HOOKWORMS

Ancylostoma duodenaleNecator americanus

Necator americanus(New World Hookworm)

Ancylostoma duodenale(Old World Hookworm)

Soil-transmitted helminths

They are blood sucking nematodes that attach to the mucosa of the small intestineAll hookworms have the meromyarian type of somatic muscle arrangement where the cells are few in number—two to five per dorsal or ventral half

Infective Stage Filariform larvaDiagnostic Stage Egg

Mode of transmission Skin penetration of infective tissue

Ancylostoma duodenale Necator americanus

Size Bigger Smaller

Body curvature C shaped S shaped

Dental pattern 2 pairs of teeth Semi-lunar cutting plates

Copulatory bursa of the male

Circle (top view)Trigiditate/tripartite with

unfused spicules

Oval (top view)Bidigitate/bipartite with

fused spicules Habitat Small intestine

(duodenum)Small intestine

(jejunum)

Necator americanus

• Small, cylindrical, fusiform, grayish-white nematodes

• Female: 9-11mm by 0.35mm

• Male: 5-9mm by 0.30mm

• Male posterior end is broad, membranous caudal bursa with rib-like rays for copulation

Ancylostoma duodenale

• Adult: buccal capsule has 2 pairs of curved ventral teeth

Rhabditiform larvae of N. americanus and A. duodenale are indistinguishable. They resemble Strongyloides stercoralis, but are somewhat larger, more attenuated posteriorly and have a longer buccal cavity.

Buccal spears of the filariform larva Necator americanus Ancylostoma duodenale

Conspicuous and parallel throughout their lengths

Insconspicuous buccal spears

Conspicuous transverse striations are present on the

sheath in the tail region

Inconspicuous transverse striations are present on the

sheath in the tail region

Eggs• Bluntly rounded ends • Single thin transparent hyaline shell• Unsegmented at oviposition and in the 2- to 8-

cell stages of division in fresh feces

Life Cycle

Pathology• Hookworm infections involve: 1. skin at the site of

entry of the filariform larvae 2. the lung during larval migration 3. the small intestine, the habitat of adult worms

• Maculopapular lesions and localized erythema• Ground itch or dew itch• Papulovesicular eruption• Lungs: bronchitis or pneumonitis• Abdominal pain, steatorrhea, blood Eosinophilia, diarrhea with blood and mucus• hypoalbuminemia

Diagnosis1. Direct fecal smear2. Kato-Katz Method3. Concentration methods (ZnSO4 centrifugal

flotation and the formalin-ether concentration method)

4. Culture method: Harada-Mori

Treatment

• Mebendazole - Not recommended for children less than 2

years of age and pregnant women- 500 mg single dose• Albendazole- Drug of choice- Larvicidal and ovicidal - 400 mg single dose