Medical Entomology and Vector Control | Essay Questions | Ompath Study

Practice 18 structured short- and long-answer medical questions on Medical Entomology and Vector Control. Review model answers for exam revision.

Essay Questions and Answers

1. Q1. ## Medical Entomology and Vector Control

   Answer: ### Section 1: Key Terminologies * **Zoophilic**: Vectors that prefer feeding on animal blood rather than human blood. * **Endophagic**: Vectors that prefer feeding indoors (inside buildings/houses). * **Fomite**: Non-living objects capable of transmitting infectious pathogens from one host to another. ### Section 2: Medical Importance of Arthropods

2. Q2. **Biological vectors of disease**: Transmit pathogens that multiply or develop within the vector. Examples: *Anopheles* mosquitoes (malaria), tsetse flies (sleeping sickness).

   Answer: Model answer pending

3. Q3. **Mechanical vectors**: Carry pathogens on body parts without pathogen development. Examples: Houseflies and cockroaches (cholera, typhoid).

   Answer: Model answer pending

4. Q4. **Direct causative agents**: Cause disease through infestation. Examples: Scabies mite (*Sarcoptes scabiei*), head lice.

   Answer: Model answer pending

5. Q5. **Venomous effects**: Cause injury through bites or stings. Examples: Scorpions, spiders, bees.

   Answer: Model answer pending

6. Q6. **Nuisance and allergic reactions**: Cause irritation and hypersensitivity. Examples: Mosquito bites, bed bugs, dust mites.

   Answer: ### Section 3: Life Cycle of a Three-Host Tick **Example**: *Rhipicephalus appendiculatus* * **Eggs**: Laid on the ground by an engorged female (2,000–20,000 eggs). * **Larvae (6-legged)**: Hatch, climb vegetation, attach to **Host 1** (small mammals/birds), feed for 3–7 days, drop off, and molt to nymph. * **Nymph (8-legged)**: Climb vegetation, attach to **Host 2** (medium mammals), feed for 4–7 days, drop off, and molt to adult. * **Adult (8-legged)**: Climb vegetation, attach to **Host 3** (large mammals/cattle), mate on host; the female feeds for 7–14 days, drops off, lays eggs, and dies. **Key Feature**: Each stage feeds on a different host and drops to the ground to molt. The complete cycle takes 6 months to 3 years depending on environmental conditions. ### Section 4: Insecticides and Mechanisms of Action | Insecticide | Target Site of Action | | :--- | :--- | | Propoxur / Bendiocarb | Acetylcholinesterase enzyme inhibition | | Avermectins | GABA (γ-aminobutyric acid) receptors | | Endosulfan | GABA chloride channels | | Deltamethrin | Voltage-gated Sodium channels | | Rotenone | NADH enzyme of oxidative phosphorylation pathway | ### Section 5: Morphological Comparison of Mosquito Genera | Feature | *Anopheles* | *Culex* | *Aedes* | | :--- | :--- | :--- | :--- | | **Resting position** | Posterior end elevated (45° angle) | Parallel to surface | Parallel to surface | | **Larval position** | Parallel to water surface | Hangs at angle (with siphon) | Hangs at angle | | **Eggs** | Laid singly with floats | Laid in rafts | Laid singly above waterline | ### Section 6: Pathogens, Vectors, and Control Measures | Pathogen | Primary Vector | Disease | Management/Control | | :--- | :--- | :--- | :--- | | *Plasmodium vivax* | *Anopheles stephensi* | Malaria | Chloroquine/Primaquine; Intact walls | | Rift Valley fever virus | *Culex* spp. | Rift Valley fever | Supportive care; CDC light trap | | *Wuchereria bancrofti* | *Culex quinquefasciatus* | Lymphatic filariasis | Diethylcarbamazine; BG sentinel trap | | *Trypanosoma rhodesiense* | *Glossina* spp. | Sleeping sickness | Melarsoprol; Blue/black cloth traps | | *Trypanosoma cruzi* | Reduviid bug | Chagas disease | Benznidazole; Improved housing | | *Onchocerca volvulus* | *Simulium neavei* | River blindness | Ivermectin; Vector control in rivers | | *Leishmania* spp. | *Phlebotomus* / *Lutzomyia* | Leishmaniasis | Pentavalent antimonials; Spraying | ### Section 7: Summary of Vector-Borne Diseases

7. Q7. **Lyme disease**: *Borrelia burgdorferi* (Ixodid tick)

   Answer: Model answer pending

8. Q8. **Relapsing fever**: *Borrelia recurrentis* (Body louse)

   Answer: Model answer pending

9. Q9. **Sleeping sickness (West Africa)**: *Trypanosoma brucei gambiense* (*Glossina palpalis*)

   Answer: Model answer pending

10. Q10. **Dengue fever**: Dengue virus (*Aedes aegypti*)

    Answer: Model answer pending

11. Q11. **Elephantiasis**: *Wuchereria bancrofti* (*Culex* spp.)

    Answer: Model answer pending

12. Q12. **Cutaneous leishmaniasis**: *Leishmania tropica* (*Lutzomyia* species)

    Answer: Model answer pending

13. Q13. **Pink eye disease**: *Chlamydia trachomatis* (*Musca* spp.)

    Answer: Model answer pending

14. Q14. **Rickettsial fever**: *Rickettsia* spp. (*Culicoides* spp.)

    Answer: Model answer pending

15. Q15. **River blindness**: *Onchocerca volvulus* (*Simulium neavei*)

    Answer: Model answer pending

16. Q16. **Cholera**: *Vibrio cholerae* (*Blatta orientalis* - mechanical)

    Answer: Model answer pending

17. Q17. **Typhoid fever**: *Salmonella typhi* (*Musca domestica* - mechanical)

    Answer: Model answer pending

18. Q18. **Plague**: *Yersinia pestis* (Rat flea)

    Answer: Model answer pending