(FINAL) CP Intestinal-Tissue Nematodes & Filarial Worms

Trichinella spiralis

INFECTIVE STAGE

• L1 Larva (encysted in muscle)

DIAGNOSTIC STAGE

• L1 Larva (encysted in "nurse cells")

HOSTS

• DH/IH: Humans, pigs, rats (Same host acts as both)

KEY MORPHOLOGY

• Larvae are coiled within striated muscle fibers; adults have a stichosome (column of secretory cells).

Dracunculus medinensis

INFECTIVE STAGE

• L3 Larva (inside copepod)

DIAGNOSTIC STAGE

• L1 Larva (released from skin blister)

HOSTS

• DH: Humans; IH: Cyclops (water flea)

KEY MORPHOLOGY

• Adult females are very long (up to 1m); larvae have a long, pointed tail.

Angiostrongylus cantonensis

INFECTIVE STAGE

• L3 Larva

DIAGNOSTIC STAGE

• Larvae are rarely found in humans (usually diagnosed via CSF eosinophilia), but in the Definitive Host (rat), the eggs/larvae are found in feces.

HOSTS

• DH: Rats (Rattus spp.); IH: Snails or Slugs (e.g., Achatina fulica). Paratenic hosts include freshwater prawns and crabs.

KEY MORPHOLOGY

• Adult females have a "barber pole" appearance (white ovaries winding around red intestines).

Wuchereria bancrofti

INFECTIVE STAGE

• L3 Larva

DIAGNOSTIC STAGE

• Microfilaria (Blood); Periodicity: 10:00 PM – 2:00 AM

IH (VECTOR)

• Culex, Anopheles, Aedes mosquitoes

TAIL MORPHOLOGY

• Sheathed; nuclei do not extend to the tip of the tail.

Brugia malayi

INFECTIVE STAGE

• L3 Larva

DIAGNOSTIC STAGE

• Microfilaria (Blood); Periodicity: 10:00 PM – 2:00 AM

IH (VECTOR)

• Mansonia, Anopheles mosquitoes

TAIL MORPHOLOGY

• Sheathed; two distinct terminal nuclei at the tip.

Loa loa

INFECTIVE STAGE

• L3 Larva

DIAGNOSTIC STAGE

• Microfilaria (Blood); Periodicity: 10:00 AM – 6:00 PM

IH (VECTOR)

• Chrysops (Deer fly/Mango fly)

TAIL MORPHOLOGY

• Sheathed; nuclei extend in a continuous row to the tip.

Onchocerca volvulus

INFECTIVE STAGE

• L3 Larva

DIAGNOSTIC STAGE

• Microfilaria (Skin snip); Periodicity: N/A (Found in skin)

IH (VECTOR

• Simulium (Blackfly)

TAIL MORPHOLOGY

• Unsheathed; nuclei do not extend to the tip; tail is often bent.

Mansonella ozzardi

INFECTIVE STAGE

• L3 Larva

DIAGNOSTIC STAGE

• Microfilaria (Blood); Periodicity: Found at any time

IH (VECTOR)

• Culicoides (Midges) or Simulium

TAIL MORPHOLOGY

• Unsheathed; nuclei do not extend to the tip; long, pointed tail.

Mansonella perstans

INFECTIVE STAGE

• L3 Larva

DIAGNOSTIC STAGE

• Microfilaria (Blood); Periodicity: Found at any time

IH (VECTOR)

• Culicoides (Midges)

TAIL MORPHOLOGY

• Unsheathed; nuclei extend to the tip; blunt/rounded tail.

Mansonella streptocerca

INFECTIVE STAGE

• L3 Larva

DIAGNOSTIC STAGE

• Microfilaria (Skin); Periodicity: N/A (Found in skin)

IH (VECTOR)

• Culicoides (Midges)

TAIL MORPHOLOGY

• Unsheathed; nuclei extend to the tip; tail is curved like a "shepherd’s crook".

Trichinella spiralis

"Trichina worm"; causes Trichinosis.

Dracunculus medinensis

"Guinea worm" or "Fiery Serpent."

Angiostrongylus cantonensis

Rat Lungworm; causes Eosinophilic Meningoencephalitis.

Wuchereria bancrofti

Bancroftian Filariasis (Elephantiasis)

Brugia malayi

Malayan Filariasis

Loa loa

"African Eye Worm"

Onchocerca volvulus

"River Blindness"

Mansonella ozzardi

Ozzard's Filariasis

Mansonella perstans

Persistent Filariasis

Mansonella streptocerca

Streptocerciasis

Intestinal-Tissue Nematodes

These species are unique because the adult worms typically inhabit the intestinal tract (at least temporarily), but the pathology is primarily caused by the larvae migrating into or encysting within various tissues.

Filarial Worms (Filariae)

Filariae are tissue-dwelling nematodes that require an arthropod vector for transmission. They are characterized by the production of microfilariae, which are pre-larval stages found in blood or skin.

Tissue nematode

Angiostrongylus cantonensis is classified strictly as a __________ – While it enters the body through the digestive tract (ingestion of L3 larvae), it does not reside or mature in the human intestines. Instead, it is an extra-intestinal parasite that migrates to the central nervous system (CNS).

Periodicity

__________ refers to the phenomenon where microfilariae appear in the peripheral blood at specific times of the day or night, usually coinciding with the peak biting hours of their respective insect vectors.

W. bancrofti, B. malayi, Loa loa

Summary for Tail Nuclei for Filariae – When identifying microfilariae under a microscope, the sheath and tail nuclei are the primary diagnostic features:

• Sheathed: __________ (no terminal nuclei), __________ (2 terminal nuclei), __________ (continuous nuclei).

• Unsheathed: O. volvulus, Mansonella spp.

O. volvulus, Mansonella spp.

Summary for Tail Nuclei for Filariae – When identifying microfilariae under a microscope, the sheath and tail nuclei are the primary diagnostic features:

• Sheathed: W. bancrofti (no terminal nuclei), B. malayi (2 terminal nuclei), Loa loa (continuous nuclei).

• Unsheathed: __________, __________