Large Round Worm & Whip Worm ~~~ http://vm.cfsan.fda.gov/~mow/chap30.html

Large Round Worm & Whip Worm



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Ascaris lumbricoides and Trichuris trichiura

1. Name of the Organism:
Ascaris lumbricoides and Trichuris trichiura Humans worldwide are
infected with Ascaris lumbricoides and Trichuris trichiura; the eggs
of these roundworms (nematode) are "sticky" and may be carried to the mouth by hands, other body parts, fomites (inanimate objects), or
foods.

2. Nature of Acute Disease: Ascariasis and trichuriasis are the
scientific names of these infections. Ascariasis is also known
commonly as the "large roundworm" infection and trichuriasis as "whip worm" infection.

3. Nature of Disease: Infection with one or a few Ascaris sp. may be
inapparent unless noticed when passed in the feces, or, on occasion,
crawling up into the throat and trying to exit through the mouth or
nose. Infection with numerous worms may result in a pneumonitis
during the migratory phase when larvae that have hatched from the
ingested eggs in the lumen of the small intestine penetrate into the
tissues and by way of the lymph and blood systems reach the lungs. In the lungs, the larvae break out of the pulmonary capillaries into the air sacs, ascend into the throat and descend to the small intestine
again where they grow, becoming as large as 31 X 4 cm. Molting
(ecdysis) occurs at various points along this path and, typically for roundworms, the male and female adults in the intestine are 5th-stage nematodes. Vague digestive tract discomfort sometimes accompanies the intestinal infection, but in small children with more than a few
worms there may be intestinal blockage because of the worms' large
size. Not all larval or adult worms stay on the path that is optimal
for their development; those that wander may locate in diverse sites
throughout the body and cause complications. Chemotherapy with
anthelmintics is particularly likely to cause the adult worms in the
intestinal lumen to wander; a not unusual escape route for them is
into the bile duct which they may occlude. The larvae of ascarid
species that mature in hosts other than humans may hatch in the human intestine and are especially prone to wander; they may penetrate into tissues and locate in various organ systems of the human body,
perhaps eliciting a fever and diverse complications.
Trichuris sp. larvae do not migrate after hatching but molt and
mature in the intestine. Adults are not as large as A. lumbricoides.
Symptoms range from inapparent through vague digestive tract distress to emaciation with dry skin and diarrhea (usually mucoid). Toxic or
allergic symptoms may also occur.


4. Diagnosis of Human Illness: Both infections are diagnosed by
finding the typical eggs in the patient's feces; on occasion the
larval or adult worms are found in the feces or, especially for
Ascaris sp., in the throat, mouth, or nose.

5. Associated Foods: The eggs of these worms are found in
insufficiently treated sewage-fertilizer and in soils where they
embryonate (i. e., larvae develop in fertilized eggs). The eggs may
contaminate crops grown in soil or fertilized with sewage that has
received nonlethal treatment; humans are infected when such produce
is consumed raw. Infected foodhandlers may contaminate a wide variety of foods.

6. Relative Frequency of Disease: These infections are cosmopolitan,
but ascariasis is more common in North America and trichuriasis in
Europe. Relative infection rates on other continents are not
available.

7. Course of Disease and Complications: Both infections may self-cure after the larvae have matured into adults or may require anthelmintic treatment. In severe cases, surgical removal may be necessary.
Allergic symptoms (especially but not exclusively of the asthmatic
sort) are common in long-lasting infections or upon reinfection in
ascariasis.

8. Target Populations: Particularly consumers of uncooked vegetables
and fruits grown in or near soil fertilized with sewage.

9. Food Analysis: Eggs of Ascaris spp. have been detected on fresh
vegetables (cabbage) sampled by FDA. Methods for the detection of
Ascaris spp. and Trichuris spp. eggs are detailed in the FDA's
Bacteriological Analytical Manual.

10. Selected Outbreaks: Literature references can be found at the
links below. Although no major outbreaks have occurred, there are many individual cases. The occurrence of large numbers of eggs in domestic municipal sewage implies that the infection rate, especially with A. lumbricoides, is high in the U. S. Morbidity and Mortality Weekly Reports For more information on recent
outbreaks see the CDC.

11. Education and Background Resources: Literature references can be
found at the links below. Loci index for genome Ascaris lumbricoides
Trichuris trichiura Available from the GenBank Taxonomy database,
which contains the names of all organisms that are represented in the genetic databases with at least one nucleotide or protein sequence.

12. Molecular Structural Data: None currently available.

13. FDA Regulations or Activity: Ascarids and trichurids are
considered pathogens and foods eaten without further cooking should
not be contaminated with viable embryonated eggs of either genus.


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