48 Year 2: Parasitology exam questions on Parasitology, Entomology and Bacteriology Question & Answers for medical students. Includes MCQs, answers, explana
This MCQ set contains 48 questions on Parasitology, Entomology and Bacteriology Question & Answers in the Year 2: Parasitology unit. Each question includes the correct answer and a detailed explanation for active recall and exam preparation.
Correct answer: D – Bulinus
Bulinus is a genus of freshwater snails that serves as an intermediate host for schistosomes (trematodes), not an insect vector. Fannia, Musca, and Blatta are all insects (flies and cockroaches) that mechanically transmit pathogens. Bulinus transmits disease through a completely different mechanism involving parasitic life cycles rather than arthropod-mediated transmission. ---
Correct answer: D – Q-fever
Q-fever is caused by Coxiella burnetii , which is transmitted by ticks (arachnids). Acaricides are chemicals that kill ticks and mites. Leishmaniasis is transmitted by sandflies, amoebiasis is spread through contaminated water/food, Katayama fever is caused by schistosomes (snail-transmitted), and sleeping sickness is transmitted by tsetse flies. Only Q-fever has a tick vector that can be controll
Correct answer: D – Leptotrombidium
Leptotrombidium (formerly Trombicula ) mites are the biological vectors of Orientia tsutsugamushi , which causes scrub typhus. The mite larvae (chiggers) transmit the pathogen through their bite. Glossina transmits trypanosomes, Blatta is a cockroach (mechanical vector), Simulium transmits onchocerciasis, and Dermacentor transmits Rocky Mountain spotted fever and other tick-borne diseases. ---
Correct answer: D – Orientia tsutsugamushi
Orientia tsutsugamushi (scrub typhus agent) is transmitted transovarially in Leptotrombidium mites, meaning the pathogen passes from infected female mites to their offspring through eggs. This maintains the infection in mite populations without requiring infected hosts. Entamoeba is not vector-borne, while Onchocerca , Loa loa , and Wuchereria are filarial nematodes that require cyclical developme
Correct answer: D – Benzyl benzoate
Benzyl benzoate is a topical scabicide used to treat Sarcoptes scabiei (scabies mite) infestations. It kills the mites and their eggs. Metronidazole treats protozoal infections, amphotericin B treats fungal infections, sodium stibogluconate treats leishmaniasis, and praziquantel treats helminthic infections. Permethrin cream is another common scabies treatment. ---
Correct answer: A – Liquid Iodine
Liquid iodine can be applied to skin to help visualize scabies burrows and mite tunnels, making them more visible for diagnosis. The iodine stains the burrows, helping identify the location of mites. Skin scrapings can then be examined microscopically. Crystal violet and safranin are bacterial stains, tetracycline is an antibiotic, and blood agar is a culture medium - none are specifically used fo
Correct answer: D – Endophilic
Indoor Residual Spraying (IRS) involves applying insecticides to interior walls and surfaces where vectors rest. It is most effective against endophilic insects that prefer to rest indoors after feeding. Exophagic insects feed outdoors, endophagic insects feed indoors but may rest outdoors, and exophilic insects rest outdoors - all reducing IRS effectiveness. Endophilic behavior maximizes contact
Correct answer: D – Ornithodoros
Ornithodoros belongs to the family Argasidae (soft ticks), which lack a hard scutum and have mouthparts not visible from above. The other genera (Hyalomma, Amblyomma, Rhipicephalus, Boophilus) belong to Ixodidae (hard ticks), which have a hard dorsal shield and visible mouthparts. Argasid ticks typically feed rapidly and live in host burrows or nests. ---
Correct answer: D – Boophilus
Boophilus ticks are one-host ticks, completing their entire life cycle (larva, nymph, adult) on a single host animal. All feeding stages occur on the same host before the engorged female drops off to lay eggs. Haemaphysalis and Amblyomma are typically three-host ticks, Hyalomma can be two or three-host, and Ornithodoros (soft tick) is a multi-host feeder. ---
Correct answer: D – Periplanetta species
Periplanetta (American cockroach) and other cockroaches are effectively controlled using boric acid powder (borax), which acts as a stomach poison when ingested during grooming. It damages the insect's digestive system and exoskeleton. Pediculus (body louse), Pthirus (crab louse), Ixodes (tick), and Tunga (jigger flea) require different control methods such as topical insecticides or acaricides. -
Correct answer: D – Lutzomyia species
Lutzomyia sandflies are the New World (Americas) vectors of leishmaniasis, commonly found in Central and South America. Phlebotomus sandflies transmit leishmaniasis in the Old World (Africa, Asia, Europe). Chrysops (deer flies) and Simulium (black flies) have wider distributions. The geographic distribution of sandfly genera is an important epidemiological distinction. ---
Correct answer: D – Nifurtimox
Triatoma (kissing bugs/reduviid bugs) transmit Trypanosoma cruzi , which causes Chagas disease (American trypanosomiasis). Nifurtimox and benznidazole are the primary treatments for acute Chagas disease. Melarsoprol, pentamidine, and eflornithine treat African trypanosomiasis (sleeping sickness), while metriphonate treats schistosomiasis. ---
Correct answer: E – None of the above
All the listed factors (A-D) have contributed to the increased geographical dispersion and resurgence of Cimex (bedbugs). Global travel spreads bedbugs between locations, insecticide resistance allows populations to survive control efforts, warmer houses provide optimal breeding conditions, and increased human population density provides more hosts and harborage sites. Therefore, none of the liste
Correct answer: B – Pthirus pubis
Petroleum jelly (Vaseline) can be used to treat Pthirus pubis (pubic lice/crab lice) infestations by smothering the lice and creating an occlusive barrier. While it can also provide some benefit for other lice species, it is particularly recommended for pubic lice due to the sensitive nature of the affected area. However, "E) All of the above" could be argued as petroleum jelly can help manage all
Correct answer: D – Pulex species
Pulex irritans (human flea) and Xenopsylla cheopis (rat flea) are the primary flea vectors of Yersinia pestis , which causes plague. Fleas transmit the bacteria from infected rodents to humans through their bite. Musca and Fannia are flies (mechanical vectors of various pathogens), Glossina transmits trypanosomiasis, and Simulium transmits onchocerciasis. ---
Correct answer: A – True flies
True flies (Order Diptera), particularly Musca domestica (housefly), are mechanical vectors of Salmonella typhi and S. paratyphi (typhoid pathogens). Flies contaminate food and water after contact with feces containing the bacteria. Haemagogus and Sabethes are mosquito genera that transmit yellow fever, Fannia flies can mechanically transmit various pathogens, and Stomoxys (stable fly) is a biting
Correct answer: E – All of the above
Arboviruses (arthropod-borne viruses) are transmitted by multiple arthropod vectors. Aedes mosquitoes transmit dengue, yellow fever, Zika, and chikungunya. Culex mosquitoes transmit West Nile virus and Japanese encephalitis. Culicoides (biting midges) transmit various arboviruses affecting livestock and occasionally humans. While Cimex (bedbugs) are not typically major arbovirus vectors, some arbo
Correct answer: B – Human hosts
Anthropophilic vectors show a feeding preference for human hosts. "Anthropo-" refers to humans, and "-philic" means loving or preferring. This host preference is epidemiologically important as it increases disease transmission to humans. Examples include Anopheles gambiae (highly anthropophilic malaria vector) and Aedes aegypti (dengue vector). Zoophilic vectors prefer animals, and ornithophilic v
Correct answer: D – Feeding outdoors
Exophagic insects prefer to feed outdoors on hosts. "Exo-" means outside, and "-phagic" refers to feeding behavior. This is distinguished from endophagic (feeding indoors), exophilic (resting outdoors), and endophilic (resting indoors). Exophagic behavior reduces the effectiveness of indoor interventions like IRS (Indoor Residual Spraying) and bed nets. ---
Correct answer: E – Conjunctivitis
Chrysops (deer flies) can transmit Loa loa (eye worm), which causes loiasis. The adult worms can migrate across the conjunctiva of the eye, causing conjunctivitis and "calabar swellings." While Chrysops is also associated with the transmission of the parasite that can cause eye irritation, conjunctivitis is the direct result of the worm's presence. River blindness is transmitted by Simulium , and
Correct answer: C – Larval stage 3
In the filarial nematode life cycle, microfilariae are ingested by the arthropod vector during a blood meal. Inside the vector, they develop through L1 and L2 stages in the midgut, then migrate to the thoracic (chest) muscles where they develop into the infective L3 (third larval stage). The L3 larvae then migrate to the mouthparts and are transmitted to a new host during the next blood meal. ---
Correct answer: D – Insecticides
Pediculosis (lice infestation) is best treated with topical insecticides such as permethrin, malathion, or pyrethrin-based products. These pediculicides kill both adult lice and nits (eggs). While fine-toothed combs (nit combs) are important adjunct tools for physically removing lice and eggs, insecticides provide the most effective treatment. Antibiotics don't kill lice, bed nets don't prevent li
Correct answer: A – Louse
Monophagous organisms feed on only one type of food source or host. Lice are highly host-specific, with each species typically feeding on only one host species (e.g., Pediculus humanus on humans only). Fleas, mosquitoes (Culex, Anopheles), and ticks are generally more polyphagous, feeding on multiple host species, though they may show preferences. ---
Correct answer: A – Asia
Aedes albopictus (Asian tiger mosquito) is native to Southeast Asia and was originally mainly found in Asia. However, it has become invasive worldwide, spreading to Africa, Europe, the Americas, and other regions through global trade (especially used tire shipments). While now found globally, Asia remains its primary native region and area of highest prevalence. ---
Correct answer: D – Four
Mosquitoes undergo complete metamorphosis with four larval instars (developmental stages between molts): L1, L2, L3, and L4. After the fourth instar, the larva molts into a pupa, which then emerges as an adult mosquito. Each larval instar is progressively larger, with the fourth instar being the largest before pupation. ---