Medical Bacteriology And Parasitology End Year 2024/2025

## 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** *