Helminths

Roundworms
Introduction
• Parasitic worms, also known as helminths, are large macroparasites;
adults can generally be seen with the naked eye
• The helminths are worm-like parasites and invertebrates
characterized by elongated, flat or round bodies
• There are both hermaphroditic and bisexual species
classification

Helminths

Flatworms Roundworms

Flukes Tapeworms Pinworm

Structure
• Helminths develop through egg, larval (juvenile), and adult stages
• The outer covering of helminths is the cuticle or tegument. Prominent
external structures of flukes and cestodes are acetabula (suckers) or
bothria (false suckers)
• Internally, the alimentary,
excretory, and reproductive
Systems can be identified
Occurance
• Helminths are one of the leading causes of morbidity in the developing
world with over two billion people affected. That's almost a third of the
world's population
• Ascaris lumbricoides (also called human roundworm), which is the most
common roundworm infection, and affects as many as one billion people
worldwide.
• Hookworm infections.
• Guinea worm disease (dracunculiasis).
• Filariasis, which is caused by thread-like filarial nematodes
• Threadworm (pinworm)
Roundworms
Pinworms
Introduction
• Roundworms (nematodes), Enterobius vermicularis or seat worm or
Pinworms found worldwide are worms with a long round body.
• They vary in length from several millimetres to up to two metres.
Roundworms are common in warm tropical countries
• Children are more often affected than adults
• About 60 types (species) of roundworm can live in (are parasites of)
humans. They usually live in the human gut
Transfer
• Roundworm eggs and tiny young worms (larvae) live in the soil. They
most commonly get into the body when a person gets them on his or
her hands and then transfers them to the mouth
• Eggs can survive for up to two weeks outside the body. They fall off
the skin around the anus and can fall on to bedding, clothes, etc. They
can then get wafted in the air as you change clothes, bedding, etc,
and become part of the dust in a home
• children may swallow some eggs by playing with other children who
have eggs on their fingers, or from food, drink, toothbrushes or dust
that have been contaminated with threadworm eggs
Size
• Threadworms are small, thin, white, thread-like worms between 2
mm and 13 mm long. They infect human guts (intestines). Worms in
children are common but anyone of any age can be affected
• The adult female has a sharply pointed posterior end, is 8 to 13 mm
long, and 0.5 mm thick.
• The adult male is considerably smaller, measuring 2 to 5 mm long and
0.2 mm thick, and has a curved posterior end
• Eggs measure 50 to 60 x 20 to 30 um, are flattened on the ventral
side. They have thick shells. The eggs mature rapidly and are infective
within a few hours
Egg and adult
Epidemiology
• This is the most common parasitic nematode of man through out the
world. The distribution is world­wide and more common in cooler
countries than in hot climate. It is prevalent in America, Europe, Africa
and Canada
• about 209,000,000 people in the
World are infected with this worm
• Enterobius vermicularis is common
among children because thumb-sucking
is common at this age
Morphology
• Enterobius vermicularis has a cylindrical body, and a cuticle with three
main outer layers made of collagen and other compounds, secreted
by the epidermis
• The mouth cavity leads to an oesophagus with an extra swelling and a
distal bulb. The anus lies at the junction of the middle and posterior
thirds of the body. The vulva is situated in front of junction of the
anterior and middle thirds of the body
• Enterobius vermicularis has a specialized tubular excretory system
system with three canals. The canals are arranged to form an "H"
Morphology
• The posterior end extended into a long slender pointed end and give
it the name of pinworm.
• The female has a vagina, vulva, ovary, uterus, and oviduct.
Nutrition
• They feed on blood and tissue cells in the host's intestine
Infection
• The infection of pinworm is called “Enterobiasis”.
• hatch in the small intestine, they take about 1 to 2 months to develop
into adult worms which happens in the small intestine
• The larvae migrate to the caecum, appendix, colon or ileum where
they mature in about a month.
• worms migrate to the large intestine
• Male and female worms may become attached to the gut wall and
produce inflammation. The adult live in the host for 20 to 30 days.
• eggs are sticky and therefore itchy to the host
Life cycle
Pathogenesis
• Nematode sperm are amoeboid-like and lack flagella.
• Copulation occurs between adults in the large intestine, and each female produces about
10,000 eggs.
• The female migrates to the perianal skin at night, spurred by the drop in body
temperature of the host.
• She will only oviposit on the perianum, because air seems to be an ovipositing stimulant.
• The expulsion of eggs is so forceful that the eggs are sent airborne, and can be spread
out over the perianum.
• After ovipositing, the female often dies, but occasionally returns (or attempts to return)
to the intestine. The male dies soon after fertilization of the female.
• The life cycle of E. vermicularis is about two months long.
Symptoms
• The person infected may experience intense itching in the anal region.
Children especially, may become irritable and not sleep well. General
symptoms are restlessness, nervousness, appendicitis, irritability
nausea, constipation, diarrhoea, abdominal pain, insomnia, loss of
appetite, bed wetting and grinding the teeth.
Diagnosis
• Enterobius can be diagnosed through a cellophane tape test or
pinworm paddle test where an adhesive tape-like material is applied
to the perianal area and then examined under a microscope. The
examination might reveal characteristic ova which are 50 by 30
microns in size and have a flattened surface on one side or may reveal
the worms
• Or touch the slide with the tape.
• 50% of the time tap will show ova and if you repeat this procedure
three times then positivity is 90%.
• Stool examination can show ova
Treatment
• Oral dose of Gentian violet is used in treating pinworm infection. Piperazine is
the most effective medicine in the treatment of ‘Enterobiasis’.
• Albendazole: Given on an empty stomach, a 400-mg, one-time dose followed by
a repeat dose in 2 weeks
• OR
• Mebendazole: A 100-mg, one-time dose followed by a repeat dose in two weeks
• OR
• Pyrantel Pamoate: Dose of 11 mg/kg up to a maximum 1 gm given 2 weeks apart
• The patients should wash his perianal region with warm water and soap on rising
from bed and before going to bed
Control:

• Good sanitary habits help in controlling reinfection.

• Frequent laundering of night clothes and bedding.
• Keeping hands and finger nails clean.
• Frequent Bathing
• Keeping rooms as dust free as posssible