Medical Bacteriology and Parasitology OmpathStudy

MEDICAL SCHOOL - DEPARTMENT OF MICROBIOLOGY BACHELOR OF MEDICINE AND BACHELOR OF SURGERY --- UNIT CODE: MBMM 3300 EXAMINATION: END OF YEAR EXAMINATION 2024/2025 DATE: Tuesday, 15th July 2025 TIME: 8:00 AM - 10:00 AM (2 Hours) TYPE: Main Exam --- ANSWER KEY AND EXPLANATIONS --- SECTION A: MULTIPLE CHOICE QUESTIONS (35 MARKS) Instructions: Answer ALL questions --- Question 1 Fish are second intermediate hosts of? a) Echinostoma ilocaanumb) Hepatic fasciac) Fasciolopsis buskid) Hymenolepis nanae) Clonorchis sinensis ANSWER: (e) Clonorchis sinensis EXPLANATION: Fish serve as the second intermediate host for Clonorchis sinensis (Chinese liver fluke). Humans get infected by eating raw or undercooked fish containing the parasite's metacercariae. --- Question 2 Which of the following secretes defensive secretions to cause irritation on human skin? a) Millipedesb) Centipedesc) American killerd) Enterobius vermicularise) All of the above ANSWER: (a) Millipedes EXPLANATION: Millipedes have defensive glands that secrete irritating chemicals (benzoquinones, hydrogen cyanide) causing skin burns and discoloration. Centipedes bite rather than secrete defensive substances. --- Question 3 Holometabolous insects have? a) 2 life stagesb) 3 life stagesc) 4 life stagesd) 5 life stagese) 1 life stage ANSWER: (c) 4 life stages EXPLANATION: Holometabolous insects undergo complete metamorphosis with four stages: egg → larva → pupa → adult. Examples include mosquitoes, flies, and beetles. --- Question 4 Which of the following transmits parasites for river blindness? a) Culex speciesb) Chrysops speciesc) Simulium speciesd) Toxorhynchitinae speciese) All of the above ANSWER: (c) Simulium species EXPLANATION: Simulium species (blackflies) are the vectors of Onchocerca volvulus, causing river blindness (onchocerciasis). They breed in fast-flowing rivers. --- Question 5 Which insecticide targets GABA in its action? a) DDTb) DEETc) Permethrind) Bendiocarbe) Malathion ANSWER: (d) Bendiocarb EXPLANATION: Bendiocarb is a carbamate insecticide that inhibits acetylcholinesterase, affecting GABA neurotransmission. DDT and permethrin target sodium channels instead. --- Question 6 Presence of triatomine bugs could predispose the population to? a) Sleeping sicknessb) Leishmaniasisc) Malariad) Chagas diseasee) River blindness ANSWER: (d) Chagas disease EXPLANATION: Triatomine bugs (kissing bugs) transmit Trypanosoma cruzi, which causes Chagas disease. They defecate while feeding, and parasites enter through the bite wound or mucous membranes. --- Question 7 People living in forested areas like Arabuko Sokoke are at a risk of? a) Sleeping sicknessb) Leishmaniasisc) Malariad) Encephalitise) River blindness ANSWER: (b) Leishmaniasis EXPLANATION: Forested areas harbor sandflies (Phlebotomus/Lutzomyia species) that transmit Leishmania parasites. Forest ecosystems provide ideal habitats for sandfly vectors and animal reservoirs. --- Question 8 Which of the following insects are commonly found in Latin America? a) Glossina speciesb) Triatomine bugsc) Cimex speciesd) Chrysops speciese) Steam bugs ANSWER: (b) Triatomine bugs EXPLANATION: Triatomine bugs are endemic to Latin America where they transmit Chagas disease. Glossina species (tsetse flies) are found only in sub-Saharan Africa. --- Question 9 Pruritus can be best diagnosed for? a) Sarcoptes scabieib) Leptothrombidium speciesc) Blattella speciesd) Pediculus speciese) Pthirus species ANSWER: (a) Sarcoptes scabiei EXPLANATION: Sarcoptes scabiei (scabies mite) burrows into skin causing intense pruritus (itching), especially at night due to mite activity and allergic reaction to mite proteins. --- Question 10 If you found lice eggs (nits) in someone's clothing, what species would they most likely be from? a) Crab liceb) Pediculus humanusc) Pediculus capitisd) Pthirus speciese) All of the above ANSWER: (b) Pediculus humanus EXPLANATION: Pediculus humanus (body lice) live and lay eggs in clothing seams, not on the body. Pediculus capitis (head lice) attach eggs to hair shafts, not clothing. --- Question 11 Which of the following is odd one out in terms of transmission? a) Vibrio choleraeb) Entamoeba histolyticac) Rotavirusd) Thelazia speciese) None of the above ANSWER: (d) Thelazia species EXPLANATION: Thelazia species (eye worm) is transmitted by flies (mechanical vectors), while the others are transmitted via fecal-oral route through contaminated water/food. --- Question 12 Which one of the following is larviparous? a) Phlebotomus speciesb) Lutzomyia speciesc) Triatomine bugsd) Glossina gambiensee) Dermacentor species ANSWER: (d) Glossina gambiense EXPLANATION: Glossina species (tsetse flies) are larviparous - they give birth to live larvae rather than laying eggs. The larva immediately pupates after birth. --- Question 13 Argasid ticks have? a) One hostb) Two hostsc) Three hostsd) Multiple hostse) Four hosts ANSWER: (d) Multiple hosts EXPLANATION: Argasid (soft) ticks are multi-host ticks that feed quick