NEMATODES

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NEMATODES

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1

NEMATODES

  • also known as ROUNDWORMS

  • Among the most abundant animals on Earth

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General Characteristics of Nematodes

  • Unsegmented

  • Measure 2mm in length to a meter

  • Sexes are separate (dioecious)

  • Males are smaller than females

  • Posterior portion of the male is curved or coiled

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TRUE

Does nematodes possess a pseudocoel? True or false?

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triradiate

lumen of the pharynx

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Composition of Cuticle

cortical, median, basal zone

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Cotical

outermost zone and contains a highly resistant protein called cuticulin

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Median

contains fine striations

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Basal zone

composed of two or three fibrous layers

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nerve ring or circumesophageal commissure

Most prominent feature of Nematodes’ Nervous System?

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Mouth

is usually a circular opening surrounded by a maximum of six lips located in the anterior end

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Buccal cavity

is tubular or funnel-shaped which for some specie is expanded for sucking purposes. Food ingested moves into a muscular region of the tract known as the esophagus, which is important for identification of the specie.

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Two basic types of excretory systems

glandular type and tubular type

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Excretory pore

Presence of a median ventral duct and pore called?

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Reproductive system (Male)

  • Are situated in the posterior third of the body as a single coiled or convoluted tube

    • Various parts are differentiated as testis, vas deferens, seminal vesicle, and ejaculatory duct.

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Reproductive System (Female)

  • may either be a single or bifurcated tube, differentiated into the ovary, oviduct, seminal receptacle or uterus, ovijector, vagina, and vulva that opens to the exterior

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Classification of Female Nematodes

Oviparous

Larvipirous/ Viviparous

Parthenogenic

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Classification of Medically significant Nematodes

  • Based on the presence and absence of caudal receptor

  • Based on habitat

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Based on the presence and absence of caudal receptor

  • Class Enoplea

  • Class Rhabditea

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Classification based on habitat

  • Small intestine

  • Large intestine

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Class Enoplea

caudal receptor and caudal gland present

1. Trichuris trichiura

2. Trichinella spiralis

3. Capillaria philippinensis

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Class Rhabditea

with caudal receptor but without a caudal gland

1. Ascaris lumbricoides

2. Strongyloides stercoralis

3. Enterobius vermicularis

4. Filarial worms

5. Hookworms

6. Dracunculus medinensis

7. Anglostrongylus cantonensis

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Small intestine

1. Ascaris lumbricoides

2. Capillaria philippinensis

3. Hookworms

4. Strongyloides stercoralis

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Large intestine

1. Trichuris trichiura

2. Enterobius vermicularis

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Ascaris lumbricoides

  • Common name: Giant Intestinal Roundworm

  • Disease caused: Human Ascariasis

  • Cylindrical, elongated, tapering, in the end,

  • Containing lateral lines seen as whitish streaks along the entire body length of the body

  • Terminal mouth with trilobate lips with a small triangular buccal cavity

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Ascaris lumbricoides MALE

10-31 cm

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Ascaris lumbricoides FEMALE

22- 35 cm in length

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Fertilized ova

  • Broadly ovoid in shape

  • Golden brown in color

  • Fertile eggs measure 45 to 70 um by 35 to 50 um

  • Includes three thick transparent layers

  • Vitelline membrane

  • Glycogen membrane

  • Albuminous/mamammillary coat

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Unfertilized ova

  • Longer, larger, elongated or sometimes irregular in shape

  • Measure 88 to 94 um by 39 to 44 um

  • Two layers present

  • Glycogen membrane

  • Albuminous/mamammillary coat

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Embryonated ova

As fertilized, but inside structure contains the larva of the embryo.

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Pathology of Ascaris lumbricoides

  • Feeds on intestinal contents

  • Abdominal pain

  • Diarrhea

  • Nausea

  • Loss of appetite

  • Eratic migration may cause regurgitation and escape through the nostrils

  • Vomitted worms may pass the larynx and might lead to suffocation or reach the lung to produce gangrene

  • Might reach the Eustachian tube to cause otitis media

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DIAGNOSIS of Ascaris lumbricoides

  • DFS

  • Kato -Thick

  • Kato Katz

  • Concentration technique

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TREATMENT of Ascaris lumbricoides

  • Piperazine citrate

  • Pyrantel pamoate

  • Mebendazole

  • Albendazole

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33

Trichuris trichiura

  • Common Name: Whipworm

  • Disease caused: Trichuriasis

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CHARACTERISTICS of Trichuris trichiura

  • Measures 30mm to 50mm long

  • Males are smaller than females

  • Esophagus is long occupying about two-thirds of the body length

  • Contains stichocytes

  • Both sexes have a single gonad

  • No excretory system

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OVA of Trichuris Trichiura

  • Unsegmented barrel shaped, lemon, football shaped ova

  • "Bipolar plugged" eggs

  • With 3 layers

  • Embryonation takes place in the soil where the first stage larvae is formed within 3 weeks

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TREATMENT of Trichuris Trichiura

  • Mebendazole - drug of choice

  • Albendazole alternative drug

  • Pyrantel pamoate

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PATHOLOGY of Trichuris Trichiura

  • Small streaked diarrheic stool

  • Abdominal pain and tenderness

  • Nausea and vomiting

  • Hypochromic anemia

  • Weight loss

  • Rectal prolapse

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DIAGNOSIS of Trichuris Trichiura

  • Direct fecal smear analysis

  • Kato-thick or kato Katz

  • Concentration technique

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39

Trichinella spiralis

  • Common name: Trichina worm

  • Disease caused: Trichinosis, Trichinellosis

  • Whitish color in color with the anterior end of the body consisting of esophagus filled with stichosomes.

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40

Adult Male of Trichinella spiralis

measures 0.62 to 1.58 mm by 0.025 to 0.033 mm with a single testis

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Adult Female of Trichinella spiralis

measures about 1.26 to 3.35 mm by 0.029 to 0.038 mm, and has a single ovary

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LARVAE of Trichinella spiralis

  • 80-120 microns by 5.6 microns at birth

  • Spear-like burrowing anterior

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PATHOLOGY of Trichinella spiralis

  • Incubation and intestinal invasion

    • Includes diarrhea, constipation, vomiting abdominal cramps, nausea

  • Larval migration muscle invasion

    • Fever, facial edema, urticaria, pain, and swelling weakness

    • Splenomegaly, gastric and intestinal hemorrhages

  • Encysment and encapsulation

    • Fever, weak, pain

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DIAGNOSIS of Trichinella spiralis

  • Muscle biopsy (0.2 to 0.5g of muscle)

  • Serological- ELISA

  • Positive (Western blot technique)

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TREATMENT for Trichinella spiralis

  • Mebendazole - larvicidal

  • Thiabendazole

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46

Enterobius vermicularis

  • Pinworm or seatworm

  • Enterobiasis or oxyuriasis

  • Small whitish or brown in color

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Enterobius vermicularis MALE

2-5 mm coiled tail end

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Enterobius vermicularis FEMALE

8-13mm pointed tail end

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OVA of Enterobius vermicularis

  • Elongated

  • 50-60 by 20-30 microns

  • Flattened lateral side, lopsided D

  • Two egg-shell layer

  • Albuminous layer- outer

  • Embryonic or lipoidal membrane- inner

  • Embryonated when laid

  • Resistant to disinfectant

  • Under favorable condition, it remains viable for 13 days

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50

PATHOLOGY of Enterobius vermicularis

  • Poor appetite

  • Insomnia

  • Weight loss

  • Irritability

  • Grinding of teeth

  • Nausea

  • Vomiting

  • Pruritus ani

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DIAGNOSIS of Enterobius vermicularis

Scotch tape swab (Perianal cellulose tape swab)

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TREATMENT for Enterobius vermicularis

  • Mebendazole - drug of choice

  • Pyrantel pamoate

  • Albendazole

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TRANSMISSION OF Enterobius vermicularis

  • Hand to mouth

  • Inhalation

  • Retroinfection - gravid female after laying their eggs in the perianal area, goes back thru the anus to the large intestine. The larvae, upon hatching, migrate back the large intestine

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Strongyloides stercoralis

  • Common name: Thread worm

  • Disease: Strongyloidiasis

  • Distribution: tropical, subtropical area and temperate climate. Mostly moist and areas of low hygiene

  • Affect 30-100 million annually

  • It is characterized by free-living rhabditiform and a parasitic filariform stages.

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Infective stage of Strongyloides stercoralis

3 stage filariform larva

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Normal habitat of Strongyloides stercoralis

duodenum & upper jejunum

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Mode of transmission of Strongyloides stercoralis

skin penetration; autoinfection

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Diagnostic stage of Strongyloides stercoralis

rhabditiform larva

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Definitive hosts of Strongyloides stercoralis

human, dogs, cat

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MORPHOLOGY (OVA) of Strongyloides stercoralis

  • Size: 50-58 x 30-34 um

  • Shape: ova, clear, thin shelled

  • Similar to hookworm but are smaller.

    • (Eggs are seldom seen in stools)

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3 PHASES OF INFECTION

  1. Invasive: Skin penetration phase (filariform larva)

  • S/S: erythema, pruritic hemorrhagic papules (pin pointed rashes)

  1. Pulmonary: Larval migration phase

  • s/s: lobar pneumonia with hemorrhages

  1. Tissue Destruction Intestinal mucosa penetration phase (adult female worm)

  • S/S; diarrhea

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Intractable

can't be stopped even with medication

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Intermittent

alternate episodes of diarrhea and no diarrhea

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Symptoms of Immunosuppressed patients (organ transplant) or immunocompromised patients (HIV):

  • Death

  • Neurological and pulmonary complications shock.

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LABORATORY TEST/S for Strongyloides stercoralis

  • CBC

  • Stool (wet, Harada Mori, Baele's String Test)

  • Baermann Funnel Method

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CBC

  • WBC usually wnl for acute and chronic cases, can be elevated in severe cases

  • Eosinophilia common during acute infection, +/- in chronic infection (75%), usually absent in severe infection

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Stool: wet mount (direct exam)

  • Microscopic ID of S. sterocoralis larvae is the definitive diagnosis

  • Ova usually not seen (only helminth to secrete larva in the feces). In chronic infection, sensitivity only 30%, can increase to 75% if 3 consecutive stool exams

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TREATMENT for Strongyloides stercoralis

  • Albendazole: 400 mg x 3days (adult)

  • Ivermectin: 200 Ug /kg/day x 1-2 days

  • Thiobendazole: 50 mg/kg/d in 2 doses (up to 3 g/d) x2 days

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