Parasitology

The adult tapeworm of Echinococcus granulosus is found in the intestine of

Dogs

A patient is suspected of having amebic dysentery. Upon microscopic examination of a fresh fecal specimen for ova and parasites, the following data were obtained: A trophozoite of 20 um with progressive, unidirectional crawl. Evenly distributed peripheral chromatin, a central karyosome and finely granular cytoplasm were observed. The probable infecting agent is

Entamoeba histolytica

Which parasite can be latent and cause neurological lesions particularly in AIDS patients?

Toxoplasma gondii

When malaria smears are requested, what patient info should be obtained?

Travel history, antimalarial medication, date of return to US

Cause of trichinoses Pigs One of the few tissue parasitic diseases still seen in the United States. Consumption of uncooked or under cooked pork. Infective state is encysted larvae in striated muscle of pork Tissue biopsy for encysted parasite Elevated eosinophil counts

Trichinella spiralis

a 45 year old hunter developed fever, myalgia, and periorbital edema. He has a history of bear meat consumption. The most likely causative agent is:

Trichinella spiralis

Parasitic organisms that are most often transmitted sexually include:

Trichomonas vaginalis

In an outbreak of diarrheal disease traced to municipal water supply, the most likely causative agent is:

Cryptosporidium spp

Patients with severe diarrhea should use "enteric precautions" to prevent nosocomial infections with?

Cryptosporidium spp

Parasite stages that are immediately infective for humans on passage from the gastrointestinal tract include

Crytosporidium oocytes

Autofluorescence requires no stain and is recommended for the identification of

Cyclosora cayetanensis oocysts

Trophozoite: Large, spherical, Granular cytoplasm with blunt pseudopods Cyst: 2-8 nuclei, Eccentric large karyosome, Splinter-shaped chromatoidal bodies

Entamoeba coli (>10um)

Trophozoite: Single nucleus, Identified by presence of RBCs Cyst: Large, spherical, Four nuclei, Small central karyosome, Dark chromatoidal, cigar-shaped bodies Causes amebiasis (amebic dysentery)

Entamoeba histolytica (10-20um)

The incorrect match between disease and symptoms is

Enterobiasis-dysentary

Pinworm Enterobiasis Infection by ingestion of egg Touching perianal area with cellophane tape 55x25um

Enterobius vermicularis

The most prevalent helminth to infect humans is

Enterobius vermicularis, the pinworm

Plasmodium vivax and Plasmodium ovale are similar because the:

Exhibit Schuffner's dots and have a true relapse in the life cycle

Trophozoite: Resembles "monkey's face", has ventral sucking disc, two large, central karyosomes, 4 pairs of flagella Most common parasite associated with gastroenteritis Symptoms are caused from mass of organisms interfering with normal intestinal absorption.

Giardia (9-12um, 12-15um)

Microsporidia have been identified as causing severe diarrhea, disseminated disease in other body sites, and ocular infections. routes of infection have been identified as

Ingestion, inhalation and direct contamination

The incorrect match between method and method objective is

Knott's concentration-the recovery of operculated helminth eggs

Causes cutaneous and visceral leishmaniases Sand fly, injecting promastigote into human host--> amastigote Diagnostic stage is the amastigote, found in *macrophages* of lesion.

Leishmania species

The incorrect match between symptoms and disease is

Malabsorption syndrome-giardiasis

A transplant patient on immunosuppressive drugs developed increasing diarrhea. The most likely combination of disease and diagnostic procedure is

Microsporidiosis and modified trichrome stain

Oocysts of Cryptosporidium spp. can be detected in stool specimens using

Midified Ziehl-Neelsen acid-fast stain

Although the pathogenicity of Blastocystis hominis remains controversial, newer information suggests that

Numerous strains/species are included in the name, some of which are pathogenic and some are nonpathogenic.

Which micro filariae are usually not found circulating in the peripheral blood?

Onchocera volvulus

Because of the possibility of drug resistance or the persistence of exoerythrocytic parasites, identification of the causative species can be important in the choice of treatment for malaria. Which species of Plasmodium may have exoerythrocytic stages capable of causing relapses up to 3 or more years after initial infection?

P. ovale

The exam of sputum may be necessary to diagnose infection with

Paragonimus westermani

Older developing stages of fifth human malaria resemble

Plasmodium malariae

Trophozoite: Very large, oval, ciliated, Kidney shaped macro-nucleus (40-60um) Cyst: Large, clear refractile wall Attaches to colon or bowel. Can cause bloody dysentery. Rarely seen outside of the tropics. (40-50um)

Balantidium coli

There are few procedures considered STAT in parasitology. The most obvious situation would be:

Blood films for malaria

Which of the following forms Toxoplasma gondii are produced in infected humans?

Bradyzoites

Blood fluke Small golden egg, oval, with tiny spine mesenteric vein around small intestine

Schistosoma japonicum

Visceral larva migrans is associated with which organism?

Toxocara-serology

Toxoplasma gondii is characterized by

Possible congenital infection and ingestion of oocysts and cosmopolitan distribution and possible difficulties with interpretation of serological results

The formalin -ether (ethyl acetate) concentration procedure for feces is used to demonstrate

Protozoan cysts and helminth eggs

Confirmation of an infection with microsporidia can be achieved by seeing

evidence of the polar tubule

Microcporidial infections can be confirmed using

light microscopy and modified trichrome stains

Ingestion of which egg will result in infection?

Toxocara canis

Cysts of Iodamoeba butschlii typicall have:

A large glycogen vacuole

Large intestinal roundworm Knobby-coated, bile-stained large oval egg with thick wall Ingested egg releases larval worm that penetrates duodenal wall enters bloodstream to alveoli of lungs. Ascariasis, the most common helminth infection 55x40um fetilized 90x40um unfertilized

Ascaris lumbricoides

These two (2) parasites are often co-infecting agents because for both the infecting stage is an egg and they are both found in the same geographical area.

Ascaris lumbricoides Trichuris trichiura

Infection resembles malaria Examination of blood smears most helpful. Sexual phase of Babesia occurs in a tick 2-5um

Babesia

An Entamoeba histolytica tropozite has the following characteristics:

Central karyosome in the nucleus, ingested RBCs, and clear pseudopodia

Which of the following are the diagnositic morphologic characteristics for Entamoeba histolytica?

Centrally located karyosome and ingested red blood cells

Hydatid tapeworm Hydated cyst disease Lancet shape egg Embryonated egg in the feces of eggs Cyst found in *liver* or lung

Echinococcus granulosus

Humans can serve as both the intermediate and definitive host in infections caused by

Hymenolepis nana

A 12 year old girl is brought to the ED with meningitis and a history of swimming in a warm-water spring. Motile amoebae that measure 10 um in size are seen in CSF and are most likely?

Naegleria Fowleri trophozoites

A 12-year-old is brought to the emergency room with meningitis and a history of swimming in a warm-water spring. Motile amoebae that measure 10 micron in size are seen in the cerebrospinal fluid, and are most likely:

Naegleria fowleri trophozoites

Hookworm Infective-- Filaform larva 50x30um

Necator americanus

Key characteristics of infection with Plasmodium knowlesi include

Rapid erythrocytic cycle, will infect all ages of RBCs, and can cause serious disease

Examination of a 24 hour unpreserved urine is sometimes helpful in the recovery of

Schistoma haematobium eggs

*Blood flukes* Cercariae from snail penetrate the skin of humans or other mammals. Do not have an operculum The eggshell splits open to liberate the larva. Recognized by shape of egg and appearance of spine on shell.

Schistosoma

Bladder fluke Large, oval (elongated) egg, with large sharp terminal spine Resides around bladder. Produces hematuria. May cause cancer of bladder.

Schistosoma haematobium

Manson's blood fluke Large, Oval (elongated) egg, with large sharp lateral spine In mesenteric vessels of lower colon *Intestinal Vein*

Schistosoma mansoni

An immunocompromised man has several episodes of pneumonia, intestingal pain, sepsis with gram neg rods, and a history of military servie in Southeast Asia 20 years earlier. The most likely cause is infection with

Strongyloides stercoralis

The term "internal autoinfection" is generally used in referring to infections with:

Strongyloides stercoralis

Threadworm Smallest *intestinal* nematode Autoinfective Filariform larva penetrates skin Only intestinal nematode that can reproduce entirely within the host "Ground itch",

Strongyloides stercoralis

Pork tapeworm Disease: Cysticercosis Can autoinfect the human host Dark brown stained shell surrounding oncosphere with six small hooklets.

Taenia Solium

Beef tapeworm Dark brown stained shell surrounding oncosphere with six small hooklets. Ingested in contaminated rare or uncooked beef. Cysts are found in striated muscle 35x45um

Taenia saginata

Select the most sensitive recovery method for Acanthamoeba spp. from lens care solutions or corneal biopies

The use of non-nutrient agar cultures seeded with Escerichia coli.

Which is the best technique to identify Dientamoeba gragilis in stool?

Trichrom-stained smear

Whipworm Barrel-shaped, bile stained, thick shelled, unembryonated, with mucoid plugs at each end Asymptomatic, secondary bacterial infection Infective is ingested egg *Intestine* 50x25um

Trichuris trichura

tsetse fly sleeping sickness. trypanosome in blood 15-30 um

Trypanosoma brucei

Chronic phase causes cellular damage Significant cause of death. Demonstration of trypomastigotes in blood smears or CSF. Reduviid bug as epimastigote

Trypanosoma cruzi,

Hemoflagellates from blood and tissue:

Trypanosomes and leishmanias

A 60 year old Brazilian patient with cardiac irregularities and congestive heart failure suddenly dies. Examination of the myocardium revealed numerous amastiogotes, and indication that the cause of death was most likely:

Trypanosomiasis with Trypanosoma cruzi

Eye infections with Acanthamoeba spp have most commonly been traced to:

Use of contaminated lens care solutions

Which parasite causes eosinophilic meningoencephalitis, a form of larva migrans causing fever, headache, stiff neck, and increased cells in the spinal fluid?

Angiostrongylus cantonensis

Organisms and infection that under normal conditions cannot be transmitted int he laboratory are

Ascaris lumbricoides- ascariasis

For which of the following diseases do reduviid bugs serve as vectors?

Chagas' disease (American trypanosomiasis)

Potential problems using EDTA anticoagulant and holding the blood too long prior to preparation of thick and thin blood films include

Changes in parasite morphology, loss of organisms within several hours, and poor staining. Loss of Schuffners dots, poor adherence of the vector cycle within the tube of blood.

Which Platyhelminth infects humans through ingestion of undercooked fish?

Clonorchis sinensis (*Liver*)

The term internal autoinfection can be associated with

Cryptosporidium and Strongyloides stercoralis

An immunocompromised patient continues to have diarrhea after repeated ova and parasites examinations. Sedimentation concentration, trichrome stain were negative. What organisms?

Cryptosporidium and microsporidia

Two helminth eggs that may resemble one another are

Diphyllobothrium latum and Paragonimus wertemani

In a condition resulting in the accidental ingestion of eggs, the human becomes the intermediate rather than the definitive host. The correct answer is?

Cysticercosis (Taenia solium)

Within the US, sporadic mini outbreaks of diarrheal disease have been associated with the ingestion of strawberries, raspberries, fresh basil, mesclun, and snow peas. The cause is?

Cystoisospora cayetanensis

An operculated cestode egg that can be recovered from human feces is

Diphyllobothrium latum

Broad fish tapeworm Largest tapeworm Crustaceans first intermediate host; humans are the definitive host Infection by ingestion of larval form eating raw or uncooked contaminated fresh water fish

Diphyllobothrium latum

Protozoan cysts were seen in a concentration sediment and tentatively identified as Entamoeba coli. However, the organisms were barely visible on the permanent stained smear because:

E. coli cysts were present but poorly fixed

The incorrect match between organism and the appropriate diagnostic procedure is

Echinococcus granulosus- routine ova and parasite examination

When humans have hyatid disease, the causative agent and host classification are:

Echinococcus granulosus-accidental intermediate host

Enterobius vermicularis infection is usually diagnosed by finding

Eggs in perianal specimens

In infections with Taenia solium, humans can serve as the

Either the definitive or the intermediate host

A gram stain from a gum lesion showed what appeared to be amoebae. A trichrome smear showed amoebae with a single nucleus and partially digested PMNs. The correct ID is

Entamoeba gingivalis

Charcot-Leyden crystals in stool may be associated with an immune response and are thought to be formed from the breakdown products of

Eosinophils

Which specimen is the least likely to provide recovery of Trichomonas vaginalis?

Feces

Which stage of Trichuris trichiura is infective for humans?

Fully embryonated egg

Organisms that should be considered in a waterborne outbreak of diarrheal disease include:

Giarda lamblia and Cryptosporidium

One of the following protozoan organisms has been implicated in waterborne and foodborne outbreaks within the US. The suspect organism is

Giardia lamblia

Fecal immunoassays have become more commonly used to diagnose infections with

Giardia lamblia and Cryptosporidium spp

Organisms that should be considered in a nursery school outbreak of diarrhea include:

Giardia lamblia, Dientamoeba fragilis, and Cryptosporidium spp

The incorrect match between organism and characteristic is:

Hymenolepis nana-striated shell

Rat tapeworm *Embryo without polar filaments seen* Infective form is egg. Requires larval insect as intermediate host Bile stained Stool sample

Hymenolepsis diminuta

Dwarf tapeworm *Six-hooked embryo with polar filaments* Can be autoinfective Reingestion of the eggs can lead to reinfection and is the most common mode of transmission *Intestine* 50x30um

Hymenolepsis nana

The microsporidia are protozoans that have been implicated in human disease primarily in

Immunocompromised patients

Humans acquire infections with Diphyllobothrium latum adult worms by

Ingestion of raw freshwater fish

Upon examination of stool material for Cystoisospora belli, one would expect to see:

Oocysts that are modified acid-fast variable

Mature trophozoites and young schizonts in blood smear show a distinct tendency toward band formation and the red blood cells are not enlarged.

P. malariae

A 44 year old man was admitted to the hospital following a 2 week history of low grade fever, malaise, and anorexia. Examination of a Giemsa stained blood film revealed many intraerythrocytic parasites. Further history revealed frequent camping trips near Martha's Vineyard and Nantucket Island, but no travel outside the continental United States. This parasite could easily be confused with;

Plasmodium falciparum

Early ring stages of the fifth human malaria, Plasmodium knowlesi, resemble those of

Plasmodium falciparum

Massice hemolysis, blackwater fever, and central nervous system involvement are most common with:

Plasmodium falciparum

Massive hemolysis, blackwater fever, and central nervous system involvement are most common with:

Plasmodium falciparum

Babesia has been implicated in disease from both splenectomized and nonsplenectomized patients. Morphologically, the parasites resemble:

Plasmodium falciparum rings

In a patient with diarrhea, occasionally Entamoeba histolytica/E. dispar (four nucleated cysts, no chromatoidal bars) are identified as being present; however, these cells, which are misdiagnosed as protozoa, are really:

Polymophonuclear leukocytes

The incorrect match between organism and characteristic is:

Schistosoma masonis-egg with terminal spine

The miracidial hatching tests helps to demonstrate the viability of eggs of

Schistosoma spp

In a pediatric patient, the recommended clinical specimen for recovery of Enterobius vermicularis is the:

Series of Scotch tape preparations

Characteristics of the rhaditiform (noninfective) larvae of Strongyloides stercoralis include a:

Short buccal capsule and large genital primordium

Eating poorly cooked pork can lead to an infection with

Taenia solium and Trichinella sprialis

When staining Cystoisopora belli oocysts with modified acid-fast stains, the important difference between these methods and the acid-fast stains used for acid-fast bacilli (AFB) is:

The decolorizer is weaker than acid alcohol used for AFB decolorizing

What is true about onchocerciasis?

The diagnositic test of choice is the skin snip

Primary infections with the microsporia may originate in:

The gastrointestinal tract

After returning from a 2 year stay in India, a patient has eosinophilia, an enlarged left spermatic cord, and bilateral inguinal lymphadenopathy. The most likely clinical specimen and organism match is:

Thick blood films-Microfilariae

A helminth egg is described as having terminal polar plugs. The most likely helminth is

Trichuris trichiura

The incorrect match between the organism and one method of acquiring the infection is

Trypanosoma brucei rhodesiense- bite of sand fleas

Chagas' disease (American trypanosomiasis) is caused by

Trypanosoma cruzi