Nematodes (roundworms)

Nursing college, Second stage Microbiology
Dr.Nada Khazal K. Hendi
L8 Nematodes (roundworms)
The nematodes are elongated, non segmented worms that are tapered at both ends. Unlike
other helminths, nematodes have a complete digestive system, including a mouth, an
intestine that spans most of the body length, and an anus. The body is protected by a tough,
non cellular cuticle. Most nematodes have separate, anatomically distinctive sexes. The
mode of transmission varies widely, depending on the species and includes direct skin
penetration by infectious larvae, ingestion of contaminated soil, eating undercooked pork,
and insect bites. The parasites can invade almost any part of the body: liver, kidneys,
intestines, subcutaneous tissue, or eyes. Generally, nematodes are categorized by whether
they infect the intestine or other tissues. Alternatively, they can be divided into those for
which the eggs are infectious and those for which the larvae are infectious.
1.Ascaris lumbricoides (Giant (roundworms)
2.Enterobes (pinworm)
3. Trichuris trichiura (Whip worm)
4.Anchylostoma (Hook worm)
1.Ascaris lumbricoides (Giant roundworms)
A more serious disease of worldwide occurrence is ascariasis, caused by Ascaris
lumbricoides. The disease transmitted by ingesting the soil containing egg. Larva grow in
the intestine, causes intestine obstruction, may pass to the blood and through the lung.
Transmitted by ingestion of soil containing the organism s eggs. Humans are the sole host.
Adults
Adult A. lumbricoides worm usually assume a creamy – white color with a tint of pink .
Fine striations are visible on the cuticle . Ascaris adult worms are the largest known
intestinal nematodes. The average adult male is small only seldom reaching 30 cm in
length. The male is characteristically slender and possesses a prominent incurved tail. The
adult female measures 22 to 35 cm in length and resembles a pencil lead in thickness.
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Nursing college, Second stage Microbiology
Dr.Nada Khazal K. Hendi
Table ( ) : A. lumbricoides adults : Typical characteristics
Characteristic Adult female Adult male
Size (length) 22 to 35 cm Up to 30 cm
Color Creamy – white pink tint Creamy – white pink tint
Other features Pencil – lead thickness Prominent incurved tail
Table ( ) : A. lumbricoides fertilized egg: Typical characteristics
Size 40 to 75 ?m by 30 to 50 ?m
Shape Rounder than nonfertilized version
Embryo Undeveloped unicellular embryo
Shell Thick , chitin
Other features My be corticated or decorticated
Table ( ) : A. lumbricoides nonfertilized egg: Typical characteristics
Size 85 to 95 ?m by 38 to 45 ?m size variations possible
Shape Varies
Embryo Unembryonated ; amorphous mass of protoplasm
Shell Thin
Other features Usually corticated
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Fig ( ) : A. lumbricoides adult worm .
Nursing college, Second stage Microbiology
Dr.Nada Khazal K. Hendi
Life cycle
The life cycle of A. lumbricoides is relatively complex compared with the parasites
presented thus far. Infection begins following the ingestion of infected eggs that contain
viable larvae. Once inside the small intestine, the larvae emerge from the eggs. The larvae
then complete a liver lung migration by first entering the blood via penetration through the
intestinal wall. the first “stop” on this journey is the liver . From there, the larvae continue
the trip via the blood stream to the second “stop” the lung . Once inside the lung, the larvae
burrow their way through the capillaries into the alveoli . Migration into the bronchioles
then follows. From here , the larvae are transferred through coughing into the pharynx,
where they are then swallowed and returned to the intestine.
Maturation of the larvae occurs, resulting in adult worms, which take up residence in the
small intestine. The adults multiply and a number of the resulting undeveloped eggs (up to
250,000 per day) are passed in the feces .
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Nursing college, Second stage Microbiology
Dr.Nada Khazal K. Hendi
Clincal symptoms
: Ascariasis / Roundworm Infection
Patients who develop symtomatic ascariasis may be infected with as few as a single worm .
such a worm may produce tissue damage as it migrates through the host . a secondary
.bacterial infection may also occur following worm perforation out of the intestine
Patients infected with many worms may exhibit vague abdominal pain, vomiting, fever,
and distention . mature worms may entangle themselves into a mass that may ultimately
obstruct the intestine, appendix, liver, or bile duct . such intestinal complications may
result in death. In addition, discomfort from adult worms exiting the body through the
anus, mouth, or nose may occur. Heavily infected children who do not practice good eating
habits may develop protein malnutrition .
Diagnosis: egg in stool, (ovum have heavy protective tuberculated shall). Treated with
mebendazole.
1. Enterobiasis (pinworm)
The most common nematode infection is Enterobies (pinworm disease) is caused by
Enterbius vermicularis, which causes anal itching with white worms visible in stool or
perianal region but otherwise does little damage. The disease transmitted by ingesting the
egg. Diagnosis: egg in stool (unembryonated ovum, flattening on side, thin shell.
Deposited on perianal skin). Treated with mebendazole.
2. Trichuris trichiura (Whip worm)
This disease is caused by Trichuris trichiura. The infection is usually asymptomatic;
however, abdominal pain, diarrhea, and rectal prolapsed can occur. The disease
transmitted by ingesting the egg. Diagnosis egg in stool, (unembryonated double plug
ovum). Treated with mebendazole.
3. Anchylostoma (Hook worm)
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Nursing college, Second stage Microbiology
Dr.Nada Khazal K. Hendi
This disease is caused by Anchylostomaduodenale. The worm attaches to the intestinal
mucosa, causing anorexia, ulcer-like symptoms, and chronic intestinal blood loss, leading
to anemia. This disease is transmitted through directed skin penetration by larvae found in
soil. Diagnosis egg in stool (thin shall, 4-8 cell stage).
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Nursing college, Second stage Microbiology
Dr.Nada Khazal K. Hendi
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Nursing college, Second stage Microbiology
Dr.Nada Khazal K. Hendi
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