Hookworms Necator americanous

Hookworms

Necator americanus

Introduction

Hookworm infection is caused by the blood-feeding nematode parasites of the species Ancylostoma duodenale and Necator americanus.

Morphology

The adults: cylindrical with the head bent sharply backwards
giving them a hooked appearance
about 10 mm in length
The males: bursa at posterior end; smaller than the females

The hookworm species are

mainly differentiated by
their buccal capsule and
the arrangement of rays
in the bursa


Morphology
The eggs:
ovoid with a thin transparent shell; easy exit for larva.

Morphologically it is not possible to differentiate between A. duodenale and N. americanus.

morphology

Scanning electron micrograph of the mouth capsule of Necator americanus, another species of human hookworm. Note the presence of two cutting "teeth“.

morphology

• Copulatory bursa of N. americanus(a side view)
•







Left picture: Copulatory bursa and spines of N. americanus(a side view);
Right picture: copulatory bursa of A. duodenale(a top view)

Acylostoma duodenale & Necator americanus -- human hookworms

Small nematodes (1-1.5 cm)
Head is slightly bend (hook) and the ‘mouth’ carries characteristic teeth (Ancylostoma) or plates (Necator, note that these are not real teeth but cuticular formations of the ‘buccal capsule)
The posterior end of the male worm is elaborated into a copulatory bursa

Necator americanus

Final host: man
Inf. Stage: Larva 3 or filariform larva.
Diagnosis stage : egg in stool.
Inf. Route: by skin
Food: blood and tissue fluid
Site of inhabitation: small intestine


Life cycle

Diagnosis

Stool examination
This is based on finding the eggs in the faeces.