Parasitology MCQs
51. Surra is caused by:
A. Trypanosoma cruzi B. Trypanosoma evansi C. Trypanosoma gambiense D. Trypanosoma brucei
Correct Answer: B. Trypanosoma evansi
Explanation: Surra is a significant disease affecting horses, camels, and cattle. Unlike many other African trypanosomes, T. evansi has lost the ability to undergo a development cycle in the tsetse fly and is instead transmitted mechanically by biting flies like Tabanus.
52. Dourine is transmitted mainly by:
A. Ticks B. Mosquitoes C. Coitus D. Tsetse fly
Correct Answer: C. Coitus
Explanation: Trypanosoma equiperdum, the cause of Dourine in equines, is unique among trypanosomes because it is a venereal disease. It does not require an invertebrate vector for transmission.
53. Sleeping sickness is caused by:
A. Trypanosoma cruzi B. Trypanosoma evansi C. Trypanosoma gambiense D. Trypanosoma equiperdum
Correct Answer: C. Trypanosoma gambiense
Explanation: Human African Trypanosomiasis (Sleeping Sickness) is caused by T. brucei gambiense (West Africa) and T. brucei rhodesiense (East Africa). T. cruzi causes Chagas disease in the Americas.
54. Vector of African trypanosomiasis is:
A. Sand fly B. Mosquito C. Tsetse fly D. Tick
Correct Answer: C. Tsetse fly
Explanation: The Tsetse fly (genus Glossina) is the biological vector. The trypanosomes undergo a complex cycle of multiplication and transformation within the fly’s midgut and salivary glands.
55. Leishmania parasites are found in:
A. RBCs B. Hepatocytes C. Macrophages D. Plasma
Correct Answer: C. Macrophages
Explanation: Leishmania exists in the host as an amastigote (a non-flagellated stage) specifically within the phagolysosomes of macrophages. They are specialized to survive and multiply within the very cells meant to destroy them.
56. Vector of Leishmania is:
A. Mosquito B. Sand fly C. Tick D. Flea
Correct Answer: B. Sand fly
Explanation: Leishmaniasis is transmitted by the bite of infected female Phlebotomine sand flies. In the fly, the parasite exists in the flagellated promastigote stage.
57. Fasciola gigantica differs from F. hepatica mainly by:
A. Shape of egg B. Size and geographic distribution C. Intermediate host D. Site of infection
Correct Answer: B. Size and geographic distribution
Explanation: F. gigantica is significantly larger (up to 75mm) and is found primarily in tropical regions (Africa and Asia), whereas F. hepatica is smaller and more common in temperate climates.
58. Fasciola infection commonly causes:
A. Hematuria B. Bottle jaw C. Nervous signs D. Skin lesions
Correct Answer: B. Bottle jaw
Explanation: Chronic fascioliasis leads to hypoalbuminemia (loss of blood protein). The resulting decrease in oncotic pressure causes fluid to leak into the tissues, appearing as submandibular edema or “bottle jaw.”
59. Hydatid cyst is a larval stage of:
A. Taenia saginata B. Dipylidium caninum C. Echinococcus granulosus D. Hymenolepis nana
Correct Answer: C. Echinococcus granulosus
Explanation: The adult E. granulosus resides in the small intestine of dogs (definitive host), while the Hydatid cyst develops in the intermediate host (sheep, cattle, or humans).
60. Proglottids are parts of:
A. Nematodes B. Trematodes C. Cestodes D. Protozoa
Correct Answer: C. Cestodes
Explanation: The body of a cestode (tapeworm) consists of a chain of reproductive segments called proglottids. As they mature, they become “gravid” (filled with eggs) and detach to be passed in the feces.
61. Oxyuris equi is commonly called:
A. Lungworm B. Pinworm C. Hookworm D. Threadworm
Correct Answer: B. Pinworm
Explanation: The female Oxyuris equi migrates to the anus of the horse to deposit eggs in a sticky cement, causing intense perianal itching (pruritus ani) and “rat-tail” appearance.
62. Toxocara vitulorum mainly affects:
A. Adult cattle B. Calves C. Sheep D. Horses
Correct Answer: B. Calves
Explanation: This large roundworm primarily affects young calves. Transmission often occurs via the milk (transmammary route) shortly after birth.
63. Lungworm of sheep is:
A. Dictyocaulus filaria B. Haemonchus contortus C. Strongyloides papillosus D. Trichuris
Correct Answer: A. Dictyocaulus filaria
Explanation: D. filaria is the most important lungworm in sheep. It has a direct life cycle where L3 larvae are ingested from pasture and migrate to the lungs via the lymphatics.
64. Habronema larvae cause cutaneous lesions known as:
A. Bottle jaw B. Summer sores C. Ringworm D. Mange
Correct Answer: B. Summer sores
Explanation: When Habronema larvae are deposited by flies into skin wounds instead of being swallowed, they cause granulated, non-healing lesions called “Summer Sores” or cutaneous habronemiasis.
65. Argas persicus is a:
A. Hard tick B. Soft tick C. Mite D. Flea
Correct Answer: B. Soft tick
Explanation: Argas persicus is the “Fowl Tick.” As a soft tick (Family Argasidae), it lacks a hard dorsal shield (scutum) and feeds rapidly on birds at night.
66. Borrelia anserina is transmitted by:
A. Ixodes B. Argas persicus C. Dermacentor D. Rhipicephalus
Correct Answer: B. Argas persicus
Explanation: A. persicus is the primary vector for Avian Spirochaetosis (caused by Borrelia anserina), a highly fatal disease in poultry.
67. Presence of scutum is characteristic of:
A. Soft ticks B. Mites C. Hard ticks D. Fleas
Correct Answer: C. Hard ticks
Explanation: Hard ticks (Family Ixodidae) possess a chitinous plate on their dorsal surface called the scutum. In males, it covers the entire back; in females, it is small, allowing the body to expand during feeding.
68. Sarcoptes scabiei is a:
A. Non-burrowing mite B. Burrowing mite C. Tick D. Flea
Correct Answer: B. Burrowing mite
Explanation: Sarcoptes mites tunnel into the stratum corneum of the skin to lay eggs, causing intense itching and “sarcoptic mange.”
69. Psoroptes is classified as:
A. Burrowing mite B. Non-burrowing mite C. Soft tick D. Louse
Correct Answer: B. Non-burrowing mite
Explanation: Psoroptes mites live on the surface of the skin and feed by piercing the epidermis to suck lymph, causing “sheep scab.”
70. Somatic myiasis is caused by:
A. Oestrus ovis B. Hypoderma C. Lucilia D. Sarcophaga
Correct Answer: B. Hypoderma
Explanation: Hypoderma (Warble flies) larvae migrate through the somatic tissues of cattle for months before settling under the skin of the back.
71. Nasal bot fly of sheep is:
A. Gastrophilus B. Hypoderma C. Oestrus ovis D. Lucilia
Correct Answer: C. Oestrus ovis
Explanation: The female fly “darts” at the sheep’s muzzle to deposit larvae in the nostrils, leading to “snotty nose” and head shaking.
72. Screw worm myiasis is caused by:
A. Calliphora B. Cochliomyia macellaris (hominivorax) C. Lucilia D. Sarcophaga
Correct Answer: B. Cochliomyia macellaris
Explanation: Screwworms are “obligate” parasites; unlike blowflies, they require living tissue to develop, making them extremely destructive.
73. Which protozoan is classified as an extracellular parasite?
A. Babesia B. Plasmodium C. Trypanosoma D. Toxoplasma
Correct Answer: C. Trypanosoma
Explanation: Unlike Babesia or Plasmodium, which live inside RBCs, Trypanosomes circulate freely in the blood plasma.
74. Which of the following is an intracellular protozoan?
A. Trypanosoma B. Entamoeba C. Leishmania D. Giardia
Correct Answer: C. Leishmania
Explanation: Leishmania is obligately intracellular in the vertebrate host, residing within macrophages.
75. Babesia, Theileria, and Anaplasma primarily infect:
A. Lymph nodes B. RBCs C. Liver cells D. Intestinal cells
Correct Answer: B. RBCs
Explanation: These are categorized as hemoparasites because the detectable and diagnostic stages of their life cycle occur within the Red Blood Cells.