Explore key topics in Medical Bacteriology and Parasitology for your 2024/2025 end-of-year review. Essential for Year 2 students and medical professionals.
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 quickly (minutes to hours) on different hosts throughout their life stages, unlike ixodid ticks. --- Question 14 Ixodid ticks have nymphal stages. a) Oneb) Twoc) Threed) Foure) Multiple ANSWER: (a) One EXPLANATION: Ixodid (hard) ticks have a single nymphal stage in their life cycle: egg → larva → nymph → adult. This is standard for hard ticks. --- Question 15 Traps for Aedes mosquitoes are composed of? a) Black and white colorsb) Black and blue colorsc) White and blue colorsd) White onlye) Black only ANSWER: (a) Black and white colors EXPLANATION: Aedes mosquitoes are attracted to contrasting black and white patterns. Ovitraps and BG-Sentinel traps use this color combination for effective Aedes surveillance and control. --- Question 16 Traps for Glossina species are composed of? a) Black and white colorsb) Black and blue colorsc) White and blue colorsd) White onlye) Black only ANSWER: (b) Black and blue colors EXPLANATION: Tsetse flies (Glossina species) are attracted to black and blue colors. Biconical traps and targets use these colors for effective tsetse fly control. --- Question 17 Black water disease is due to presence of in the environment. a) Simulium speciesb) Anopheles speciesc) Culicoides speciesd) Lutzomyia speciese) Musca species ANSWER: (b) Anopheles species EXPLANATION: Blackwater fever is a severe complication of falciparum malaria (transmitted by Anopheles mosquitoes), characterized by massive intravascular hemolysis causing dark urine. --- Question 18 Hepatitis B virus has been associated with? a) Cimex speciesb) Xenopsylla speciesc) Pthirus speciesd) Tabanids speciese) Steam bugs ANSWER: (a) Cimex species EXPLANATION: Cimex species (bed bugs) have been studied for potential mechanical transmission of Hepatitis B virus, though their role remains controversial and not definitively proven. --- Question 19 Which of the following statements regarding vaccination for Bacillus anthracis is correct? a) It is routinely available for all citizens of the United Statesb) Recombinant vaccine trials have shown good safety and efficacyc) The current vaccine is well toleratedd) A single dose is adequate after exposure to sporese) Vaccination of animals is not useful ANSWER: (b) Recombinant vaccine trials have shown good safety and efficacy EXPLANATION: Newer recombinant protective antigen vaccines have demonstrated good safety and efficacy in trials. The current AVA vaccine requires multiple doses and has tolerability issues. --- Question 20 Lowenstein Jensen media is used to isolate? a) Streptococcus speciesb) Proteus speciesc) E. colid) Mycobacterium tuberculosise) None of the above ANSWER: (d) Mycobacterium tuberculosis EXPLANATION: Lowenstein-Jensen medium is an egg-based selective medium specifically designed for culturing Mycobacterium tuberculosis and other mycobacteria, which grow slowly and require special nutrients. --- Question 21 All of the following statements regarding Clostridium perfringens are correct EXCEPT: a) It produces an ente