NEMATODES

NEMATODES

NEMATODES

• also known as ROUNDWORMS

• Among the most abundant animals on Earth

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

TRUE

Does nematodes possess a pseudocoel? True or false?

triradiate

lumen of the pharynx

Composition of Cuticle

cortical, median, basal zone

Cotical

outermost zone and contains a highly resistant protein called cuticulin

Median

contains fine striations

Basal zone

composed of two or three fibrous layers

nerve ring or circumesophageal commissure

Most prominent feature of Nematodes’ Nervous System?

Mouth

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

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.

Two basic types of excretory systems

glandular type and tubular type

Excretory pore

Presence of a median ventral duct and pore called?

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.

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

Classification of Female Nematodes

Oviparous

Larvipirous/ Viviparous

Parthenogenic

Classification of Medically significant Nematodes

• Based on the presence and absence of caudal receptor

• Based on habitat

Based on the presence and absence of caudal receptor

• Class Enoplea

• Class Rhabditea

Classification based on habitat

• Small intestine

• Large intestine

Class Enoplea

caudal receptor and caudal gland present

1. Trichuris trichiura

2. Trichinella spiralis

3. Capillaria philippinensis

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

Small intestine

1. Ascaris lumbricoides

2. Capillaria philippinensis

3. Hookworms

4. Strongyloides stercoralis

Large intestine

1. Trichuris trichiura

2. Enterobius vermicularis

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

Ascaris lumbricoides MALE

10-31 cm

Ascaris lumbricoides FEMALE

22- 35 cm in length

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

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

Embryonated ova

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

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

DIAGNOSIS of Ascaris lumbricoides

• DFS

• Kato -Thick

• Kato Katz

• Concentration technique

TREATMENT of Ascaris lumbricoides

• Piperazine citrate

• Pyrantel pamoate

• Mebendazole

• Albendazole

Trichuris trichiura

• Common Name: Whipworm

• Disease caused: Trichuriasis

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

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

TREATMENT of Trichuris Trichiura

• Mebendazole - drug of choice

• Albendazole alternative drug

• Pyrantel pamoate

PATHOLOGY of Trichuris Trichiura

• Small streaked diarrheic stool

• Abdominal pain and tenderness

• Nausea and vomiting

• Hypochromic anemia

• Weight loss

• Rectal prolapse

DIAGNOSIS of Trichuris Trichiura

• Direct fecal smear analysis

• Kato-thick or kato Katz

• Concentration technique

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.

Adult Male of Trichinella spiralis

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

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

LARVAE of Trichinella spiralis

• 80-120 microns by 5.6 microns at birth

• Spear-like burrowing anterior

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

DIAGNOSIS of Trichinella spiralis

• Muscle biopsy (0.2 to 0.5g of muscle)

• Serological- ELISA

• Positive (Western blot technique)

TREATMENT for Trichinella spiralis

• Mebendazole - larvicidal

• Thiabendazole

Enterobius vermicularis

• Pinworm or seatworm

• Enterobiasis or oxyuriasis

• Small whitish or brown in color

Enterobius vermicularis MALE

2-5 mm coiled tail end

Enterobius vermicularis FEMALE

8-13mm pointed tail end

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

PATHOLOGY of Enterobius vermicularis

• Poor appetite

• Insomnia

• Weight loss

• Irritability

• Grinding of teeth

• Nausea

• Vomiting

• Pruritus ani

DIAGNOSIS of Enterobius vermicularis

Scotch tape swab (Perianal cellulose tape swab)

TREATMENT for Enterobius vermicularis

• Mebendazole - drug of choice

• Pyrantel pamoate

• Albendazole

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

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.

Infective stage of Strongyloides stercoralis

3 stage filariform larva

Normal habitat of Strongyloides stercoralis

duodenum & upper jejunum

Mode of transmission of Strongyloides stercoralis

skin penetration; autoinfection

Diagnostic stage of Strongyloides stercoralis

rhabditiform larva

Definitive hosts of Strongyloides stercoralis

human, dogs, cat

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)

3 PHASES OF INFECTION

1. Invasive: Skin penetration phase (filariform larva)

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

2. Pulmonary: Larval migration phase

• s/s: lobar pneumonia with hemorrhages

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

• S/S; diarrhea

Intractable

can't be stopped even with medication

Intermittent

alternate episodes of diarrhea and no diarrhea

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

• Death

• Neurological and pulmonary complications shock.

LABORATORY TEST/S for Strongyloides stercoralis

• CBC

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

• Baermann Funnel Method

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

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

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