[NOTES] INTESTINAL NEMATODES (2nd Year BS Medical Technology) PDF

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CLINICAL PARASITOLOGYModule 2 – Intestinal NematodesTranscribed by PORPION References: Powerpoint presentation and discussionTABLE OF CONTENTSNematodes Chemoreceptors Habitat Life Cycle ✓ Basic Developmental Cycle Intestinal Nematodes ✓ Ascaris lumbricoides ✓ Trichiuris trichiura ✓ Enterobius vermic...

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CLINICAL PARASITOLOGY Module 2.1 – Intestinal Nematodes

All nematodes except o T. trichiura o Capillaria philippinensis o T. spiralis Aphasmids (Class Adenophorea) • Without caudal chemoreceptors •

Transcribed by PORPION References: Powerpoint presentation and discussion

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TABLE OF CONTENTS Nematodes Chemoreceptors Habitat Life Cycle Intestinal Nematodes

HABITAT Intestinal Nematodes ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓

Laboratory Diagnosis

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Basic Developmental Cycle Ascaris lumbricoides Trichiuris trichiura Enterobius vermicularis Capillaria philippinensis Necator americanus Ancylostoma duodenale Strongyloides stercoralis Hookworm and Strongyloides diagnosis

Treatments

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NEMATODES Also known as ‘roundworms’ Elongated, cylindrical, and bilaterally symmetrical Unsegmented Has complete digestive system No circulatory system Dioecious • They have separate sexes (they can ONLY be male or female, NEVER both) Some are parthenogenic • Parasites that may or may not require males for reproduction • E.g. S. stercoralis

SMALL INTESTINE ✓ C. philippinensis ✓ A. lumbricoides ✓ S. stercoralis ✓ Hookworms ✓ T. spiralis (adult) Mnemonic: C.A.S.H & T

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LARGE INTESTINE E. vermicularis T. trichiura

Mnemonic: E.T

Extraintestinal Nematodes MUSCLE LYMPH NODES & SUBCUTANEOUS TISSUES ✓ T. spiralis ✓ Filarial worms (larva)

EYES MENINGES ✓

&

A. cantonensis

LIFE CYCLE NOTE: The larval stage has three stages: ✓ L1 and L2 (Rhabditiform larva) ✓ L3 (Filariform larva) BASIC DEVELOPMENTAL CYCLE

General Characteristics ✓

Male • Smaller • Curved posterior • Has spicule ✓ Female • Larger • Pointed posterior • No spicule • Produces eggs o OVIPAROUS – lays immature/nonembryonated eggs (e.g. A. lumbricoides) o OVIVIPAROUS – lays mature/embryonated eggs (e.g E. vermicularis) o VIVIPAROUS/LARVIPAROUS – doesn’t lay eggs, but lays larva (e.g. T. spriralis) NOTE: Spicules are needle-like structures used for reproduction CHEMORECEPTORS Classification Based on Location ✓ Amphids • Cephalic chemoreceptor • All nematodes contain amphids ✓ Phasmids • Caudal chemoreceptors • Located in the posterior tail Classification According to the Presence of Phasmids ✓

Phasmids (Subclass Secernentia) • With caudal chemoreceptors

Terms ✓ MOLTING – when a newly hatched larva, who feeds on bacteria, outgrows and is constrained by its cuticle ✓ SYNTHESIS – when a larva creates a new cuticle while within its old cuticle ✓ EXSHEATHEMENT – the casting off of the old cuticle Cycle Interpretation STAGE EXPLANATION/NOTES Egg The egg is released from the parent parasite L1 Nematode develops inside the egg H The egg hatches and produces LARVA 1 M1 L1 grows quickly and undergoes molting L2 After molting, it becomes LARVA 2 and undergoes another growth spurt M2 Second molting L3 After the second molting, it becomes LARVA 3 M3 LARVA 3 undergoes molting again L4 Becomes LARVA 4 M4 LARVA 4 undergoes final molting Adult Adult stage NOTE: The L3 stage is the most infective stage for many species. Not all parasites have an L4 stage; the medically important nematodes stop at L3 | 2-3-2020 |

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Color INTESTINAL NEMATODES Other features ✓ ✓

Ascaris lumbricoides Most common intestinal parasite in humans in the Philippines Largest intestinal nematode

Creamy white with a pink tint Pointed posterior tail

Creamy white with a pink tint Curved posterior tail

NOTE: See ‘Intestinal Nematodes’ table in page 3 for details and information and refer to the Powerpoint for the life cycle Eggs/Ova ✓ ✓ ✓ ✓ ✓

Adults lay 200,000 eggs per day • It’s the nematode that lays the most amount of eggs Become infective 2-6 weeks after deposition Can survive harsh environments (dry/freezing temperatures) Size • Length: 85-95micrometers • Width: 38-45micrometers Egg shell layers • Inner Vitelline Membrane o ‘Lipoidal or lecithin membran’ • Middle glycogen layer • Outermost mammillation

Pathology (Ascariasis) ✓

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Stages of Ascaris Egg STAGE

IMAGE

DESCRIPTION ✓

Unfertilized

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No inner vitelline layer Has lecithin granules ✓

Fertilized Corticated

All layers are present

Fertilized Decorticated

No outermost mammillation layer

With embryo inside

Embryonated

Adult Worm The anterior head has trilobate lips

CHARACTERISTICS Size (length)

FEMALE 22-35cm

MALE Up to 30cm

Member of the ‘Unholy Three’ (The three nematodes that have a high chance of infecting a child simultaneously) • A. lumbricoides • T. trichiura • Hookworms Due to Ascaris larva • Ascaris pneumonitis o Loeffler’s pneumonia The larva travels to lungs once the intestine becomes unfavorable o Increased eosinophils o Charcot-Leyden crystals (eosinophil degradation products) • Visceral Larva Migrans (VLM) o Due to non-human parasites (incidental parasites) o Toxocara canis (Dog ascaris) o Toxocara cati (Cat ascaris) o Ascaris suum (Pig ascaris) Due to adult Ascaris spp. • Erratic o Parasites become erratic once their habitat becomes unfavorable so they migrate to favorable locations (e.g. the SI becomes unfavorable due to medication) • Obstruction by bolus formation o BOLUS – group of adult worms o Treatment is surgery by bolus removal

Trichuris trichiura NOTE: See ‘Intestinal Nematodes’ table in page 3 for details and information and refer to the Powerpoint for the life cycle Adult Worm ✓ Anterior • 3/5 attenuated • Used for pinfashion attachment o May cause lacerations in the large intestine ✓ Male • Curved posterior is the fleshy portion ✓ Female • Pointed posterior is the fleshy portion

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Most common intestinal nematode in humans in the U.S.A. Other name is Oxyuris vermicularis Threadworm is no longer used for this parasite because another parasite is known as threadworm (S. stercoralis) Adult males usually die after copulation, so they are rarely seen in stools or in the perianal region

NOTE: See ‘Intestinal Nematodes’ table for details and information and refer to the Powerpoint for the life cycle INTESTINAL NEMATODES A. duodenale & N. americanus

A. lumbricoides

T. trichirua

E. vermicularis

C. philippinensis

Common Name

Giant intestinal roundworm

Whipworm

Pinworm, seatworm, society worm, Tiwa

Pudoc worm

Habitat

Small Intestine

Large Intestine

Large Intestine

Small Intestine

Small Intestine

Soil (free-living state) or man (parasitic state)

Definitive Host/Final Host

Man

Man

Man (only host)

Man, other vertebrae

Man

Man

Diagnostic Stage

Ova, adult

Egg

Ova

Larva or ova found in stool

Larva or ova found in stool

Rhabditiform larva

Ova (embryonated egg)

Fully embryonated egg

Ova

Larva found in fishes

3rd stage larva (filariform)

Filariform larva

Skin penetration of infective larva

Skin penetration of infective larva, autoinfection, and hyperinfection

Infective Stage

Mode of Transmission

Ingestion

Ingestion

Ingestion, inhalation etc.

Ingestion of raw fish with the larva

Eggs/Ova

Modes of Transmission

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✓ ✓ ✓

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Adults lay 100,000 eggs per day Mucoid prominent bipolar plugs • This is the only parasite with this characteristic Shape • Japanese lantern/football/barrel/lemonshaped Yellow-ish brown in color • Due to bile Size • Length: 50-55micrometers • Width: 25micrometers

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Bloody diarrhea • Caused by the pin-fashion attachment Epigastric pain Iron deficiency anemia • Caused by excessive bloody diarrhea Rectal prolapse • In children with large amount of worms in the rectum, leading to an edema, leading to prolapse Hypoalbuminemia • T. trichiura competes for the nutrients, specifically albumin, in the large intestine

Threadworm

Ingestion Inhalation Retroinfection • Newly hatched larva migrates back into host ✓ Autoinfection • Hand-to-mouth transmission NOTE: It has familial or group infection tendencies Eggs/Ova ✓ ✓ ✓

Pathology (Trichuriasis)

Hookworms

S. stercoralis

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Adults lay 15,000 eggs per night • The females are nocturnal Incubation to become infection is 4-6 hours Oval shaped, flattened on one side With double-layered shell Size • Length: 48-60micrometers • Width: 20-35micrometers

Adult Worm FEMALE Gravid uterus is filled with eggs Pointed posterior end Has cephalic alae (lateral wing)

MALE Flask-shaped/bulb-like esophagus Curved posterior end Has cephalic alae (lateral wing)

Enterobius vermicularis | 2-3-2020 |

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Pathology (Enterobiasis) ✓ Nocturnal pruritus ani • Intense itching due to the female laying eggs in the anal area ✓ Loss of appetite ✓ Extraintestinal enterobiasis • Usually occurs in women wherein the eggs are seen in the uterus, vagina, or the fallopian tube ✓ ✓

Capillaria philippinensis Discovered by Nelia Salazar at Pudoc, Ilocos Sur in 1963 Some books mention that the C. philippinensis is a close relative of T. trichiura

NOTE: See ‘Intestinal Nematodes’ table in page 3 for details and information and refer to the Powerpoint for the life cycle

Mystery disease (Pudoc disease) • People of Pudoc believe they are destined to die due to this disease Borborygmus • Gurgling sound of stomach Severe diarrhea

HOOKWORMS Second most common helminth to infect humans NOTE: See ‘Intestinal Nematodes’ table in page 3 for details and information and refer to the Powerpoint for the life cycle Human Hookworms ✓ Anclyostoma duodenale (Old world hookworm) ✓ Necator americanus (New world hookworm) • American hookworm, American murderer Animal Hookworms ✓ Anclyostoma caninum (Dog hookworm) • Has 3 pairs of teeth ✓ Anclyostoma braziliense (Cat hookworm) • Has 2 pairs of teeth (small medial teeth) A. ceylanicum Emerging human hookworm

Natural Hosts Migratory birds (herons, egrets, bitterns)

Eggs/Ova

Intermediate Hosts

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Freshwater fishes, brackish water fishes, glass fishes • Bagtu • Bagsang • Birot • Ipon (Hypselotris bipartita)

Adult Worm ✓ Delicate tiny worms ✓ Male • With chitinized spicules ✓ Female • Usually with eggs in utero

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Adults lay 10k-20k eggs per day Ovoidal, thin-shelled, and colorless The egg characteristics are the same for all hookworms, so the larva is used as the diagnostic stage

Larva RHABDITIFORM LARVA Feeding stage (open mouth) Short and stout Long buccal cavity Short/small genital primordium

FILARIFORM LARVA Non-feeding stage (closed mouth) Long and slender Sheathed, pointed tail Infective stage

Eggs/Ova ✓ ✓ ✓ ✓

Guitar, peanut-shaped Striated cell Flattened mucoid bipolar plugs Morphologically similar with T. trichiura

Adult Worm

C. philippinensis and T. trichiura Eggs/Ova Comparison

Size Shell Shape

C. philippinensis Smaller Striated Peanut/guitar

Mucus Flattened plugs Pathology (Capillariasis)

T. trichiura

Shape Buccal cavity Copulatory bursa Image

N. americanus S-shaped Semilunar cutting plates Bipartite (2 digits); barbed/bristle like

A. duodenale C-shaped 2 pairs of teeth Tripartite (3 digits); simple, not barbed

Larger No striations Japanese lantern/barrel/football/lemon Prominent Pathology | 2-3-2020 |

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Due to larva • Allergic reaction (dermatitis) o Ground itch, dew itch, colic itch, water sore, Mazza Mora • Pneumonitis (WAKANA disease) o Hookworms can also migrate from intestine to lungs • Cutaneous Larval Migrans (CLM) o Also known as ‘creeping eruptions’ o Caused by animal hookworms Due to adult • Epigastric discomfort • Malnutrition, edema o Parasite competes with host for nutrition • Iron deficiency anemia o Microcytic, hypochromic anemia RBCs are small with low hemoglobin content o Adult hookworms competes with the host for nutrients as they eat

Strongyloides stercoralis NOTE: See ‘Intestinal Nematodes’ table in page 3 for details and information and refer to the Powerpoint for the life cycle

Pathology (Strongyloidiasis) ✓

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Rare Human-Infecting Strongyloides spp. ✓ S. fullerborni subspp. fullerborni • Primate parasite • Causes life-threatening condition called ‘swollen belly syndrome’ ✓ S. fullerborni subspp. kellyi Habitat ✓ Soil (Indirect/heterogenic forms) • During its free-living state ✓ Small intestine (Direct/homogenic forms) • During its parasitic state

Due to larva • Allergic reaction o At the site of penetration (Larva currens) • Pneumonitis o Presenting Loeffler’s pneumonia Due to adult • Cochin-China diarrhea or Vietnamese diarrhea o Intermittent diarrhea (on and off) o Reported first from French soldiers returning from the Indo-China region

LABORATORY DIAGNOSIS Stool Exam For Ascaris, Trichuris, and Capillaria

Mode of Transmission ✓ Skin penetration of infective larva ✓ Autoinfection • Intrinsic/internal infection • The rhabditiform larva develops into filariform larva in the host, penetrates the intestinal wall, and enters the lymphatic system or the bloodstream to initiate new infection ✓ Hyperinfection • Exaggeration in the life cycle which results in increased worm burden • Occurs in immunocompromised patients

Direct Fecal Smear ✓ 2mg stool + 1 drop 0.85% NaCl (NSS) ✓ Routine method of stool examination ✓ Stains • Lugol’s iodine • Nair’s buffered methylene blue (BMB) ✓ Examined using LPO and HPO ✓ Used in specific species identification ✓ Reasons for not detecting ova • There is no infection • It is still an early infection (no eggs have been deposited) • The infection is all male (no eggs will be seen/produced)

Eggs/Ova

Kato-Thick

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✓ ✓

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Adults are parthenogenic Clear and thin shell Chinese lantern appearance Indistinguishable with hookworm ova, so the ova is not used the diagnostic stage

✓ ✓

Qualitative technique 50-60mg stool covered with cellophane • Cellophane is soaked in mixture of glycerin and malachite-green solution Glycerin • Clearing agent Malachite green • Gives pale green color

Kato-Katz ✓ ✓ Larva RHABDITIFORM LARVA Short buccal cavity Prominent genital primordium

FILARIFORM LARVA Notched tail Unsheated

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Known as ‘cellophane-covered thick smear’ Recommended method for egg counting • Recommended by WHO Quantitative method

Concentration Techniques ✓ ✓

Sedimentation techniques Floatation techniques

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Cellulose Tape/Scotch Tape Method For Enterobius vermicularis

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HOOKWORM AND Strongyloides DIAGNOSIS Diagnostic stage is rhabditiform larva

Rhabditiform Larva and Filariform Larva Comparison RHABDITIFORM Buccal cavity Genital primordium FILARIFORM Tail Sheath

HOOKWORMS Long

S. Stercoralis Short

Small

Prominent

Pointed Sheathed

Notched Unsheathed

Techniques Used ✓ ✓

DFS Concentration techniques

Harada Mori Stool Culture Technique ✓ ✓ ✓

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Another technique used for hookworms and Strongyloides Recovery of nematode larva Always wear PPE (gloves) because these parasites are capable of skin penetration

Procedure 1. Inoculate filter paper with stool (stool specimen should ideally be positive for parasites) 2. Put the filter paper with the stool in the conical tube which contains water at the bottom tip to prevent dehydration 3. Cover the tube 4. Incubate the tube at room temperature in the dark for seven days o After 48-72 hours we can see rhabditiform larva o Afer about 7 days we can see filariform larva

Technique for Strongyloides Only ✓ Beale’s string test • Uses duodenal aspiration technique TREATMENTS PARASITE Enterobius vermicularis

Hookworms Strongyloides spp.

MEDICINE Albendazole Mebendazole NOTE: These antiparasitic drugs Mebendazole Pyrantel pamoate Ivermectin Albendazole

are

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