Q.How does the transmission of each of the following diseases take place?
Concept understanding — Disease Transmission Modes
Let’s begin with something you already know. When someone in your family catches a cold, you instinctively avoid sharing their glass or sitting too close. That instinct is your brain recognising that something — a disease — can travel from one person to another. The how of that travel is what we call disease transmission modes.
In everyday language, a transmission mode is simply the route a germ takes to leave an infected person and reach a healthy one. Think of it as the germ’s travel plan. If the germ cannot travel, it cannot cause new infections. So understanding these routes is the first step in stopping outbreaks — whether it’s a common flu or a more serious epidemic.
The two big families: Direct and Indirect transmission
The NCERT textbook (Class XII, Biology, Chapter 8 — Human Health and Disease) divides transmission into two main categories. This is the standard classification you need to remember.
1. Direct Transmission — The germ moves straight from the infected person to the healthy person, with no intermediate object or living being involved. This can happen through:
- Physical contact: Touching, shaking hands, kissing, or sexual contact. Diseases like the common cold, scabies, and sexually transmitted infections (e.g., syphilis, HIV) spread this way.
- Droplet infection: When an infected person coughs, sneezes, or even talks, tiny droplets of saliva or mucus fly out. If you are within about a metre, you can inhale them. This is how influenza, the common cold, and COVID-19 spread.
- Direct exposure to infected tissue or blood: For example, a needle-stick injury in a hospital, or a mother passing an infection to her baby during pregnancy (congenital transmission).
Direct transmission is often the easiest to interrupt. Simple actions — like maintaining distance, wearing a mask, or washing hands — break the chain because the germ has no vehicle to ride on.
2. Indirect Transmission — Here, the germ needs a middleman to reach a new host. The middleman can be:
- A vehicle: This is a non-living thing that carries the germ. Common vehicles include:
- Air: Dust particles or droplet nuclei (the dried remnants of droplets) can float for hours. Measles and tuberculosis spread through air.
- Water: Contaminated drinking water spreads cholera, typhoid, and hepatitis A.
- Food: Improperly cooked or stored food can carry salmonella or E. coli.
- Fomites: Inanimate objects like door handles, towels, syringes, or surgical instruments. Hepatitis B can spread through contaminated needles.
- A vector: This is a living organism — usually an insect or animal — that carries the germ from one host to another. The vector itself is not infected (or is only incidentally infected). Classic examples:
- Mosquitoes: Female Anopheles mosquito transmits malaria; Aedes mosquito transmits dengue and chikungunya.
- Fleas: Rat fleas transmit the plague bacterium.
- Ticks: Spread Lyme disease.
The key difference between a vehicle and a vector is that a vehicle is non-living, while a vector is a living creature. Both are intermediate agents — the germ does not jump directly from person to person.
Why this matters beyond biology
For a commerce or humanities student, the importance of transmission modes is not just medical — it is social and economic. Think about it:
- If a disease spreads through water (like cholera), the solution is not a vaccine alone — it is clean water supply, sanitation infrastructure, and public awareness campaigns. That is a government policy and budget issue.
- If a disease spreads through vectors (like malaria), the solution involves mosquito nets, insecticide spraying, and urban planning to eliminate stagnant water. That is a logistics and community management problem.
- If a disease spreads through direct contact (like HIV), the solution involves education, behaviour change, and stigma reduction — which is a social science challenge.
In short, the mode of transmission determines the type of intervention needed. That is why public health officials always ask: “How is this disease spreading?” before they decide what to do.
A quick summary for revision
| Transmission Type | Sub-type | Example Disease | Key Interruption Strategy |
|---|---|---|---|
| Direct | Contact | Common cold, scabies | Hand hygiene, avoid sharing personal items |
| Direct | Droplet | Influenza, COVID-19 | Masks, physical distancing |
| Direct | Congenital | HIV (mother to child) | Antiretroviral therapy during pregnancy |
| Indirect | Vehicle (water) | Cholera, typhoid | Boil water, improve sanitation |
| Indirect | Vehicle (food) | Food poisoning | Proper cooking and storage |
| Indirect | Vehicle (air) | Tuberculosis, measles | Ventilation, masks |
| Indirect | Vector (mosquito) | Malaria, dengue | Mosquito nets, insecticide, drain stagnant water |
| Indirect | Vector (flea) | Plague | Rodent control, flea repellents |
The NCERT textbook also mentions vertical transmission (from mother to foetus) as a special case of direct transmission, and horizontal transmission (between any two individuals, directly or indirectly) as the broader category covering everything else. You may encounter these terms in exam questions.
One final thought
You do not need to memorise every disease name. What matters is the logic: every germ has a preferred travel route. If you block that route, you stop the disease. That is the core idea — and it applies whether you are studying biology, economics, or public policy.
This topic shows up often in student searches, usually phrased as "NCERT biology syllabus disease transmission modes", "Disease Transmission Modes class 12 biology", or "Disease Transmission Modes diagram and explanation". This concept is directly part of the Human Health and Disease chapter in the NCERT/CBSE Class 12 Biology syllabus, and it is also an important topic for NEET and state medical/CET entrance exams, making it worth mastering for both board and competitive-exam preparation.
Disease transmission happens through different routes depending on the pathogen and how it survives outside the host. Understanding these modes helps in prevention and control.
Amoebiasis spreads through the faecal-oral route. The causative protozoan Entamoeba histolytica forms cysts that pass out with the faeces of an infected person. These cysts contaminate food and water, and when a healthy person consumes contaminated items, the infection enters the body. Houseflies act as mechanical carriers, transferring cysts from faeces to food.
Malaria transmission requires a vector. The Plasmodium parasite is transmitted by the bite of an infected female Anopheles mosquito. When the mosquito feeds on human blood, sporozoites are injected into the bloodstream. This is a biological vector-borne disease because the parasite completes part of its life cycle inside the mosquito.
Ascariasis also follows the faecal-oral route. Eggs of the roundworm Ascaris are excreted in faeces and contaminate soil, water, and vegetables. Infection occurs when these eggs are ingested through contaminated food or water, or through dirty hands. Internal autoinfection can also happen in some cases.
Pneumonia spreads through airborne droplets. The bacteria Streptococcus pneumoniae or Haemophilus influenzae are released into the air when an infected person coughs or sneezes. A healthy person inhales these droplet nuclei, and the pathogens reach the alveoli, causing infection. Close contact facilitates transmission.
Amoebiasis and ascariasis spread via contaminated food/water (faecal-oral), malaria through the bite of infected Anopheles mosquitoes (vector-borne), and pneumonia through inhaled respiratory droplets (airborne).
Amoebiasis and ascariasis spread through contaminated food and water (faecal-oral route), malaria through mosquito bites, and pneumonia through airborne droplets from infected persons.
Understanding how diseases spread is fundamental to preventing them. Each pathogen has evolved specific strategies to move from one host to another, and recognizing these transmission modes helps us break the chain of infection. The four diseases you've asked about represent three distinct transmission pathways that are particularly relevant in the Indian context.
Amoebiasis
This intestinal infection is caused by the protozoan parasite Entamoeba histolytica. The transmission follows what we call the faecal-oral route. An infected person passes cysts of the amoeba in their faeces. These microscopic cysts are remarkably hardy and can survive outside the body for extended periods.
The disease spreads when these cysts contaminate food or drinking water. This happens most commonly through:
- Unwashed hands of food handlers who are infected
- Vegetables grown in soil fertilized with human waste
- Water sources polluted by sewage
- Houseflies that carry cysts from faeces to food
Once ingested, the cysts reach the intestine, where they develop into the active form that causes infection. Poor sanitation and lack of clean drinking water are the primary reasons amoebiasis remains common in many parts of India.
Malaria
The transmission of malaria is entirely different — it requires a living vector. The disease is caused by Plasmodium parasites and spreads exclusively through the bite of an infected female Anopheles mosquito. This is a classic example of vector-borne transmission.
Here's how the cycle works: when a mosquito bites a person suffering from malaria, it picks up the parasites along with the blood meal. Inside the mosquito's body, the parasites undergo part of their life cycle. When this infected mosquito then bites a healthy person, it injects the parasites along with its saliva (which contains anticoagulants). The parasites travel to the liver and then to red blood cells, where they multiply and cause the characteristic fever cycles.
Malaria cannot spread directly from person to person through casual contact, sharing utensils, or even through contaminated water. The mosquito vector is essential for transmission.
Ascariasis
This is an intestinal infection caused by the roundworm Ascaris lumbricoides, and like amoebiasis, it follows the faecal-oral route. However, the infective stage here is eggs rather than cysts.
An infected person passes thousands of microscopic eggs in their faeces daily. These eggs need to mature in soil for about two to three weeks before they become infective. Transmission occurs when someone ingests these mature eggs through:
- Eating unwashed vegetables grown in contaminated soil
- Drinking water contaminated with soil containing eggs
- Children playing in contaminated soil and then putting their hands in their mouths
- Food contaminated by dirty hands
The eggs hatch in the intestine, and the larvae take a remarkable journey through the bloodstream to the lungs, are coughed up, swallowed again, and finally mature into adult worms in the intestine. This complex life cycle means that improving sanitation and washing vegetables thoroughly are key preventive measures.
Pneumonia
Pneumonia stands apart from the others because it spreads through the airborne or droplet route. The infection affects the lungs and can be caused by several bacteria (commonly Streptococcus pneumoniae and Haemophilus influenzae) or viruses.
When an infected person coughs, sneezes, or even talks, they release tiny droplets containing the pathogens into the air. A healthy person nearby can inhale these droplets, and the bacteria or viruses then reach the lungs and cause infection. The disease can also spread through direct contact with nasal or throat discharge of an infected person.
Pneumonia is more likely to develop in people whose immune systems are already weakened — young children, elderly individuals, or those suffering from other illnesses. The pathogen's presence alone isn't always enough; the body's defences play a crucial role.
Crowded living conditions, poor ventilation, and close contact with infected individuals all increase the risk of transmission. This is why pneumonia often spreads rapidly in schools, hospitals, and densely populated areas.
In short, amoebiasis and ascariasis are waterborne/foodborne diseases spreading via the faecal-oral route, malaria requires a mosquito vector and cannot spread person-to-person, and pneumonia spreads through airborne droplets when infected individuals cough or sneeze. Each mode of transmission points to specific preventive strategies.
Method: Classify the Route First, Then Slot in the Disease
The existing answer works disease-by-disease. This method inverts the order: fix the
transmission categories first, then place each of the four diseases into the category it
belongs to — useful when a paper gives you an unfamiliar disease and asks the same kind of
question, since you only need to recognise the pattern, not memorise every disease
individually.
Step 1 — List the possible categories for gut/respiratory infections:
- Faecal-oral (via contaminated food/water, hands, or flies)
- Vector-borne (via a biting insect that carries the parasite through part of its own life cycle)
- Airborne/droplet (via coughing, sneezing, or talking)
Step 2 — Test each disease against the categories:
| Disease | Causative agent type | Category it fits |
|---|---|---|
| Amoebiasis | Protozoan cyst | Faecal-oral |
| Ascariasis | Helminth egg | Faecal-oral |
| Malaria | Protozoan needing a vector | Vector-borne (Anopheles) |
| Pneumonia | Bacterium/virus in the lungs | Airborne/droplet |
Step 3 — Note the diagnostic clue that sorts them: if the infective stage is a cyst or
egg passed in faeces, it's faecal-oral; if the pathogen needs part of its life cycle inside
an insect, it's vector-borne; if the pathogen targets the respiratory tract and spreads via
coughing, it's airborne. This three-way sort works for almost any disease this chapter asks
about, not just these four.
Showing the 12 most recent of 50 on this concept.
- AP EAPCET 2026Set ap-2026-05-19-FN1 markMCQQ.Statement I: Due to presence of mitochondria, Entamoeba histolytica is a facultative anaerobe. Statement II: Entamoeba histolytica causes abscesses in the wall of large intestine of man. (A) Both statements I and II are true (B) Both statements I and II are false (C) Statement I is true. But II is false (D) Statement I is false. But II is true
›Reveal solutionSolution
Entamoeba histolytica is actually an amitochondriate anaerobic parasite (statement I is false for the wrong reason given), while it genuinely does cause abscesses/ulcers in the large intestine wall (statement II is true).
Concept and Intuition
Entamoeba histolytica is the protozoan parasite responsible for amoebiasis (amoebic dysentery) in humans. It lives in the human large intestine, where it can invade the mucosal lining, forming characteristic flask-shaped ulcers and abscesses in the intestinal wall; in severe cases it can travel via the bloodstream to cause liver abscesses. Unlike many free-living or aerobic protozoans, E. histolytica is adapted to the low-oxygen environment of the gut and lacks classical, fully-functional mitochondria — it possesses reduced mitochondrion-derived organelles ("mitosomes") instead, and its energy metabolism is essentially anaerobic, not facilitated by conventional mitochondria.
Step-by-Step Solution
- Statement I claims the parasite is a facultative anaerobe "due to presence of mitochondria" — but E. histolytica is notable precisely for lacking standard mitochondria; its anaerobic lifestyle is not attributable to having mitochondria. So statement I is false.
- Statement II states it causes abscesses in the wall of the large intestine — this matches the well-documented pathology of amoebic dysentery (ulcers/abscesses in the colon wall). So statement II is true.
- Hence I is false, II is true.
Common Mistakes
- Assuming any anaerobic organism must simply "have fewer" mitochondria rather than genuinely lacking the canonical organelle — E. histolytica is a classic amitochondriate/mitosome-bearing example.
✓Final answerThe correct option is (D) — Statement I is false. But II is true.
ANSWER: D
- AP EAPCET 2026Set ap-2026-05-19-AN1 markMCQQ.Study the following statements: Statement I: Malaria fever occurs due to release of haemozoin into the blood. Statement II: Haemozoin is formed during the digestion of haem by Plasmodium in RBC. (A) Statement I and II are correct (B) Statement I and II are incorrect (C) Statement I is correct II is incorrect (D) Statement I is incorrect II is correct
›Reveal solutionSolution
Both statements describe the same well-established malaria pathophysiology correctly: haemozoin formation during haemoglobin digestion, and its release causing the fever paroxysm.
Concept and Intuition
Plasmodium feeds on the haemoglobin inside the red blood cell it has invaded. Haemoglobin's haem component is toxic to the parasite in its free form (it generates reactive oxygen species), so Plasmodium neutralises it by polymerising/crystallising the haem into an insoluble, biologically inert pigment called haemozoin ("malaria pigment"). When the infected RBC finally ruptures to release a new generation of merozoites (schizogony), haemozoin and other cellular debris/toxins spill into the bloodstream. The host's immune system reacts to this material (triggering cytokines such as TNF-α), producing the classic cyclical fever, chills and rigor that define a malarial paroxysm.
Step-by-Step Solution
- Track the parasite's intra-erythrocytic cycle: invasion → trophozoite feeding on haemoglobin → schizont → merozoite release via RBC rupture.
- During haemoglobin digestion, the haem moiety is detoxified into haemozoin (Statement II — describes the formation correctly).
- RBC rupture releases haemozoin (and other toxins) into circulation, and this release is what is understood to precipitate the fever/chill cycle (Statement I — describes the cause of fever correctly).
- Both are independently true and mutually consistent (II explains where the substance in I comes from).
Common Mistakes
- Thinking haemozoin is formed outside the RBC — it is formed inside, during digestion, and only released upon rupture.
- Confusing haemozoin (a haem-derived pigment) with haemoglobin itself.
✓Final answerThe correct option is (A) — Statement I and II are correct.
ANSWER: A
- AP EAPCET 2026Set ap-2026-05-19-AN1 markMCQQ.Pneumonia mainly affects (A) Bronchi (B) Trachea (C) Alveoli (D) Larynx
›Reveal solutionSolution
Pneumonia is an alveolar disease — inflammation and fluid-filling of the alveoli impairs gas exchange, distinguishing it from airway diseases like bronchitis or laryngitis.
Concept and Intuition
The respiratory tract can be divided into conducting airways (larynx, trachea, bronchi, bronchioles) that merely transport air, and the respiratory zone (alveoli) where actual gas exchange with blood happens across a thin epithelial-capillary membrane. Pneumonia specifically targets this respiratory zone: infectious agents provoke an inflammatory response, and the alveolar spaces (normally air-filled for efficient diffusion) become filled with inflammatory exudate, pus and fluid. This directly compromises oxygen diffusion into the pulmonary capillaries, explaining the hypoxia and laboured breathing seen in pneumonia patients, and why it appears radiographically as opacities ("consolidation") of lung tissue.
Step-by-Step Solution
- Recall the functional distinction between conducting airways (bronchi, trachea, larynx) and the exchange surface (alveoli).
- Recall pneumonia's defining pathology: alveolar inflammation with exudate/fluid accumulation.
- Eliminate bronchi/trachea/larynx — these are affected in bronchitis, tracheitis and laryngitis respectively, not the hallmark of pneumonia.
- Select alveoli as the primary site affected in pneumonia.
Common Mistakes
- Confusing pneumonia (alveolar) with bronchitis (bronchial) — both cause cough/breathlessness but affect different structures.
- Assuming pneumonia is confined to the upper airway (larynx/trachea) rather than the deep lung tissue.
✓Final answerThe correct option is (C) — Alveoli.
ANSWER: C
- AP EAPCET 2026Set ap-2026-05-20-FN1 markMCQQ.Assertion (A): Ascaris lumbricoides completes its entire life cycle within the small intestine. Reason (R): Larvae of Ascaris undergo extra intestinal migration. (A) Both (A) and (R) are true. (R) is correct explanation for (A) (B) Both (A) and (R) are true. (R) is not correct explanation for (A) (C) (A) is true. But (R) is false (D) (A) is false. But (R) is true
›Reveal solutionSolution
Ascaris larvae leave the intestine and migrate through blood, liver, heart and lungs before returning to mature in the gut — so the life cycle is NOT confined to the small intestine, making the Assertion false while the Reason (which describes exactly this migration) is true.
Concept and Intuition
Many intestinal nematodes, including Ascaris lumbricoides, have a life cycle where the adult and egg-laying stage occurs in the intestine, but the larval stage takes a detour through the circulatory and respiratory systems — this is called extra-intestinal (or hepato-pulmonary/tracheal) migration, and it is central to how the parasite establishes and matures.
Step-by-Step Solution
- Ingested embryonated eggs hatch into larvae in the small intestine.
- The larvae penetrate the intestinal wall and enter the portal blood/lymphatics, travelling to the liver, then the heart, then the lungs.
- In the lungs the larvae break into the alveoli, migrate up the bronchi, trachea, and pharynx, and are then swallowed again.
- Only after re-entering the small intestine a second time do the larvae mature into egg-laying adults.
- This means the life cycle genuinely leaves the intestine during larval development — so "completes entire life cycle within the small intestine" (the Assertion) is false, while "larvae undergo extra-intestinal migration" (the Reason) is a true and directly relevant fact.
Common Mistakes
- Assuming that because the adult worm and the eggs are both intestinal, the whole life cycle must be intestinal — the crucial larval detour through blood/liver/lungs is easy to overlook.
✓Final answerThe correct option is (D) — (A) is false, but (R) is true.
ANSWER: D
- AP EAPCET 2026Set ap-2026-05-20-FN1 markMCQQ.Statement I: Ringworm is caused by Epidermophyton. Statement II: Ringworm commonly affects skin folds such as groin or among toes. (A) Statement I and II are correct (B) Statement I and II are incorrect (C) Statement I is correct II is incorrect (D) Statement I is incorrect II is correct
›Reveal solutionSolution
Both statements about ringworm are textbook-accurate: it is caused by dermatophyte fungi including Epidermophyton, and it typically affects moist skin folds like the groin and toe-webs.
Concept and Intuition
Ringworm (dermatophytosis) is a fungal skin infection, not caused by a worm despite the name. The causative fungi (genera Trichophyton, Microsporum, Epidermophyton) thrive in warm, moist environments, which is exactly why body folds — groin, armpits, and between toes — are the classic sites of infection.
Step-by-Step Solution
- Confirm causative organism: ringworm is a dermatophytosis, and NCERT/standard texts name Trichophyton, Microsporum, and Epidermophyton as the causative fungal genera — so Statement I is accurate.
- Confirm site of infection: dermatophyte fungi favour keratinized, moist skin — groin folds and interdigital spaces of the feet are the most commonly affected regions, matching Statement II.
- Both statements hold, so the joint answer is that both are correct.
Common Mistakes
- Assuming "ringworm" implies a helminth infection because of the name — it is fungal, not parasitic-worm related.
- Overlooking that moist, occluded skin regions (not just visible ring-shaped patches anywhere) are the classic sites.
✓Final answerThe correct option is (A) — Statement I and II are correct.
ANSWER: A
- AP EAPCET 2026Set ap-2026-05-20-AN1 markMCQQ.Assertion (A): Elephantiasis is due to the obstruction of lymphatic vessels by accumulation of dead filarial worms. Reason (R): First stage microfilaria larva is the infective stage to humans. (A) Both (A) and (R) are true. (R) is correct explanation for (A) (B) Both (A) and (R) are true. (R) is not correct explanation for (A) (C) (A) is true. But (R) is false (D) (A) is false. But (R) is true
›Reveal solutionSolution
This tests filarial worm life cycle and pathology — elephantiasis truly results
from lymphatic blockage by dead worms (A, true), but the human-infective stage
is the mosquito-borne third-stage (L3) larva, not the first-stage microfilaria
(R, false).
Concept and Intuition
Lymphatic filariasis (elephantiasis) is caused by thread-like filarial worms
(e.g. Wuchereria bancrofti) that lodge in the lymphatic vessels and lymph nodes.
Chronic infection, with accumulation of both living and dead adult worms, provokes
inflammation and fibrosis that progressively blocks lymphatic drainage — this
obstruction is what causes the grotesque swelling (elephantiasis) of limbs and
other body parts. This makes Assertion (A) an accurate description of the disease
mechanism.
The filarial life cycle, however, has a specific infective-stage detail that
Reason (R) gets wrong: microfilariae (first-stage larvae) circulate in the
peripheral blood of an infected person and are picked up by a biting mosquito.
Inside the mosquito, these larvae undergo further development (moulting through
additional larval stages) to become the third-stage (L3) infective/filariform larva. It is this L3 stage — not the original microfilaria — that the mosquito
then transmits into a new human host during a subsequent bite, where it develops
into an adult worm.
Step-by-Step Solution
- Evaluate (A): elephantiasis is caused by lymphatic vessel obstruction due to accumulated (living and dead) filarial worms — this is the well-established disease mechanism. (A) is true.
- Evaluate (R): it claims the first-stage microfilaria larva is infective to humans. In reality, microfilariae are the stage found in human blood (picked up from humans by mosquitoes), while the stage that is infective to humans is the third-stage (L3) larva developed inside the mosquito. (R) is false.
- Since (A) is true and (R) is false, and (R) does not correctly explain (A) regardless, the correct choice is "(A) is true, (R) is false."
Common Mistakes
- Assuming microfilaria (the blood stage found in infected humans) is also the stage transmitted back to new hosts — the infective stage requires further development inside the mosquito to become the L3 larva.
✓Final answerThe correct option is (C) — (A) is true. But (R) is false.
ANSWER: C
- AP EAPCET 2026Set ap-2026-05-20-AN1 markMCQQ.Statement I: Typhoid bacteria are transmitted through contaminated food and water. Statement II: Salmonella typhi is a gram-positive bacterium. (A) Statement I and II are correct (B) Statement I and II are incorrect (C) Statement I is correct II is incorrect (D) Statement I is incorrect II is correct
›Reveal solutionSolution
This tests basic microbiology of typhoid fever — transmission via contaminated
food/water is correctly stated (I, true), but Salmonella typhi is Gram-negative,
not Gram-positive as claimed in II (false).
Concept and Intuition
Typhoid fever is a classic water/food-borne bacterial disease. Its causative
agent, Salmonella typhi (also called Salmonella enterica serovar Typhi), is
transmitted through the faecal-oral route: contaminated drinking water or food
handled/prepared under poor hygienic conditions carries the bacterium from an
infected person (or carrier) to a new host, who ingests it. On Gram staining,
Salmonella typhi is a Gram-negative, rod-shaped bacterium (it has a thin
peptidoglycan layer surrounded by an outer membrane, characteristic of
Gram-negative bacteria, and appears pink/red after Gram staining) — it is not
Gram-positive.
Step-by-Step Solution
- Statement I: "Typhoid bacteria are transmitted through contaminated food and water" — this matches the well-documented faecal-oral transmission route of typhoid. Correct.
- Statement II: "Salmonella typhi is a gram-positive bacterium" — in reality, Salmonella typhi is Gram-negative. Incorrect.
- So Statement I is correct and Statement II is incorrect, matching option (C).
Common Mistakes
- Assuming all disease-causing rod-shaped bacteria are Gram-positive; many important enteric pathogens (Salmonella, E. coli, Shigella) are in fact Gram-negative.
✓Final answerThe correct option is (C) — Statement I is correct II is incorrect.
ANSWER: C
- AP EAPCET 2025Set ap-2025-05-19-FN1 markMCQQ.Match the following. Parasites - Infective stages to man A) Entamoeba histolytia - I. Sporozoite B) Plasmodium vivax - II. 3rd stage microfilaria C) Ascaris lumbricoides - III. 2nd stage rhabditiform larva D) Wuchereria bancrofti - IV. Tetranucleate cyst
- V. Gametocyte (A) A - III, B - IV, C - II, D - I (B) A - IV, B - I, C - V, D - II (C) A - IV, B - I, C - III, D - II (D) A - I, B - IV, C - III, D - II
›Reveal solutionSolution
This tests recall of the human-infective stage for four medically important parasites; the correct match is A-IV, B-I, C-III, D-II.
Concept and Intuition
Each parasite has a specific developmental stage that is capable of infecting a new human host, and this stage differs across life cycles:
- Amoebic and protozoan cysts are ingested.
- Malarial sporozoites are injected by mosquito bite.
- Nematode eggs/larvae are either ingested (Ascaris) or transmitted by insect vectors (Wuchereria).
Step-by-Step Solution
- Entamoeba histolytica — infects a new host via ingestion of the tetranucleate cyst (IV) present in contaminated food/water.
- Plasmodium vivax — infects a new host when an infected female Anopheles mosquito injects sporozoites (I) during a blood meal.
- Ascaris lumbricoides — infects a new host via ingestion of eggs containing the 2nd-stage rhabditiform larva (III).
- Wuchereria bancrofti — infects a new host when an infected mosquito introduces the 3rd-stage (infective) larva (II) during a bite.
- This gives A-IV, B-I, C-III, D-II, matching option (C).
Common Mistakes
- Confusing the infective stage (entering the new host) with the diagnostic stage (found in blood/stool samples, e.g. trophozoite or microfilaria).
✓Final answerThe correct option is (C) — A-IV, B-I, C-III, D-II.
ANSWER: C
- AP EAPCET 2025Set ap-2025-05-19-FN1 markMCQQ.Parasite that causes african sleeping sickness. (A) Ascaris (B) Trypanosoma (C) Plasmodium (D) Wuchereria
›Reveal solutionSolution
This tests the causative agent of African sleeping sickness, which is the flagellate protozoan Trypanosoma.
Concept and Intuition
African trypanosomiasis, commonly called "sleeping sickness," is caused by protozoan parasites of the genus Trypanosoma (subspecies T. brucei gambiense and T. brucei rhodesiense), transmitted through the bite of the tsetse fly (Glossina). The parasite invades the bloodstream and eventually the central nervous system, causing the characteristic disturbed sleep-wake cycle that gives the disease its name.
Step-by-Step Solution
- Ascaris — a roundworm causing intestinal ascariasis, not sleeping sickness.
- Trypanosoma — the flagellate protozoan parasite that causes African sleeping sickness, transmitted by the tsetse fly.
- Plasmodium — causes malaria, not sleeping sickness.
- Wuchereria — causes lymphatic filariasis, not sleeping sickness.
- Hence the correct causative agent is Trypanosoma.
Common Mistakes
- Confusing Trypanosoma (sleeping sickness, tsetse fly vector) with Plasmodium (malaria, Anopheles mosquito vector) — both are blood/tissue protozoan parasites but cause very different diseases.
✓Final answerThe correct option is (B) — Trypanosoma.
ANSWER: B
- AP EAPCET 2025Set ap-2025-05-19-FN1 markMCQQ.Pick up the wrongly matched pair. (A) Entamoeba histolytica - Cart wheel shaped nucleus (B) Plasmodium vivax - Haemozoin granules (C) Ascaris lumbricoides - Mammillated eggs (D) Wuchereria bancrofti - Oviparous
›Reveal solutionSolution
This tests distinguishing features of common human parasites; the wrongly matched pair is Wuchereria bancrofti-Oviparous, since filarial worms are ovoviviparous, not oviparous.
Concept and Intuition
Each parasite has a well-documented diagnostic feature used in identification:
- Entamoeba histolytica trophozoites/cysts show a characteristic cartwheel-shaped nucleus (central karyosome with radiating chromatin).
- Plasmodium vivax infected red blood cells contain haemozoin (malarial pigment), a breakdown product of haemoglobin digestion.
- Ascaris lumbricoides fertilized eggs have a characteristic mammillated (bumpy) outer coating.
- Wuchereria bancrofti females do not lay eggs that hatch externally; instead eggs develop and hatch within the female's uterus, and she releases already-motile larvae (microfilariae) directly — this reproductive mode is called ovoviviparous, not oviparous.
Step-by-Step Solution
- (A) Entamoeba histolytica - Cart wheel shaped nucleus — correctly matched, a genuine diagnostic feature.
- (B) Plasmodium vivax - Haemozoin granules — correctly matched, the malarial pigment seen in infected RBCs/tissues.
- (C) Ascaris lumbricoides - Mammillated eggs — correctly matched, a classic identifying feature of fertilized Ascaris eggs.
- (D) Wuchereria bancrofti - Oviparous — incorrect; Wuchereria bancrofti is ovoviviparous (produces live microfilariae, not laid eggs).
- Hence (D) is the wrongly matched pair.
Common Mistakes
- Assuming all worm parasites lay eggs (oviparous); filarial worms specifically retain and hatch eggs internally, releasing live larvae.
✓Final answerThe correct option is (D) — Wuchereria bancrofti - Oviparous.
ANSWER: D
- AP EAPCET 2025Set ap-2025-05-20-AN1 markMCQQ.Pneumonia is caused by (A) Salmonella (B) Haemophilus (C) Rhino virus (D) Microsoprum
›Reveal solutionSolution
This tests knowledge of causative organisms of common human diseases. Pneumonia (alveolar
infection) is caused by bacteria such as Streptococcus pneumoniae and Haemophilus influenzae — the answer is (B) Haemophilus.
Concept and Intuition
Human Health and Disease pairs each common illness with its causative agent so that
similar-sounding organisms are not confused. Pneumonia specifically inflames the alveoli,
filling them with fluid and impairing gas exchange; this is classically produced by the
bacteria Streptococcus pneumoniae and Haemophilus influenzae.
Step-by-Step Solution
- Salmonella typhi is the causative agent of typhoid fever, not pneumonia.
- Haemophilus influenzae is a well-known bacterial cause of pneumonia (and also of meningitis/ear infections) — this matches the question.
- Rhinovirus is one of the viruses responsible for the common cold, not pneumonia.
- Microsporum is a fungus causing ringworm (a skin infection), not pneumonia.
- Only option (B) correctly names a pneumonia-causing organism.
Common Mistakes
- Confusing Salmonella (typhoid) with pneumonia-causing bacteria.
- Assuming any respiratory-sounding virus (like Rhinovirus) must cause pneumonia rather than the common cold.
✓Final answerThe correct option is (B) — Haemophilus.
ANSWER: B
- AP EAPCET 2025Set ap-2025-05-20-AN1 markMCQQ.Pick up the wrongly matched pair (A) Typhoid - Salmonella (B) Pneumonea - Streptococcus (C) Ring worm - Sacculina (D) Filaria - Wuchereria
›Reveal solutionSolution
Three of the four pairs correctly link a disease to its causative organism; only the
ringworm pairing is wrong because Sacculina is a parasitic barnacle of crabs, not a
fungus, and does not cause ringworm.
Concept and Intuition
This is a disease-organism matching question. Each disease must be checked against the
correct kingdom and species of its causative agent, since superficially plausible
pairings (organism names that "sound right") are the usual distractors.
Step-by-Step Solution
- Typhoid is caused by the bacterium Salmonella typhi — pair (A) is correct.
- Pneumonia is caused by bacteria including Streptococcus pneumoniae — pair (B) is correct.
- Ringworm is a fungal skin disease caused by fungi of the genera Microsporum, Trichophyton, or Epidermophyton — not by Sacculina, which is a parasitic barnacle (crustacean) that castrates crabs; it has nothing to do with human skin infection. Pair (C) is therefore wrong.
- Filariasis is caused by the nematode Wuchereria bancrofti — pair (D) is correct.
- Hence the wrongly matched pair is (C).
Common Mistakes
- Assuming any parasite name automatically fits a human skin disease.
- Not recalling that Sacculina is a well-known example of a barnacle parasite on crabs from the Animal Kingdom/parasitism topic, unrelated to fungal skin infections.
✓Final answerThe correct option is (C) — Ring worm - Sacculina (wrongly matched; ringworm is
caused by a fungus, not by Sacculina).
ANSWER: C
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