PARA_Finals_Lec: Nematodes

Nematoda characteristics

Unsegmented, cylindrical, elongated, dioecious worms with complete digestive tract and no circulatory system

Layers of nematode body wall

Cuticle, hypodermis, and somatic muscle

Layers of cuticle

Cortical layer, homogenous matrix, fibrous layer

Nervous system of nematodes

Pharyngeal nerve ring

Oviparous nematodes

Produce unsegmented eggs without larvae

Ovoviviparous/Viviparous nematodes

Produce eggs with larvae inside

Larviparous nematodes

Female gives rise directly to larva

Ascaris lumbricoides

Giant intestinal roundworm

Disease caused by Ascaris lumbricoides

Ascariasis

Habitat of Ascaris lumbricoides

Small intestine (duodenum)

Infective stage of Ascaris lumbricoides

Embryonated ova

Diagnostic stage of Ascaris lumbricoides

Fertilized or unfertilized ova

Transmission of Ascariasis

Ingestion of contaminated food containing ova

Unfertilized Ascaris egg

Longer, narrow, thin shell with lecithin granules

Fertilized Ascaris egg

Rounded egg with undeveloped unicellular embryo and thick shell

Characteristic adult morphology of male Ascaris

Shorter worm with incurved tail

Characteristic adult morphology of female Ascaris

Longer worm with straight tail

Loeffler syndrome

Ascaris pneumonitis causing asthmatic cough

Erratic migration of Ascaris

Migration to mouth, nose, liver, lungs, gallbladder, appendix, and pancreas

Complication of heavy Ascaris infection

Intestinal obstruction/intussusception

Diagnostic methods for Ascariasis

DFS, concentration techniques, Kato-Katz, chest X-ray

Drugs for Ascariasis

Mebendazole, Albendazole, Pyrantel

Trichuris trichiura

Human whipworm

Disease caused by Trichuris trichiura

Trichuriasis

Habitat of Trichuris trichiura

Colon and cecum

Infective stage of whipworm

Embryonated ova

Diagnostic stage of whipworm

Fertilized egg

Characteristic morphology of Trichuris egg

Barrel/lemon/Japanese lantern-shaped egg with bipolar plugs

Heavy Trichuris infection may cause

Rectal prolapse

Attachment of Trichuris to intestine

Pin cushion manner

Treatment for Trichuriasis

Mebendazole and Albendazole

Capillaria philippinensis

Pudoc worm

Disease caused by Capillaria philippinensis

Intestinal capillariasis

Who discovered Capillaria philippinensis?

Dr. Nelia Salazar in Ilocos Norte in 1963

Habitat of Capillaria philippinensis

Jejunum

Infective stage of Capillaria philippinensis

2nd stage larva

Mode of transmission of Capillaria philippinensis

Eating raw or undercooked fish

Intermediate host of Capillaria philippinensis

Freshwater/brackish fish (ipon fish)

Characteristic Capillaria egg

Peanut/guitar-shaped egg with flattened bipolar plugs

Major pathology of intestinal capillariasis

Malabsorption syndrome and severe diarrhea

Treatment for Capillaria philippinensis

Albendazole

Enterobius vermicularis

Human pinworm/seatworm

Disease caused by Enterobius vermicularis

Enterobiasis/Oxyuriasis

Habitat of Enterobius vermicularis

Cecum, colon, large intestine

Transmission of Enterobius vermicularis

Anus-to-mouth, finger-to-mouth, airborne autoinfection

Characteristic morphology of Enterobius egg

D-shaped egg flattened on one side

Classic symptom of Enterobiasis

Anal pruritus

Diagnostic method for Enterobius vermicularis

Scotch tape swab/Graham’s method

Special adult structures of Enterobius vermicularis

Cephalic alae and esophageal bulb

Hookworms are also called

Blood-sucking nematodes

Species of hookworms

Ancylostoma duodenale, Necator americanus, Ancylostoma caninum, Ancylostoma braziliense

Disease caused by hookworms

Uncinariasis

Habitat of hookworms

Duodenum

Infective stage of hookworms

Filariform larva

Mode of transmission of hookworms

Skin penetration

Characteristic hookworm egg

Oval transparent egg with 2–8 blastomeres

Hookworm rhabditiform larva

Long buccal cavity with small genital primordium

Hookworm filariform larva

Infective stage with pointed tail

Ground itch

Dermatitis caused by hookworm larval penetration

Severe hookworm infection causes

Microcytic hypochromic anemia

Wakana disease

Severe pulmonary symptoms due to hookworm infection

Diagnostic methods for hookworm

DFS, Harada-Mori, Baermann technique

Treatment for hookworm infection (in general)

Albendazole, Mebendazole, Pyrantel pamoate, Levamisole

Old World hookworm

Ancylostoma duodenale

New World hookworm

Necator americanus

Ancylostoma duodenale mouthparts

Two pairs of ventral teeth

Necator americanus mouthparts

Semilunar cutting plates

Strongyloides stercoralis

Human threadworm

Smallest nematode of man

Strongyloides stercoralis

Disease associated with Strongyloides stercoralis

Cochin China diarrhea/Vietnam diarrhea

Habitat of Strongyloides stercoralis

Small intestine (duodenum)

Infective stage of Strongyloides stercoralis

Filariform larva

Diagnostic stage of Strongyloides stercoralis

Rhabditiform larva

Transmission of Strongyloides stercoralis

Skin penetration

Hookworm vs Strongyloides rhabditiform larva

Hookworm has long buccal cavity; Strongyloides has short buccal cavity

Strongyloides filariform larva characteristic

Forked tail and unsheathed

Larva currens

Dermatitis caused by Strongyloides stercoralis

Autoinfection in Strongyloides

Ability to reinfect the same host internally or externally

Diagnostic methods for Strongyloides

DFS, flotation techniques, Harada-Mori, Beale’s string test