Communicable diseases.
ALICE MUTHONI JOHN.
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Objectives.
By the end of the lesson you should be able to;
I.
Define what are helmenthics.
II.
Explain the classification of helmenthics.
III. Discuss different types of nematodes and life cycle of
every nematode.
IV. State different signs and symptoms of each nematode.
V. Explain morphology of each class.
VI. State the diagnosis of each class.
VII. Discuss the treatment prevention and control of every
class.
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HELMINTHIC DISEASES.
They are also known as intestinal worms.
Many helminths are free-living organisms in aquatic and
terrestrial environments
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Classification of helminths.
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NEMATODES
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The parasitic nematodes are divided into:
Intestinal nematodes
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I.
II.
III.
.
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Ascariasis lumbricoides
Ankylostoma duodenale. (hookworm)
Strongyoides stercoralis.
Intestinal nematodes without tissue stage
I.
A. Enterobius vermicularis (pinworm or threadorm)
II.
B. Trichuris trichiura. .(whipworm)
 Tissue and blood dwelling nematodes
I.
Filarial worms
II.
Dracunculus medinensis
III. Trichinella
IV. Larva migrans.
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CESTODES.
1) Taenia solium (pork tapeworm)
2) T. saginata (beef tapeworm)
3) Echinococcusgranulosus(dog tapeworm)
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1)
2)
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FLUKES.
Schistoma mansoni
Schistoma haemotonium
NEMATODES
GENERAL CHARACTERISTICS OF NEMATODES
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 Nematodes
are cylindrical rather than flattened; hence
the common name roundworm.
 They are un-segmented
 They have separate sexes with separate appearances.
 They have a tough protective covering or cuticle.
 They have a complete digestive tract with both oral and
anal openings.
 The nematodes are free living (Majority) or parasites of
humans, plants or animals
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roundworm
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Causes of roundorm infection.
A roundworm infection begins when you swallow
roundworm eggs.
Eggs can be present in food or drink, or in the soil in
which food has grown.
Eating food grown in contaminated soil can expose you
to infection.You may also become infected if you touch
contaminated soil with your hands and then eat without
first washing them.
Contaminated soil or stools can also contaminate the
water, making it possible to develop a roundworm
infection by drinking contaminated water.
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1. Ascaris lumbricoides
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Ascaris lumbricoid ecauses ascariasis
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Its one of the commonest and most spread nematode
infestation of the small intestines.
Symptoms are usually vague or absent.
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Symptoms of a ascariasis infection.
In most cases, a roundworm infection doesn't cause any
noticeable symptoms.
 When symptoms occur, they usually follow a two-stage
course:
1) Early-phase symptoms – these are caused by the
larvae (newly-hatched worms) moving from the small
intestine to the lungs.
 It's unclear why some people develop these symptoms
while others don't.
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Cont,
2. Late-phase symptoms – these are caused by adult
worms living in the intestine.
 Early-phase symptoms
 Symptoms usually begin 4-16 days after swallowing the
eggs and last up to three weeks.
 They include:
 a fever (high temperature) of 38C or above
 a dry cough.
 shortness of breath.
 Wheezing.
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Cont,
Late-phase symptoms
 Signs and symptoms associated with mature
worms include:
 passing a worm in the faeces.
 mild stomach (abdominal) pain.
 nausea and vomiting.
 diarrhoea ( blood in the stools may also be noticed)
 However, most people have no symptoms.
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Lifecycle.
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Humans ingest embryonated eggs containing infective
larvae.
Larvae hatch from the eggs in the small intestine, to
reach maturity, the larvae need to pass through the
lungs ,penetrate the intestine wall and reach the liver
via the portal system through bloodstream and
migrate to the liver, travel to right side of the heart
then into the lung.
Larvae break out of lung capillaries into alveoli, travel
to the bronchioles, and are coughed up to the
pharynx. They are swallowed and return to the
intestine. Two molts to 4th stage larvae take place in
alveoli.
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After they're swallowed, the larvae will end up in the
main part of the small intestine, where they'll mature into
adult worms.
Adult worms can live for up to two years.
Female worms can lay up to 200,000 eggs a day. The eggs
are released in the stools (faeces).
It takes 60 to 70 days from the initial ingestion of eggs to
the production of new ones.
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Lifecycle.
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Morphology:
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Adults - males are 15 to 30 cm long, with strongly
curved tails; females are 20 to 35 cm long, with
straight tails.
Eggs - one female produces 200,000 per day. The
egg has an outer shell membrane which is heavily
mamillated.
This layer is sometimes rubbed off in passage
down the fecal stream. Infertile eggs often appear
longer, and thinner shelled.
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Diagnosis  Identification
of eggs and/or adults in fecal samples.
 Major pathology and symptoms:
 Pneumonia associated with migration of larvae in the
lungs.
 Obstruction of the intestines, appendix, or common
bile duct.
 Vomiting and abdominal pain.
 May cause malnutrition in children with heavy
infections or poor diet.
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Risk factors.
Roundworm infections are most common in parts of the
world where:
 access to sanitation is either limited or non-existent
 there's overcrowding
 there are high levels of poverty
 there's a high population of children under five years of
age
 human faeces are commonly used as fertiliser (known as
"night soil")
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Treatment
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Albedazole is the drug of choice since its a broad
spectrum anti-helminthic.100mg bd for 3 days.
Levamisole 3 tablets as a single dose 5mgs/kg
Piperazine syrup150mg single dose.
Surgery for pt with intestinal obstruction.
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Prevention and control.
Prevention includes environmental measures such as:
I.
provision of adequate and safe water supplies.
II.
facilitate for safe faecal disposal.
III. Prevention of feacal contamination of food.
IV. Discourage use of fresh feaces for manuaring.
V. Health education that should focus on:
 The need for and proper use of latrines and toilet.
 Handwashing
 Proper disposalof faeces
 Washing of fruits and vegetables' before eating
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 Training
of children to use latrine.
 Use of drying rank for utensils so that they are above the
soil and dust.
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