Human Parasites

Abdominal pain
Crampy abdominal pain may be seen in amebic colitis; right upper quadrant pain in amebic abscess; severe duodenitis or jejunitis with Strongyloides penetrating the mucosa; pain suggestive of gastric ulcer or appendicitis with anisakid larvae (penetration of gut wall).

A localized collection of pus caused by liquifaction necrosis of tissue (amebiasis, filariasis).

Early ring form of Plasmodium falciparum found at margin of red cell: appliqué.

Acute abdomen
An abdominal condition of abrupt onset usually associated with abdominal pain resulting from inflammation, perforation, obstruction, infarction, or rupture of intra-abdominal organs; surgical intervention is usually necessary (ascariasis, anisakiasis).

Acquired immune deficiency syndrome.

Pronounced, longitudinal cuticular ridges in nematodes, usually found in larval stages (Ascaris), although occasionally present in adult worms (Enterobius vermicularis).

A hypersensitive condition acquired by exposure to a particular allergen (helminth infections, ectoparasite bites, or stings).

Small, round, intracellular stage of Leishmania spp. And Trypanosoma cruzi in which the base of the flagellum is anterior to the nucleus but there is no external flagellum; also called Leishman-Donovan body, L-D body, or leishmanial stage.

Hypersensitivity produced by exposure to further doses of the same protein, usually when exposure is within less than 2 weeks (bee stings, echinococcosis).

A reduce number of erythrocytes per cubic millimeter, reduction in amount of hemoglobin, or reduction in volume of packed red cells per 100 mL of blood (malaria, hookworm, Diphyllobothrium latum infections).

Absence of sensitivity to an antigen or the condition resulting from desensitization (cutaneous leishmaniasis).

Absence of appetite.

Absence of urine secretion (scorpion sting).

Partial or complete inability to speak and/or understand spoken words.

Inflammation of the vermiform appendix (amebiasis, Ascaris, Trichuris, Enterobius).

Thick-walled fingerlike projection at the end of the cecum.

Early ring form of Plasmodium falciparum found at the margin of the red cell; accolé.

Effusion of serous fluid into the abdominal cavity (schistosomiasis).

Fluid removed from a cavity or lesion (leishmaniasis, hydatid disease, amebiasis).

Asthma, bronchial
Disease characterized by difficulty in breathing, wheezing, and coughing caused by spasmodic contraction of the bronchi; may be the result of allergic reaction (ascariasis, strongyloidiasis).

Indigenous or normally found in a particular area.

Reinfection by an organism already present in the body with an increase in the number of parasites without their undergoing a cycle outside the body; self-infection (Strongyloides, Hymenolepis nana).

Gross and microscopic postmortem examination of the organs of the body to determine cause of death or pathological changes.

Rodlike supporting structure in some flagellates that gives rigidity to the body (Trichomonas spp.).

Occasionally a disease of humans caused by a blood protozoan of various animals; tick-borne; organism morphology similar to young rings of Plasmodium falciparum; more severe in compromised patient.

Band form
Older trophozoites of Plasmodium malariae that may stretch across the red cell in the form of a band.

Basket nucleus
Nuclear structure that may be seen in Iodamoeba bütschlii cysts (occasionally trophozoites); in well-stained organisms fibrils may be seen running between the karyosome and the chromatin granules. The “basket of flowers” has been described as follows: karyosome forms the basket, fibrils the stems, and the granules the flowers.

Baylisascaris procyonis
A common roundworm of raccoons (ingestion of infective eggs from the environment) that can cause larva migrans (CNS). Human cases present with eosinophilic meningoencephalitis (two fatal cases in the United States).

Benign tertian malaria
Malaria caused by Plasmodium vivax.

Another name for schistosomiasis; often used to indicate infection with either Schistosoma mansoni or S. haematobium.

Removal of tissue from a living person; examination, usually microscopic, used to make diagnosis (Chagas’ disease, leishmaniasis, schistosomiasis, visceral larva migrans, amebiasis).

Blackwater fever
A condition in which the diagnostic symptom is the passage of reddish to black urine (hemoglobin), indicating massive intravascular hemolysis (Plasmodium falciparum).

A small, dark-staining body near the base of the flagellum that is associated with fibrillar portions of the flagellum (blood flagellates).

One of the two shallow grooves on the scolex of Diphyllobothrium latum.

Buccal cavity/capsule
The space between the oral opening and the beginning of the esophagus in nematodes; useful diagnostically in rhabditiform larvae (Strongyloides, hookworm).

Buccal teeth/plates
Toothlike structure in the mouth cavity of the adult hookworms of the genus Ancylostoma (compared with buccal plates found in the mouth cavity of the genus Necator).

Production of daughter cell as outward growth from the original cell or germinal layer (yeast-like fungi, hydatid cyst).

Buffy coat
Grayish white layer of fibrin and leukocytes that composes the upper part of the sedimented cells in whole blood after the addition of anticoagulant (examined in visceral leishmaniasis, trypanosomiasis).

Umbrella-like expansion of the cuticle at the posterior end of male nematodes; it is supported by muscular rays and aids in copulation (hookworms, trichostrongyles).

Severe debilitated states (heavy worm infestation, visceral leishmaniasis).

Calabar swellings
Transient swellings of subcutaneous tissues; associated with Loa loa infection.

Calcareous corpuscles
Rounded masses composed of concentric layers of calcium carbonate that are found in the tissue of tapeworms; characteristic of tapeworm tissue; certain fixatives must be avoided in order to preserve presence of corpuscles for identification purposes (tapeworms).

Portions of tissue (host, parasite) that become hardened by the deposition of calcium salts; may be visible on radiographic studies (toxoplasmosis, cysticercosis, trichinosis, schistosomiasis).

Inflammation of the heart tissues (Chagas’ disease).

Casoni antigen
Skin-test antigen composed of sterile hydatid fluid (hydatid disease).

A substance causing evacuation of bowels by increasing bulk, stimulating peristalsis.

A blindly ending appendage of the intestine.

Free-living, tailed larval stage of trematodes; may infect humans by direct penetration (schistosomes); may attach to vegetation and encyst to metacercarial stage (Fasciola, Fasciolopsis), or may penetrate tissues of vertebrates or invertebrates and encyst to metacercarial stage (Clonorchis)).


Small granuloma in the skin caused by early multiplication of Trypanosoma cruzi (Chagas’ disease).

Chagas’ disease
Infection caused by Trypanosoma cruzi (South American trypanosomiasis).

Charcot-Leyden crystals
Slender crystals that are formed from the breakdown products of eosinophils; shaped like double, elongated pyramids with pointed ends; can be found in feces, sputum and tissues; indicates an immune response that may or may not be related to a parasitic infection.

Chiclero ulcer
Single, self-limiting cutaneous papule, nodule, or ulcer (usually on the face or ears) (leishmaniasis).

Inflammation of the posterior coat and retina of the eye (toxoplasmosis).

Deep-staining DNA-containing portion of the nucleus (protozoa).

Chromatoidal bar/body
Deep-staining, barshaped/round/splinter-shaped inclusions found in the cytoplasm of certain amebae (Entamoeba spp.).

The presence of lymph and emulsified fat in the urine (filariasis).

Small, hairlike cytoplasmic projections from a cell or organism; used for motility (Balantidium coli).

Disruption of normal structure of the liver; destruction of liver cells and increase in connective tissue (schistosomiasis).

Tapeworm larva of the genus Multiceps characterized by multiple scolices invaginated into the fluid-filled bladder; no daughter cysts produced.

Inflammation of the colon.

That portion of the large intestine from the cecum to the rectum.

Absolute unconsciousness.

Association in which one individual receives benefits and the other is neither helped nor harmed.

Concentration techniques
Procedures, usually in fecal examinations, allowing the examination of large amounts of feces (flotation or sedimentation procedures; some available for blood specimens and urine specimens).

Present at, and usually before, birth (regardless of cause).

Inflammation of the membrane that lines the eyelids and covers the surface of the eyeball.

A violent, involuntary contraction of an extensive group of muscles; distrubance of cerebral function (spider, scorpion envenomation).

A ciliated larval tapeworm stage that occurs in the eggs of cestodes such as Diphyllobothrium and Spirometra spp. (pseudophyllidian tapeworms); this is a free-swimming stage, containing six hooks like those found in the oncospheres of other tapeworms.

Cor pulmonale
Cardiopulmonary problems which may terminate in congestive heart failure; obstructive vascular disease (Schistosoma mansoni infection).

Creeping eruption
Penetration and migration through subcutaneous tissues by skin-penetrating nematodes, resulting in intense pruritis and sometimes secondary bacterial or fungal infection (Strongyloides, hookworm, cutaneous larva migrans).

Old term for epimastigote.

Intestinal infection caused by coccidia (Cryptosporidium spp.).

Pertraining to the skin.

Outermost, three-layered portion of the body wall of nematodes (Ascaris, etc.).

Tapeworm larval stage of Hymenolepis spp. and Dipylidium caninum that occurs in arthropod intermediate hosts.

Tissue infection with larval tapeworms in which the scolex in inverted into a fluid-filled bladder (Taenia solium).

Tapeworm larva of the family Taeniidae (includes Taenia solium and T. saginata) in which a single scolex in invaginated into a fluid-filled bladder.

The protoplasm of a cell exclusive of the nuclear material.

Definitive host
Host in which the sexual reproduction of a parasite occurs.

Inflammation of the skin (filariasis; schistosomiasis; Strongyloides, hookworm larvae; leishmaniasis; Sarcoptes).

Frequent passage of soft or liquid stool (no blood); may be caused by any parasite normally found in any part of the intestine.

Having the male and female sexes of a species as separate individuals.

Direct smear (stool)
Approximately 2-mg suspension of feces in water or saline for the purpose of examination for parasites; primary aims is to see motility.

Pertaining to the daylight portion of the 24-hour day.

The proximal portion of the small intestine (Strongyloides stercolaris, Giardia lamblia).

Frequent watery stools, usually containing blood/mucus; associated with inflammation of the intestine, usually the colon (Entamoeba histolytica, Trichuris trichiura).

Difficulty in breathing.

Painful or difficult urination.

Organism that lives on or within the skin of its host (lice, mites, ticks).

Outer layer of the cytoplasm of a cell.

Presence of large amounts of fluid, usually in subcutaneous tissues (filariasis, trypanosomiasis, hookworm).

Inflammation and obstruction of the lymphatic system, resulting in hypertrophy and thickening of the surrounding tissues, usually involving the extremities and external genitalia (filariasis).

Active process of walling off a parasite by the host through the formation of a connective tissue capsule (trichinosis).

Inflammation of the brain (Chagas’ disease, trichinosis).

Formation of a resistant external wall by protozoa to enable them to survive drying and adverse environmental conditions; encysted forms are infective to humans.

Disease present in a localized community or area at all times.

Parasite that lives within the body of the host.

Inner portion of the cytoplasm of a cell.

Formation of large numbers of eosinophilic leukocytes caused by some type of immune response; usually found in helminth infections, particularly with tissue invasion (visceral larva migrans, trichinosis).

Disease that spreads rapidly and infects many people in a community/area (usually within a short time frame).

Pertraining to the outer layer of the skin.

Developmental stage of the family Trypanosomatidae; the base of the flagellum is in front of the nucleus and, as the flagellum passes through the body to merge as the free flagellar portion, it is attached to the body by the undulating membrane (old term: crithidia).

Diffuse or patchy redness of the skin; blanching on pressure, due to congestion of cutaneous capillaries.

Erythrocytic cycle
Developmental cycle of malarial parasites within the red blood cells.

Exoerythrocytic cycle
A part of the malarial life cycle in which the mosquito introduces sporozoites into the vertebrate host; sporozoites penetrate the parenchymal liver cells and undergo schizogony, resulting in the production of liver merozoites which then initiate the erythrocytic cycle.

The unabsorbed residue of the digestive process, along with sloughed epithelium, mucus, and bacteria.

Filariform larvae
Slender, infective larvae of Strongyloides and hookworm.

Flame cell
Primitive, ciliated excretory cell in trematodes; the movement of the cilia on this cell within the miracidium larva (within a schistosome egg) indicates egg viability.

Trematode (Clonorchis, Paragonimus, Fasciola, Schistosoma).

Inflammation of the spermatic cord (filariasis).

In malaria the sexual cell (male microgametocyte or female macrogametocyte) occurs in peripheral blood; fertilization will occur in the mosquito stomach/formation of the zygote.

Inflammation of the stomach and small and large intestines.

Genital primordium
Ovoid clump of cells that becomes the reproductive system (seen in the rhabditiform larvae of Strongyloides and hookworm).

Tumor-like nodule of firm tissue formed as a reaction to chronic inflammation, usually of lymphoid and epithelioid cells.

Presence of worms on pharyngeal mucosa; congestion of tissues accompanied by difficulty in breathing and possible asphyxiation (Fasciola hepatica, pentastome infection).

Harada-Mori culture
Method of incubating fecal material on a filter paper strip in a test tube containing water (cover 1/3 length a paper strip) for the purpose of culturing/recovering nematode larvae (Strongyloides, hookworm.

May refer to a nematode (roundworm), cestode (tapeworm), or trematode (fluke).

Passage of blood in urine (Schistosoma haematobium).

Any flagellated protozoan blood parasite (Trypanosoma spp.).

Passage of free hemoglobin in the urine (Plasmodium falciparum).

Expectoration of blood or sputum containing blood (Paragonimus).

Also called malarial pigment; composed of hematin and excess protein left over after metabolism of hemoglobin by the parasite; usually appears as brownish pigment in a Giemsa-stained preparation (term malarial pigment preferred).

Inflammation of the liver (amebiasis, schistosomiasis, liver flukes).

Enlargement of the liver.

Presence of both male and female reproductive systems in the same individual; most trematodes and cestodes are hermaphroditic.

Small intestinal flukes parasitic in humans and animals (Heterophyes, Metagonimus).

Hexacanth embryo
Six-hooked tapeworm embryo (oncosphere).

Human immunodeficiency virus.

See Urticaria.

An organism in or on which a parasite lives.

Hydatid cyst
Tapeworm larval stage of genus Echinococcus; consists of large bladder with an inner germinal layer from which daughter cysts and scolices develop (some of which will break off and drop into the fluid-filled bladder).

Hydatid sand
Consists of scolices, degenerating scolices, daughter cysts, hooks, and calcareous corpuscles found in the fluid within the hydatid cyst (Echinococcus granulosus).

Hydatid thrill
A delicate vibration felt by the hand after quick palpation or percussion over the area of the body where the hydatid cyst is located (Echinococcus).

An abnormal accumulation of fluid in the cerebral ventricles or in the subarachnoid space of the brain (cysticercosis).

Intensification of pigment; most obvious in dark-skinned races (leishmaniasis, onchocerciasis).

The ability of an individual to resist and/or control the effects of antigens (antigen sources could be animal, plant, mineral).

Incubation period
Time span from introduction of disease-causing organisms until symptoms of the disease occur.

Induced malaria
Malaria infection acquired by blood transfusions or possible sharing of needles by drug addicts (Plasmodium spp.).

Presence of arthropods on the surface of the body; does not refer to endoparasites (Pediculus).

Result of tissue reaction to injury; symptoms would be redness, pain, swelling, and fever.

To chicken or dry a substance by removing liquids by evaporation (preparation of certain types o media used to grow some of the amebae).

Intermediate host
A required host in the life cycle in which larval development takes place; this must occur before the stage is infective for the definitive host or secondary intermediate hosts.

A condition caused by excess bilirubin and bile pigment deposition in the skin which may give the patient a yellow appearance, especially the eyes (Plasmodium falciparum).

This is another name for visceral leishmaniasis (Leishmania donovani).

Concentrated clumps of chromatin material within the nucleus; position and morphology often used to differentiate intestinal protozoa.

Kerandel’s sign
Delayed sensation to pain (African trypanosomiasis).

Inflammation of the cornea (Chagas’ disease, onchocerciasis, Acanthamoeba).

Knott technique
Concentration procedure using blood and dilute formalin; designed to detect microfilaria (Wuchereria, Brugia).

Lagochilascaris minor
An unusual nematode parasite of humans (ingestion of infective eggs from the environment or ingestion of infective larvae in the tissues of an intermediate host). In most cases, the worms are located in the soft tissues of the neck and throat, tonsils, mastoids, and paranasal sinuses (chronic or recurrent abscesses). Fatal encephalopathy (one case) has also been reported. All cases were in the tropical regions of the western hemisphere.

Larva migrans, cutaneous/visceral/ocular
Disease characterized by thin, red, convoluted papular or vesicular lines of eruption that extend at one end while fading at the other (dog or cat hookworm). Visceral: migration of larvae through the deep tissues, including the eye (dog or cat ascarids, Toxocara sp.).

Leishman-Donovan body
Small, round, intracellular form of Leishmania spp. (reticuloendothelial system) and Trypanosoma cruzi (striated muscle); they are also called amastigotes or L-D bodies.

This is the old term for the promastigote stage, which is long and slender and found in the insect vector for Leishmania spp.; it is also recovered in artificial culture media (NNN).

Increase in the number of white blood cells, usually over 10’000/mm3

A decrease in the number of white blood cells, usually less than 1’000/mm3.

Loeffler's syndrome
Transient pulmonary infiltration; day to day clearing in 3 to 14 days; associated with marked peripheral eosinophilia (Ascaris).

Cavity of hollow, tubular organ, such as the intestine or blood vessels.

Plasma and white blood cells that bathe the tissue cells.

Inflammation of the lymph nodes (filariasis).

Inflammation of the lymphatic vessels (filariasis).

Absolute or relative increase of lymphocytes in the blood.

Lymph varices
Dilated lymph vessels secondary to lymphatic blockage (filariasis).

large, kidney bean – shaped nucleus in Balantidium coli (Shape is not always consistent).

Motile, phagocytic, mononuclear cell that originates in the tissues and may be confused morphologically with protozoan trophozoites (particularly Entamoeba histolytica).

Poor fat absorption in upper small bowel (giardiasis).

Vague feeling of discomfort throughout the whole body; tired.

Malarial pigment
Composed of hematin and excess protein left over from the metabolism of hemoglobin; will appear as brownish pigment after Giemsa staining (Plasmodium spp.).

Malignant tertian malaria
Malaria caused by Plasmodium falciparum.

Maurer’s dots or clefts
Irregular dots occur infrequently in red blood cells infected with Plasmodium falciparum (dots tend to be more blue after Giemsa staining than the Schüffner’s dots).

Dilation of the colon (Chagas’ disease).

Dilation of the esophagus (Chagas’ disease).

Inflammation of the brain and its surrounding membranes (trypanosomiasis, malaria, Naegleria, Angiostrongylus cantonensis).

Product of schizogonic cycle in malaria; produced in the liver (preerythrocytic cycle) and in the red blood cells (erythrocytic cycle).

Tissue that supports the intestinal tract.

The infective, encysted larval form of a trematode; found within the tissues of an intermediate host or on plant material (Paragonimus, Clonorchis, Fasciolopsis).

Embryos produced by filarial worms (nematodes); usually found in the blood or tissues of patients with filariasis (Wuchereria, Brugia, Onchocerca).

Micrometer (micron)
Unit of measure equal to 0.001 mm; abbreviated mm.

See Micrometer

Small, dotlike nucleus found in Balantidium coli; often very difficult to see, even in stained preparations.

Free-living, ciliated larva released from a trematode egg and infective for the snail intermediate host.

Increase in the number of monocytes in the peripheral blood; may be found in both helminth and protozoan infections.

Both male and female reproductive organs occur in the same individual (hermaphroditic) trematodes, cestodes).

Montenegro test
Delayed hypersensitivity skin test; injection of leishmanial antigen; read after 72 hours; positive reaction in cured individuals, negative in early cases (visceral and mucocutaneous leishmaniasis).

Multiocular cyst
Cyst containing many cavities (Echinococcus multilocularis).

Association in which both parties benefit and cannot survive without each other.

Infestation with maggots (fly larvae).

Inflammation of the heart muscles (trichinosis, trypanosomiasis, toxoplasmosis).

Inflammation of voluntary muscles (trichinosis).

Nanophyetus salmincola
Human infections with this digenetic trematode (ingestion of raw, undercooked, or smoked salmon) have now been reported from North America. Symptoms include gastrointestinal complaints or unexplained eosinophilia. Eggs were also recovered from the stool specimens.

See Autopsy.

Pertaining to the dark portion of a 24-hour day; active at night (filariasis).

A small, hard node that can be felt by touch (onchocerciasis, myiasis).

A cellular inclusion composed of chromatin; morphology often used to help identify intestinal protozoa (Entamoeba, Dientamoeba).

Obligate parasite
Parasite that must always live in contact with the host.

Occult blood
Blood present in very small amounts; usually detectable by chemical means; specimen is most often stool; may or may not be related to parasitic infection.

Nodule containing the adult worms (onchocerciasis).

Spherical, six-hooked tapeworm larva within the egg shell (Taenia spp., Hymenolepsis spp.).

Operculate egg
Egg with lid (trap door) at one end through which the larva escapes (Diphyllobothrium, Clonorchis, Paragonimus).

A lid-like structure on one end of the egg shell through which the larval form escapes (Diphyllobothrium, Clonorchis, Paragonimus).

Small, solid evaluation of the skin.

An organism living on or in, and at the expense of, another organism.

Rapid onset/return of symptoms or increased intensity of symptoms; usually applies to periodicity of malaria symptoms (chills, fever, sweats).

Slight paralysis (cysticercosis).

Form of sexual reproduction in which the organism develops without fertilization by the male gamete (Strongyloides, parasitic generation).

Any organism or substance that produces a disease state.

Recurrence of an event t regular intervals (nocturnal periodicity of microfilariae of Wuchereria bancrofti; malarial symptoms).

Movement of food through the intestine by contractions of the intestinal musculature.

Inflammation of the membrane that lines the abdominal cavity and covers the viscera.

Minute, hemorrhagic spots in the skin or mucosa.

Human roundworm parasite of the colon and rectum; extremely common in children; diagnostic approach/scotch tape preparation (Enterobius vermicularis).

Pipe-stem fibrosis
Granulomatous reaction around schistosome eggs in periportal tissues; fibrous tissue is white and hard (Schistosoma japonicum, S. mansoni).

The liquid portion of the blood or lymph.

A tapeworm larva of the genera Diphyllobothrium and Spirometra; also known as a sparganum larva.

Inflammation of the pulmonary tissue.

Polar filaments
Filaments arising from opposite poles of oncosphere membrane of Hymenolepsis nana; they lie between the egg shell and the oncosphere.

Polar plugs
Mucoid plugs present at both ends of the egg (Trichuris trichiura).

Prepatent period
Time from entry of a parasite into the body until the infection is manifested clinically or can be detected by routine diagnostic methods.

Segments of the tapeworm containing male and female reproductive systems; may be immature, mature, or gravid Taenia spp., Hymenolepsis spp.).

Development stage of the family Trypanosomatidae; the base of the flagellum is anterior to the nucleus and the free flagellar portion is short; there is no undulating membrane present.

Protein in the urine (Plasmodium falciparum).

Severe itching (cutaneous larva migrans, infection with Scabies/itch mite).

Usually refers to a large number of Toxoplasma gondii trophozoites enclosed in a macrophage or some other host cell; parasites bound by host cell tissue.

Producing fever.

The presence of pus in the urine (bacteria, white blood cells).

Quartan malaria
Malaria caused by Plasmodium malariae.

Quotidian malaria
Type of malaria in which fevers occur every 24 hours; may indicate early infection or mixed infection.

A superficial skin eruption; may be macular, maculopapular, blotchy, etc.

Rectal prolapse
Extrusion of the rectal mucosa through the anus; may occur in children with heavy Trichuris trichiura infections; usually no sequelae after therapy.

An elongated sac with a mouth, muscular pharynx, primitive gut, birth pore, and germinal cells, which may develop into cercariae or daughter rediae (stage within snail host trematodes).

Inflammation of both the retina and the choroid/vascular coat of the eye (toxoplasmosis).

Rhabditoid (rhabditiform) larvae
Noninfective, thick, rod-shaped larvae of hookworm and Strongyloides; rhabditoid refers to the shape of the larval esophagus.

Romaña’s sign
Marked edema of one or both eyes; usually dry and unilateral (Chagas’ disease).

Arrangement of merozoites in mature schizont of Plasmodium malariae in a circle around a clump of excess pigment; also uterine arrangement in the proglottid of Diphyllobothrium latum.

A stage in the asexual cycle of the malarial parasite that occurs within the red blood cells; results in the formation of merozoites (Plasmodium spp.).

Schüffner’s dots
Tiny, red-staining granules in the cytoplasm of red cells infected with either Plasmodium vivax or P. ovale: true stippling (using Giemsa stain).

The head/attachment portion of a tapeworm; attachment may be by suckers or hooklets (Taenia, Diphyllobothrium, Hymenolepsis).

Another name for pinworm (Enterobius vermicularis).

Cuticle of a larval nematode that is retained around the body; may serve as protection; used to help identify microfilariae (Wuchereria, Brugia, Loa)

Marked decrease in blood pressure; rapid pulse, decreased kidney function (Plasmodium falciparum).

Visual examination of the rectum and sigmoid flexure of the colon using a lighted tube; often performed for suspect amebiasis cases (Entamoeba histolytica).

A migrating tapeworm larva that invades the subcutaneous tissues with inflammation and fibrosis (Diphyllobothrium, Spirometra).

Accessory reproductive structure in male nematodes; useful in speciation.

Enlargement of the spleen (leishmaniasis).

Splinter hemorrhages
Effects of vasculitis in trichinosis (larval migration).

An elongated sac without a mouth or other distinct internal or external structure, formed after the miracidium infects a snail. May give rise to cercariae (schistosomes) or rediae (Paragonimus)

A stage in the sexual cycle in the malarial parasite that takes place in the mosquito; eventual production of the infective sporozoites.

Slender, spindle-shaped organism that is the infective stage of malaria; inoculated into humans by the bite of an infected female mosquito; the result of the sexual cycle in the mosquito.

Spurious parasite
Organisms that parasitize other hosts that pass through the human intestine and are detected in the stool after ingestion; not a true infection (ingestion of animal liver containing Capillaria eggs).

Malabsorption characterized by the presence of fat in the stool (giardiasis).

The entire chain of tapeworm proglottids, excluding the scolex and neck.

Reinfection b a parasite that is already present in the body (Strongyloides, Hymenolepis).

Swimmer’s itch
Dermatitis caused by skin penetration of humans by cercariae of schistosomes (normally infect birds and semi-aquatic animals).

Close association between two different organisms; living together.

Fainting or loss of consciousness due to a temporary deficiency of blood supply to the brain (Dracunculus infection).

Involving the entire body.

Rapid heartbeat, usually more than 100 beats per minute.

Training to defecate; may be painful and unproductive.

Tremor felt on palpation of a hydatid cyst (Echinococcus granulosus).

Ringing or buzzing in the ear not resulting from an external source.

Traveler’s diarrhea
Often related to giardiasis or cryptosporidiosis.

The feeding, motile stage of protozoa.

Slender, flagellate protozoan found in the blood of humans (Trypanosoma spp.); also referred to as trypomastigote (new term).

Newer terminology for the trypanosome stage in human blood (Trypanosoma spp.).

An open sore on the skin or mucous membrane characterized by the disintegration of the tissue and often the discharge of pus.

Cyst containing only one cavity.

Inflammation of the urethra (trichomoniasis).

An allergic reaction seen on the skin characterized by the development of wheals and intense itching/burning sensations; onset and disappearance are often sudden (filarial infections).

Inflammation of the uvea (pigmented, vascular layer of the eye) (Acanthamoeba).

Cavity in the cytoplasm of a cell that may contain ingested bacteria, yeast, or debris; vacuole contents and/or morphology may be helpful in identification of some of the intestinal protozoa (Entamoeba spp., Iodamoeba bütschlii).

Inflammation of the vagina; prolific, irritating green or yellowish, thin discharge; there may be punctate, hemorrhagic spots (trichomoniasis).

Vinegar eel
Free-living nematode, Turbatrix aceti, occasionally occurring as a contaminant in laboratory solutions.

Pertaining to the internal organs of the body; especially those within the abdominal cavity.

Visceral larva migrans
Tissue migration of dog and cat ascarid larvae in humans; the life cycle can not be completed in the human host; often characterized by high peripheral eosinophilia (Toxocara cati and T. canis).

Common name for the roundworm, Trichuris trichiura.

Winterbottom’s sign
Enlargement of the posterior cervical lymph nodes (African trypanosomiasis).

Procedure allowing the feeding of laboratory-raised triatomid bugs (known to be infection-free) on the blood of patients suspected of having Chagas’ disease; after several weeks, the bug feces are checked for the intermediate stages of Trypanosoma cruzi; a type of concentration procedure.

A disease of animals that is transmissible to humans (Cryptosporidium).

The cell resulting from the fusion of male and female gametes; occurs in the mosquito stomach (Plasmodium spp.).