Infectious Diseases — MCQs

Infectious Diseases Indian Medical PG Practice Questions and MCQs

Question 641: Which of the following statements best describes the operational definition of onchocerciasis elimination?

A. All interventions have been successfully implemented.
B. There is no recrudescence of the disease after a defined period.
C. All of the options are true.
D. Transmission of O. volvulus has been reduced to a level where it cannot sustain itself in the population. (Correct Answer)

Explanation: **Transmission of O. volvulus has been reduced to a level where it cannot sustain itself in the population.** - This statement accurately reflects the definition of **disease elimination**, where the incidence of infection is reduced to zero in a defined geographical area, signifying that the **transmission cycle can no longer be sustained**. - For onchocerciasis, this means the **vector (blackfly)** is no longer transmitting the parasite (*Onchocerca volvulus*) between humans at a rate that allows the disease to persist. *All interventions have been successfully implemented.* - While successful implementation of interventions is crucial for elimination, it is a **process goal**, not the **ultimate outcome** or operational definition of elimination itself. - Elimination is defined by the **absence of sustained transmission**, which is a direct measure of disease burden, not intervention fidelity. *There is no recrudescence of the disease after a defined period.* - The **absence of recrudescence** (re-emergence) after a defined period is an important indicator of successful elimination validation, but it is a **consequence** or **part of the verification process**, not the primary operational definition. - The operational definition focuses on the **state of transmission** that leads to this sustained absence. *All of the options are true.* - This option is incorrect because only one of the provided statements accurately describes the **operational definition of elimination** in the context of parasitic diseases like onchocerciasis. - The other options describe aspects related to the elimination process or its verification, but not the core definition.

Question 642: Which of the following IS included in the NVBDCP?

A. Leprosy
B. Malaria
C. Dengue
D. Chikungunya (Correct Answer)

Explanation: ***Chikungunya*** - **Chikungunya** is one of the six diseases covered under the **National Vector Borne Disease Control Programme (NVBDCP)** in India. - The NVBDCP specifically includes: **Malaria, Dengue, Chikungunya, Lymphatic Filariasis, Kala-azar (Visceral Leishmaniasis), and Japanese Encephalitis**. - Chikungunya, transmitted by *Aedes* mosquitoes, represents a significant public health concern requiring vector control measures. *Leprosy* - **Leprosy** is NOT covered under NVBDCP as it is **not a vector-borne disease**. - Leprosy is caused by *Mycobacterium leprae* and spreads through prolonged close contact with infected individuals, not through vectors. - It is managed under a separate program: **National Leprosy Eradication Programme (NLEP)**. *Malaria* - **Malaria** is indeed included in NVBDCP and is actually the **primary focus** of the program. - However, since the question asks for which disease IS included and all vector-borne options would be correct, the presence of Leprosy as a distractor makes Chikungunya the correct choice among valid NVBDCP diseases. *Dengue* - **Dengue** is also covered under NVBDCP as one of the six priority vector-borne diseases. - Like Malaria and Chikungunya, Dengue receives focused surveillance and control interventions under this national program.

Question 643: In which condition is a night blood survey performed?

A. Lymphatic filariasis (Correct Answer)
B. Typhoid fever
C. Malaria infection
D. Visceral leishmaniasis

Explanation: ***Lymphatic filariasis*** - A **night blood survey** is crucial for diagnosing lymphatic filariasis because the microfilariae of species like *Wuchereria bancrofti* and *Brugia malayi* exhibit **nocturnal periodicity**, meaning they are most abundant in peripheral blood between 10 PM and 2 AM. - Collecting blood at night maximizes the chance of detecting these parasites, which are responsible for the disease. *Typhoid fever* - Diagnosis of **typhoid fever** primarily relies on **blood cultures** taken during the febrile phase, or stool/urine cultures later in the disease. - A night blood survey is not relevant for detecting the causative bacterium, *Salmonella Typhi*. *Malaria infection* - While a **blood smear** is essential for diagnosing malaria, the timing of blood collection is less critical than for filariasis, although peak parasite density can vary. - **Malaria parasites** are typically detected in blood samples taken during symptomatic periods, regardless of specific time of day. *Visceral leishmaniasis* - **Visceral leishmaniasis** is diagnosed by detecting parasites in samples from **bone marrow**, spleen, or lymph nodes, or through serological tests for antibodies. - A night blood survey is not used in the diagnosis of *Leishmania donovani* infection.

Question 644: Malaria is transmitted in Rural areas by?

A. Anopheles stephensi
B. Anopheles dirus
C. Anopheles culicifacies (Correct Answer)
D. None of the options

Explanation: ***Anopheles culicifacies*** - **_Anopheles culicifacies_** is the **primary vector of malaria in rural areas of India** and is also found in Southeast Asia. - Its breeding habitats often include **rice fields, irrigation channels, and temporary water collections** common in rural agricultural settings. - It accounts for a major proportion of rural malaria transmission in the Indian subcontinent. *Anopheles stephensi* - **_Anopheles stephensi_** is a significant malaria vector primarily found in **urban and semi-urban areas**, including parts of the Middle East, India, and Iran. - Its preferred breeding sites are **artificial containers found in urban environments**, such as water storage tanks, overhead tanks, and cisterns. *Anopheles dirus* - **_Anopheles dirus_** is a dominant malaria vector in **forested and hilly regions of Southeast Asia**, often associated with forest malaria. - It's known for outdoor feeding behavior and maintaining transmission in relatively undisturbed natural environments. *None of the options* - This option is incorrect because **_Anopheles culicifacies_** is a well-established and significant vector for malaria in rural areas of India. - Identification of a specific primary vector for rural transmission makes this choice invalid.

Question 645: Which of the following diseases is NOT transmitted by sandflies?

A. Visceral Leishmaniasis
B. Oriental sore
C. Relapsing fever (Correct Answer)
D. Cutaneous Leishmaniasis

Explanation: ***Relapsing fever*** - **Relapsing fever** is primarily transmitted by **ticks** (tick-borne relapsing fever) or **lice** (louse-borne relapsing fever), not sandflies. - It is caused by **spirochetes** of the genus *Borrelia*, which are distinct from the *Leishmania* parasites transmitted by sandflies. *Cutaneous Leishmaniasis* - **Cutaneous leishmaniasis** is a **sandfly-borne disease** caused by *Leishmania* parasites, leading to skin sores. - Sandflies (genus **Phlebotomus** in the Old World and **Lutzomyia** in the New World) transmit these parasites. *Visceral Leishmaniasis* - **Visceral leishmaniasis**, also known as **kala-azar**, is a severe form of leishmaniasis transmitted by the bite of **infected female sandflies**. - It affects internal organs like the **spleen**, **liver**, and **bone marrow**. *Oriental sore* - **Oriental sore** is another name for **cutaneous leishmaniasis**, indicating that it is also transmitted by **sandflies**. - It refers to the characteristic **skin lesions** caused by *Leishmania* parasites following a sandfly bite.

Question 646: Which indicator best measures the operational efficiency of a malaria control programme?

A. Infant parasite rate
B. Slide positivity rate
C. Mosquito bite rate
D. Annual blood examination rate (Correct Answer)

Explanation: ***Annual blood examination rate*** - The **Annual Blood Examination Rate (ABER)** directly reflects the proportion of the population that has been tested for malaria, indicating the reach and effectiveness of surveillance activities. - A high ABER suggests that active case detection and diagnosis are being effectively implemented, which is crucial for operational efficiency in identifying and managing cases. *Infant parasite rate* - The **infant parasite rate** measures the prevalence of malaria infection among infants, serving as an indicator of recent transmission intensity. - While important for assessing disease burden and transmission, it doesn't directly measure the operational effectiveness of interventions like testing or treatment programs. *Slide positivity rate* - The **slide positivity rate (SPR)** is the proportion of positive malaria slides among all slides examined, indicating the likelihood of an individual seeking testing to actually have malaria. - While SPR helps understand disease activity among tested individuals, it doesn't reflect the full operational reach of a program in the general population or the overall testing effort. *Mosquito bite rate* - The **mosquito bite rate** measures the number of mosquito bites per person per night, indicating the level of human exposure to malaria vectors. - This is an entomological indicator of transmission risk and the impact of vector control, but it does not directly assess the operational efficiency of human-centric interventions like diagnosis and treatment programs.

Question 647: Based on the type of life cycle, zoonoses are classified into all of the following except -

A. Cyclo-zoonoses
B. Anthropozoonoses (Correct Answer)
C. Sporozoonoses
D. Meta-zoonoses

Explanation: ***Anthropozoonoses*** - This is **NOT a life cycle-based classification** of zoonoses. - It describes the **direction of transmission** (animals to humans), not the complexity or types of hosts required in the parasite's life cycle. - While a valid classification of zoonoses, it is based on **transmission pattern**, not life cycle characteristics. *Cyclo-zoonoses* - These are zoonoses that require **more than one vertebrate host species** to complete their life cycle, but **no invertebrate host** is involved. - This IS a life cycle-based classification. - Examples include **taeniasis** (tapeworm infections) where the parasite cycles between humans and livestock. *Meta-zoonoses* - These zoonoses require **both vertebrate and invertebrate hosts** to complete their life cycle. - This IS a life cycle-based classification. - The **invertebrate host** acts as an essential part of the life cycle for maturation or multiplication of the pathogen (e.g., **arboviruses** transmitted by mosquitoes, **plague** via fleas). *Sporozoonoses* - While this term is **not part of the standard WHO classification** of zoonoses by life cycle, the prefix "sporo-" refers to **spore-forming stages** in parasitic life cycles. - The standard WHO classification includes: **Orthozoonoses** (direct), **Cyclozoonoses**, **Metazoonoses**, and **Saprozoonoses** (requiring inanimate environment). - However, this term relates to life cycle characteristics (spore stages), not transmission direction.

Question 648: What is the most common Anopheles mosquito responsible for malaria in India?

A. Anopheles stephensi
B. Anopheles subpictus
C. Anopheles culicifacies (Correct Answer)
D. Anopheles fluviatilis

Explanation: ***Anopheles culicifacies*** - This species is the **most common and primary malaria vector in India**, responsible for approximately 60-70% of all malaria transmission in the country. - It is the **major rural vector** of malaria, especially in agricultural areas, and transmits both *Plasmodium vivax* and *P. falciparum*. - Given that the majority of India's population resides in rural areas where malaria burden is highest, *A. culicifacies* is the most important vector overall. *Anopheles stephensi* - This species is recognized as the **primary urban vector** of malaria in India, particularly for *P. vivax* and *P. falciparum*. - Its ability to breed in artificial containers makes it well-adapted to urban environments, but it accounts for a smaller proportion of total malaria cases compared to *A. culicifacies*. *Anopheles fluviatilis* - This species is an **important vector in hilly and forest areas** of India, rather than being the most common overall. - It is known to transmit both *P. vivax* and *P. falciparum* in these specific ecological niches. *Anopheles subpictus* - While present in India, *A. subpictus* is generally considered a **poor vector** of malaria due to its low susceptibility to Plasmodium infection. - It mainly breeds in diverse habitats including paddy fields and brackish water.

Question 649: Infectivity period of chickenpox is ?

A. 1 day before and 4 days after appearance of rash (Correct Answer)
B. Only when scab falls
C. Entire incubation period
D. 4 days before and 5 days after appearance of rash

Explanation: ***1 day before and 4 days after appearance of rash*** - The infectivity period of **chickenpox (varicella)** begins approximately **1-2 days (24-48 hours) before the rash appears**. - It extends until **all lesions have crusted over**, which typically occurs around **5-6 days after rash onset**, though some sources cite **4-5 days**. - This option represents the **commonly accepted timeframe** taught in Indian medical curricula and NEET PG examinations. *4 days before and 5 days after appearance of rash* - The **pre-rash infectivity period is too long** in this option; chickenpox is infectious for only **1-2 days before rash**, not 4 days. - While the "5 days after" is medically accurate, the incorrect pre-rash duration makes this option wrong. *Only when scab falls* - This statement is **incorrect**; infectivity starts much earlier, **1-2 days before the rash appears**. - By the time scabs fall, the person is **no longer infectious**, as crusted lesions contain non-infectious material. - This option ignores the critical **pre-rash and early rash infectious period**. *Entire incubation period* - The **incubation period** for chickenpox is usually **10-21 days**, during which the individual is **not infectious** for most of this time. - Infectivity begins only in the **last 1-2 days of incubation** (just before rash onset) and continues into the eruptive phase, not for the entire duration.

Question 650: The international quarantine period for yellow fever as approved by the Government of India is ?

A. 6 days (Correct Answer)
B. 9 days
C. 10 days
D. 12 days

Explanation: ***6 days*** - The **incubation period** for yellow fever is typically 3-6 days, and the 6-day quarantine period is internationally accepted to cover this range. - This period is established to prevent the importation and spread of the disease by ensuring that individuals arriving from endemic areas do not develop symptoms after arrival. *9 days* - This duration is **longer than the internationally recognized incubation period** for yellow fever and is not the standard quarantine period. - Implementing a 9-day quarantine would be excessive and not based on the typical disease progression. *10 days* - A 10-day quarantine period is also **not the standard** for yellow fever as approved by international health regulations or by the Government of India. - While some diseases may require a 10-day quarantine, yellow fever's incubation period makes 6 days sufficient. *12 days* - A 12-day quarantine is **significantly longer** than necessary for yellow fever, as virtually all cases would manifest symptoms within the first 6 days. - This period is typically associated with diseases with much longer incubation periods, which is not the case for yellow fever.

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Communicable Disease Control Principles

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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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Integrated Disease Surveillance Project

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