Practice 21 structured short- and long-answer medical questions on Medical Entomology. Review model answers for exam revision.
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Answer: **C. Diagnosis** Diagnosis is made by finding fly larvae in tissue. Identification involves morphological analysis of anterior/posterior spiracles, mouthparts, cephalopharyngeal skeleton, and cuticular spines. **D. Treatment** * **Simple removal:** For larvae in wounds or dermal tissues under aseptic conditions. * **Complex removal:** Surgery may be required for deeply embedded larvae in mucous membranes, eyes, or cavities. **E. Control** * Use of insecticides and electric fly traps. * Physical barriers: screens on windows, curtains at entrances. * Hygiene: washing fruits/vegetables, covering food and water, and using ash/salt in latrines. #### 3. Medical Importance of Arthropods
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Answer: #### 4. Genetic-Based Control Methods **1. Genetic Suppression of Vector Competence:** Modifying vectors so they are unable to transmit pathogens (e.g., making mosquitoes refractory to *Plasmodium*). **2. Genetic Suppression of Insect Populations:** * **Sterile Male Release:** Releasing large numbers of males sterilized by radiation or chemosterilants. They compete with wild males, leading to infertile matings and population collapse. #### 5. Indoor Residual Spraying (IRS) IRS involves coating indoor surfaces with residual insecticide. It targets endophilic mosquitoes that rest on walls after a blood meal. * **Mechanism:** Kills the mosquito after it has fed, preventing it from surviving long enough to transmit the parasite to the next person. * **Requirements:** High household coverage, endophilic vector behavior, and vector susceptibility to the insecticide. #### 6. Medical Importance of Fleas
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Answer: #### 7. Medical Importance of Ixodes Species
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Answer: #### 1. Life Cycle of a Three-Host Tick **Outline the life cycle of a three-host tick with an illustration of stages.** **Life Cycle Stages:** * **Egg Stage (Fall):** Adult females drop off the third host after feeding, usually in the fall. Females lay eggs in the environment. Eggs hatch into six-legged larvae. Larvae overwinter in this stage. * **Larval Stage (Spring - First Host):** In spring, larvae seek out and attach to the first host, usually a small rodent. Larvae feed on the first host. Later in summer, engorged larvae leave the first host and molt into nymphs, usually in fall. Ticks overwinter in the nymphal stage. * **Nymphal Stage (Following Spring - Second Host):** During the following spring, nymphs seek out and attach to the second host (usually another rodent or lagomorph). Nymphs feed on the second host and drop off later in summer. Nymphs molt into adults off the host in late summer or fall. Adults overwinter in this stage. * **Adult Stage (Next Spring - Third Host):** The next spring, adults seek out and attach to a third host, usually a larger herbivore (cervids, bovids), carnivore, or human. Adults feed and mate on the third host during summer. Females drop off the host in fall to continue the cycle. **Important Notes:** * The three hosts do not necessarily have to be different species. * Humans may serve as first, second, or third hosts. #### 2. Myiasis **Discuss myiasis under the following sub-headings:** **A. Aetiology** Myiasis is the invasion of organs and tissues of humans or other vertebrates by fly larvae. Larvae feed on living or dead tissues or, in intestinal myiasis, on the host's ingested food. * **Important Species:** *Dermatobia hominis* (Human bot fly), *Cochliomyia hominivorax* (New World screwworm), *Chrysomya bezziana* (Old World screwworm), *Cordylobia anthropophaga* (Tumbu fly). **B. Pathogenesis**