Infectious Diseases — MCQs

Infectious Diseases Indian Medical PG Practice Questions and MCQs

Question 711: Which bacterial disease is commonly associated with the three "Rs": rats, rice fields, and rainfall?

A. Leptospirosis (Correct Answer)
B. Bubonic plague
C. Haverhill fever
D. Melioidosis

Explanation: ***Leptospirosis*** - This disease is directly associated with exposure to environments contaminated by **animal urine**, often linked to **rats** in environments like **rice fields** where **rainfall** creates favorable conditions for bacterial survival and transmission. - The classic **"3 Rs" mnemonic** (Rats, Rice fields, Rainfall) specifically describes leptospirosis epidemiology. - **Leptospira** bacteria typically enter the body through cuts or abrasions in the skin or through mucous membranes, especially when prolonged exposure to contaminated water occurs. - Common in **occupational groups**: farmers, sewer workers, veterinarians, and military personnel. *Bubonic plague* - Characterized by acute onset of fever, chills, weakness, and painful, swollen lymph nodes called **buboes**, caused by **Yersinia pestis**. - Primarily transmitted to humans through bites of **infected fleas** that have fed on rodents, not directly through contaminated water or rice fields. - While associated with rats, lacks the rice field and rainfall environmental components. *Haverhill fever* - Caused by **Streptobacillus moniliformis**, a form of **rat-bite fever** contracted through rodent contact or ingestion of contaminated food/water. - While associated with rats, it doesn't have the specific environmental triad of **rice fields** and **rainfall** as central to its epidemiology like leptospirosis. - Transmission is primarily through rat bites or contaminated milk products. *Melioidosis* - Caused by **Burkholderia pseudomallei**, found in soil and water in tropical and subtropical regions. - While found in water and soil with potential agricultural exposure, it is **not specifically linked** to the "rats, rice fields, and rainfall" triad that defines leptospirosis. - More commonly associated with direct soil contact rather than rat-contaminated environments.

Question 712: Who is credited with introducing the practice of hand hygiene in medical settings?

A. Joseph Lister
B. Ignac Semmelweis (Correct Answer)
C. Louis Pasteur
D. Oliver Wendell Holmes

Explanation: ***Ignác Semmelweis*** - **Ignác Semmelweis** observed a correlation between physician handwashing and reduced rates of **puerperal fever** in maternity wards in the mid-19th century. - He implemented a policy of using **chlorinated lime solutions** for hand disinfection, significantly decreasing mortality rates. - His empirical evidence and observational studies form the foundation of modern hand hygiene practices in healthcare. *Joseph Lister* - **Joseph Lister** is known for introducing **antiseptic surgery**, using carbolic acid to sterilize surgical instruments and wounds. - While a pioneer in infection control, his focus was on antisepsis during surgical procedures rather than routine hand hygiene. *Oliver Wendell Holmes* - Dr. **Oliver Wendell Holmes Sr.** also advocated for the importance of handwashing to prevent the spread of infectious diseases, particularly puerperal fever, around the same time as Semmelweis. - However, Semmelweis's observational studies and empirical evidence are more widely credited as the foundational work in establishing hand hygiene protocols. *Louis Pasteur* - **Louis Pasteur** was a French chemist and microbiologist renowned for his groundbreaking discoveries in **vaccination**, **microbial fermentation**, and **pasteurization**. - His work established the **germ theory of disease**, but he did not directly introduce the practice of hand hygiene in medical settings.

Question 713: What is the correct schedule for pre-exposure prophylaxis for rabies vaccination?

A. 0, 7 days
B. 0, 3, 7, 14 days
C. 0, 3, 7, 14, 30 days
D. 0, 7, 28 days (Correct Answer)

Explanation: ***0, 7, 28 days*** - The CDC recommends a **three-dose schedule** for rabies pre-exposure prophylaxis (PrEP) on days 0, 7, and 28 or 21. - This schedule ensures adequate **antibody production** before potential exposure to the rabies virus. *0, 7 days* - This two-dose schedule is typically used for **post-exposure prophylaxis (PEP)** in individuals who are already previously vaccinated, not for initial pre-exposure prophylaxis. - It would not provide sufficient **long-term immunity** for unvaccinated individuals. *0, 3, 7, 14 days* - This schedule is **not the standard** pre-exposure prophylaxis regimen recommended by major health organizations. - While it includes multiple doses, it deviates from the **established and proven 3-dose PrEP schedule**. *0, 3, 7, 14, 30 days* - This is an **overly extensive** and incorrect schedule for routine pre-exposure prophylaxis. - A more frequent and prolonged schedule like this is **unnecessary** and not part of current guidelines for rabies PrEP.

Question 714: Which of the following infectious diseases is characterized by the most consistent and characteristic clinical presentation?

A. Rubella
B. Influenza
C. Measles (Correct Answer)
D. Polio

Explanation: **Correct Option: Measles** - Measles, caused by the **measles virus**, has a highly characteristic clinical presentation including a prodrome of fever, cough, coryza, and conjunctivitis (the 3 C's), followed by **Koplik spots** (pathognomonic) and a maculopapular rash that spreads in a **cephalocaudal pattern**. - The disease progression and symptomology are quite **predictable and consistent**, making it one of the most recognizable childhood exanthems. - Clinical features follow a characteristic timeline making diagnosis reliable on clinical grounds alone. *Incorrect Option: Rubella (German Measles)* - Rubella often presents with milder and less distinctive symptoms compared to measles, including a **milder rash** and **postauricular/occipital lymphadenopathy**. - A significant number of **rubella infections are asymptomatic** or subclinical (up to 50%), making its presentation less consistent and characteristic. *Incorrect Option: Influenza* - Influenza symptoms can vary widely, ranging from **mild respiratory illness** to severe disease with pneumonia, and are often indistinguishable from other viral respiratory infections without laboratory testing. - The clinical presentation is highly variable depending on the **specific viral strain**, age, and immune status of the individual. *Incorrect Option: Polio (Poliomyelitis)* - While known for its potential to cause paralytic disease, **most poliovirus infections (about 95%) are asymptomatic** or present as mild, non-specific febrile illness without paralysis. - The variable presentation, with only a small proportion developing the characteristic paralytic form, means it lacks a consistently characteristic clinical picture for most infected individuals.

Question 715: Chandler's Index is used for:

A. Hookworm infections (Correct Answer)
B. Lymphatic filariasis
C. Intestinal ascariasis
D. Dracunculiasis

Explanation: **Hookworm infections** ✓ - **Chandler's Index** is a method used to assess the **severity** and **intensity** of **hookworm infection** within a community. - It calculates the average number of hookworms per infected person, helping determine prevalence and infection burden. - This epidemiological tool is specific to hookworm surveillance and control programs. *Lymphatic filariasis* - Assessed using different metrics such as microfilaremia prevalence, lymphedema rates, and circulating filarial antigen detection. - Diagnosis involves identifying **microfilariae** in blood smears, not Chandler's Index. *Intestinal ascariasis* - Assessed by detecting *Ascaris lumbricoides* eggs in stool samples. - Severity measured by worm burden or egg count intensity, not by a community-level index like Chandler's. *Dracunculiasis* - Diagnosed by the emergence of *Dracunculus medinensis* worm from the skin. - Eradication efforts focus on case detection and containment, with no application of Chandler's Index.

Question 716: In which of the following conditions is post-exposure prophylaxis recommended and effective?

A. Measles
B. Hepatitis B
C. Pertussis
D. Rabies (Correct Answer)

Explanation: ***Rabies*** - **Post-exposure prophylaxis (PEP) for rabies is the gold standard example of highly effective prophylaxis**, with near **100% efficacy** when administered correctly. - Consists of **thorough wound washing**, **rabies immunoglobulin (RIG)**, and **rabies vaccine** given according to the recommended schedule. - **Universally recommended** for all animal bite exposures where rabies cannot be ruled out, as untreated rabies is **uniformly fatal**. - PEP must be initiated as soon as possible after exposure but remains effective even if started several days after the bite. *Hepatitis B* - Hepatitis B PEP is also **highly effective (70-95%)** and well-established, using **HBIG and vaccine series**. - Recommended for occupational exposures, sexual contacts, and perinatal transmission. - While very effective, rabies PEP is considered the paradigm example due to its near-perfect efficacy and the invariably fatal outcome without treatment. *Measles* - Post-exposure prophylaxis with **MMR vaccine within 72 hours** or **immunoglobulin within 6 days** can be **moderately effective**. - Time-sensitivity limits effectiveness, and vaccine may not prevent disease if given too late after exposure. - Not as universally effective as rabies PEP. *Pertussis* - **Chemoprophylaxis with azithromycin** is recommended for close contacts of pertussis cases. - However, effectiveness is **limited** - primarily reduces transmission rather than reliably preventing disease in exposed individuals. - Not considered as definitively effective as rabies or hepatitis B PEP.

Question 717: Which of the following is an example of a non-venereal disease?

A. Endemic syphilis (Correct Answer)
B. Gonorrhoea
C. Chancroid
D. LGV

Explanation: ***Endemic syphilis*** - **Endemic syphilis**, also known as bejel, is caused by *Treponema pallidum endemicum* and is primarily transmitted through **non-sexual skin-to-skin contact** or sharing contaminated utensils. - It is prevalent in arid, temperate regions and differs from venereal syphilis in its mode of transmission and clinical presentation, often affecting children. *Gonorrhoea* - **Gonorrhoea** is a classic example of a **venereal disease** caused by *Neisseria gonorrhoeae*, transmitted almost exclusively through sexual contact. - It typically manifests with urethritis, cervicitis, and other genitourinary symptoms, and can lead to serious complications if untreated. *Chancroid* - **Chancroid** is a sexually transmitted infection caused by *Haemophilus ducreyi*, characterized by painful genital ulcers. - Its transmission is predominantly through sexual contact, making it a venereal disease. *LGV* - **Lymphogranuloma venereum (LGV)** is a sexually transmitted infection caused by specific serovars of *Chlamydia trachomatis*. - It is characterized by small, painless genital lesions followed by painful lymphadenopathy, and is transmitted through sexual contact.

Question 718: Which of the following are key strategies for managing acute vector-borne infections?

A. Presumptive treatment of fever cases
B. Regular insecticide spraying
C. Daily surveillance
D. All of the options (Correct Answer)

Explanation: ***All of the options*** - **Regular insecticide spraying** is a crucial vector control measure that reduces the population of disease-carrying insects, thereby decreasing transmission rates. - **Daily surveillance** of cases helps in early detection, monitoring disease trends, and implementing timely public health interventions to control outbreaks. - **Presumptive treatment of fever cases** in endemic areas allows for rapid intervention, reducing disease severity, preventing complications, and limiting further transmission, especially when diagnostic tests are not immediately available. *Regular insecticide spraying* - This intervention targets the **vector population** directly, aiming to reduce their numbers and interrupt the disease transmission cycle. - It is effective in controlling outbreaks and preventing widespread disease, particularly for diseases like **malaria** and **dengue**. *Daily surveillance* - Involves continuous monitoring of disease incidence, which helps in identifying new cases quickly and tracking the spread of the infection. - **Early detection** through surveillance is essential for deploying rapid response teams and implementing containment strategies effectively. *Presumptive treatment of fever cases* - This strategy involves administering anti-malarial or other appropriate treatments to individuals presenting with fever in endemic regions, even without laboratory confirmation. - It is critical in situations where rapid diagnostic facilities are limited, ensuring that patients receive timely treatment and reducing the **morbidity** and **mortality** associated with vector-borne infections.

Question 719: Tonsillectomy and intramuscular injections should be avoided during a polio epidemic because

A. It is a surgical procedure
B. It can lead to unrelated infections
C. It may lead to complications in infected individuals
D. It increases the risk of paralytic poliomyelitis (Correct Answer)

Explanation: ***It increases the risk of paralytic poliomyelitis*** - **Tonsillectomy** and **intramuscular injections** can cause localized trauma and inflammation, which increases the risk of **provocation poliomyelitis** - where the poliovirus preferentially localizes to the site of injury and causes **paralytic disease**. - This phenomenon, known as **provocation paralysis**, occurs because trauma facilitates viral neurotropism, leading to **bulbar paralysis** (from tonsillectomy) or **limb paralysis** (from IM injections at the affected site). - During a polio epidemic, avoiding these procedures is a critical **preventive measure** to reduce the risk of severe neurological complications. *It is a surgical procedure* - While tonsillectomy is indeed a surgical procedure, this explanation is too general and fails to address the **specific risk of provocation poliomyelitis** during an epidemic. - Many surgical procedures do not carry the same polio-specific risk, making this rationale insufficient. *It can lead to unrelated infections* - This is **medically inaccurate** - the primary concern is not about secondary bacterial infections but about the **poliovirus itself** causing paralytic disease at the trauma site. - The risk is directly related to polio, not "unrelated infections." *It may lead to complications in infected individuals* - This statement is too **vague and non-specific** - it fails to identify the precise complication of **paralytic poliomyelitis**. - The mechanism of **provocation paralysis** is specific to the nature of the poliovirus and its affinity for sites of inflammation or trauma.

Question 720: Which of the following statements about viral diseases is true?

A. Hanta virus pulmonary syndrome is caused by inhalation of rodent urine and feces (Correct Answer)
B. Lyssa virus is transmitted by ticks
C. None of the options
D. Kyasanur forest disease is caused by bite of wild animal

Explanation: ***Hanta virus pulmonary syndrome is caused by inhalation of rodent urine and feces*** - **Hantavirus pulmonary syndrome (HPS)** is a severe, often fatal, respiratory disease in humans. - Humans can contract the disease when they breathe in **aerosolized virus** particles from **rodent urine, droppings, or saliva**. *Kyasanur forest disease is caused by bite of wild animal* - **Kyasanur Forest Disease (KFD)** is primarily transmitted by the bite of infected ticks, specifically **Haemaphysalis spinigera**, not directly by wild animal bites. - While wild animals (like monkeys and rodents) can be hosts for the ticks, the direct transmission to humans is via the **tick vector**. *Lyssa virus is transmitted by ticks* - **Lyssaviruses** (which include the rabies virus) are primarily transmitted to humans through the bite or scratch of an infected mammal, most commonly a **rabid animal**. - **Ticks** are not known vectors for Lyssaviruses.

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Leprosy Elimination

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Emerging and Re-emerging Infections

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Integrated Disease Surveillance Project

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