Deck 28: Diagnostic Parasitology

Question 1

A young man from rural Brazil is visiting family in the United States when he becomes ill with muscle pains, high fever, and hepatosplenomegaly.A blood sample taken in the emergency room reveals the following organism.The most likely identification of this organism is:

A)Leishmania donovani.
B)Babesia microti.
C)Plasmodium falciparum.
D)Trypanosoma cruzi.

Answer 1

D
The primary diagnostic stage in the blood is the trypomastigote.It is an elongated structure 15 to 20 mm long that often appears in a C or U shape.Individuals in the acute phase may be asymptomatic or have local symptoms including the presence of a chagoma (ulcerative skin lesion at the site of the insect bite) or a unilateral edema around the eye (Romaña sign) if the bite is on the ocular conjunctiva.Systemic manifestations include fever, lymphadenitis, hepatosplenomegaly, malaise, muscular pains, and diarrhea and vomiting.The latent phase can last 10 to 40 years after infection, but only about 30% to 40% of patients develop the chronic form of Chagas disease.CDC PHIL #3013

Question 2

A patient with a history of eating wild game comes to the physician with a history of diarrhea over the past 3 weeks.In addition he complains of fever, muscular pain and tenderness, headache, and general weakness.The patient also has a significant eosinophilia.A biopsy of a nodular area on his forearm is seen in the image below.This is consistent with a diagnosis of:

A)Leishmania donovani.
B)Wuchereria bancrofti.
C)Trichinella spiralis.
D)Loa loa.

Answer 2

C
Trichinosis is the infection of muscle tissue with the larval form of T.spiralis, a helminth whose adult stages live in the human intestine.Humans acquire the infection by eating undercooked meat, particularly pork that contains the larval forms.In recent years ingestion of wild game has led to infection by other species of Trichinella.Because it is difficult to recover adults or larvae in a stool sample, the diagnosis is often based on clinical symptoms and the patient's history.Biopsy of muscle tissue and identification of encapsulated, coiled larva is the definitive diagnostic method.CDC PHIL #10142

Question 3

A patient finds a small ribbon-like piece in his stool sample and reports this to his physician.The physician orders a fecal O&P analysis that reveals the following egg in the sample.The most likely identity of this parasite is:

A)Hymenolepis nana.
B)Taenia spp.
C)Diphyllobothrium latum.
D)Paragonimus westermani.

Answer 3

B
Laboratory diagnosis of Taenia spp.infection can be made by finding the egg, scolex, or proglottid in the feces.The egg is yellow-brown and surrounded by a thick wall with radial striations; it measures 30 to 43 mm.The egg is embryonated with a six-hook oncosphere when passed in the feces.Eggs of this species are indistinguishable and must be reported as "Taenia spp." eggs.CDC PHIL #906

Question 4

A patient comes to the emergency room stating that he has fever and chills every 48 hours.The patient has a history of travel to Central America in the past month and did not take any preventative measures against malaria.A complete blood count (CBC) shows the following RBC inclusions.This organism is most likely:

A)Plasmodium malariae.
B)P.ovale.
C)P.falciparum.
D)P.vivax.

Question 5

When a request is submitted to examine a blood sample for malaria, which of the following procedures should be performed?

A)A thick smear for maximum detection and to determine morphology
B)A PVA trichrome-stained blood smear
C)A Giemsa thick blood smear preparation for maximum detection and a thin smear for speciation
D)A formalin-ethyl acetate concentration for detection and a thin smear for speciation

Question 6

A woman patient with history of travel to tropical Africa was noncompliant with her antimalarial medications.She now has a cyclical fever and paroxysm every 72 hours.The following organism is seen in her peripheral blood smear consistent with an infection caused by:

A)Plasmodium ovale.
B)P.vivax.
C)P.falciparum.
D)P.malariae.

Question 7

The following organism was found in the fecal sample of a patient with diarrhea and elevated liver enzymes.This organism is most likely:

A)Entamoeba histolytica.
B)E.hartmanni.
C)Giardia lamblia.
D)E.coli.

Question 8

An international male student from Egypt comes to the campus clinic complaining of blood in his urine.A urinalysis reveals the parasite seen below.This organism is:

A)Schistosoma mansoni.
B)S.japonicum.
C)S.haematobium.
D)S.madurella.

Question 9

A farmer who raises sheep and cattle shows signs of jaundice.Along with elevated liver enzymes, he also has an elevated eosinophil count.A fecal sample for O&P shows the parasite form seen below.The organism causing this infection is:

A)Wuchereria bancrofti.
B)Brugia malayi.
C)Loa loa.
D)Fasciola hepatica.

Question 10

A woman who just returned from a trip to Southeast Asia has signs of biliary obstruction, which is confirmed by CT scan.Due to her recent travel history, the physician orders an O&P examination before considering surgical intervention.The following element is found in her fecal sample.The most likely identity of this organism is:

A)Schistosoma mansoni.
B)Opisthorchis sinensis.
C)Fasciola hepatica.
D)Heterophyes heterophyes.

Question 11

A recent emigrant from Somalia develops high fever, chills, and severe headache.Blood work on admission to the hospital reveals the following in his blood smear.This patient is most likely infected with:

A)Plasmodium ovale.
B)P.malariae.
C)P.falciparum.
D)P.vivax.

Question 12

A patient with recent history of travel to the Philippines has bloody diarrhea.An O&P sample shows the following parasite egg.What is this called?

A)Schistosoma mansoni
B)S.japonicum
C)S.haematobium
D)S.madurella

Question 13

A 15-year-old boy spent most of the summer at the northern Minnesota family cabin on a lake in a densely wooded area.After returning to school in the fall, he was frequently tired and listless with periods of fever and chills.A blood sample taken at the physician's office revealed the following organism.The most likely identification is:

A)Plasmodium ovale.
B)Babesia microti.
C)Plasmodium malariae.
D)Trypanosoma cruzi.

Question 14

A housewife from the Great Lakes area comes to her family physician with fatigue and malaise.Blood tests show that she has enlarged but pale red blood cells (RBCs) (megaloblastic anemia) along with a vitamin B₁₂ deficiency.Her history includes a dietary habit of making pickled fish, a family favorite.Because of this, an O&P is also requested and reveals the following parasite egg.What is the identity of this parasite?

A)Hymenolepis nana
B)Taenia saginata
C)Diphyllobothrium latum
D)Taenia solium

Question 15

Five members of a family develop a sudden onset of watery diarrhea, nausea, vomiting, headache, and cramps.They go to the family physician who orders fecal cultures and complete ova and parasites (O&P) analysis.Each sample reveals the presence of organisms seen below.The most likely cause of the infection is:

A)Cryptosporidium parvum.
B)Isospora belli.
C)Cyclospora cayetanensis.
D)Encephalitozoon intestinalis.

Question 16

A young man who returned a week ago from a family vacation to Kenya, develops a high fever and delirium.Although he was compliant with his antimalarial medications, a blood sample is taken to rule out malaria.The laboratory scientist sees the following on the blood smear.This organism is most likely:

A)Trypanosoma brucei.
B)Leishmania donovani.
C)Wuchereria bancrofti.
D)Loa loa.

Question 17

What is the organism shown below?

A)Brugia malayi
B)Loa loa
C)Wuchereria bancrofti
D)Onchocerca volvulus

Question 18

A patient who has traveled to the Puerto Rico comes to clinic with a history of diarrhea for the past 2 weeks.A fecal sample collected for O&P shows the following parasite.This organism is most likely:

A)Schistosoma mansoni.
B)S.japonicum.
C)S.haematobium.
D)S.madurella.

Question 19

A 4-year-old child has been complaining of a stomachache and has had intermittent episodes of diarrhea.Physical examination reveals an apparently healthy child with a mildly distended abdomen.Because of the diarrhea, a fecal sample is sent for culture and for O&P.What is the identity of that found in the child's fecal sample?

A)Ascaris lumbricoides
B)Strongyloides stercoralis
C)Hookworm
D)Schistosoma haematobium

Question 20

Several children at a daycare center are having trouble sleeping and are showing increasing signs of restlessness.Because one child was recently diagnosed with a parasite, the parents are informed that other children should be tested.The organism below is found during examination.This organism is:

A)Trichuris trichiura.
B)Enterobius vermicularis.
C)Ascaris lumbricoides.
D)hookworm.