Intestinal Nematodes part 1

Phylum Nematoda

Nematode

Means “thread-like”

Nema

“Thread”

Nematode general characteristics

Elongated, cylindrical, unsegmented worms with tapering ends, have separate sexes.

Dioceious

Separate sexes

Monocious

harbor both reproductive structure on a single individual. Can self pollinate and fertilize themselves.

Types of Ova

1. Fertilized egg (Single celled Structure) (Embryo or protopolasm)

2. Embryonated (Larval developed)

L1 - L2

Immature/larval referred to as FEEDING STAGE

Rhabditiform Larva.

L1 - L2 stage

Rhabditiform

L3 - L4

• Filariform larva

• Mature Larval Stage

• Closed moutth/non feeding stage

L4

Adult Form

Embryonated Egg

• Larval inside the egg/ova

• Sometimes harbor the L3 which is the infective stage

Diagnostic Stage

1. Ova

2. Larva

Intestinal Nematodes in Small Intestine (CASH)

1. Capillaria Philippinensis

2. Ascaris Lumbricoides

3. Strongyloides Stercoralis

4. Hookworms (infecting humans)

Large Intestinal roundworm, roundworm of man

Ascaris lumbricoides

Ascariasis (roundworm infection)

intestinal infection caused by the parasitic roundworm Ascariasis lumbricoides

Unfertilized egg (A. lumbricoides)

Do not undergo development

Unfertilized egg shape (A. lumbricoides)

Varies

Unfertilized egg: Embryo (A. lumbricoides)

Unembryonated - Amorphous mass of protoplasm

Unfertilized egg (A. lumbricoides ova)

• Elongated

• both decorticated and corticated

Fertilized Egg

• Single celled/multi celled protoplasm

• Embryo

Embryonated Egg

• Larva inside

Unfertilized Egg: size (A. lumbricoides)

85-95 UM by 34-45 UM

Fertilized/embryonated egg: SIZE (A. lumbricoides OVA)

• 40-47 um by 30-50 um

Fertilized/embryonated egg: shape (A. lumbricoides OVA)

• Rounder than nonfertilized

Fertilized/embryonated egg: embryo (A. lumbricoides OVA)

• Underdeveloped unicellular embryo

Fertilized/embryonated egg: shell (A. lumbricoides OVA)

• Thick Chitin

Unfertilized egg of A. Lumbricoides

• Elongated

• protoplasm mass inside

• decorticated (usually)

Fertilized egg (A. lumbricoides ova)

• Single cell protoplasm

• Almost larvalike (embryonated)

A. lumbricoides female parameter: size

22-35 cm

A. lumbricoides female parameter: color

Cream white, pink tint

A. lumbricoides female parameter: tail

Pencil lead thickness

A. lumbricoides male parameter: size

up to 30 cm

A. lumbricoides male parameter: color

Cream white, pink tint

A. lumbricoides male parameter: tail

Prominent incurved tail

A. lumbricoides amount of lips:

Trilobate lips - three lips

A necessary step mostly in intestinal nematodes especially A. lumbricoides to gain oxygen and continue further development

Heart to lung migration

The sudden migration of parasites they don’t normally infect and is mainly due to response of treatment

Erratic response

Ascariasis asymptomatic or not?

Ascariasis usual infection of 10-20 worms may not show symptoms.

Ascariasis pneumonitis: pathophysiology

chest pain, cough, fever, increased eosinophil (with heart to lung migration)

• Lung infiltration, asthmatic attacks, and edema of the lips, difficulty in breathing

Ascaris lumbricoides treatment:

Albendazole & Mebendazole (mebendazole being the usual)

The most common intestinal nematode of man

Ascaris lumbricoides

What type of somatic muscle arrangement is found in Ascaris lumbricoides?

Polymyarian type

Name the parasite with three lips and sensory papillae.

Ascaris lumbricoides

What is the function of lips and papillae? (A. lumbricoides)

Feeding + sensory (touch/chemical detection)

How can you identify a male Ascaris?

• Posterior end is ventrally curved

• Has two copulatory spicules

How can you identify a female Ascaris?

• Posterior end is straight

• No spicules

• Larger in size

What is the function of spicules in male Ascaris?

Help in copulation (sperm transfer)

Describe the reproductive system of the female.

• aired organs (two ovaries, oviducts, uteri)

• Occupy posterior two-thirds of the body

Describe the reproductive system of the male.

• Single long, tortuous tubule

Why is the female reproductive system larger?

To produce and store a large number of eggs

What is Pepsin Inhibitor-3 (PI-3) in Ascaris lumbricoides?

👉 A protein secreted by the parasite that inhibits the host’s digestive enzyme pepsin

Q2. What is the function of PI-3?

👉 It protects the parasite from digestion in the host’s stomach by inhibiting pepsin

Why is PI-3 important for parasite survival?

👉 It allows Ascaris to:

• Resist host digestive enzymes

• Survive in the harsh gastrointestinal environment

What is phosphorylcholine in Ascaris?

A molecular component on parasite secretions/surface involved in immune modulation

What is the function of phosphorylcholine?

It suppresses lymphocyte proliferation

Why is suppression of lymphocyte proliferation important for the parasite?

It helps the parasite:

• Evade the host immune response

• Survive longer inside the host

Name two biochemical adaptations of Ascaris lumbricoides for survival in the host.

• Pepsin Inhibitor-3 (protects from digestion)

• Phosphorylcholine (suppresses immune response)

Q7. Classify the following adaptations: PI-3 and phosphorylcholine.

• PI-3 → Anti-digestive adaptation

• Phosphorylcholine → Immunomodulatory adaptation

How does Ascaris lumbricoides overcome host defenses?

• Inhibiting digestive enzymes (PI-3)

• Suppressing immune cell activity (phosphorylcholine)

What is present inside a fertilized egg of Ascaris lumbricoides?

An ovoid mass of protoplasm (fertilized ovum/zygote)

What is meant by “ovoid mass of protoplasm” in Ascaris egg?

It refers to the single fertilized cell (zygote) that will develop into an embryo

How long does it take for a fertilized egg to develop into a larval stage?

About 10–14 days under favorable conditions

Why is the fertilized egg considered infective only after development?

Because it must contain a fully developed larva to infect the host

Differentiate the contents of fertilized and unfertilized Ascaris eggs.

👉 Fertilized egg:

• Ovoid mass of protoplasm

• Develops into embryo

👉 Unfertilized egg:

• Disorganized refractile granules

• No development

Which type of egg undergoes larval development? Why?

Fertilized egg, because it contains a viable zygote

What type of larval migration occurs in Ascaris lumbricoides?

Hepato-tracheal migration

Q2. What does “hepato-tracheal migration” mean?

Migration of larvae from intestine → liver → lungs → trachea → back to intestine

When these eggs are ingested, they hatch in the ____ of the small intestines

Lumen, then releasing the larvae.

Hepato-tracheal migration takes:

14 days

Development of egg-laying adult form is: (A. lumbricoides)

9-11 weeks after ingestion

The life span of an Adult worm: (A. lumbricoides)

1 year.

Female ascaris produces about ______ eggs per day?

200,000 eggs

How long for a fertilized egg to developed into the infective stage in the soil environment? (A. lumbricoides)

2-3 weeks.

How long can embryonated eggs survive in tropical and subtropical regions?

From a few months up to about 2 years

Loffler’s phenomenon

Allergic reaction/immunologic reaction caused by the parasite.

Also known as Whipworm

Trichuris trichiura

Infection of T. trichiura

Trichuriasis, whipworm infection

3rd most common helminth; found primarily in warm climates

T. trichiura (whipworm)

Trichuris trichiura ova parameter: fertilized: size

50-55 by 25 um

Trichuris trichiura ova parameter: fertilized: shape

1. barrel, foot-ball shaped,

2. hyaline bi-polar plugs

Trichuris trichiura ova parameter: fertilized: embryo

Unicellular; underdeveloped

Trichuris trichiura ova parameter: fertilized: shell:

Smooth yellow brown because of bile contact

Bi-polar plugs functions:

• Portal of entry - nutrients

• Protection (harmful substances) (Desiccation)

• Portal of exit - larva once maturation

Trichuris trichiura ADULT parameter: adult (male & female): Size:

• 2.5 - 5 cm long

• Males usually smaller than femles

Trichuris trichiura ADULT parameter: adult (male & female): Anterior End

• Colorless

• Resembles a whip handle

• Contains slender esophagus

Trichuris trichiura ADULT parameter: adult (male & female): Posterior end

• Pinkish gray

• Resembles whip itself

• Contains digestive and reproductive system

  • Males: possess prominent curled tail

Feeding mechanism of whipworm of Trichuris trichiura

• Anterior part attached to the intestinal mucosa.

Trichuris trichiura habitat:

Large intestine

• Cecum

• Colon

Rectal Prolapse

Trichuris trichiura: Pathophysiology

Trichuris trichiura (children) : pathophysiology

• Ulcerative colitis, chronic dysentery, severe anemia, and possible growth retardation

Trichuris trichiura (ADULT) : pathophysiology

• inflammatory bowel disease, weight loss, weakness, and mucoid or blood-y diarrhea

T. trichiura male (size)

30 to 45 mm

T. trichiura female (size)

35 to 50 mm

T. trichiura female characteristics

blunt posterior end

T. trichiura male characteristics

• Coiled posterior with a single spicule and retractile sheath

Approximate number of eggs lay by T. trichiura female

3,000 to 10,000 eggs per day

T. trichiura eggs (measurement)

50-54 um by 23 um

How long does the T. trichurae larva remain in the intestinal villi after penetration?

3 to 10 days

A pore forming protein secreted by T. trichiura, allows them to inbed their entire whip-like portion into the intestinal wall

TT47

T. trichiura process upon ingestion of embryonated egg to adult worms

12 weeks.