Ancylostomiasis HOOKWORMS Ancylostoma duodenale. Prof. of Parasitology Eman khalifa

Ancylostoma duodenale Diseases: Ancylostomiasis, Hookworm disease Morphology: Ancylostoma adults. At the anterior end there is a big cup shaped mouth called buccal capsule. They have a club shaped oesophagus The male worm measures nearly 1 cm by 0.5 mm and is provided with a copulatory bursa at the posterior end with two free spicules The female is larger and stouter (1.2 cm by 0.6 mm). The posterior end is straight and pointed.

24-Ancylostoma duodenale adult male

25-Ancylostoma duodenale adult female

The eggs Size: 60 X 40  in diameter, Shape: oval with blunt poles, thin-walled, Colour: colourless Content: four cell stage (immature).

Ancylostoma duodenale Life cycle Habitat: Adults live in the small intestine of man attached by the mouth capsule to the mucosa. Eggs passed in faeces mature rapidly, hatch and produce the first stage rhabditiform larvae (250 ) in 1 to 2 days under favourable conditions (humidity and temperature 25°C), feed actively upon organic debris and grow rapidly to a size of 500  second stage rhabditiform larvae in 5 days.  

They moult for a second time to become infective ensheathed filariform larvae (700 ) after about 7 days. Mode of infection: Man is infected when the filariform larva penetrates his intact skin or mucous membrane of the mouth.

Miners and farmers may acquire the infection on the hands chiefly in the interdigital spaces, dorsum of foot and between toes. The filariform larva moves towards warmth (+ve thermotropism), moist areas (+ve hygrotropism) and host tissues (+ve histotropism) but against gravity (-ve geotropism). The strong +ve histotropism facilitates access to the host. The –ve geotropism helps the larva to move towards the surface to reach human skin.

The larvae enter the lymphatics or venules and are carried in the blood through the heart to the lungs, where they break out of the capillaries into the alveoli. They ascend the bronchi and trachea. Finally they are swallowed and pass down to the intestine. This migration takes about one week, during which the larvae undergo a third moult and acquire a temporary buccal capsule. The fourth moult occurs in the intestine at about the 13th day. The egg-laying females are developed in 5 to 6 weeks after infection.

 

Clinical picture Invasion stage: Larval penetration leads to local dermatitis and localized erythema, usually between the toes, dorsal surface of the foot. Itching is often severe. This condition is known as “ground itch”. Migration stage: Passage of larvae in the lungs leads to minute haemorrhages and pneumonitis. There may be cough, expectoration, haemoptysis, fever, leucocytosis and eosinophilia (verminous pneumonia or Loeffler's syndrome).

Intestinal stage : Severe gastroenteritis often develops about 6 weeks after infection due to ulceration of mucous membrane. The gastroenteric phase is self-limited. Symptoms due to the adult worms occur later only if anaemia develops. An adult hookworm sucks about 0.3 ml blood / day. The previous points of attachment bleed for sometime after movement of the worms to new sites because adult secrets antiplatelet agents that help the continuous oozing of blood, this blood loss leads to hypochromic normocytic or microcytic anaemia, which leads to dyspnoea on exertion, palpitation, pallor, puffiness of the face, weakness and dizziness.

Diagnosis: I- Clinical picture: II- Laboratory: Direct: Final diagnosis depends upon finding the eggs in the faeces

Infective stage of Ancylostoma duodenale is Filariform larva Egg containing four cell stage is the diagnostic stage of Ancylostoma duodenale Microcytic hypochromic anamia is a complication of

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