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Parasitology Exam (HELMINTHS)   ***Reminder: Slide s and ex amina tion questions questions are copyrighted and cannot be copied for publication.   1. The incorrect match betwe en organism and the appropriate diagnostic procedure i s:   a. Onchocerca volvulus volvulus  - examination of skin snips   b. Cryptosporidium Cryptosporidium  - modified acid fast stain   c. Echinococcus granulosus granulosus - routine ova and parasite examination   d. Schistosoma haematobium --- examination of urine sediment   ANSWER (c): The appropria te procedure for the diagnosis of Echinococcus granulosus (hydatid disease) would involve the microscopic examination of hydatid fluid aspirated from a cyst. cyst. Imma ture s scolices colices and/or hooklets would be found in the centrifuged fluid sediment and could be identified under the microscope.   2. Charcot-Leyden Charcot-Leyden crys crystals tals in stool may be associated associated with an immune rrespons esponse e and are thought to be the breakdown products of:   a. neutrophils   b. eosinophils   c. mono monocytes cytes   d. lymphocytes   ANSWER (b): Whe n eosinophils disintegrate disintegrate , the granule s rreform eform into Charcot-Leyden crystals. Eos crystals. Eosinophils inophils are more likel y tto o be present in patients with helmi nth infections (rather than protozoa).   3. Morphological characterist characteristics ics of the rhabditiform (non-infective) larvae of  Strongyloides stercoralis are: stercoralis are:   a. a short buccal capsule and large genital primordium   b. a long buccal capsule and pointed tail   c. a short buccal capsule and small gen genital ital primordium primordium   d. a small genital primordium and notch in tail   ANSWER (a): The rhabditiform larvae of Strongyloides stercoralis are stercoralis are characterized by the short buccal capsule (mouth) and large genital primordium; these hookworm larvae have a long buccal capsule and very small genital primordium. 4.

Visceral Visceral and ocular larva migrans are ass associated ociated with which of the followi ng organisms and diagnostic test?

a. Toxocara - serology   b. Onchocerca - skin snips   c. Dracunculus - skin biopsy   d.  Angiostrongylu  Angiostron gylus s - CSF examination   ANSWER (a): Toxocara Toxocara sp  spp. p. cause cause visceral and/or ocula r larva migra ns, ns, which occurs whe n humans accidental ly ingest ingest the infective eggs of the dog or cat ascarid. ascarid. The larvae migrate through the deep tissues, including the eye; and the appropriate test of  choice is the serology.   5. The followi ng organisms are linked with specific, rele vant information. The incorrect combination is: is:   a. Strongyloides stercoralis stercoralis  - internal autoinfection b. Echinococcus granulosus granulosus  - hydatid disease c. Taenia solium – solium – human can serve as definitive and intermediate hosts   d. Schistosoma mansoni  mansoni    - common within the United States   ANSWER (d): Schistosoma mansoni   is a blood fluke that is pathogenic for humans; these thes e particula r worms reside in the veins over the large inte stine. The egg has a v very ery large la teral spine; eggs can be recovered from the stool stool in infected infected patients. The infection is not endemic w ithin tthe he United States. States. However, the e ggs may be seen in proficiency test testing ing specimens. So, a lthough it is not common, labora tories mus mustt s still till be able to identify these organisms.

 

  6.

Examina tion of a 24 hour unpreserved urine specime n is sometime s helpful in the recovery of:

  a. b. c. d.

Trichomonas vaginalis trophozoites vaginalis  trophozoites Schistosoma haematobium haematobium eggs  eggs Enterobius vermicularis eggs vermicularis  eggs Strongyloides stercoralis larvae stercoralis  larvae

        ANSWER (b): Schistosoma haematobium  haematobium  blood flukes reside in the veins over the bladde r. Whe n the eggs are pass passed ed from the body, they are often found in urine; egg viability can also be determined.   7. The exa mination of sputum and stool may be necessary necessary to diagnose infection with:   a. Paragonimus westermani    b. Trichinella spiralis   c. Wuchereria Wucherer ia bancrofti    d. Fasciola hepatica   ANSWER (a): Paragonimus westermani   adult worms are found in the lung and eggs may be coughed up in the s sputum. putum. Cons Conseque eque ntly, both s sputum putum and/or stool stool (if the sputum containing the eggs is swallowed) are the recommended specimens for  examination for the eggs.   8. Two helmi nth eggs that may resemble one another are:   a. Diphyllobothrium latum and latum and Paragonimus westermani    b. Opisthorchis Opisthor chis sinensis sinensis and  and Fasciol Fasciolop opsis sis busk i    c. Taenia saginata and saginata and Hymenolepis nana   d.  Ascaris lumb ricoides ricoides and  and Trichostrongylus   ANSWER (a): Both Diphyllobothrium latum  latum  and Paragonimus westermani   eggs are operculated and approx imate ly the s same ame size. The morphology is simila r, in spite spite of  the fact that D. latum  latum  has a knob at the abopercular end and P. westermani   has a thickened abopercular end and shoulders into which the operculum fits.   9. Eating poorly cooked pork can lea d to an infection with:   a. Taenia solium and solium and Trichinella spiralis   b. Taenia saginata and saginata and Hymenolepis nana   c.  c.   Trichuris trichiura and and Hymenolepis  Hymenolepis diminuta  diminuta   d. Diphyllobothrium latum and latum and Ascaris  Ascaris lumbricoides l umbricoides   ANSWER (a): Both Taenia solium  solium  (pork tapeworm) and Trichinella spiralis  spiralis  can be acquired from the ingestion of raw or poorly cooked infective pork.   10. An operculated cestode cestode egg that can be recovered in human feces is is::   a. Clonorchis Clon orchis sinensis   b. Diphyllobothrium latum   c. Paragonimus westermani    d. Dipylidium caninum   ANSWER (b):  (b):  Diphyllobothrium latum latum is  is the only operculate d ces cestode tode egg that is found in humans; the infection is acquired from the ingestion of raw fresh water fish.   11. The adult tapew orm of Echinococcus granulosus is granulosus is found in the intestine intestine of:   a. Humans   b. Sheep   c. Dogs   d. Cattle   ANSWER (c): While the hydatid cysts are found in sheep or in humans (accidental intermediate host), the adult tapeworms of Echinococcus granulosus  granulosus  are found in the intestine of the dog.   12.          

In infections with Taenia solium, solium, man can serve as the: a. b. c. d.

definitive host intermediate host definitive and/or the intermediate host none of the above above

 

ANSWER (c): If humans inge st Taenia solium cysticerci solium cysticerci in uncooked or rare pork, the adult tapeworm will mature within the intestine (human will serve as definitive host); if  eggs from the adult tapeworm are ingested, then the cysticerci will develop in human tissues (accidental intermediate host), causing cysticercosis. 13.  

Humans acquire infections with Diphyllobothrium latum adult latum adult worms by:

a. ingestion of fresh water crabs   b. sk skin in penetration of cercariae   c. ingestion of water chest nuts   d. ingestion of infected raw fresh water fish   ANSWER (d): The inge stion of raw fresh wa ter fish containi containi ng the encysted encysted larvae of  Diphyllobothrium latum will latum will result result in the development of an adult tapew orm within the human intestine.   14. Humans can serve as both the intermedi ate and definitive host host in infections caused by:   a. Enterobius vermicularis   b Hymenolepis Hymenolep is nana   c. Schistosoma japonicum japonicum   d.  Ascaris lumb ricoides   ANSWER (b): Hymenolepis nana is nana is one of the tapeworms where humans serve as both interme diate and definitive hosts hosts.. Whe n ingest ingested, ed, the oncosphere oncosphere penetrate s the intestinal mucosa, develops into the mature cysticercoid (human is intermediate host), and returns to the gut where the adult tapeworm matures (human is definitive host).   15. Organisms (and infections) infections) that under normal conditions could not be transmitted in the laboratory are:   a. Hymenolepis Hymenolep is nana nana –  – dwarf tapeworm disease   b. Taenia solium solium - cy sticercosis   c.  Ascaris lumb ricoides ricoides  - ascariasis   d. Enterobius vermicularis vermicularis  - pinworm infection   ANSWER (c):  Asc  Ascaris aris lumbricoides  lumbricoides  eggs require a period of development in the soil before they are i nfective for humans. humans. The othe r organis organisms ms listed listed could be transmitted transmitted within the laboratory or in the hospital setting.   16.  

Which microfilaria e are us usually ually not found circulating in the periphe ral blood?

a. Brugia malayi    b.  b.  Loa loa   c. Wuchereria Wucherer ia bancrofti    d. Onchocerca volvulus   ANSWER (d): The microfilariae of Onchocerca volvulus volvulus   are normally found in the fluid right under the outer la yer of skin. skin. Therefore, the sk skin in snip is the proper specimen to examine.   17. The miracidia l hatching test test helps to demonstrate the viabili ty of:   a. eggs of Taenia Taenia species.  species.   b. eggs of Schistosoma Schistosoma species.  species.   c. eggs of hookworm species .   d. eggs of Opisthorchis Opisthorchis..   ANSWER (b): The determ ination of egg viability is important in s schis chistos tosomia omia sis is;; therefore, the miracidial hatching test would be helpful in demonstrating the egg viability of Schistosoma Schistosoma   species. species. Once the the eggs we re ha tched, the living miracidium larvae would be visible visible in the w ater.   18. The incorrect match betwe en organism and characteristic is is::   a. Fasciola hepatica and hepatica and liver infection   b. Trichuris t richiura and eggs with polar plugs   c. Echinococcus granulosus granulosus and  and daughter cysts   d. Schistosoma mansoni and egg with terminal spine   ANSWER (d): The egg of Schistosoma mansoni   is characterized by having a large lateral spine; S. haematobium has haematobium has the characteristic terminal spine.   19. An immunosuppress immunosuppressed mal e had severa l episodes of pneumonia , intestinal intestinal

 

pain, and sepsis with Gram negative rods, and a history of military service in Southeast As Asia 20 years earlie r. The organism is is:: a. Fasciolop Fascio lopsis sis busk i   b. Strongyloides stercoralis  stercoralis   c. Hookworm d. Paragonimus westermani 

    ANSWER (b): A late nt infection with Strongyloides stercoralis  stercoralis  acquired years before may cause severe symptoms in the immunosuppressed patient (“autoinfective” capability of life cycle and migratory route through the body). 20.

Eos Eosinophilic inophilic meni ngoencephal itis is a form of larva migrans causing causing fever, hea dache, stiff stiff neck, and increased cells in the spinal spinal fluid. It is genera lly a mild and self-limited infection and is caused by:

 

   

a. b. c. d.

Necator americanus  americanus    Angiostrongylus  Angiostrongylu s c anton antonensis ensis    Ancylostoma braziliense Strongyloides stercoralis

ANSWER (b): Eosinophilic Eosinophilic meningoe ncephali tis is a form of larva migrans and is caused by Angiostro by Angiostrongylus ngylus cantonens cantonensis is,, the rat lungworm. This Pacific area infection is ass associated with CSF symptoms symptoms and sometimes eye involveme nt.

21.

Whe n humans have cystic cystic hydatid dis disea ea se, the causative causative age nt and host host classification are: classification

   

a. b. c. d.

Echinococcus granulosus granulosus  - accidental intermediate host. Echinococcus granulosus granulosus  - definitive host. Taenia solium solium - acc idental idental intermediate ho host. st. Taenia solium solium - definitive host.

ANSWER (a): The ca use of cys cystic tic hydati hydatid d disease is Echinococcus granulosus  granulosus  and the human is classified classified a s the accidental intermedi ate host host.. Infection occur occurs s whe n humans ingest E. granulosus eggs granulosus eggs and the hydatid cyst(s) develop in the liver and lung of the human instead of sheep (normal cycle). 22. 22. A 45 year old hunter hunter developed fever, myalgia, and periorbital periorbital edema. He has a history history of bear mea t cons consumption. umption. The most likely causative agent is:   a. Toxoplasma gondii    b. Taenia solium  solium  c. Hymenolepis Hymenolep is nana nana   d. Trichinella spiralis   ANSWER (d): Infected bea r meat is an ex celle nt source source of Trichinella spiralis. piralis. In this case, the patient had evidently consumed poorly cooked bear meat, thus ingesting the encysted larvae of T. spiralis. spiralis. 23.

This condition results from the accidental ingestion of helmi nth eggs. In this instance the human becomes the intermediate rather than the definitive host. The correct a ns nswe we r is:

   

a. b. c. d.

trichinosis cysticercosis. ascariasis. strongyloidiasis.

  ANSWER (b): The a ccidental ingestion of Taenia solium  solium  eggs can result in the disease we call cysticercos cysticercosis. is. The cys cysticerci ticerci wil l deve lop in a numbe r of different tis tiss sues, including the brain, and the human is the accidental intermediate host.   24. After returning from a 2 year stay in India, the patie nt had eosinophilia, an enla rged left sperma tic cord and bilateral inguinal lymphadenopathy. The most likely clinical specimen and organism match would be:   a. thin blood films and Leishmania spp. b. urine and concentrat concentration ion for Trichomonas vaginalis. vaginalis .  

c. d.

thin blood films and Babesia Babesia.. thick thic k blood films and microfilariae. mic rofilariae.

  ANSWER (d): Based Based on the hist history, ory, the most relevant procedure to perform woul d be the preparation and examination of thick blood films for the recovery and identification of microfilari ae . The sy symptoms mptoms suggest earl y filariasis filariasis..  

 

25.  

Which of the followi ng is true about onchocerciasis onchocerciasis? ? a. b. c. d.

The adult worm is present in the blood. The microfilariae mic rofilariae are in the blood during the late ev evening ening hours. The Th e diagnostic diagnostic test of choice is the skin snip. The parasite resides in the deep lymphatics lym phatics .

        ANSWER (c): The adult Onchocerca volvulus reside volvulus reside in subcutaneous nodules and the microfilariae are found in the fluids right under the outer layers of skin; thus the appropriate diagnostic test is the microscopic examination of skin snips for the presence of microfilariae.   26. Worldw ide, the most prevale nt helm inth to infect humans is is::   a. Enterobius vermicularis, vermicularis , the pinworm.   b.  Ascaris lumb ricoides ricoides,, the large intestinal roundworm.   c. Taenia saginata, saginata, the beef tapeworm.   d. Schistosoma mansoni  mansoni , one of the blood flukes   ANSWER (a): The pinworm, Enterobius vermicularis, vermicularis, may be the most common parasitic infection throughout the world and the eggs are infective within just a few hours.. Some ha ve s hours said aid that “You either had the infe ction as a child, have it now, or  will ha ve it again whe n you hav have e children.”   27. A helmi nth egg is described described as having termina l polar plugs plugs.. The most most likely helminth would be:   a. Hookworm   b. Trichuris trichiura  trichiura  c. Fasciola hepatica   d. Dipylidium caninum   ANSWER (b): The eggs of Trichuris trichiura (the trichiura (the whipworm) have been described as being barrel-shaped with a thick shell and two polar plugs. 28.  

Ingestion of which of the followi ng wil l result in human infection: a. b. c. d.

Egg Egg Egg Egg

of Strongyloides stercoralis of Schistosoma japonicum japonicum of Toxocara canis of Opisthorchis sinensis

        ANSWER (c): The eggs of Toxocara canis are canis are infectious for humans and cause visceral larva migrans. These ascarid ascarid e ggs of the dog can infect humans; humans; the eggs hatch and the larvae w ande r though though the deep tissues, tissues, occasionall occasionall y tthe he eye. In this case, case, the human becomes the accidental intermediate host.   29. A helmi nth egg is desc described ribed as having a thick radia lly striated shell and the shell contai ns a six-hooked embryo called the oncosphere. This egg is:   a. Hookworm   b. Schistosoma spp. Schistosoma  spp.   c. Strongyloides stercoralis   d. Taenia spp. Taenia  spp.   ANSWER (d): Taenia Taenia spp.  spp. cestode eggs have a thick radially striated shell that contains a six-hooked six-hooked e mbryo c call all ed the oncosphere. oncosphere. Although the oncosphere oncosphere can usuall usuall y be seen in eggs found in fresh or recently preserved stool, occasionally the embryo may be more difficult to see in eggs that have been stored for long periods in formalin. The radial striations can be seen more closely in the middle and right eggs.  

31.

The followi ng proglottid wa s see n in a fresh fresh stool specime n; the proglottid wa s subs ubseque eque ntly injected with India ink. Which of the followi ng is the correct

 

identification?  

a. b. c. d.

     

Taenia saginata Hymenolepis diminuta Dipylidium caninum Taenia solium

  ANSWER (a): Bas Based ed on the number of uterine branches (counted on one side side only), T. saginata   generally has around 16-18 lateral branches (more than 12), while T. solium saginata tends to to have a bout 8-10 8-10 (less than 12). It is important to remem ber to count the branches right where they come off the central stem and to count one side only.   32. A freshwa freshwa ter snail is alw ays a part of the life cycle cycle in which of the followi ng groups?   a. Cestodes   b. Trematodes Trematodes   c. Filarial worms worms   d. Intestinal nematodes   ANSWER (b): In a ll groups of trematodes, th there ere is a freshwa freshwa ter snail snail in the life cycle. cycle. These worms are represented by liver and lung flukes, intestinal flukes, and the blood flukes, all of which are trematodes.   33. In the left hand column fill in the blank preceding the name of the organism or  topic with one letter from the right hand column. Us Use e ea ch letter only onc once. e.   1. _____ Hymenolepis nana  nana  a. proglottids wider than long 2. _____ Schistosoma manson mansoni  i   egg b. 3/8" long 3. _____ Enterobius ver vermicularis micularis   adult adult c.giant intestinal fluke 4. _____ Taenia solium  solium  egg d.large lateral spine 5. _____ Trichuris t richiura egg e internal infection, hyperinfection sy syndrome ndrome 6. _____ Taenia solium  solium  proglottid f. sheathed microfilariae mic rofilariae 7. _____ Hymenolepis diminuta egg g. egg similar sim ilar to Trichuris Trichuris,, but with st riated shell 8. _____ Wuchereria Wucherer ia bancrofti   h.responsible for blood-loss anemia 9. _____ Echinococcus granulosus granulosus   i. egg with polar filaments 10._____ Fasciola hepatica  hepatica  j. daughter daughter cys ts 11. _____ Paragonimus spp spp..  k.rec k.recov overy ery of helminth eggs and larv larvae ae 12. _____  Ascaris lumbricoides l umbricoides egg l. egg with bumpy shell 13. _____ Sedimentati Sedimentation on concentrati concentration on m. sc scolex olex with four suck ers and no hooks 14. _____ Hookworm spp. n less than 12 lateral uterine branches 15. _____ Permanent stained stai ned smear o. egg with no polar filaments 16. 17. _____ _____ 18. _____ 19. _____ 20. _____  

Fasciol Fasciolop opsis sis i   Capillaria spp.busk spp .  Strongyloides stercoralis  stercoralis   Diphyllobothrium latum  latum  Taenia saginata  saginata adult

p.confirm p.conf protozoa protowith zoa polar (troph (trophozoites, ozoites, cys ts) q.oval q.ov al irm shaped plugs r.examine r.exami ne both stool and sputum for eggs s.radially striated shell containing containing oncosph oncosphere ere t.l t.live iverr fluke

ANSWER: The appropria te respons ANSWER: responses es are li sted below : 1. i 6. n 11. r 2. d 7. o 12. l 3. b 8. f 13. k 4. s 9. j 14. h 5. q 10. t 15. p 34.

16. 17. 18. 19. 20.

c g e a m

Because mature infectious eggs are ingested from the soil, which of the following parasites might be seen in the same patient at the same time?

  a. Hookworm and and Ascaris  Ascaris lumb ricoides   b.  Ascaris lumb ricoides ricoides and  and Trichuris trichiura   c. Trichuris trichiura and trichiura and Schistosoma japonicum japonicum   d. Schistosoma japonicum japonicum and  and Hookworm   ANSWER (b): The egg eggs s of both  Asc  Ascaris aris lumbricoides  lumbricoides  and Trichuris trichiura  trichiura  must mature for a period of time in the soil before they are infectious. infectious. Infection occurs whe n the human inge sts these infectious eggs from from the soil. soil. Since both ne matodes

 

are endemic in the same areas of the world, they are often seen as a mixed infection in humans who have accidentally ingested the mature eggs from contaminated soil.   35. Which of the followi ng helmi nth eggs would not float using using the zinc sulfate flotation concentration method?   a. Paragonimus spp. Paragonimus  spp. and Diphyllobothrium latum   b. Opisthorchis Opisthor chis sinensis sinensis and  and Taenia Taenia spp.  spp.   c. Fasciola hepatica and hepatica and Hymenolep Hymenolepis is nana   d. Unfe Unfertili rtilized zed Ascaris  Ascaris lumb ricoides ricoides and  and Trichuris trichiura   ANSWER (a): Us Using ing the zinc s sulfate ulfate flota tion concentration concentration method, hea vy eggs (unfertilized  A. lumbricoides lumbricoides   eggs) and operculated eggs (Paragonimus, (Paragonimus, D. latum, O. sinensis inensis,, F. hepatica hepatica)) wil l not ffloat loat using using this method. The egg opercula pop open due to the high specific gravity of the zinc sulfate, fill with zinc sulfate, and sink to the bottom of the tube. Therefore, us using ing this method, both the surface surface film and sedime nt must be examined before reporting the concentration as negative.  negative.  

REFERENCES Garcia, L.S. 2007. Diagnostic Medical Parasitology , 5th Ed., ASM Press, Washington, D.C.  

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