Ancylostoma duodenale - Introduction, Classification, History, Habitat, Morphology

Introduction to Ancylostoma duodenale

Ancylostoma duodenale is a common hookworm infecting humans and is also known as an Old World hookworm. It is the causative agent of ancylostomiasis in humans and is characterized by hypoalbuminaemia and iron-deficient anaemia.

Classification of Ancylostoma duodenale

Classification of Ancylostoma duodenale is done by:

Kingdom: Animalia

Phylum: Nematoda

Class: Chromadorea

Order: Rhabditida

Family: Ancylostomatidae

Genus: Ancylostoma

Species: A. duodenale

History of Ancylostoma duodenale

Italian physician Dubini was the first person to give an accurate description of the Ancylostoma duodenale parasite in the year 1843. The specimen was retrieved in 1838 from an autopsy material of a Milanese woman.

In 1896, Looss described the mode of infection as well as the pathogenesis of Ancylostoma duodenale infection in humans.

Habitat of Ancylostoma duodenale

The adult stage of Ancylostoma duodenale habitats in the lumen of the small intestine – commonly in the jejunum, less commonly in the duodenum, and rarely in the ileum. The parasite adheres to the intestinal wall with the help of their mouthparts.

Morphology of Ancylostoma duodenale

The morphological forms of Ancylostoma duodenale are as follows:

Adult worm

• adult Ancylostoma duodenale is greyish white in color

• cylindrical in shape

• the slight curve at the anterior end is in the same direction as the body curve, giving the appearance of a hook

• buccal capsule, mouth lined with a chitinous material

• contains 6 teeth, 2 pairs of curved teeth on the ventral surface on the ventral surface

• the dorsal surface consists of a pair of knob-like triangular plates

• the life span of the adult is 1 to 2 years

• the posterior part of the intestine has a small refractile body

Male

• measures 8-12 cm, smaller than female

• copulatory bursa, a characteristic bell-shaped bursa, is present at the posterior end of the male hookworm

• the caudal end is expanded with umbrella-like shape

• genital opening in the posterior end

• the bursa is used to catch and hold the female Ancylostoma duodenale during mating

Bursa

• copulatory organ present in male Ancylostoma duodenale

• membranous, symmetrical

• consists of 13 finger-like rays in 3 lobes (1 dorsal side, 2 lateral side)

• three rays – one single dorsal ray and two exterodorsal ray – is present in the dorsal lobe

• ten rays – 3 pairs of dorsal rays and 2 pairs of ventral rays – are present in two lateral lobes

Female

• in female Ancylostoma duodenale, the vulva is present near the centre of the body

• female Ancylostoma duodenale lays 10,000 to 25,000 eggs per day

• measures 10-15 cm, larger than male

• the caudal end is tapering, not expanded

• the posterior spine is present

• genital opening is present at the junction between the posterior part and the middle third part of the body

Infective form

Filariform larva

• is the infective stage of Ancylostoma duodenale

• causes infection by penetrating the host skin

• third stage larvae (L3)

• non-feeding form of the parasite

• slender in shape

• measures 500μm to 600μm in length

• pointed tail

• oesophagus, which is present in the anterior third of the body, is much shorter