small intestinal nematodes

• Hookworm These worms are parasitic nematode that lives in the

small intestine of human. Two species of hookworms commonly infect humans:

• Ancylostoma duodenale - Old World Hook worm.

• Necator americanus - New World Hook worm.

and causing Ancylostomiasis

• Ancylostomiasis: is the disease caused by hookworms. It is caused when hookworms, present in large numbers, produce an abdominal pain and iron deficiency anemia by contineous sucking blood from the host's intestinal walls.

• There are other species of Ancylostoma infect animals like A. braziliense species which infect cats, while A. caninum infects dogs.

“Morphology” Egg… The only difference between the eggs of both

species is the size, the average Necator egg range in

length from (60 – 75) µm, whereas the typical

Ancylostoma measure (55 – 60) µm…so, recovered

eggs are usually reported as “Hook worm eggs”.

Hook worm egg may be unsegmented or embryonic

cleavage, usually at the two, four, or eight cell

stage….under warm conditions may reveal a developing

larva. A thin , smooth, colorless shell provides protection for the developing worm.

“Hook worm eggs”

Rhabditiform

larvae… • feeds on bacteria and

debris in the feces & soil.

Filiariform larvae… • Infective stage

• Has a distinct pointed tail.

“Morphology”

Adult… appear grayish to white in color with thick cuticle…

• The anterior end of the body forms a conspicuous bend referred to as

a “HOOK” , so named the Hookworm.

• The average female size measure about (9-12 x 0.5)mm.

• The average male size measure about (7-16 x 0.4)mm.

• The male equipped with a prominent posterior “Copulatory bursa”

consist of 3 lobes: 1 dorsal & 2 lateral.

• The posterior end of female is tapering …no expanded bursa are seen.

• Buccal capsule characteristics…..

Necator………Contain pair of cutting plates.

Ancylostoma……. Contain actual teeth.

Male of hook worm

Female of hook worm

Morphology of Ancylostoma duodenale

Ancylostoma duodenale

Morphology of Necator americanus

Man is the only definitive host.

Mode of infection by penetration of skin or ingestion of contaminated food.

Humans are exposed to hookworm infection by Filariform larval stage.

Egg→1st Rhabditiform larvae →2nd Rhabditiform larvae → Filariform larval

stage → adult.

HooKWorm In Small Intestine Section

Laboratory Diagnosis

• The specific diagnosis of the hookworm infection is made by demonstration of eggs & larval stage in the faeces by direct evidence.

• Demonstration of eggs is made by the permanent stained smear & morphology is more easily seen in wet preparation

• The larval stage can be demonstrated by concentration method.

• The stool can be cultured using Harada-Mori filter paper strip technique for recovery of the Filariform larval stage.

• Recent research has focused on the development of DNA-based tools for diagnosis of infection.