intestinal roundworms pdf - د. جبار

Ascaris lumbricoides and

Ascaris suum

(intestinal roundworms of

humans and pigs)

Phylum Nematoda

Class Secernenta

Order Ascaridia

Family Ascarididae

Genus Ascaris

A. lumbericoides

Introduction

As.Lumbricoides

is the giant

roundworm of human, belonging to

the phylum Nematode. It is the largest

and most common parasitic

worm in human

It is responsible for the disease

called ascariasis

in human

One sixth of the human population is

estimated to be infected by this

parasite. Ascariasis is prevalent

worldwide and more so in Tropical

and Subtropical countries

Ascariasis can occur at all ages, but is

prevalent in 5-9 years old group.

The incidence is higher in poor rural

population.

Ascaris lumbricoides is one of the

largest and most common

parasites found in humans. The

adult females of this species

can measure up to 18 inches long

(males are generally shorter),

It is estimated that 25% of the

world's population is

infected with this nematode. The

adult worms live in the small

intestine and eggs are passed in the

feces.

Habitat:-

The adult worm lives in the small

intestine of man.

Morphology :-

The adult worm is the largest round

worm parasitizing the human

intestinal tract. It is elongeted,

cylindrical, and tapers both anteriorly

&posteriorly to relatively blunt

conical ends. The head is provided

with three fleshy lips .

The digestive &reproductive organs

float inside the body cavity which

contain an irritating allergic fluid .The

irritant action is due to the presence

of atoxin called a scarone or a scarase

which is probably of the nature of

primary albomenoses

Egg:

The fertilized egg of Ascaris

lumbricoides at the time of

oviposition is spherical or sub-

spherical,measures 65-75um

by35-50um &consists of the

following observable structures

1-A coarsely granular ,spherical

ovumthat usually does not completely

fill the shell.

2-A thin innermost membrane that is

highly impermeable.

3-A relatively thick,colorless middle

layer that is smooth on both inner

&outer surfaces .

4-An outer most ,coarsely mammilated

Female worms without males

produce infertile eggs that are

markedly subspherical

(88um by38-44um),internally they

contain

a mass of disorganized granules

that completely fill the shell

Life cycle

A single female

can produce up to 200,000 eggs

each day! About two weeks

after passage in the feces the eggs

contain an infective larval

or juvenile stage, and humans are

infected when they ingest

such infective eggs. The eggs hatch

in the small intestine

the juvenile penetrates the small

intestine and enters the circulatory

system, and eventually the juvenile

worm enters the lungs.

In the lungs the juvenile worm

leaves the circulatory system and

enters the air passages of the lungs.

The juvenile worm then migrates

up the air passages into the pharynx

where

it is swallowed, and once in the

small intestine the juvenile

grows into an adult worm.

Why Ascaris undergoes such a

migration through the body to only

end up where it started is

unknown.

Such a migration is not unique to

Ascaris, as its close relatives

undergo a similar migration in the

bodies of Ascaris

infections in

humans can cause significant

pathology.

Pathology :

The migration of the larvae through

the lungs causes

the

blood vessels of the lungs to

hemorrhage, and there is an

inflammatory response accompanied

by edema.

The resulting

accumulation of fluids in the lung

results in "ascaris pneumonia," and

this can be fatal

2-The large size of the adult

worms also presents problems,

especially if the worms

physically block the

gastrointestinal tract.

Ascaris is not orious

for it reputation to migrate within

the small intestine, and when

large worm begins to migrate there

is not much that can stop it

Instances have been reported in

which Ascaris have migrated

into and blocked the bile or

pancreatic duct or in which

the worms have penetrated the

smallintestine resulting in acut and

fatal peritonitis.

Ascaris seems to be especially

sensitive to anesthetics, and numerous

cases have been

documented where

3-patients in surgical recovery

rooms have had

worms migrate from the small

intestine, through the stomach,

and out the patient's nose or

mouth

Ascaris

suum is found in pigs. Its life

cycle is identical to that of

A. lumbricoides. If a human ingests

eggs of A. suum the

larvae will migrate to the lungs and die

." Adult worms

of this species do not develop in the

human's intestine

. (Some parasitologists believe that

there is but one species of

Ascaris that infects both pigs and

humans, but any commentary

on this issue is beyond the scope of

this web site.)

Infections of Ascaris are diagnosed

by:

1-finding characteristic eggs in

the feces of the infected host

2-the presence of three large lips, a characteristic of ascarids.

Ascaris lumbricoides, fertilized egg.

Ascaris lumbricoides,
fertilized egg.

Another example of a fertilized Ascaris
lumbricoides egg. (Original image from

An example of an unfertilized A.

lumbricoides egg. (Original image

from:

Atlas of Medical

Parasitology

An example of an unfertilized A. lumbricoides egg. (Original image from:

Atlas of Medical Parasitology

A "decorticated," fertilized, Ascaris lumbricoides. (Original image from:

Atlas of Medical Parasitology

Eggs of Ascaris suum. A. suum is a common parasite of pigs.
The eggs are virtually indistinguishable from those of A.lumbricoides.
(Original image from

Oklahoma State University, College of Veterinary Medicine

Female and male Ascaris lumbricoides; the female measures

female Ascaris lumbricoides. Females of this

species can measure over 16 inches long. This

specimen was passed by a

young girl in Florida.

Note : up stream movement this

movement for A. lumbericoides

through mouth or nose.

Note:

some times the infected man may die

due to this irritation action after

changing to anaphylatic or HSR.

Lecture 2 Dr. Jabar Etaby

Hookworms

Introduction

Patients with hookworm

infection often are

asymptomatic; however,

chronic hookworm infection

is a common cause of

moderate and severe

hypochromic, microcytic

anemia

in people living in

tropical developing

countries, and heavy

infection can cause

hypoproteinemia with

edema.

EPIDEMIOLOGY

Humans are the only reservoir.

Hookworms are

prominent in rural, tropical, and

subtropical areas where

soil contamination with human

feces is common.

Although the prevalence of both

hookworm species is

equal in many areas, A. duodenale is

the predominant species in the

Mediterranean region, northern Asia,

and

selected foci of South America.

N. americanus is

predominant in the Western

hemisphere, sub-Saharan

Africa, Southeast Asia, and

a number of Pacific islands

Larvae and eggs survive in loose,

sandy, moist, shady,

well-aerated, warm soil (optimal

temperature 23°C–33°C)

[73°F–91°F]).

Life cycle

Hookworm eggs from stool hatch

in soil in 1 to 2 days

as rhabditiform larvae. These

larvae develop into infective

filariform larvae in soil within 5 to

7 days and can persist for weeks to

months.

Percutaneous infection occurs after

exposure toinfectious larvae.

A.duodenale transmission can occur by

oral ingestion

and possibly through human milk.

Untreated infected patients

can harbor worms for 5

years or longer.

The time from exposure to

development

of noncutaneous symptoms

is 4 to 12 weeks.

Clinical signs

Patients with hookworm infection

often are

asymptomatic; however, chronic

hookworm infection is a

common cause of moderate and

severe hypochromic

microcytic anemia in people living in

tropical developing

countries, and heavy infection can

cause

hypoproteinemia with edema

Chronic hookworm

infection in children may lead

to physical growth delay,

deficits in cognition, and

developmental delay.

After

contact with contaminated

soil, initial skin penetration of

larvae, often involving the feet,

can cause a stinging

burning sensation followed

by pruritus and a

papulo vesicular rash that

may persist for 1 to 2

weeks

Pneumonitis associated with migrating

larvae is

uncommon and usually mild, except

in heavy infections.

Colicky abdominal pain, nausea,

and/or diarrhea and

marked eosinophilia can develop 4

to 6 weeks after exposure

Blood loss secondary to hookworm

infection

develops 10 to 12 weeks after initial

infection and

symptoms related to serious iron-

deficiency anemia can

develop in long-standing moderate

or heavy hookworm

infections.

After oral ingestion of

infectious Ancylostoma

duodenale larvae, disease

can manifest withpharyngeal

itching, hoarseness, nausea,

and vomiting shortly after

ingestion.

ETIOLOGY

Necator americanus is the

major cause of hookworm

infection worldwide, although

A. duodenale also is an

important hookworm in

someregions.

Mixed infections

are common. Both are

roundworms (nematodes)

with

similar life cycles

Ancylostoma spp. and Necator spp.

(hookworms)

There are many species of

hookworms that infect mammals

The most important, at least from the

human standpoint, are

the human hookworms, Ancylostoma

duodenale and Necator

americanus, which infect an estimated

800,000,000 persons,

and the dog and cat hookworms,

A.caninum and A. braziliense,

respectively. Hookworms average

about 10 mm in length

and live in the small intestine of the

host

The males and

females mate, and the female

produces eggs that are passed in

the feces. Depending on the species,

female hookworms can

produce 10,000-25,000 eggs perday.

About two days after

passage the hookworm egg

hatches, and the juvenile worm (or

larva) develops into an infective

stage in about five days.

The next host is infected when an

infective larva penetrates the

host's skin.

The juvenile worm migrates

through the host's

body and finally ends up in the

host's small intestine where it

grows to sexual maturity.

The presence of hookworms can

be demonstrated by finding the

characteristic eggs in the feces; the

eggs can not, however, be

differentiated to species

Juveniles (larvae) of the dog and

cat hookworms can infect

humans, but the juvenile worms

will not mature into adult worms.

This results in a condition known

as "cutaneous" or

"dermal larval migrans" or

"creeping eruption." Hence the

importance of not allowing dogs

and cats to defecate

indiscriminately.

The following image provides an

excellent

example of how hookworms are

attached to and embedded in

the epithelium of the host's

gastrointestinal tract.

DIAGNOSTIC TESTS

1- Microscopic demonstration of

hookworm eggs in feces is

diagnostic.

Adult worms or larvae rarely are

seen.

2-Approximately 5 to 8

weeks are required after

infection

for eggs to appear in feces.

3-A direct stool smear with

saline solution or potassium iodide

saturated with iodine

is adequate for diagnosis of heavy

hookworm infection;

4-light infections require

concentration techniques.

Quantification techniques

5-, Kato-Katz, Beaver direct

smear, or Stoll egg-counting

techniques) to determine

the clinical significance of infection

and the response to

treatment may be available from

state or reference

laboratories.

CONTROL MEASURES

Sanitary disposal of feces to

prevent contamination of

soil is necessary in areas with

endemic infection

Treatment of all known infected

people and screening of

high-risk groups (ie, children and

agricultural workers) in

areas with endemic infection can

help decrease environmental

contamination.

. Wearing shoes may not be

fully protective, because cutaneous

exposure to

hookworm larvae over the entire

body surface of children
could result in infection.

Despite relatively rapid

reinfection, periodic

deworming treatments

targeting

preschool-aged and school-

aged children have been

advocated to prevent

morbidity associated with

heavy

intestinal helminth

infections`

A histological section of a hookworm in the host's small

intestine. Original image copyrighted and provided

byDr. A.W.

Shostak, and used with permission