Medical Parasitology: Intestinal and Tissue Nematodes

Vocabulary practice flashcards covering nematode biology, life cycles, clinical manifestations, diagnosis, epidemiology, and control from Medical Parasitology lecture notes.

Polymyarian Muscle Arrangement

A type of somatic muscle cell arrangement in nematodes where cells are numerous and project well into the body cavity, characteristic of Ascaris lumbricoides.

Pepsin Inhibitor 3 (PI-3)

A substance produced by Ascaris lumbricoides that protects the adult worms from host enzymatic digestion in the small intestine.

Phosphorylcholine

A molecule secreted by Ascaris lumbricoides that suppresses host lymphocyte proliferation.

Ascaris lumbricoides Eggs

Ova of the giant roundworm presenting as unfertilized (elongated, thin-shelled with irregular mammillated coating, measuring $88$ to $94\,\mu\text{m}$ by $39$ to $44\,\mu\text{m}$), fertilized (round to ovoid, thick hyaline shell with a coarse mammillated albuminous coat, measuring $45$ to $70\,\mu\text{m}$ by $35$ to $50\,\mu\text{m}$), or embryonated (infective stage containing a third-stage larva).

Decorticated Egg

A fertile Ascaris lumbricoides egg that has lost or lacks its outer, coarsely mammillated albuminous layer.

Hepato-tracheal Migration Phase

The approximately $14\text{-day}$ developmental pathway during which hatched Ascaris lumbricoides larvae penetrate the intestinal wall, travel via the portal vein through the liver and heart to the lungs, break into alveoli, ascend the respiratory tree, and are swallowed back into the gut.

Biliary Ascariasis

A painful complication occurring when adult Ascaris worms migrate erratically into the bile ducts via the ampulla of Vater, causing severe colicky abdominal pain, cholangitis, or liver abscesses.

Kato-Katz Technique

A standardized quantitative stool examination method that measures helminth infection intensity in eggs per gram (epg) of feces, widely used in clinical trials and mass screening programs.

WASHED Framework

A comprehensive strategy for soil-transmitted helminth control consisting of Water, Sanitation, Hygiene Education, and Deworming.

Holomyarian Muscle Arrangement

A somatic muscle arrangement in cross-section where cells are small, numerous, and closely packed together in a narrow continuous zone, characteristic of Trichuris trichiura.

TT47

A pore-forming protein secreted by Trichuris trichiura that allows the whipworm to embed its attenuated whip-like anterior portion into the intestinal mucosa.

Trichuris trichiura Egg

A lemon- or football-shaped ovum measuring $50$ to $54\,\mu\text{m}$ by $23\,\mu\text{m}$, characterized by a yellowish outer shell, transparent inner shell, and prominent, translucent bipolar plugs.

Trichuris Dysentery Syndrome (TDS)

A severe clinical manifestation of heavy chronic whipworm infection characterized by chronic bloody diarrhea, tenesmus, abdominal pain, severe anemia, and rectal prolapse with visible adult worms attached to the rectal mucosa.

Meromyarian Muscle Arrangement

A somatic muscle arrangement where two to five cells are situated per dorsal or ventral half, characteristic of hookworms and Enterobius vermicularis.

Hookworm Buccal Capsules

Anterior feeding apparatuses distinguishing the two major human hookworms: Necator americanus exhibits a pair of semilunar ventral cutting plates, whereas Ancylostoma duodenale possesses two pairs of curved ventral teeth.

Hookworm Egg

An ovum with bluntly rounded ends and a single, thin, transparent hyaline shell, typically passed in fresh feces in the two- to eight-cell stage of cleavage.

Ground Itch (Dew Itch)

An intensely pruritic, maculopapular and papulovesicular dermatitis occurring at the site of skin penetration by infective hookworm filariform larvae.

Cutaneous Larva Migrans (CLM)

A creeping, serpiginous skin eruption caused by percutaneous penetration and migration of non-human animal hookworm larvae, predominantly Ancylostoma braziliense and Ancylostoma caninum.

Harada-Mori Culture

A coproculture method using filter paper strips in test tubes or plastic bags containing water to allow hookworm and Strongyloides eggs to hatch into diagnostic larvae for species differentiation.

Parthenogenesis

A form of reproduction in which unfertilized females produce viable offspring without male fertilization, utilized by parasitic female Strongyloides stercoralis in the human duodenum.

Strongyloides stercoralis Rhabditiform Larva

The diagnostic larval stage passed in fresh feces, measuring approximately $225\,\mu\text{m}$ by $16\,\mu\text{m}$, characterized by a short buccal cavity, a large genital primordium, and an elongated esophagus with a pyriform posterior bulb.

Autoinfection

A process in Strongyloides stercoralis infection where rhabditiform larvae develop prematurely into infective filariform larvae within the intestinal lumen or perianal skin, re-penetrating the mucosa or skin to sustain decades-long infection without leaving the host.

Cochin China Diarrhea

Intractable, painless, intermittent diarrhea characterized by watery and bloody stools seen in severe or heavy Strongyloides stercoralis infections.

Larva Currens

A rapidly advancing, pruritic, urticarial linear skin lesion caused by the rapid subcutaneous migration of Strongyloides stercoralis filariform larvae during autoinfection.

Cephalic Alae

Bilateral, wing-like cuticular expansions located at the anterior extremity of adult Enterobius vermicularis worms.

Enterobius vermicularis Egg

An asymmetrical, D-shaped ovum flattened on one side and convex on the other, measuring $50$ to $60\,\mu\text{m}$ by $20$ to $30\,\mu\text{m}$, enveloped by a triple albuminous covering and containing a tadpole-like embryo that matures in $4$ to $6\,\text{hours}$.

Graham's Scotch Adhesive Tape Swab

The gold standard diagnostic technique for pinworm infection, performed in the early morning by pressing cellulose tape against the perianal folds to collect deposited eggs.

Retroinfection

A mode of Enterobius vermicularis infection in which eggs hatch on the perianal skin and the emerging larvae migrate back through the anus into the rectum and colon to mature into adults.

Stichosome

A specialized glandular esophageal structure composed of a column of single secretory cells called stichocytes, found in Trichinelloidea nematodes such as Capillaria philippinensis and Trichuris trichiura.

Capillaria philippinensis Egg

A peanut-shaped ovum measuring $36$ to $45\,\mu\text{m}$ by $20\,\mu\text{m}$, featuring a striated shell and distinctive flattened bipolar plugs.

Protein-Losing Enteropathy

A severe intestinal complication of Capillaria philippinensis infection resulting from epithelial micro-ulceration, flattened villi, and mucosal degeneration, leading to extreme hypoalbuminemia, anasarca, and emaciation.

Bagsit

A small freshwater or brackish water fish consumed raw in Northern Luzon, Philippines, that acts as an intermediate host harboring the infective larvae of Capillaria philippinensis.

Wuchereria bancrofti Microfilaria

A sheathed blood parasite measuring $270$ to $290\,\mu\text{m}$ in length with a $1:1$ cephalic space-to-breadth ratio, an unstained sheath in Giemsa, discrete regularly spaced nuclei, a smoothly curved posture, and a tail tip devoid of terminal nuclei.

Brugia malayi Microfilaria

A sheathed microfilaria measuring $111$ to $230\,\mu\text{m}$ in length with a $2:1$ cephalic space-to-breadth ratio, a sheath that stains pink in Giemsa, confluent overlapping nuclei, a kinky posture, and two distinct terminal nuclei that bulge the tail cuticle.

Aedes poecilus

The principal mosquito vector of Wuchereria bancrofti in most provinces of the Philippines, which breeds in rainwater collected in the axils of abaca and banana plants.

Acute Dermatolymphangioadenitis (ADLA)

The primary acute presentation of lymphatic filariasis, characterized by localized pain, lymphadenitis, cellulitis, warmth, and systemic fever, triggered predominantly by secondary Group A Streptococcal bacterial infections through cutaneous entry points.

Acute Filarial Lymphangitis (AFL)

An inflammatory syndrome caused by the spontaneous or diethylcarbamazine-induced death of adult filarial worms, resulting in retrograde (distal) lymphangitic cord formation without secondary bacterial involvement.

Chylocele

The accumulation of milky lymph-containing fluid in the tunica vaginalis of the testis due to lymphatic obstruction and rupture caused by adult Wuchereria bancrofti worms.

Chyluria

A condition in which urine contains chyle, giving it a milky appearance, resulting from the rupture of obstructed retroperitoneal and renal lymphatics below the cisterna chyli in lymphatic filariasis.

Tropical Pulmonary Eosinophilia (TPE)

An occult manifestation of filariasis caused by immunological hyper-responsiveness to trapped microfilariae in pulmonary vasculature, characterized by paroxysmal nocturnal cough, extreme eosinophilia ($3,000$ to $5,000\,\text{cells/mm}^3$), elevated serum IgE, and rapid response to diethylcarbamazine.

Expatriate Syndrome

An intense immunologic and clinical hyper-responsiveness seen in non-immune individuals moving to lymphatic filariasis-endemic areas, presenting early with acute lymphangitis, lymphadenitis, hives, rashes, and prominent hypereosinophilia.

Wolbachia

An intracellular bacterial endosymbiont essential for the fertility and survival of lymphatic filarial worms, targeted therapeutically using doxycycline to achieve worm sterilization and death.

DEC Provocative Test

A diagnostic procedure where a single oral dose of diethylcarbamazine ($3\,\text{mg/kg}$) is administered to stimulate nocturnally periodic microfilariae into entering the peripheral blood during daytime hours.

Barber's Pole Pattern

The characteristic macroscopic morphology of the adult female Parastrongylus cantonensis, caused by the milk-white uterine tubules winding spirally around the blood-filled red intestine beneath a transparent cuticle.

Achatina fulica

The giant African snail, which serves as a major molluscan intermediate host harboring infective third-stage larvae of Parastrongylus cantonensis.

Eosinophilic Meningoencephalitis

A central nervous system condition caused by human infection with Parastrongylus cantonensis larvae, characterized by intense headache, neck stiffness, paresthesias, and a CSF pleocytosis with greater than $10\%$ eosinophils.

Charcot-Leyden Crystals

Slender, diamond-shaped crystalline structures derived from the breakdown products of eosinophils, frequently observed in the meninges and cerebrospinal fluid of patients with eosinophilic meningitis.

Trichinella spiralis Larva in Muscle

An infective nematode larva encysted in a modified, collagen-encapsulated skeletal muscle fiber (nurse cell), which remains viable for years until ingested by a carnivore or omnivore.

Trichinella britovi

The second most common cause of human trichinellosis, widely distributed in wild carnivores across temperate and Mediterranean zones of Europe, Asia, and North Africa.

Tingling Throat Syndrome

An ectopic form of anisakidosis characterized by a foreign-body sensation, tickling, or coughing in the pharynx caused by an Anisakis larva lodging in the oropharyngeal mucosa.

Visceral Larva Migrans (VLM)

A systemic syndrome caused by the prolonged migration and arrest of dog or cat roundworm larvae (Toxocara canis or Toxocara cati) through internal organs, provoking eosinophilic granulomatous hepatitis, pneumonitis, hepatomegaly, and hypereosinophilia.

Ocular Larva Migrans (OLM)

A syndrome caused by the entry of a Toxocara larva into the eye, typically in older children, producing retinal granulomas, localized endophthalmitis, strabismus, and unilateral visual loss.

Covert Toxocariasis (CoTOX)

A mild, non-specific presentation of human toxocariasis characterized by low-grade symptoms such as coughing, wheezing, abdominal pain, sleep disturbances, and behavioral changes with minimal eosinophilia.

Toxocara Excretory-Secretory (TES) Antigens

Diagnostic antigens harvested from culture fluids of living Toxocara larvae, used in enzyme-linked immunosorbent assays (ELISA) to detect specific anti-Toxocara IgG antibodies in human serum.