Coccidian Parasites Multiple Choice Question & Answers

Question 1. Which of the following is true regarding the transmission of Toxoplasma?

1. Vertical
2. Ingestion of uncooked cyst
3. Organ transplantation
4. All of the above

Answer. (4) (All of the above)

T. gondii is unique among the protozoa as all three morphological forms can transmit the infection.

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Question 2. Sabin Feldman dye test used for:

1. Leishmaniasis
2. Malaria
3. Toxoplasmosis
4. Trypanosomiasis

Answer. (3) (Toxoplasmosis)

• Sabin Feldman dye test is the gold standard serological test for toxoplasmosis.

Question 3. Oocyst and pseudocyst of toxoplasmosis is seen in:

1. Cat, human
2. Human, cat
3. Stool, tissue
4. Tissue, stool

Answer. (1) (Cat, human)

• Oocyst seen in cats and pseudocyst seen in humans were.
• Oocyst is the sexual form of T. gondii found in cats and other felines.
• They are released in the cat’s feces, which are unsporulated & noninfective, and later undergo maturation in the humid environment.
• Infected human host cells become distended by the proliferating tachyzoites and appear as pseudocysts.

Question 4. The Triad of congenital toxoplasmosis is all except:

1. Intracranial calcification
2. Hydrocephalus
3. Chorioretinitis
4. Convulsion

Answer. (4) (Convulsion)

The characteristic triad of manifestations seen in congenital toxoplasmosis include chorioretinitis, hydrocephalus, and cerebral calcifications.

Question 5. An immunosuppressed patient is presented with features of encephalopathy. Blood smear examination reveals the image given below. Indentify the parasite?

1. Toxoplasma
2. Sarcocystis
3. Plasmodium
4. Trypanosoma

Answer. (1) (Toxoplasma)

• Clue for diagnosis:
• Immunosuppressed patient, features of encephalopathy.
• A blood smear shows coma shaped tachyzoites.

Question 6. All are true about Toxoplasma infection except:

1. This may occur due to the ingestion of oocyst from cat’s feces
2. May spread by organ transplantation
3. Toxoplasmosis is usually symptomatic in an immunocompetent person
4. Infection is severe and progressive in immunocompromised host
5. Human infection is a dead end for parasite

Answer. (3) (Toxoplasmosis is usually symptomatic in immunocompetent person)

Question 7. A pregnant lady presented with cervical lymphadenopathy. She was prescribed Spiramycin but was non-compliant. The baby has intracerebral calcification. What is the most probable diagnosis:

1. Toxoplasma
2. Cytomegalovirus
3. Cryptococcus
4. Rubella

Answer. (1) (Toxoplasma)

• Lymphadenopathy is the classical clinical sign of Toxoplasmosis and deep cervical lymph node are most commonly affected.
• When pregnant lady was noncompliant, i.e. did not take spiramycin properly (which is the DOC of toxoplasmosis in pregnancy), the baby has developed congenital toxoplasmosis with intracerebral calcification.

Question 8. True about Toxoplasma gondii:

1. Direct spread by blood/urine is main mode of transmission
2. Cerebellum is MC site of brain involvement
3. Isolation of parasite from blood is very easy
4. Laboratory test are useful for making diagnosis
5. Infection is severe and progressive in immunocompromised host

Answer. (4, 5) (Laboratory test are useful for making diagnosis, Infection is severe and progressive in immunocompromised host)

• Option a: The principal route of human toxoplasma infection is by the oral route by ingestion of either sporulated oocysts from contaminated soil, food, or water or bradyzoites from undercooked meat. Other Route-Transmission Via Blood or Organs and Transplacental Transmission……Harrison 18/e p1723
• Option b: Although lesions can occur anywhere in the CNS, the areas most often involved appear to be the brainstem, basal ganglia, pituitary gland, and
  corticomedullary junction.
• Option c: Although difficult and available only at specialized laboratories, the isolation of T. gondii from blood or other body fluids can be accomplished ……….
• Option d: Serological procedures have great diagnostic value and has become the routine method of diagnosis.
• Option e: Immunocompromised patients are at the greatest risk for acute toxoplasmosis

Question 9. Cat acts as reservoir is which of the following?

1. Toxoplasma gondii
2. Rabies
3. Streptocerca infection
4. Plague

Answer. (1) (Toxoplasma gondii)

• The life cycle of Toxoplasma gondii involves two hosts:
• Definitive hosts are cat and other felines; where the sexual cycle takes place.
• Intermediate hosts are man and other mammals (goat, sheep, pigs, cattle, and certain birds); where the asexual cycle takes place.

Question 10. Toxoplasmosis in the fetus can be best confirmed by:

1. IgM antibodies against Toxoplasma in the mother
2. IgM antibodies against Toxoplasma in the fetus
3. IgG antibodies against Toxoplasma in the mother
4. IgG antibodies against Toxoplasma in the fetus

Answer. (2) (IgM antibodies against Toxoplasma in the fetus)

Question 11. Congenital toxoplasmosis false is:

1. IgA is better than IgM in detention
2. Diagnosed by detection of IgM in cord blood
3. The dye test is the gold standard and it detects IgG
4. An avidity test must be done to differentiate IgA and IgM

Answer. (4) (Avidity test must be done to differentiate IgA and IgM)

• An avidity test is done for IgG to differentiate between recent and past infections. Avidity low indicates recent infection, Avidity strong- indicates past infection
• Test to differentiate recent and past infections:
• IgG Avidity test: Avidity low- indicates recent infection, Avidity strong- indicates past infection
• IgM detection by ELISA or IFA: Indicates recent infection
• Detection of Toxoplasma antigen or genes.

Question 12. Postrenal transplant patient presents with diarrhea after 3 months; it was showing spherical organism measuring 2—6 mm and Kinyoun stain positive.

1. Most likely it is caused by:
2. Balantidium coli
3. Clostridium difficile
4. Cystoisospora belli
5. Cryptosporidium hominis

Answer. (4) (Cryptosporidium hominis)

• Diarrhea in a post-transplant patient, stool examination shows 2–6 µm, round, acid-fast (Kinyoun) stain positive is suggestive of oocyst of Cryptosporidium hominis.
• The oocyst of Cystoisospora belli is also acid-fast (Kinyoun) stain positive, but it is oval-shaped and larger in size (20–30 µm) and, therefore can be ruled out.

Question 13. A known HIV patient on anti-retroviral therapy presented with diarrhea of six months duration. Stool microscopy was done in which 10–30 µm cysts were seen, Kinyoun stain was positive. What is the most likely diagnosis?

1. Cystoisospora
2. Cryptosporidium
3. Balantidium coli
4. Strongyloides

Answer. (1) (Cystoisospora)

• 10–30 µm oval oocysts which is acid-fast (Kinyoun) stain positive- suggestive of Cystoisospora (old name-Isospora)
• Cystoisospora can cause diarrhea in HIV-positive patients.

Question 14. A patient with HIV is presented with diarrheStool examination revealed a round acid fast cyst with 8–12 µmdiameter, The diagnosis is:

1. Cryptosporidium
2. Cyclospora
3. Cystoisospora

Answer. (2) (Cyclospora)

• Cyclospora oocysts are around 8–12 µm, Cryptosporidium oocysts are around 4–6 µm,
• Isospora oocysts are oval, 23–36 µm. All are acid-fast.

Question 15. A patient has diarrhea for 3 days. Acid-fast stained smears made from stool samples as given in the picture. Identify the pathogen.

1. Cyclospora
2. Cystoisospora
3. Cryptosporidium
4. Cryptococcus

Answer. (2) (Cystoisospora)

• Clue for diagnosis- Acid-fast stained of stool sample shows oval oocysts of Cystoisospora of 20–30 µm size.

Question 16. About Cryptosporidium. All are true except:

1. Shape round
2. Size (4–6 μm)
3. Causes cholangitis
4. Having two sporozoites

Answer. (4) (Having two sporozoites)

• Cryptosporidium parvum is round, 4–6 μm in size, having four sporozoites inside.
• Reversible sclerosing cholangitis secondary to cryptosporidiosis in a renal transplant patient.

Question 17. A patient was given a drug to inhibit the oxidase-reductase system. What infestation was he having?

1. Beef tapeworm
2. Whipworm
3. Cryptosporidium
4. Roundworm

Answer. (3) (Cryptosporidium)

Drug to inhibit oxidase-reductase system: Suggestive of Nitazoxanide and this drug is usually indicated in Cryptosporidium parvum infections.

Question 18. True about cryptosporidium are all except:

1. Oocyst chorine resistant
2. Acid-fast oocyst
3. Oocyst > 100 micrometers
4. Enzyme immune assay done

Answer. (3) (Oocyst > 100 micrometers)

• Oocyst – round, 4–6 µm size, contains four sporozoites
• Oocysts of Cryptosporidium are resistant to many disinfectants including chlorine
• Oocysts are acid-fast to 1% sulfuric acid or acid alcohol ELISA has been developed to detect parvum-specific coproantigen from stool, and shows a sensitivity ranging from 66% to 100% with excellent specificity.

Question 19. Which of the following is not a coccidian?

1. Cystoisospora
2. Cyclospora
3. Cryptosporidia
4. Enterocytozoon

Answer. (4) (Enterocytozoon)

• Coccidian parasites include: Toxoplasma, Cryptosporidium, Cyclospora, and Isospora
• Enterocytozoon belongs to the phylum Microspora.

Question 20. Cryptosporidium cyst identified by which stain in a stool sample?

1. PAS
2. H and E
3. Giemsa
4. Acid-fast stain

Answer. (4) (Acid fast stain)

• Acid-fast staining: The oocysts of parvum are acid-fast to 1% sulfuric acid or acid alcohol and appear as round, 4–6 µm red color oocysts against a blue background.
• The sensitivity of acid-fast staining is low and it requires a minimum concentration of > 50,000 oocysts/mL of stool.
• Direct Fluorescent Antibody staining is done to detect parvum oocyst by using fluorescent-labeled monoclonal antibodies directed against cyst wall antigens.
• This is more sensitive (10 times) and specific than acid-fast staining. It is also useful to detect oocysts from water and other environmental samples.
• Currently, this method is considered the gold standard test for cryptosporidiosis.

Question 21. A 25-year-old male presented with diarrhea for 6 months. On examination, the causative agent was found to be acid-fast with 12 micrometer diameter. The most likely agent is:

1. Cryptosporidium
2. Cystoisospora
3. Cyclospora
4. Giardia

Answer. (3) (Cyclospora)

• All the parasitic agents provided in the options above can cause chronic diarrhea
• Among which Cysts of Giardia: Nonacid fast
• Acid-fast oocyst with 12 µm in size: Suggestive of Cyclospora (8–12 µm)
• Isospora (23–36 µm) or Cyclospora (4–6 µm) are also acid-fast but of different sizes.

Question 22. Which of the following is/are true with microsporidia?

• It is fungus
• It is a protozoa
• It is a bacteria
• It is associated with diarrhea in HIV

Answer. (1, 4) (It is a fungus, It is associated with diarrhea in HIV)

• Microsporidium is a recently been classified under Fungi.
• It mostly causes infection in severely immunocompromised patients with AIDS (diarrhea).
• Microsporidium is characterized by a unicellular spore containing a coiled spring-like tubular polar filament through which the sporoplasm is forcibly discharged into a host cell.