functional reserve, much of the host iron is reabsorbed before the caesium is reached.
Life cycle of hookworm
The early signs of infection may include ground itch or water sour on the skin. There is intense itching with inflammation, which usually subsides after two weeks. The passage of larvae through the lungs may produce coughing owing to alveoli damage.
Anorexia and general debility are the most typical and most insidious effects. The disease is thus particularly dangerous during pregnancy because the worms reduce the hemoglobin content of the blood. Abortions and stillbirths may occur.
Light skinned patients exhibit a typical grey pallor, often with yellow linge. In a dark-skinned person, the pallor is less noticeable but is usually apparent on the lips and conjecture. Clinical symptoms may be caused by larvae or adult worm when it enters the skin it gives rise to severe itching. The erythematous rash may develop. Scratching may lead to secondary bacterial infection.
The larva migration causes vesicular lesion with the advancing movement of the larva, the rear portion may be intense and pruritic.
The most important manifestation of Hookworm infection is caused by the adult worm in the intestine. They attach themselves to the gut mucosa by their buccal capsule. They suck blood into their mouth, a portion of intestinal villi. They utilize gut epithelial cells and plasma for their food. The worm sucks blood which passes out undigested and unutilized through the intestine. They frequently leave one site and attach to another site.
This chronic blood loss over a period of time leads to a microcytic hypochromic type of iron deficiency anaemia, the degree of anemia the degree of anaemia is proportional to the wormload. Worm load of up to 100 worms are light and cause no symptoms. Load of 500-1000 or more causes significant blood loss and anaemia.
The worm load is indicated by egg count on faeces. A count of fewer than 5 eggs per mg of faeces seldom causes clinical disease while counting of 20 eggs or more are associated with significant anaemia. Egg count of 50 or more represents massive infection. Hookworm infection may cause intestinal syndrome resembling peptic ulcer with epigastric pain and vomiting. There may be diarrhea. In acute cases, the stool may be reddish or black.
It leads to severe lassitude and dullness affecting the working and learning capacities of patients. The haemoglobin level may drop drastically causing a characteristic shallow appearance of the skin, conjunctiva and tongue, Severe infection cardiac failure.