Medical Bacteriology and Entomology Exam 2020/2021

# Medical Bacteriology and Entomology Exam 2020/2021 ** --- ## SECTION A: Answer ALL Questions (35 marks) ### Question 1 Which of the following is the odd one out in terms of its mode of transmission? **A) ** *Vibrio cholerae*** B) ** *Entamoeba histolytica*** C) ** Rotavirus** D) ** *Thelazia* species** E)** None of the above **Answer: D) *Thelazia* species** **Explanation:** *Vibrio cholerae*, *Entamoeba histolytica*, and Rotavirus are all transmitted through the fecal-oral route (contaminated water/food). *Thelazia* species (eyeworms) are transmitted by flies that feed on lacrimal secretions, making it the odd one out. --- ### Question 2 Which one of the following is larviparous? **A) ** *Phlebotomus* species** B) ** *Lutzomyia* species** C) ** Triatomine bugs** D) ** *Glossina* species** E)** *Dermacentor* species **Answer: D) *Glossina* species** **Explanation:** Larviparous insects give birth to live larvae rather than laying eggs. Tsetse flies (*Glossina* species) are larviparous, producing one larva at a time that pupates immediately after birth. --- ### Question 3 Argasid ticks have: **A) ** One host** B) ** Two hosts** C) ** Three hosts** D) ** Four hosts** E)** Multiple hosts **Answer: E) Multiple hosts** **Explanation:** Argasid (soft) ticks are multi-host ticks that can feed on different hosts throughout their life cycle and can take multiple blood meals at each life stage. --- ### Question 4 Ixodid ticks have how many nymphal stages? **A) ** One** B) ** Two** C) ** Three** D) ** Four** E)** Multiple **Answer: A) One** **Explanation:** Ixodid (hard) ticks have a single nymphal stage in their life cycle: egg → larva → nymph → adult. --- ### Question 5 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: A) Black and white colors** **Explanation:** *Aedes* mosquitoes are attracted to contrasting black and white patterns. Ovitrap designs often use black containers with white interiors or black and white striped patterns. --- ### Question 6 Traps for *Glossina* species are composed of: **A) ** Black and white colors** B) ** Black and blue colors** C) ** White and blue colors** D) ** Blue only** E)** Black only **Answer: B) Black and blue colors** **Explanation:** Tsetse flies (*Glossina* species) are attracted to blue and black colors. Standard tsetse traps use blue cloth with black panels to attract the flies effectively. --- ### Question 7 Blackwater fever is due to presence of which species in the environment? **A) ** *Simulium* species** B) ** *Anopheles* species** C) ** *Culicoides* species** D) ** *Lutzomyia* species** E)** *Musca* species **Answer: B) *Anopheles* species** **Explanation:** Blackwater fever is a severe complication of falciparum malaria characterized by massive hemolysis and dark urine. It's associated with *Plasmodium falciparum* infection transmitted by *Anopheles* mosquitoes. --- ### Question 8 Hepatitis B virus has been associated with: **A) ** *Cimex* species** B) ** *Xenopsylla* species** C) ** *Pthirus* species** D) ** *Tabanids* species** E)** *Glossina* species **Answer: A) *Cimex* species** **Explanation:** While not definitively proven, bed bugs (*Cimex* species) have been investigated as potential mechanical vectors for Hepatitis B virus, though human-to-human transmission remains the primary route. --- ### Question 9 Snails are both first and second intermediate hosts of: **A) ** *Echinostoma ilocanum*** B) ** *Fasciola hepatica*** C) ** *Fasciolopsis buski*** D) ** *Hymenolepis nana*** E)** *Paragonimus westermanii* **Answer: A) *Echinostoma ilocanum*** **Explanation:** *Echinostoma ilocanum* uses snails as both first and second intermediate hosts in its complex life cycle, unlike other flukes that use different intermediate hosts. --- ### Question 10 How can millipedes cause medical problems? **A) ** Stinging** B) ** Spraying defensive secretions** C) ** Transmitting viruses** D) ** Laying eggs under skin** E)** None of the above **Answer: B) Spraying defensive secretions** **Explanation:** Millipedes defend themselves by secreting toxic chemicals (hydrogen cyanide, quinones) that can cause skin irritation, burns, and eye damage in humans. --- ### Question 11 Holometabolous insects have: **A) ** 2 life stages** B) ** 3 life stages** C) ** 4 life stages** D) ** 1 life stage** E)** None of the above **Answer: C) 4 life stages** **Explanation:** Holometabolous insects undergo complete metamorphosis with four distinct stages: egg, larva, pupa, and adult. Examples include flies, beetles, and butterflies. --- ### Question 12 Rift Valley fever is mainly transmitted by: **A) ** *Culex* species** B) ** *Aedes* species** C) ** *Anopheles* species** D) ** *Toxorhynchites* species** E)** None of