SDSU GENERAL PARASITOLGY: 467
LECTURE EXAM #2: MARCH 13, 2008
NAME: ____________________
For questions 1-25, choose the best answer; if all of the answers are correct, you must choose that option.
1. Identify the drug that is commonly used to kill hypnozoites (pre-erythrocytic schizonts) of malaria.
a. quinine
b. chloroquin
c. primaquin
d. DDT
e. pyrethrin
2. Which group of listed protozoans utilizes sexual reproduction during their life-cycle?
a. mastigophorans
b. sarcodines
c. sporozoans
d. ciliates
e. all can utilize sexual reproduction during a portion of their life-cycles
3. Secondary amebic abscesses are most commonly associated with which organ?
a. large intestine
b. lung
c. central nervous system
d. liver
e. cardiac muscle
4. Identify the least likely protozoans to be found in males living in South Dakota:
a. Toxoplasma gondi
b. Giardia intestinalis
c. Entamoeba coli
d. Leishmania tropica
e. Trichomonas vaginalis
5. The kinetoplast was primarily filled with what material,
a. proteins
b. carbohydrates
c. nucleic acids
d. lipids
e. whipped cream
For questions 6-8, consult the paragraphs below.
The surface coats of African trypanosomes contain variable surface glycoproteins (VSGs). When these trypanosomes are ingested by its vector, they lose their VSGs and transform to the metacyclic form, which possesses a different surface coat. When the fly bites the next victim, it injects the metacyclic form. This form changes rapidly to a proliferative form that first invades the host’s blood and lymph, and later the central nervous system.
The host’s antibodies kill about 99% of the proliferative typanosomes in the original infection; however, the remainder activates a different VSG gene and produce VSGs that the host antibodies do not recognize. The surviving trypanosomes proliferate, and when the host produces antibodies against their surface coats, the cycle repeats itself until the host eventually dies.
Although a single trypanosome expresses only 1 VSG at a time, it may possess anywhere from several hundred to 1,000 genes capable of coding for different VSGs. Expression of a VSG gene occurs only if it is located toward the end of a chromosome. Given the size of the population gene pool and the number of recombination events, the proliferation form can generate an almost infinite number of VSCs.
6. Based on the above passage, the most likely role of the host antibodies in the expression of new VSGs is to:
a. produce new VSGs by changing the structure of the existing VSGs.
b. stimulate the mutation of existing genes into new VSG genes.
c. directly induce the switch from one existing VSG gene to another.
d. act as a selective agent favoring the switch from one VSG gene to another.
e. serve no role.
7. It is known that the surface glycoproteins of African trypanosomes change during a trypanosome infection because:
a. the host immune system does not recognize glycoproteins as foreign molecules.
b. antibodies produced against early-stage VSGs do not react with late-stage VSGs.
c. patients often recover when the trypanosomes changes its surface coat.
d. trypanosomes infect different organs as the disease progresses.
e. they switch to the metacyclic form.
8. Development of vaccines capable of eradicating human African trypanosomiasis is unlikely because:
a. trypanosomiasis occurs in too large a geographic area to allow control by vaccination.
b. trypanosomes infect hosts of several species
c. trypanosomes are genetically capable of producing a vast array of surface antigens.
d. trypanosomes are injected in the metacyclic form, which is unaffected by vaccines.
e. these trypanosomes quickly penetrate host cells (i.e. become intracellular)
9. Identify the most common species of Plasmodium.
a. falciparum
b. vivax
c. ovale
d. malariae
e. hildreae
10. The current economic and social impact of African trypanosomiasis is:
a. negligible, because only cattle die from the disease.
b. negligible, because it is almost never fatal in humans.
c. negligible, because we have virually eliminated its vector with insecticides.
d. great, because it may spread to all regions of the world.
e. great, because it kills both humans and their cattle.
11. Which protozoan from the list below is the most deadly to the most number of humans?
a. Trypanosoma brucei
b. Plasmodium falciparum
c. Giardia lamblia
d. Toxoplasma gondi
e. Entamoeba coli
12. Identify the protozoan from the list below that can occasionally contain both a flagellum and pseudopods.
a. Toxoplasma gondi
b. Giardia intestinalis
c. Naegleria fowleri
d. Trypanosoma cruzi
e. Trichomonas vaginalis
13. Leishmania amastigotes evade the mammalian immune system by .......
a. becoming intracellular
b. penetrating into privileged sites in the body
c. the process of antigenic variation
d. masking with host antigens
e. causing polyclonal stimulation
14. Entamoeba hartmanni is most closely related to which species from the list below?
a. Endolimax nana
b. Iodamoeba buetschlii
c. Entamoeba histolytica
d. Entamoeba coli
e. Entamoeba gingivalis
15. The definitive host for Plasmodium vivax is a .....(where syngamy occurs)
a. human
b. penguins
c. Culex mosquitoes
d. Anopheles mosquitoes
e. Aedes mosquitoes
16. How do Giardia trophozoites adhere to the intestinal mucosa of their host
a. hooks
b. glue
c. velcro
d. adhesive tape
e. suction
17. Identify the false statement regarding Trichomonas vaginalis.
a. Trichomonas vaginalis is transmitted via sexual intercourse.
b. Trichomonas vaginalis has been associated with an increased risk for cervical cancer.
c. Trichomonas vaginalis is more commonly present in men than in women.
d. Trichomonas vaginalis trophozoites contain a skeletal-like structure knows as an axostyle
e. Some women can serve as asymptomatic carriers of Trichomonas vaginalis
18. Sporulated Isospora oocysts contain ......
a. 2 sporocysts - 2 sporozoites
b. 4 sporocysts - 2 sporozoites
c. 2 sporocysts - 4 sporozoites
d. 4 sporocysts - 4 sporozoites
e. 2 sporocysts - variable number of sporozoites
19. If you were to develop a vaccine to prevent the initial stage of the malaria parasite from reaching the liver cells, which developmental stage would you target?
a. gametocytes
b. trypomastigotes
c. sporozoites
d. merozoites
e. epimastigotes
20. A stage that is resistant to most chemical treatments is produced by all of the following parasites, except ...........
a. Cryptosporidium parvum
b. Trichomonas vaginalis
c. Giardia lamblia
d. Entamoeba histolytica
e. Isospora belli
21. Identify the true statement regarding Trichonympha sp.
a. Trichonympha is an intestinal-dwelling protozoan
b. This protozoan is covered by a large number of cilia.
c. Trichonympha is a facultative parasite
d. This protozoan undergoes sexual reproduction
e. All are true statements
22. Sporozoans can be characterized by all of the following, except:
a. reproduces via conjugation
b. adult stage contains no organelles of motility
c. form a "spore-like" stage (termed an oocyst)
d. generally utilizes schizogony in its life-cycle
e. entirely parasitic
23. Which parasite transmittal stage from the list below is not immediately infectious when consumed orally in fully-formed feces?
a. Isospora belli oocysts
b. Iodamoeba buetschlii cysts
c. Giardia intestinalis cysts
d. Cryptosporidium parvum oocsts
e. Entamoeba histolytica cysts
24. Small numbers of Toxoplasma gondii cysts can cause problems even in immunocompetent (normal) individuals when located in which location in the body?
a. brain
b. skeletal muscle
c. liver
d. retina
e. spleen
25. After developing blurred vision, you visit your optometrist (eye doctor) who explains that you are suffering from severe keratitis (disease of the outer covering of skin surrounding the cornea) caused by some kind of protozoan. Which parasite from the list below would most likely be responsible for this condition?
b. Entamoeba corneae
a. Leishmania tropica
c. Naegleria fowleri
d. Acanthamoeba polyphagia
e. Entamoeba histolytica
SDSU GENERAL PARASITOLGY: 467
LECTURE EXAM #2: MARCH 13, 2008
MATCHING PORTION
NAME: ____________________
26. Match the protozoan with the best method for diagnosing the infectious agent in humans. The "best" method includes factors such as reliability, sensitivity, specificity, availability and cost. Answers can be used more than once or not at all. In some cases, I will be accepting more than one answer. You can provide a short justification for your choice if you really feel that you need to (on the back of this sheet). [48 points]
Infectious Agent
____ Acanthamoeba spp.
____ Cyclospora spp.
____ Cryptosporidium parvum
____ Entamoeba coli
____ Entamoeba gingivalis
____ Entamoeba histolytica (intestinal stage)
____ Entamoeba histolytica (abscess stage)
____ Giardia intestinalis
____ Iodamoeba buetschlii
____ Isospora belli
____ Leishmania donovani
____ Leishmania tropica
____ Naegleria fowleri
____ Plasmodium falciparum
____ Plasmodium vivax
____ Sarcocystis hominis (humans are definitive host)
____ Toxoplasma gondi
____ Trichomonas hominis
____ Trichomonas tenax
____ Trichomonas vaginalis
____ Trypansoma cruzi (acute stage)
____ Trypansoma cruzi (chronic stage)
____ Trypanosoma brucei (acute stage)
____ Trypanosoma brucei (chronic stage)
Methods for Diagnosis
A. fecal antigen ELISA
B. routine blood smear
C. routine fecal floatation or sedimentation method
D. serological antibody ELISA
E. stained vaginal smear
F. stained fecal smear
G. stained skin scraping
H. tissue biopsy as either a smear or section
I. wet mount of spinal tap
J. wet mount of gum scrap
K. xenodiagnosis
ESSAY PORTION
27. Who would you credit with making the biggest contribution to "breaking" the malaria life-cycle (Ronald Ross, Louis Laveran or Patrick Mason) and why. (all 3 could be correct if it is substantiated well, none are correct if it is not; 10 points)
SDSU GENERAL PARASITOLGY: 467
LECTURE EXAM #2: MARCH 13, 2008
ESSAY PORTION
NAME: _______________________
28. A 21-year-old male heterosexual leukemia patient completed radiation therapy three week prior to celebrating 4 days in Cancun, Mexico on “spring break”. Upon his return, he developed severe diarrhea that has already lasted 9 days. While in Mexico, he consumed a wide variety of local food and drink, including tap water. List four potential enteric protozoans (Genus only) that might be responsible for this condition. [12 points]
List the four potential protozoans: a. _______________________________
b. _______________________________
c. _______________________________
d. _______________________________
29. Why is Trypanosoma lewisi not generally lethal to rats, while Trypanosoma brucei is often lethal to cattle? (8 points)
30. Describe three situations when Toxoplasma gondii can cause serious problems. [10 points]
1. _________________________________________________________________________
2. _________________________________________________________________________
3. _________________________________________________________________________
31. As the manager of a water treatment facility in a small town along the Big Sioux River, last year you suffered through a major Cryptosporidium outbreak in your community that resulted from a failure in your water filtration system. This outbreak involved three quarters of the town’s population (i.e. those potential individuals drinking water). Last month, you discovered another major failure in the water filtration system resulting in the contamination of drinking water with Cryptosporidium oocysts at levels three times that of the previous outbreak. However, you are surprised to find out today that the case numbers of cryptosporidiosis in town are well below that of the previous outbreak after a similar period of time. Describe why this latest failure generated only a few cases of cryptosporidiosis [7 points].