Clinical Helminthology: Tissue Nematode (Part 1)

Trichinella spiralis
Dracunculus medinensis
Capillaria hepatica
Toxocara canis and Toxocara cari
Ancylostoma braziliense and Ancylostoma caninum
Dioctophyma renale
Gnathostoma spinigerum
Angiostrongylys cantonensis

Tissue Nematodes

encysted larva

Trichinella spiralis Infective Stage (IS)

encysted larva in muscles

Trichinella spiralis Diagnostic Stage (DS)

Trichinella spiralis

larviparous and autoheteroxenous

eating undercooked meat

Trichinella spiralis Mode of Transmission (MOT)

pork, bear, walruses, horsemeat, (and other) mammals

Trichinella spiralis Types of Meat:

Trichinella spiralis

Its larvae are resistant to the gastric pH

mammal (for encysted larvae)

Trichinella spiralis Intermediate host:

mammal (for adult worm)

Trichinella spiralis Definitive host:

walruses, pigs, rodents

Trichinella spiralis Animal reservoir hosts:

Encysted larva

Adult Stage

Trichinella spiralis morphology

(It appears) coiled
Encysted (in nurse cells of striated muscle) inflammatory infiltrate (is present around nurse cell)

Trichinella spiralis Encysted Larva

Male: curved posterior end

Female: blunt, round posterior end

Both male and female have thin anterior end, small mouth, long slender digestive tract.

Trichinella spiralis adult stage

Trichinellasis or Trichinosis or Trichiniasis

-intestinal stage: nausea, diarrhea, or constipation
-larval migration: periorbital edema, fever, muscle pain, myalgia, splinter hemorrhages

Trichinella spiralis diseases

• muscle biopsy
• Beck's xenodiagnoses using albino rats
• Bachman intradermal test
• increased creatine kinase
• marked peripheral eosinophilia

Trichinella spiralis diagnosis

Thiabendazole

Trichinella spiralis Treatment

Dracunculus medinensis

longest nematode parasite that infect humans

ingestion of larvae-infected copepods

Dracunculus medinensis Mode of Transmission (MOT)

mouth

Dracunculus medinensis Portal of entry:

subcutaneous (muscle)

Dracunculus medinensis Final site:

cyclops (copepods, water fleas)

Dracunculus medinensis Intermediate host:

Larval and Adult

Dracunculus medinensis morphology

coiled, rounded anterior end and tapering pointed tail

Dracunculus medinensis larval

catgut thread

Dracunculus medinensis adult

Dracunculosis or Dracunculiasis
-The blisters formed by the gravid female worm cause burning and itching.

Dracunculus medinensis diseases

identification of larvae or adult worms

Dracunculus medinensis diagnosis

total worm removal

Dracunculus medinensis treatment

Capillaria hepatica

Oviparous parasite common to rodents

ingestion of dirt-containing eggs

Capillaria hepatica Mode of Transmission (MOT)

embryonated egg

Capillaria hepatica Infective Stage (IS)

Eggs in liver biopsy

Capillaria hepatica Diagnostic Stage (DS)

Egg stage

Adult stage

Capillaria hepatica morphology

lemon shaped
outer shell is pitted like a gold ball

Capillaria hepatica egg stage

resembles Trichuris trichiura

Capillaria hepatica adult stage

mimics visceral larva migrans
mimics hepatitis
amebic liver abscess

Capillaria hepatica diseases

liver biopsy microscopy

Capillaria hepatica diagnosis

albendazole with corticoids

Capillaria hepatica treatment

embryonated egg

Toxocara canis/cati Infective Stage (IS)

encysted larva in tissue or sputum

Toxocara canis/cati Infective Stage (IS)

Oviparous

Toxocara canis/cati are both

ingestion of soil contaminated with dog or cat feces

Toxocara canis/cati Mode of Transmission (MOT)

Dogs and cats

Toxocara canis/cati definitive host

Egg stage

Adult stage

Toxocara canis/cati morphology

resemble Ascaris eggs but are larger and less elongate

has thinner shell and albuminoid outer covering

Toxocara canis/cati egg stage

Toxocara canis: bow cervical alae

Toxocara cati: arrowhead cervical alae

Toxocara canis/cati adult stage

Visceral larva migrans: with eosinophilia

Ocular larva migrans: without eosinophilia

Toxocara canis/cati diseases

• exposure to dogs and cat and pica are important in patient's medical history.
•identification of encysted larvae through muscle biopsy

Toxocara canis/cati diagnosis

1:8 - significant for OLM
1:32 - significant for VLM

Toxocara canis/cati Serology (antibody titer/concentration)

thiabendazole, ivermectin, albendazole, diethylcarbamazine

Toxocara canis/cati treatment

Skin

Ancylostoma baziliense/caninum portal of entry

intredermal

Ancylostoma baziliense/caninum final site

Egg stage, Buccal capsule, Copulatory bursa

Ancylostoma baziliense/caninum morphology

resembles the Ancylostoma duodenale but are smaller in size

Ancylostoma baziliense/caninum egg stage

3 ventral pairs of fused teeth

Ancylostoma caninum buccal capsule

2 ventral pairs of unfused teeth

Ancylostoma baziliense buccal capsule

shape: large-flamed

rays: long and slender

Ancylostoma caninum copulatory bursa

shape: as broad as long rays: stunted

Ancylostoma baziliense copulatory bursa

Creeping eruption

Ancylostoma baziliense/caninum diseases

Creeping eruption

dermatitis characterized by erythematous serpiginous, intracutaneous tunnels

Fecal microscopy: recovery of eggs
Eggs can mature and hatch larva if the stool is kept at RT, without fixative.
Kato technique, concentration techniques, Harada-Mori Culture

Ancylostoma baziliense/caninum diagnosis

Thiabendazole
Ivermectin

Ancylostoma baziliense/caninum treament

mouth

Dioctophyma renale Portal of entry:

kidney

Dioctophyma renale Final site of infection:

earthworms

Dioctophyma renale Intermediate hosts:

fish and frogs

Dioctophyma renale Paratenic hosts:

man

Dioctophyma renale Incidental host:

Egg stage

Adult stage

Dioctophyma renale morphology

barrel-shaped, thick, and pitted like a golf ball

Dioctophyma renale egg stage

cylindrical, blood-red bell-shaped bursa with spicule

Dioctophyma renale adult stage

destruction of kidney tissue

Dioctophyma renale diseases

urine microscopy (recovery of eggs)

Dioctophyma renale diagnosis

surgical removal of the worm

Dioctophyma renale Treatment

ingestion of infective larva in fish and snakes

Gnathostoma spinigerum Mode of Transmission (MOT)

has a rust-colored, cephalic bulb with
four rows of hooks

Gnathostoma spinigerum morphology

gnasthomiasis
visceral and cutaneous larva migrans-like syndrome
eosinophilic myeloencephalitis

Gnathostoma spinigerum diseases

serology and histological analysis

Gnathostoma spinigerum diagnosis

supportive corticosteroid

Gnathostoma spinigerum treatment

ingestion of infective larva in snails and prawn

Angiostrongylus cantonensis Mode of Transmission

Uterine tubules of female worm:
barber's pole appearance

Angiostrongylus cantonensis morphology

Eye invasion
Eosinophilic myeloencephalitis

Angiostrongylus cantonensis diseases

Mebendazole

Angiostrongylus cantonensis treatment