Medical Bacteriology and Parasitology OmpathStudy

--- EXAM INFO Unit Code: MBMM 3300 — Medical Bacteriology and Parasitology Date: Tuesday, 15th July 2025 Time: 8:00 AM, Main Exam Duration: 2 Hours --- SECTION A: MCQs (35 Marks) Q1. Fish are second intermediate hosts of? a) Echinostoma ilocanum b) Fasciola hepatica c) Fasciolopsis buski d) Hymenolepis nana e) Clonorchis sinensis Answer: e) Clonorchis sinensis Explanation: Clonorchis sinensis uses snails as the first intermediate host and freshwater fish as the second intermediate host, where metacercariae encyst before human ingestion. Q2. Which of the following secretes defensive secretions to cause irritation on human skin? a) Millipedes b) Centipedes c) Necator americanus d) Enterobius vermicularis e) All of the above Answer: a) Millipedes Explanation: Millipedes release defensive fluids (e.g., benzoquinones) that cause skin irritation or burns on contact. Centipedes envenomate by biting, not by secretion. Q3. Holometabolous insects have? a) 2 life stages b) 3 life stages c) 4 life stages d) 5 life stages e) 1 life stage Answer: c) 4 life stages Explanation: Complete metamorphosis (holometabolous) proceeds through egg, larva, pupa, and adult. Q4. Which of the following transmits parasites for river blindness? a) Culex species b) Chrysops species c) Simulium species d) Toxorhynchintinae species e) All of the above Answer: c) Simulium species Explanation: Simulium (blackfly) transmits Onchocerca volvulus, causing river blindness (onchocerciasis). Chrysops instead transmits Loa loa. Q5. Which insecticide targets GABA in its action? a) DDT b) DEET c) Permethrin d) Bendiocarb e) Malathion Answer: No listed option is correct. Explanation: DDT and permethrin modify voltage-gated sodium channels, while bendiocarb inhibits acetylcholinesterase. GABA-gated chloride-channel antagonists include cyclodienes such as dieldrin. Q6. Presence of triatomine bugs could predispose the population to? a) Sleeping sickness b) Leishmaniasis c) Malaria d) Chagas disease e) River blindness Answer: d) Chagas disease Explanation: Triatomine ("kissing") bugs transmit Trypanosoma cruzi, causing Chagas disease, mainly endemic in Latin America. Q7. People living in forested areas like Arabuko Sokoke are at risk of? a) Sleeping sickness b) Leishmaniasis c) Malaria d) Encephalitis e) River blindness Answer: a) Sleeping sickness Explanation: Arabuko Sokoke forest is a known tsetse fly (Glossina) habitat; tsetse flies transmit Trypanosoma brucei, causing African sleeping sickness. Q8. Which of the following insects are commonly found in Latin America? a) Glossina species b) Triatomine bugs c) Cimex species d) Chrysops species e) Steam bugs Answer: b) Triatomine bugs Explanation: Triatomine bugs, vectors of Chagas disease, are widely distributed across Latin America; Glossina (tsetse flies) are African. Q9. Pruritis can be best diagnosed for? a) Sarcoptes scabiei b) Leptothrombidium species c) Blattella species d) Pediculus species e) Pthirus species Answer: a) Sarcoptes scabiei Explanation: Scabies classically presents with intense pruritis, worse at night, from hypersensitivity to mites, eggs, and feces burrowed in skin. Q10. If you found lice eggs (nits) in someone's clothing, what species would they most likely be from? a) Crab lice b) Pediculus humanus c) Pediculus capitis d) Pthirus species e) All of the above Answer: b) Pediculus humanus Explanation: The body louse (Pediculus humanus corporis) lays eggs in clothing seams, unlike the head louse (P. capitis) or crab louse (Pthirus pubis). Q11. Which of the following is odd one out in terms of transmission? a) Vibrio cholera b) Entamoeba histolytica c) Rotavirus d) Thelazia species e) None of the above Answer: e) None of the above (as marked) — but functionally d) Thelazia species stands out Explanation: Vibrio cholera, Entamoeba histolytica, and Rotavirus are all fecal-oral transmitted; Thelazia (eyeworm) is transmitted by flies directly to the eye, making it the outlier by transmission route. Q12. Which one of the following is larviparous? a) Phlebotomus species b) Lutzomyia species c) Triatomine bugs d) Glossina gambiense e) Dermacentos species Answer: d) Glossina gambiense Explanation: Tsetse flies show adenotrophic viviparity — they nourish a single larva internally and deposit it, rather than laying eggs. Q13. Argasid ticks have? a) One host b) Two hosts c) Three hosts d) Multiple hosts e) Four hosts Answer: d) Multiple hosts Explanation: Argasid (soft) ticks feed briefly and repeatedly on multiple hosts across life stages, unlike ixodid (hard) ticks. Q14. Ixodid ticks have nymphal stage(s). a) One b) Two c) Three d) Four e) Multiple Answer: a) One Explanation: Ixodid (hard) ticks have a simple life cycle with a single nymphal stage. Q15. Traps for Aedes mosquitoes are composed of? a) Black and white colors b) Black and blue colors c) White and blue colors d) White only e) Black only Answer: b) Black and blue colors Explanation: Aedes mosquitoes are strongly attracted to dark, con