Infectious Diseases — MCQs

Infectious Diseases Indian Medical PG Practice Questions and MCQs

Question 411: Chiggerosis is due to

A. Louse
B. Chigger (Correct Answer)
C. Tick
D. Bed bug

Explanation: ***Chigger (Trombiculid mite larva)*** - **Chiggerosis**, also known as **trombiculosis**, is an intensely itchy dermatitis caused by the bite of the larval stage of **trombiculid mites**. - These larvae attach to the skin, inject digestive enzymes, and feed on liquefied tissue, causing characteristic **pruritic red papules**. *Louse* - **Lice** (e.g., *Pediculus humanus* or *Pthirus pubis*) cause **pediculosis**, characterized by pruritus, excoriations, and nits attached to hair shafts. - Their bites are typically small, red papules, but do not produce the intense, persistent inflammatory reaction associated with chigger bites. *Tick* - **Ticks** are larger arachnids that burrow their mouthparts into the skin to feed on blood, which can transmit various **pathogens** (e.g., Lyme disease, Rocky Mountain spotted fever). - While tick bites can cause localized irritation, they do not typically result in the widespread, intensely itchy rash seen in chiggerosis. *Bed bug* - **Bed bugs** (*Cimex lectularius*) are nocturnal insects that feed on human blood, typically producing small, **itchy red welts** often arranged in a linear pattern ("breakfast, lunch, and dinner"). - The rash is distinct from chiggerosis, which presents as highly inflammatory, localized papules often found in skin folds or tight clothing areas.

Question 412: World Malaria Day is observed in which month?

A. April (Correct Answer)
B. September
C. May
D. June

Explanation: ***April*** - **World Malaria Day** is observed annually on **April 25th**. - Its purpose is to raise awareness about malaria and celebrate the efforts made globally to control and eradicate this disease. *September* - While September hosts various health observances, it is not the month for **World Malaria Day**. - Other public health campaigns, such as **World Alzheimer's Month**, are observed in September. *May* - May is recognized for several health-related days, but not specifically for **World Malaria Day**. - For example, **World Hypertension Day** is observed in May. *June* - June includes observances like **World Blood Donor Day**, but it is not the month designated for **World Malaria Day**. - Public health calendars indicate April 25th for this specific event.

Question 413: White death is

A. Plague
B. Yellow fever
C. HIV
D. TB (Correct Answer)

Explanation: ***TB*** - **Tuberculosis (TB)**, particularly the pulmonary form, has historically been known as the **"White Death"** due to the characteristic pallor, weight loss, and widespread prevalence it caused, leading to death. - This term reflects the devastating impact of the disease, which left victims looking pale and wasted due to chronic illness and cachexia. *Plague* - The **Plague** is famously known as the **"Black Death"** due to the development of **gangrene** and **hemorrhages** that turned the skin black. - It is caused by the bacterium *Yersinia pestis* and is characterized by rapidly progressing, severe symptoms, often in the form of bubonic, pneumonic, or septicemic plague. *Yellow fever* - **Yellow fever** is named for the **jaundice (yellowing of the skin and eyes)** that affects some patients due to liver damage. - It is a viral hemorrhagic disease transmitted by mosquitoes and is not associated with the term "White Death." *HIV* - **HIV (Human Immunodeficiency Virus)** infection leads to **AIDS (Acquired Immunodeficiency Syndrome)**, which was historically known as the **"slim disease"** due to the severe weight loss and wasting it caused, but not specifically the "White Death." - HIV primarily targets the immune system, leading to opportunistic infections and cancers, rather than the pallor associated with chronic lung disease.

Question 414: The following statements are true regarding leptospirosis, except -

A. Lice act as reservoirs of infection (Correct Answer)
B. It is zoonosis
C. Man is the dead end host
D. Man is an accidental host

Explanation: ***Lice act as reservoirs of infection*** - **Lice** are not known reservoirs or vectors for leptospirosis; the infection is primarily spread through the urine of infected animals. - The main reservoirs are **rodents**, **livestock**, and **wild animals**, which excrete bacteria in their urine. *It is zoonosis* - **Leptospirosis** is indeed a **zoonotic disease**, meaning it is transmitted from animals to humans. - Humans typically acquire the infection through contact with the urine of infected animals or contaminated water/soil. *Man is the dead end host* - Humans are considered **dead-end hosts** for leptospirosis, meaning they typically do not transmit the infection to others. - While humans can become severely ill, their role in maintaining the natural cycle of the disease is minimal. *Man is an accidental host* - Humans are also considered an **accidental host**, as they contract the disease incidentally from the environment rather than being a natural part of the pathogen's life cycle. - The primary cycle of transmission occurs between infected animals and the environment.

Question 415: True statement regarding RNTCP includes all except

A. Sputum microscopy
B. Exclusion of private practitioners (Correct Answer)
C. Participation of all health workers
D. Provides latest equipment

Explanation: ***Exclusion of private practitioners*** - The **Revised National Tuberculosis Control Program (RNTCP)** actively encourages and facilitates the engagement of **private practitioners** in TB care and management. - This involvement is crucial for expanding reach, ensuring correct diagnosis, and completing treatment in a country like India where a significant portion of healthcare is provided by the private sector. *Sputum microscopy* - **Sputum microscopy** is a cornerstone diagnostic tool within the RNTCP for identifying **acid-fast bacilli (AFB)** in patients suspected of having pulmonary tuberculosis. - It is a cost-effective and readily available method for confirming TB and monitoring treatment response. *Participation of all health workers* - The RNTCP emphasizes the engagement of **all health workers**, including community health workers, nurses, and doctors, across various levels of healthcare delivery. - This broad participation is essential for **case finding**, treatment adherence, and community education efforts regarding TB. *Provides latest equipment* - The RNTCP continually strives to upgrade its diagnostic and treatment infrastructure by providing **latest equipment** such as **Gene Xpert machines** for rapid molecular diagnosis and drug susceptibility testing. - This ensures access to modern diagnostic tools for more accurate and timely TB diagnosis and management, especially for drug-resistant forms of TB.

Question 416: All of the following statements about tetanus are true except:

A. Soil and intestines of infected humans and animals act as chief reservoirs.
B. Incubation period is 6-12 days.
C. Tetanospasmin is the neurotoxin responsible for clinical manifestations
D. Uterine tetanus is the least severe. (Correct Answer)

Explanation: ***Uterine tetanus is the least severe.*** - Uterine tetanus (or **puerperal tetanus**) is actually a severe form of tetanus, often leading to high morbidity and mortality in mothers and neonates due to complications associated with childbirth. - The severity of tetanus is generally related to the **amount of toxin produced** and disseminated, and uterine infections can lead to significant toxin production due to anaerobic conditions. *Soil and intestines of infected humans and animals act as chief reservoirs.* - **Clostridium tetani** spores are widely distributed in the environment, especially in **soil contaminated with feces** from humans and animals. This makes soil a primary reservoir. - The gastrointestinal tracts of humans and animals can harbor the bacterium without causing disease, thus serving as an additional reservoir. *Incubation period is 6-12 days.* - The typical incubation period for tetanus is generally reported to be **3 to 21 days**, with a common range of **6 to 12 days**. - A shorter incubation period is often associated with more severe disease and a worse prognosis due to greater toxin load or closer proximity to the central nervous system. *Tetanospasmin is the neurotoxin responsible for clinical manifestations* - **Tetanospasmin** is indeed the potent neurotoxin produced by *Clostridium tetani* that is responsible for all the clinical manifestations of tetanus. - This toxin acts by blocking the release of **inhibitory neurotransmitters** (glycine and GABA) in the spinal cord, leading to uncontrolled muscle spasms and rigidity.

Question 417: The most practical way of treating typhoid carrier is -

A. Chemotherapy
B. Vaccination
C. Cholecystectomy (Correct Answer)
D. Isolation

Explanation: ***Correct Option: Cholecystectomy*** - **Cholecystectomy** (surgical removal of the gallbladder) is the **most practical and definitive treatment** for chronic typhoid carriers - Chronic carriers harbor *Salmonella typhi* in the **gallbladder**, especially when **gallstones** are present, where bacteria form biofilms - **Success rate >90%** in eliminating the carrier state permanently - Particularly important for **food handlers** and healthcare workers where definitive cure is essential - While surgical, it provides a **permanent solution** unlike antibiotics which have high failure/relapse rates *Incorrect Option: Chemotherapy* - Antibiotic therapy alone has a **poor success rate** (~80% failure) in chronic typhoid carriers - Bacteria in the gallbladder are protected by **biofilms** on gallstones and poor antibiotic penetration - High **relapse rates** even after prolonged courses of ciprofloxacin or ampicillin - May be attempted first but is not the most practical definitive treatment *Incorrect Option: Isolation* - **Isolation** is a public health measure to prevent transmission, not a treatment - Does not eliminate the bacteria from the carrier's body - Only controls spread to others, not a therapeutic intervention *Incorrect Option: Vaccination* - Provides **prophylactic immunity** against future infection but does not treat existing carrier state - Does not eliminate *Salmonella typhi* bacteria already colonizing the gallbladder - Used for prevention, not treatment of carriers

Question 418: All of the following statements about plague are wrong except -

A. Incubation period for pneumonic plague is 10-14 days
B. Bubonic is the most common variety (Correct Answer)
C. The causative bacillus can survive up to 10 years in the soil of rodent burrows
D. Domestic rat is main reservoir

Explanation: ***Bubonic is the most common variety*** - **Bubonic plague** is indeed the most frequent clinical form of plague, accounting for 80-95% of cases. - It results from the bite of an infected flea, leading to the development of **buboes** (swollen, tender lymph nodes). *Incubation period for pneumonic plague is 10-14 days* - The incubation period for **pneumonic plague** is typically much shorter, usually 1 to 3 days, not 10-14 days. - A longer incubation period would be atypical for such an aggressive and rapidly progressing disease. *The causative bacillus can survive up to 10 years in the soil of rodent burrows* - While *Yersinia pestis* can survive in the environment, its survival in soil is typically for days to weeks, not years. - The primary survival mechanism is within infected animals and fleas, not as dormant free-living bacteria for a prolonged period in soil. *Domestic rat is main reservoir* - While domestic rats (Rattus species) can be involved in urban plague cycles, the main reservoirs of *Yersinia pestis* are wild rodents such as **ground squirrels, marmots, and prairie dogs**. - These wild rodents maintain the enzootic cycle in nature, and fleas often transmit the bacteria between them.

Question 419: H5N1 Avian influenza has not become an epidemic till now. What is the most important reason for this?

A. Seen only in wild birds and not in domestic poultry
B. It causes serious illness leading to death of the patient
C. It has avian influenza genes
D. Human to human transmission is rare (Correct Answer)

Explanation: ***Human to human transmission is rare*** - While H5N1 can infect humans, its **limited ability to spread efficiently from person to person** is the primary reason it has not caused a human pandemic. - Efficient human-to-human transmission is a prerequisite for any widespread epidemic or pandemic. *Seen only in wild birds and not in domestic poultry* - H5N1 can affect both **wild birds and domestic poultry**, contradicting the statement. - The virus's presence in domestic poultry has historically been a significant source of human exposure. *It causes serious illness leading to death of the patient* - The **severity of illness and high mortality rate** in infected humans actually makes epidemic control more challenging, not less, if human-to-human transmission were efficient. - However, this characteristic alone does not prevent the virus from becoming an epidemic unless it can spread between people. *It has avian influenza genes* - The presence of avian influenza genes is simply a **description of the virus's genetic makeup** and its origin in birds. - It does not explain why the virus has or has not become an epidemic in humans; rather, it indicates the source of the virus.

Question 420: Zoonoses are all except-

A. Plague
B. Guinea worm infestation (Correct Answer)
C. Rabies
D. Hydatid cyst

Explanation: ***Guinea worm infestation*** - **Dracunculiasis (Guinea worm disease)** is exclusively a human disease (anthroponosis), meaning humans are the only definitive hosts. - The life cycle involves humans as the primary host and **copepods** (small crustaceans) as intermediate hosts; there is no animal reservoir or transmission to/from other vertebrate animals. - This is **NOT a zoonosis** because it does not involve animal-to-human transmission. *Plague* - **Plague** is a classic zoonosis caused by *Yersinia pestis*, primarily affecting rodents and transmitted to humans via **flea bites**. - Rodents (especially rats) serve as natural reservoirs, making this a clear example of animal-to-human disease transmission. *Rabies* - **Rabies** is a viral zoonotic disease transmitted to humans through the saliva of infected animals, most commonly via **bites from infected animals**. - The main reservoirs are **carnivorous mammals** such as dogs, foxes, bats, and raccoons, making it a classic zoonosis. *Hydatid cyst* - **Hydatid disease (echinococcosis)** is a zoonosis caused by the larval stage of *Echinococcus* tapeworms. - Definitive hosts are **carnivores** (e.g., dogs, wolves), and humans are accidental intermediate hosts who acquire infection through contact with infected animal feces or contaminated food/water.

Practice by Chapter

Communicable Disease Control Principles

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Vector-Borne Diseases

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Water-Borne Diseases

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Air-Borne Diseases

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Zoonotic Diseases

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Sexually Transmitted Infections

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HIV/AIDS Control Program

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Tuberculosis Control

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Leprosy Elimination

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Emerging and Re-emerging Infections

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Hospital-Acquired Infections

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Integrated Disease Surveillance Project

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