Infectious Diseases — MCQs

Infectious Diseases Indian Medical PG Practice Questions and MCQs

Question 441: Which of the following infectious diseases are transmitted through rats?

A. Measles
B. Influenza
C. Tetanus
D. Leptospirosis (Correct Answer)

Explanation: ***Leptospirosis*** - **Leptospirosis** is a bacterial infection primarily transmitted through contact with urine from infected animals, particularly **rats**, which are the most important reservoir host. - Humans contract the disease through contact with contaminated water, soil, or food, or through direct contact with infected animal tissues or urine. - In Community Medicine, **rodent control and proper sanitation** are key preventive measures. - Other rat-transmitted diseases include **Plague** (via rat fleas), **Rat-bite fever**, and **Hantavirus infections**. *Measles* - **Measles** is a highly contagious viral infection transmitted through respiratory droplets from person to person. - It is not transmitted through rats or other animals; **humans are the only natural host**. - Not a zoonotic disease. *Influenza* - **Influenza** is a viral infection that primarily spreads through airborne respiratory droplets from infected individuals. - While some strains originate in animals like birds (avian flu) or pigs (swine flu), **rats are not a reservoir** for human influenza. - Direct transmission through rats is not a recognized mode of infection. *Tetanus* - **Tetanus** is caused by *Clostridium tetani* bacteria found in soil and feces, entering the body through breaks in the skin, typically deep puncture wounds. - It is **not vector-borne or transmitted by rats** but rather through environmental exposure to spores. - Prevention relies on wound care and vaccination, not rodent control.

Question 442: Which is most dangerous for transmitting plague?

A. Partially blocked flea
B. Both
C. Unblocked flea
D. Blocked flea (Correct Answer)

Explanation: ***Blocked flea*** - A **blocked flea** is most dangerous for transmitting plague because the proventriculus becomes obstructed by a biofilm of *Yersinia pestis* bacteria. - The blockage prevents normal blood ingestion, causing the flea to **regurgitate infected blood back into the bite wound** with each feeding attempt. - The blocked flea remains persistently hungry and makes **repeated desperate attempts to feed**, injecting bacteria into multiple hosts before eventually dying of starvation. - This mechanism results in highly efficient transmission with multiple bacterial inoculations per bite attempt. *Partially blocked flea* - While a partially blocked flea can transmit plague, it is less efficient than a fully blocked flea because some blood can still pass through. - The partial blockage means less regurgitation occurs compared to complete blockage, resulting in lower bacterial loads being transmitted. *Unblocked flea* - An **unblocked flea** can feed normally and may transmit bacteria during feeding, but lacks the regurgitation mechanism that makes blocked fleas so dangerous. - It typically feeds once, becomes satiated, and is less likely to make repeated feeding attempts on the same or multiple hosts. *Both* - This option is incorrect because there is a clear difference in transmission efficiency between blocked and unblocked fleas. - The blocked flea's unique regurgitation mechanism makes it distinctly more dangerous than other flea states.

Question 443: Infections transmitted to man from vertebrate animals are known as:

A. Zooanthroponoses
B. Anthropozoonoses (Correct Answer)
C. Exotic
D. Epizootic

Explanation: ***Anthropozoonoses*** - **Anthropozoonoses**, also known simply as **zoonoses**, are diseases primarily of animals that can be transmitted to humans. - This term specifically refers to infections that are naturally transmissible from **vertebrate animals** to humans. *Zooanthroponoses* - **Zooanthroponoses** refer to infections that are naturally transmissible from humans to animals. - While reflecting a human-animal disease relationship, the direction of transmission is opposite to what is described in the question. *Exotic* - An **exotic** disease refers to an infection or pathogen that is not native or endemic to a particular geographic region. It does not describe the mode of transmission from animals to humans. - This term describes the geographical origin or presence of a disease, not its interspecies transmissibility. *Epizootic* - An **epizootic** describes a disease outbreak in an animal population, analogous to an epidemic in humans. - This term defines the pattern and occurrence of disease within animal populations, rather than transmission to humans.

Question 444: Soft tick transmits:

A. Tularemia
B. Indian tick typhus
C. Relapsing fever (Correct Answer)
D. KFD

Explanation: ***Relapsing fever*** - **Soft ticks** (Ornithodoros species) are the primary vectors for **tick-borne relapsing fever**, specifically transmitting spirochetes of the genus *Borrelia*. - The disease is characterized by recurrent episodes of **fever**, **headache**, and **fatigue**, alternating with afebrile periods. *Tularemia* - While tularemia can be transmitted by ticks, it is primarily associated with **hard ticks** (e.g., Dermacentor, Amblyomma) and not typically soft ticks. - The causative agent is *Francisella tularensis*, which can also be acquired through contact with infected animals or contaminated water. *Indian tick typhus* - This is a form of spotted fever group rickettsiosis caused by *Rickettsia conorii*, typically transmitted by **hard ticks** like *Rhipicephalus sanguineus*. - It is characterized by fever, rash, and a characteristic **eschar** at the bite site. *KFD* - **Kyasanur Forest Disease (KFD)** is a viral hemorrhagic fever transmitted by **hard ticks**, particularly *Haemaphysalis spinigera*. - It is endemic to India and involves symptoms such as high fever, headache, and hemorrhage.

Question 445: All the following statements regarding transmission of HIV are true EXCEPT:

A. Even after vigorous screening, HIV transmission can occur through blood transfusion
B. Associated STDs will not influence the transmission (Correct Answer)
C. Heterosexual contact is the most common route of transmission of HIV
D. Circumcision will decrease the frequency of transmission

Explanation: ***Associated STDs will not influence the transmission*** - The presence of **sexually transmitted diseases (STDs)**, particularly those causing genital ulcers (e.g., syphilis, herpes), significantly **increases the risk** of both acquiring and transmitting HIV. - STDs create breaks in the skin or mucous membranes and increase inflammatory cells, providing easier entry and exit points for the HIV virus. *Even after vigorous screening, HIV transmission can occur through blood transfusion* - Despite rigorous screening of blood products, there is a very small, but non-zero, residual risk of HIV transmission due to the **"window period"** during which an infected donor may test negative. - This risk has been drastically reduced but not entirely eliminated, making it a true statement that transmission *can* still occur. *Heterosexual contact is the most common route of transmission of HIV* - Globally, **heterosexual contact** is indeed the predominant mode of HIV transmission, especially in regions with high HIV prevalence like Sub-Saharan Africa. - This route accounts for the majority of new infections worldwide. *Circumcision will decrease the frequency of transmission* - Studies have shown that **male circumcision reduces the risk** of heterosexually acquired HIV infection in men. - This protection is thought to be due to the removal of the inner foreskin, which contains a higher density of HIV target cells (Langerhans cells) and is more susceptible to micro-tears during intercourse.

Question 446: Which of the following is known as monkey fever?

A. Plague
B. Trench fever
C. Yellow fever
D. KFD (Correct Answer)

Explanation: ***KFD*** - **Kyasanur Forest Disease (KFD)** is also known as "monkey fever" due to its primary hosts and the observed mortality in monkeys before human outbreaks. - It is a **viral hemorrhagic fever** endemic to certain parts of India, transmitted by **ticks** (primarily *Haemaphysalis spinigera*). *Plague* - **Plague** is a bacterial infection caused by *Yersinia pestis*, primarily transmitted by **fleas** from rodents to humans. - While it can cause severe systemic illness, it is not colloquially known as "monkey fever." *Trench fever* - **Trench fever** is caused by the bacterium *Bartonella quintana* and is transmitted by **body lice**. - It is characterized by recurrent fevers, headaches, and often shin pain, and is not associated with monkeys or called "monkey fever." *Yellow fever* - **Yellow fever** is a viral hemorrhagic disease transmitted by mosquitoes, primarily *Aedes* and *Haemagogus* species. - While it can affect primates, its common name refers to the **jaundice** seen in some patients, not specifically "monkey fever."

Question 447: Xavier and Yogender stay in the same hostel of the same university. Xavier develops an infection due to group B meningococcus. After a few days, Yogender develops an infection due to Group C meningococcus. All of the following statements are true except -

A. Vaccine prophylaxis of contacts of Yogendra
B. No Chemoprophylaxis available against both group B and group C (Correct Answer)
C. Vaccine prophylaxis of contacts of Xavier
D. Educate students about meningococcal transmission and take preventive measures

Explanation: ***No Chemoprophylaxis available against both group B and group C*** - This statement is incorrect because **chemoprophylaxis** *is* available for contacts of individuals with meningococcal disease, regardless of the serogroup. - **Rifampicin**, **ciprofloxacin**, or **ceftriaxone** are commonly used to eradicate nasopharyngeal carriage and prevent secondary cases. *Vaccine prophylaxis of contacts of Yogendra* - **Vaccines are recommended** for contacts of individuals with **Group C meningococcal disease** if the serogroup is known, as specific conjugate vaccines are available. - This aims to provide **active immunity** and prevent further spread within a close-contact community. *Vaccine prophylaxis of contacts of Xavier* - **Vaccines for Group B meningococcus** are available (e.g., MenB-4C, MenB-FHbp) and may be considered for close contacts during outbreaks or in high-risk settings. - However, the decision for **mass vaccination** depends on local guidelines and the specific outbreak characteristics. *Educate students about meningococcal trans-mission and take preventive measures* - **Health education** is a crucial public health measure in any meningococcal outbreak, as it empowers individuals to reduce transmission risk. - Preventive measures include **avoiding sharing personal items** like drinks and cigarettes, and practicing good hand hygiene.

Question 448: Mass chemoprophylaxis in endemic areas is recommended for all of the following, except:

A. Leprosy (Correct Answer)
B. Trachoma
C. Yaws
D. Filaria

Explanation: ***Leprosy*** - **Mass chemoprophylaxis** for leprosy is generally *not recommended* due to concerns about drug resistance and the long incubation period. - Instead, the focus is on **early detection** and *multi-drug therapy (MDT)* for diagnosed cases, and contact tracing with single-dose rifampicin (SDR) as post-exposure prophylaxis for close contacts in some settings. *Trachoma* - **Mass drug administration (MDA)** of *azithromycin* is a cornerstone of the **SAFE strategy** (Surgery, Antibiotics, Facial cleanliness, Environmental improvement) for eliminating trachoma, recommended in endemic areas. - This aims to reduce the community reservoir of *Chlamydia trachomatis* infection, thus preventing new infections and progression of the disease. *Yaws* - **Mass treatment programs** with a *single oral dose of azithromycin* have been highly effective and are recommended by the WHO for the eradication of yaws in endemic communities. - This strategy aims to interrupt transmission and eliminate the *Treponema pallidum subspecies pertenue* bacterium. *Filaria* - **Mass drug administration (MDA)** with anti-filarial drugs (e.g., *diethylcarbamazine and albendazole*) is a key strategy for the elimination of lymphatic filariasis in endemic areas. - MDA aims to reduce the microfilaria burden in infected individuals, thereby interrupting transmission of the parasite by mosquitoes.

Question 449: False about Japanese encephalitis is -

A. Pigs are amplifiers
B. Primary dose of vaccine consists of two doses
C. Overhead tanks serve as breeding site (Correct Answer)
D. Transmitted by Culex mosquitoes

Explanation: ***Overhead tanks serve as breeding site*** - The primary vector for **Japanese encephalitis (JE)** is the *Culex* mosquito, which typically breeds in **rice paddies** and other ground-level water sources, not overhead tanks. - While *Culex* mosquitoes need water to breed, overhead tanks generally circulate human-used water and are not their preferred or typical breeding sites, making this statement false regarding JE transmission. *Pigs are amplifiers* - **Pigs** are known to be **amplifying hosts** for the Japanese encephalitis virus. They develop high viremia (high viral load in the blood) without becoming severely ill, allowing mosquitoes to pick up the virus from them and transmit it to other hosts. - This cycle is crucial for the maintenance and spread of the virus in endemic areas, making the statement true. *Primary dose of vaccine consists of two doses* - The **Japanese encephalitis vaccine** often requires a primary series of **two doses** for optimal protection, administered at least 28 days apart, followed by a booster dose if continued exposure is anticipated. - This regimen ensures a robust and lasting immune response against the virus, making the statement true. *Transmitted by Culex mosquitoes* - **Japanese encephalitis** is predominantly transmitted through the bite of infected **Culex mosquitoes**, particularly *Culex tritaeniorhynchus*. - These mosquitoes are ubiquitous in endemic regions of Asia and are the main vector responsible for spreading the virus between animal hosts and to humans, making the statement true.

Question 450: Guineaworm infestation is common in workers of:

A. Fields
B. Cotton mills
C. Step wells (Correct Answer)
D. Ponds

Explanation: ***Step wells*** - **Guineaworm disease (Dracunculiasis)** is contracted by ingesting water contaminated with **Cyclops (water fleas)** that host the parasite larvae. - **Step wells** often serve as communal water sources in affected regions, making them common sites for transmission due to repeated human contact. *Fields* - Working in fields does not directly expose individuals to the contaminated water sources responsible for Guineaworm transmission. - While agricultural workers may come into contact with water, it typically isn't stagnant water containing the specific intermediate host. *Cotton mills* - Cotton mills are indoor industrial environments and do not involve exposure to freshwater sources where **Guineaworm** is commonly transmitted. - This occupation has no direct link to the lifecycle of **Dracunculus medinensis**. *Ponds* - While ponds can contain **Cyclops**, the term "ponds" is broad and doesn't specifically imply the high concentration of human activity and dependence on these sources for drinking water that **step wells** often represent in affected communities. - **Step wells** are particularly implicated due to their role as shared, often stagnant, drinking water sources in endemic areas.

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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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