Question 1

A clinical sign that may suggest the presence of a filarial nematode infection is:
A) Diarrhea
B) Eosinophilia
C) Jaundice
D) Microcytic anemia

Accepted Answer

Migrating nematodes, especially filarial parasites, are usually associated with blood or tissue eosinophilia.

Question 2

The nematode infection that may become more severe through ingestion of infective eggs, especially in infected infants, is:
A) Ancylostoma duodenale
B) Enterobius vermicularis
C) Strongyloides stercoralis
D) Trichinella spiralis

Accepted Answer

Enterobius vermicularis infections become more severe due to the pruritus caused by new eggs released by dying females, which leads to autoreinfection through ingestion of these new eggs.

Question 3

In the Ascaris lumbricoides life cycle, after eggs are ingested, the next stage in the life cycle that must occur before a mature adult can live in the host's intestine is called the:
A) Diagnostic stage
B) Infective stage
C) Liver-lung migration
D) Method of infection

Accepted Answer

The liver-lung migration phase of the Ascaris lumbricoides life cycle occurs as the larva form migrates from the intestine to the lungs before returning to the intestine to become a mature adult worm. See life cycle, p. 17.

Question 4

Patients who have heavy infections with Necator americanus may exhibit all of the following symptoms EXCEPT:
A) Diarrhea
B) Larval dermatitis
C) Macrocytic anemia
D) Microcytic anemia

Accepted Answer

Macrocytic anemia does not occur because this disease is caused by a vitamin B₁₂ deficiency. Hookworm infection is a cause of microcytic anemia, which may result from reduced plasma iron levels due to red blood cell loss; heavy worm burdens may result in 100 ml of blood loss per day.

Question 5

The nematode egg that appears as a barrel-shaped structure with clear polar plugs at each end of the egg belongs to:
A) Ascaris lumbricoides
B) Enterobius vermicularis
C) Strongyloides stercoralis
D) Trichuris trichiura

Accepted Answer

Trichuris trichiura eggs appear as a barrel-shaped structure with clear polar plugs at each end. See drawing and photograph.

Question 6

A slender round worm measuring 25 cm was recovered from a toilet following a child's trip to the bathroom. The specimen most likely is:
A) Ascaris lumbricoides
B) Enterobius vermicularis
C) Strongyloides stercoralis
D) Trichuris trichiura

Accepted Answer

Ascaris lumbricoides measure 22 to 35 cm in length and are often recovered in feces. The adult worm is active and may migrate up the esophagus as well. See life cycle, p. 17.

Question 7

A 7-year-old boy's CBC revealed a microcytic anemia with eosinophilia during an office visit for symptoms of diarrhea. The most likely parasite involved in the infection is:
A) Enterobius vermicularis
B) Necator americanus
C) Trichuris trichiura
D) Wuchereria bancrofti

Accepted Answer

Necator spp. often causes iron-deficient anemia. Diarrhea and eosinophilia are common symptoms.

Question 8

Which of the following infections is not diagnosed by finding eggs or lava in fecal specimens?
A) Ascaris lumbricoides
B) Necator spp.
C) Trichinella spiralis
D) Trichuris trichiura

Accepted Answer

Trichinella spiralis larvae are ingested in undercooked meat. Freed larvae invade muscle tissue and encyst. Diagnosis is based on finding encysted larvae in biopsied muscle.

Question 9

Which of the following parasitic diseases is a zoonosis?
A) Ascaris lumbricoides
B) Dracunculus medinensis
C) Strongyloides stercoralis
D) Trichinella spiralis

Accepted Answer

Trichinella spiralis infection is a zoonosis. See life cycle, p. 23; the normal hosts include carnivorous mammals.

Question 10

Cutaneous larvamigrans is caused by:
A) Ascaris lumbricoides
B) Necator americanus
C) Strongyloides stercoralis
D) Toxocara canis

Accepted Answer

Free-living filariform larvae of Necator spp. may invade broken skin. See life cycle, p. 19.

Question 11

The nematode parasite that may complete its life cycle without leaving the host is:
A) Ascaris lumbricoides
B) Necator americanus
C) Strongyloides stercoralis
D) Toxocara canis

Accepted Answer

Strongyloides stercoralis is parthenogenic; therefore, fertile eggs hatch inside the host and may become infective without leaving the host.

Question 12

All of the following have life cycles that require larval lung migrations EXCEPT:
A) Ascaris lumbricoides
B) Necator americanus
C) Strongyloides stercoralis
D) Trichuris trichiura

Accepted Answer

Trichuris trichiura eggs are swallowed and hatch to become mature adults in the intestine. All of the parasites mentioned in choices A through C have migrations through the lungs in order to complete the life cycle. See individual life cycle diagrams; A=p. 17, B=p. 19, C=p. 21, D=p. 15.

Question 13

The diagnostic form recovered in feces in Strongyloides stercoralis infections is the:
A) Adult worm
B) Egg
C) Filariform larva
D) Rhabditiform larva

Accepted Answer

Eggs released by the adult worm hatch in the intestinal mucosa, releasing immature rhabditiform larvae.

Question 14

A soldier returning from Iraq noticed a blister above his ankle that subsequently opened while he was swimming in his family pool. On further examination, he noticed a worm in the open blister. The possible parasite in this lesion is:
A) Ancylostoma duodenale
B) Dracunculus medinensis
C) Toxocara canis
D) Visceral larva migrans

Accepted Answer

The soldier was returning from an endemic area for D. medinensis. This parasite produces a blister that ruptures in water, so larvae may be released.

Question 15

All of the following infections are diagnosed by finding microfilaria in blood EXCEPT:
A) Wuchereria bancrofti
B) Onchocerca volvulus
C) Loa loa
D) Brugia malayi

Accepted Answer

Microfilaria of Onchocerca volvulus are found in the dermis, with adults residing in subcutaneous nodules.

Question 16

A microfilaria recovered in a blood sample from a patient from Vietnam had two nuclei at the tip of the tail. The worm was enclosed in a sheath. This parasite is:
A) Brugia malayi
B) Loa loa
C) Onchocerca volvulus
D) Wuchereria bancrofti

Accepted Answer

Microfilariae are identified by examining their morphologic features. The presence or absence of structures such as sheaths and nuclei in the posterior end of the parasite are characteristics used to identify microfilaria. Brugia malayi may be identified when two nuclei are found at the tip of the parasite's tail that is enclosed in a sheath.

Question 17

An immigrant from central Africa is exhibiting transient subcutaneous swelling in the arm. A blood smear revealed a sheathed microfilaria with a single row of nuclei present in the posterior of the parasite. The most likely identification is:
A) Brugia malayi
B) Loa loa
C) Onchocerca volvulus
D) Wuchereria bancrofti

Accepted Answer

Microfilariae are identified by examining their morphologic features. The presence or absence of structures such as sheaths and nuclei in the posterior end of the parasite are characteristics used to identify microfilaria. Loa loa is identified when a sheathed organism with a single row of nuclei extending to the tip of the tail of the parasite is observed.

Question 18

The diagnosis of Enterobius vermicularis infection is accomplished by observing:
A) Eggs in feces
B) Eggs recovered from the perianal region
C) Larva in feces
D) Trophozoites in feces

Accepted Answer

The female worm leaves the anus and dies, releasing eggs into the perianal region.

Question 19

The rhabditiform larva of Strongyloides stercoralis has a:
A) Long buccal cavity
B) Sheath
C) Large genital primordium
D) Notched tail

Accepted Answer

Strongyloides stercoralis larvae can be identified when a large genital primordium is noted. A short buccal cavity is also noted. The parasite's eggs hatch in the intestinal mucosa of the host. Larvae are noted in fecal specimens.

Question 20

Closed fecal sanitation systems had directly led to the reduction of all of the following nematode infections EXCEPT:
A) Ascariasis
B) Hookworm disease
C) Strongyloidiasis
D) Trichinosis

Accepted Answer

Trichinosis is acquired by eating infected pork. The other parasitic infections have fecal-oral components in the life cycle. Sanitary systems reduce human exposure to contaminated feces.

Quiz 1: Introduction and Nematoda

A clinical sign that may suggest the presence of a filarial nematode infection is:

The nematode infection that may become more severe through ingestion of infective eggs, especially in infected infants, is:

In the Ascaris lumbricoides life cycle, after eggs are ingested, the next stage in the life cycle that must occur before a mature adult can live in the host's intestine is called the:

Patients who have heavy infections with Necator americanus may exhibit all of the following symptoms EXCEPT:

The nematode egg that appears as a barrel-shaped structure with clear polar plugs at each end of the egg belongs to:

A slender round worm measuring 25 cm was recovered from a toilet following a child's trip to the bathroom. The specimen most likely is:

A 7-year-old boy's CBC revealed a microcytic anemia with eosinophilia during an office visit for symptoms of diarrhea. The most likely parasite involved in the infection is:

Which of the following infections is not diagnosed by finding eggs or lava in fecal specimens?

Which of the following parasitic diseases is a zoonosis?

Cutaneous larvamigrans is caused by:

The nematode parasite that may complete its life cycle without leaving the host is:

All of the following have life cycles that require larval lung migrations EXCEPT:

The diagnostic form recovered in feces in Strongyloides stercoralis infections is the:

A soldier returning from Iraq noticed a blister above his ankle that subsequently opened while he was swimming in his family pool. On further examination, he noticed a worm in the open blister. The possible parasite in this lesion is:

All of the following infections are diagnosed by finding microfilaria in blood EXCEPT:

A microfilaria recovered in a blood sample from a patient from Vietnam had two nuclei at the tip of the tail. The worm was enclosed in a sheath. This parasite is:

An immigrant from central Africa is exhibiting transient subcutaneous swelling in the arm. A blood smear revealed a sheathed microfilaria with a single row of nuclei present in the posterior of the parasite. The most likely identification is:

The diagnosis of Enterobius vermicularis infection is accomplished by observing:

The rhabditiform larva of Strongyloides stercoralis has a:

Closed fecal sanitation systems had directly led to the reduction of all of the following nematode infections EXCEPT: