THE NEMATODESG. Biteno, K.R. Feranil, K.K. Gregorio, K. Medina, C.W.

Mendoza

NEMATODE

Multicellular parasites that appear round in cross

section

Adult nematodes have a tapered, cylindric body with

an esophagus and longitudinal muscles.

Nematodes cause disease associated with the

intestines and the skin.

What’s AheadIn

testi

nal

Sp

ecie

sEnterobius vermicularis –

Pinworm/ Seat worm/ Society worm

Trichuris trichiura –

Whipworm

Ascaris lumbricoides –

Large Intestinal Roundworm

Necator americanus –

New World Hookworm

Ancylostoma duodenale –

Old World Hookworm

Strongyloides stercoralis –Threadworm

Inte

sti

na

l-T

iss

ue

S

pe

cie

s Trichinella spiralis –Trichina worm

Dracunculus medinensis– Guinea Worm

DEFINITION OF TERMS

Copulation Mating of select

worms

Cuticle Surface covering

present on adult

nematodes

Embryonated Fertilized egg

Decorticated Eggs lacking an

outer mammillated

albuminous coating

Larva Juvenile worms

Unembryonated Unfertilized egg

INFECTIVE STAGE Stage in the parasitic

life cycle that is

capable of invading a

definitive host.

AUTOREINFECTION Reinfecting oneself

Buccal capsule Long oral cavity; also

known as a buccal

cavity

Buccal cavity Long oral cavity; also

known as a buccal

capsule

Chitin Shell made up of a

thick nitrogen-

containing

polysaccharide

coating

Corticated Eggs containing a

mammillated

albuminous material

Morphology and Life Cycle

Members of the class Nematoda assume three

basic morphologic forms:

• Vary in size and shape

• Located inside the fertilized eggs; emerge and continue to mature

• Develop from the maturing larvae

• Sexes separate (females larger than males)

• Equipped with a digestive and reproductive system

Morphology and Life Cycle

Life cycles of individual nematodes are similar

but organism specific

Intestinal nematode infection may be initiated in

several ways.

Fertilized adult female nematodes lay their eggs

in the intestine and are then shed in the stool;

they mature in the soil and infect a new host in 2-

4 weeks.

Most members have the ability to exist

independent of a host (free living).

ASCARIS

LUMBRICOIDESG. Biteno, K. Feranil, K.K. Gregorio, K. Medina, C.W.

Mendoza

Ascaris lumbricoides

COMMON NAMES:

Common associated disease and condition

names:

Large Intestinal Roundworm

Roundworm of man

Ascariasis

Roundworm Infection

Ascaris lumbricoides

A soil – transmitted helminth.

Usual infection of 10-20 worms may not cause symptoms.

Causes varying degrees of pathology:

Tissue reaction to the invading larvae

Intestinal irritation to the adult

Other complications due to extraintestinalmigration.

Ascaris lumbricoides

Most common complain of the patient:

VAGUE ABDOMINAL PAIN

Fatal effects of A. lumbricoides are due to

erratic migration of adult worms.

MORPHOLOGY

UNFERTILIZED EGGS

PARAMETER DESCRIPTION

SIZE 85-95 um by 38-45 um;

Size variations possible

SHAPE Varies

EMBRYO Unembryonated;

Amorphous mass of

protoplasm

SHELL Thin

Other

features

Usually corticated

A. lumbricoides, unfertilized egg

Amorphous mass of protoplasm

Heavy Albuminous Coating

Thin Shell

MORPHOLOGY

A. lumbricoides, fertilized egg

PARAMETER DESCRIPTION

SIZE 40-75 um by 30-50 um

SHAPE Rounder than non-fertilized

version

EMBRYO Undeveloped unicellular

embryo

SHELL Thick chitin

Other

features

May be corticated or

decorticated

FERTILIZED EGGS

Undeveloped unicellular embryo

Thick chitin shellCoarse MammilatedAlbuminous Coating(Corticated)

Unfertilized and Fertilized Eggs:

Females will release unfertilized

eggs, which are more elongated

(left) than fertilized eggs (right).

Unfertilized eggs may also lack the

mammillated layer.

Fertilized Egg:

Undeveloped eggs are passed in the

stool.

Stained brown from bile.

Fertilized Egg:

Can be Decorticated.

Developed Egg:

This egg contains an infective larvae

(L2) that could infect a person if

ingested.

MORPHOLOGY

ADULTS

CHARACTERIS

TIC

FEMALE

ADULT

MALE

ADULT

SIZE (LENGTH) 22-35 cm Up to 30

cm

COLOR Creamy white

pink tint

Creamy

white pink

tint

Other features Pencil lead

thickness;

Paired

reproductive

organs

Prominent

incurved

tail with 2

spicules

200,000

eggs/female/day

A pair of female and male worms of A. lumbricoides. Notice the vulvarwaist(arrow)of the female worm and the coiled end of the male worm.

Adult male

Adult female

LABORATORY DIAGNOSIS

Specimen of choice for A. lumbricoides eggs:

Stool

Adult worms: may be recovered in several

specimen types, depending on the severity of

infection. (Intestine, Gallbladdder, Liver and

Appendix)

Sto

ol Tests • DFS

• Kato-katzTechnique

• Kato technique or cellophane thick methoda

• BEAVER DIRECT SMEAR METHOD (semi-quantitative)

• STOLL’S EGG COUNTING TECHNIQUE

Blo

od

Tests • CBC

• ELISA

Ima

gin

g T

ests • X-Ray

• CT Scan

• Ultasound

LABORATORY DIAGNOSIS

LIFE CYCLE

1. Adult worms live in the lumen of the small intestine.

* A female may produce up to 240,000 eggs per day, which are

passed with the feces.

LIFE CYCLE

2.-3. Fertile eggs embryonate and become infective after

18 days to several weeks depending on the

environmental conditions (optimum: moist, warm,

shaded soil).

LIFE CYCLE

Infective Stage: FULLY EMBRYONATED (with 2nd

stage

Larvae or Rhabditiform Larvae) EGG

LIFE CYCLE

3

.

4-5. After infective eggs are swallowed , the larvae hatch

in

the lumen of the SI and penetrate the intestine wall.

LIFE CYCLE

Larvae enters the venule to go to the liver (through the portal vein) or

to

the heart and pulmonary vessels (7-10 days), where they break out

the capillaries and enter the air sacs, ascend the bronchial tree.

LIFE CYCLE

6.

In the lungs, larvae undergo molting before migrating to

the larynx and oropharynx to be swallowed in the

digestive tract.

LIFE CYCLE

6.

LIFE CYCLE

During the lung migration, the larvae may cause host sensitization resulting in allergic manifestations such as

Eosinophilia and Loeffler’s syndrome may also be present during lung migration.

Lung infiltration

Asthmatic attacks

Edema of the lips

Upon reaching the small intestine, they develop into adult

worms.

*Between 2 and 3 months are required from ingestion of the infective

eggs to oviposition by the adult female. Adult worms can live 1 to 2 years.

LIFE CYCLE

7.

EPIDEMIOLOGY

Estimated worldwide prevalence of 25% (0.8-1.22 billion people).

Most common intestinal helminth infection in the world.

Children are particularly vulnerable.

Risk infection exists wherever fecal disposal is improper.

EPIDEMIOLOGY

Remains endemic in Africa, South and Central America.

The global prevalence in 2010:

Estimated at 464.6 million people.

In tropical countries, it ranges from 60 to 85%.

DISEASE PREVALENCE

Philippines: 31 million

East Asia and the Pacific: 204 million

Sub-Saharan Africa: 173 million

India: 140 million

South Asia: 97 million

China: 86 million

Latin America and Carrabean: 84 million

Middle East and North Africa: 23 million

TREATMENT

Anti – helminthic drugs:

Albendazole

– drug of choice

Mebenazole

Pyrantel pamoate

Piperazine citrate

PREVENTION AND CONTROL

Prevention and control measures involve the ff:

Sanitary disposal of

human feces

Health education (personal, family, and community hygiene)

Mass chemotherapy

done periodically

TRICHURIS TRICHIURA

Trichuris trichiura

COMMON NAME:

Common associated disesase and condition names:

A soil – transmitted helminth frequently observed occuring with A. lumbricoides.

Trichuriasis

Whipworm infection

Whipworm

HISTORY

(1740)Morgani –.

discovered the

residence of adult T.

Trichuria worms in

colon

(1761) Roedere –

gave a report of the exact

morphologic description

and provided accurate

drawings of the parasite

MORPHOLOGY

EGGS

PARAMETER DESCRIPTION

SIZE 50 – 55 um by 25 um

SHAPE Barrel-shaped / Lemon

shaped/ Football-

shaped;

Translucent hyaline

polar plug at each end.

SHELL Smooth; yellow-brown

color because of host

bile contact

Smooth

shell

surface

Hyaline polar plug

NICE TO KNOW

Can you identify??

MORPHOLOGY

• Less resistant to desiccation than A. lumbricoides

EGGS

• the larvae escape and penetrate the intestinal villi where they remain for 3 to 10 days.

LARVA

MORPHOLOGY

ADULTS

PARAMETE

R

DESCRIPTION

SIZE Male – 30-45 mm

Female – 35-50 mm

A female lays approximately

3000 to 10000 eggs per day.

ANTERIOR

END

Colorless; resembles a whip

handle; contains a slender

esophagus resembling a

string of beads

Female worm

Male worm

MORPHOLOGY

PARAMETER DESCRIPTION

POSTERIOR END Pinkish-gray;

resembles whip

itself;

contains digestive

and reproductive

systems;

Male- possess

prominent curled

tail with a single

spicule and

retractile sheath.

Female -has a

bluntly rounded

posterior end.

•ADULTS

Posterior part of male T.

trichuria

Posterior part of female T.

trichuria

LABORATORY DIAGNOSIS

Specimen of choice for T. trichiura eggs: Stool

Adult worms may be visible on macroscopic examination of the intestinal mucosa.

Adults may also be seen in the rectum in heavy infections.

LABORATORY DIAGNOSIS

– highly recommended in diagnosis

of trichuriases

– used for egg counting to

determine cure rate (CR), egg

reduction rate (ERR), and intensity

of infection.

The T. trichiura eggs are particularly

prominent in infected samples

processed using ZSFMethod.

DFS

Kato thick smear method

Kato-Katz technique

Zinc Sulfate Floatation Method

- Oval with transparent bipolar plugs

LIFE CYCLE

LIFE CYCLE

The unembryonated eggs

are passed with the

stool.

LIFE CYCLE

The unembryonated eggs

are passed with the

stool.

In the soil, the eggs develop

into a 2-cell stage , an

advanced cleavage stage

and then they

embryonate

The unembryonated eggs

are passed with the

stool.

Eggs become infective in 15 to 30 days. After

ingestion (soil-contaminated hands or food), the

eggs hatch in the small intestine, and release

larvae

IS: EMBRYONATED EGG

In the soil, the eggs

develop into a 2-cell

stage , an advanced

cleavage stage and then

they embryonate

The unembryonated eggs

are passed with the

stool.

Eggs become infective in 15 to 30 days. After

ingestion (soil-contaminated hands or food), the

eggs hatch in the small intestine, and release

larvae

In the soil, the eggs

develop into a 2-cell

stage , an advanced

cleavage stage and then

they embryonate

Larva mature and

establish

themselves as

adults in the colon

The unembryonated eggs

are passed with the

stool.

Eggs become infective in 15 to 30 days. After

ingestion (soil-contaminated hands or food), the

eggs hatch in the small intestine, and release

larvae

In the soil, the eggs

develop into a 2-cell

stage , an advanced

cleavage stage and then

they embryonate

Larva mature and

establish

themselves as

adults in the colon

The adult worms live in

the cecum and

ascending colon.

LIFE CYCLE

Each female worm can produce a total of over

60 million eggs over an average lifespan of 2

years.

Unlike A. lumbricoides, there is no heart to

lung migration.

PATHOGENESIS AND CLINICAL

MANIFESTATIONS

The anterior portion of the worms (embedded

in the mucosa) cause petechial haemorrhage

which predispose amebic dysentery presumably

because the ulcers provide suitable site for tissue

invasion of E. histolytica

Mucosa is hyperemic and edematous

Enterorrhagia is common

PATHOGENESIS AND CLINICAL

MANIFESTATIONS

RECTAL PROLAPSE may occur if heavily infected

Lumen of the appendix may be filled with worms and consequent irritation and inflammation may lead to appendicitis or granulomas

Infection with 5,000 eggs/gram of feces is symptomatic.

Infection with 20,000 eggs/gram of feces often develop severe diarrhea or dysenteric volume.

EPIDEMIOLOGY

Considered as the 3rd

most common helminth.

Found primarily in warm climates of the world where poor sanitation practices are common, such as defecating directly into the soil or using human feces as fertilizer.

EPIDEMIOLOGY

Estimated that 902 million are infested (as compare to 355 million in 1947).

The global prevalence in 2010:

Estimated at 464.6 million people.

In tropical countries, it ranges from 60 to 85%.

DISEASE PREVALENCE

Philippines:Prevalence is from 80 to 84%.

Sub-Saharan Africa: Estimated at 20.9% (100million cases).

Oceania: Estimated 1.2million infested persons, accounting for <1% of the global burden of Trichuriasis.

South America: Estimated prevalence rates of 12.5%

TREATMENT

Mebendazole –drug of choice

Abendazole

PREVENTION AND CONTROL

Infection in highly endemic areas may be

prevented by:

Treatment of infected individuals

Sanitary disposal of human feces by construction of toilets and their proper use.

Washing of hands with soap and water before and after meals

Health education on sanitation and personal hygiene

Through washing and scalding of uncooked vegetables especially in areas where night soil is used as fertilizer.

THANK YOU!