Infectious Diseases — MCQs

Infectious Diseases Indian Medical PG Practice Questions and MCQs

Question 371: Which of the following diseases is transmitted by rat flea?

A. Oriental sore
B. Endemic typhus (Correct Answer)
C. Trench fever
D. Chagas disease

Explanation: ***Endemic typhus*** - **Endemic (murine) typhus** is caused by *Rickettsia typhi* and is primarily transmitted to humans by the **rat flea** (*Xenopsylla cheopis*) - The rat flea typically acquires the bacteria by feeding on infected rodents (e.g., rats), and then transmits it to humans through its feces while feeding. *Oriental sore* - **Oriental sore** refers to cutaneous leishmaniasis, caused by *Leishmania* parasites. - It is transmitted by the bite of infected **sandflies**, not rat fleas. *Trench fever* - **Trench fever** is caused by *Bartonella quintana* and is transmitted to humans by **human body lice** (*Pediculus humanus corporis*). - This disease is historically associated with crowded and unsanitary conditions, particularly during wartime. *Chagas disease* - **Chagas disease** (American trypanosomiasis) is caused by the parasite *Trypanosoma cruzi*. - It is primarily transmitted by the feces of infected **reduviid bugs** (also known as kissing bugs), which typically bite humans around the face.

Question 372: The chemoprophylaxis in malaria is an example of -

A. Primary prevention (Correct Answer)
B. Tertiary prevention
C. Secondary prevention
D. Primordial prevention

Explanation: ***Primary prevention*** - **Chemoprophylaxis** aims to prevent the **onset of disease** in individuals who are at risk, but currently healthy. - It involves administering medication to individuals before exposure to the malaria parasite to prevent infection or clinical disease. *Tertiary prevention* - Focuses on **reducing the impact of an existing disease** and preventing disability or complications. - This would include rehabilitation or long-term management for individuals who have already suffered from malaria. *Secondary prevention* - Involves **early detection and prompt treatment** of existing disease to prevent its progression. - An example would be screening for malaria in endemic areas and treating positive cases early. *Primordial prevention* - Aims to prevent the development of risk factors themselves, often at a population level. - This would involve addressing broader **socioeconomic determinants** that contribute to malaria transmission, not directly preventing the disease in individuals.

Question 373: All of the following are zoonosis, except:

A. Japanese Encephalitis
B. Plague
C. Tuberculosis
D. HIV (Correct Answer)

Explanation: ***HIV*** - While HIV originated from **simian immunodeficiency virus (SIV)** in non-human primates, it is **no longer considered a zoonosis** because transmission now occurs exclusively **human-to-human**. - The virus has fully adapted to **human hosts**, and there is **no ongoing animal reservoir** contributing to the current epidemic. - Zoonotic diseases require **active animal-to-human transmission**, which does not apply to HIV in its current form. *Japanese Encephalitis* - This is a **mosquito-borne viral disease** that primarily circulates between **mosquitoes, pigs, and birds**. - Humans are **accidental dead-end hosts**, making this a true **zoonotic disease**. *Plague* - Caused by **Yersinia pestis**, which naturally infects **small mammals (rodents)** and their fleas. - Humans become infected through **flea bites** or direct contact with infected animals, making it a **classic zoonosis**. *Tuberculosis* - While most human TB is caused by **M. tuberculosis** (human-to-human), **M. bovis** causes **zoonotic TB**. - Transmitted from **infected cattle** to humans via **unpasteurized dairy products** or close contact with infected animals. - This animal-to-human transmission qualifies TB as a **zoonotic disease**.

Question 374: What should the Aedes aegypti index be to effectively control yellow fever?

A. An index below 10%.
B. An index below 5%. (Correct Answer)
C. An index below 20%.
D. An index below 1%.

Explanation: ***An index below 5%.*** - For effective yellow fever control, the *Aedes aegypti* index needs to be **below 5%** according to WHO guidelines and standard public health practices. - This threshold is considered adequate to significantly reduce the risk of yellow fever transmission and prevent outbreaks. - The 5% threshold applies to House Index (HI) or Breteau Index measurements of *Aedes aegypti* presence. *An index below 1%.* - An index below 1% is the **stringent threshold for dengue control**, not yellow fever. - Dengue requires a lower vectorial capacity threshold because it has higher transmission efficiency even at lower mosquito densities. - While achieving below 1% would also control yellow fever, it is **not the standard target** specified for yellow fever programs. *An index below 10%.* - An index below 10% indicates **moderate to high risk** for *Aedes*-borne disease transmission. - This level is **insufficient for effective yellow fever control** and would still allow significant transmission potential. - Control programs aim for much lower indices to prevent epidemic spread. *An index below 20%.* - An index below 20% indicates a **very high risk** of transmission for yellow fever and other *Aedes*-borne diseases. - This level is **far from adequate** for any meaningful vector control and suggests imminent outbreak risk. - Urgent intervention would be needed at this threshold level.

Question 375: The most sensitive index for surveillance of malaria transmission is -

A. Proportional case rate
B. Infant parasite rate (Correct Answer)
C. Spleen rate
D. Parasite density index

Explanation: ***Infant parasite rate*** - The **infant parasite rate**, specifically in children aged 0-11 months, is considered the most sensitive indicator of active malaria transmission. - This is because these infants have had minimal exposure to malaria, and a positive parasite finding indicates recent and ongoing transmission within the community. *Proportional case rate* - The **proportional case rate** indicates the proportion of all diseases that are malaria, which is useful for understanding disease burden but less sensitive for transmission changes. - It does not specifically target a population group directly reflecting recent transmission as accurately as the infant parasite rate. *Spleen rate* - The **spleen rate** (percentage of children with enlarged spleens) reflects cumulative exposure to malaria over a longer period, acting as a historical indicator. - It is a good measure of endemicity but does not rapidly capture recent changes or sensitivities in ongoing transmission. *Parasite density index* - **Parasite density index** measures the average number of parasites per unit of blood in infected individuals. - While it reflects the intensity of infection, it is not as direct or sensitive an indicator of current transmission events within a community as the infant parasite rate.

Question 376: You are the MO in charge in a PHC and there has been a plague epidemic in your area. Which of the following measures is the LEAST appropriate for controlling epidemic?

A. Isolation of contacts
B. Rapid treatment of cases with streptomycin
C. Vaccination of all susceptible individuals (Correct Answer)
D. Early diagnosis and notification

Explanation: ***Vaccination of all susceptible individuals*** - While beneficial for prevention, mass vaccination during an ongoing plague epidemic is **logistically challenging** and **too slow** to effectively control the immediate spread. - The incubation period of plague is short, and an effective vaccine often requires multiple doses and time to induce immunity, making it less suitable for **rapid epidemic containment**. *Isolation of contacts* - **Isolating contacts** helps prevent the disease from spreading further by separating potentially infected individuals who may be asymptomatic or in the incubation period. - This measure is crucial in **breaking chains of transmission** and limiting the epidemic's reach. *Rapid treatment of cases with streptomycin* - **Early and rapid treatment** of confirmed plague cases with effective antibiotics like **streptomycin** is a cornerstone of epidemic control, significantly reducing mortality and infectivity. - This intervention quickly minimizes the source of infection, preventing further transmission to others. *Early diagnosis and notification* - **Early diagnosis** allows for prompt initiation of treatment and isolation, while **notification** triggers public health responses such as contact tracing and surveillance. - These steps are essential for understanding the scope of the epidemic and implementing appropriate control measures efficiently.

Question 377: Not transmitted by mite -

A. Rickettsialpox
B. Scabies
C. Kyasanur forest disease (Correct Answer)
D. Scrub typhus

Explanation: ***Kyasanur forest disease*** - **Kyasanur forest disease (KFD)** is a viral hemorrhagic fever transmitted by the **hard tick** (*Haemaphysalis spinigera*), not mites. - Humans typically acquire KFD through contact with infected ticks or sick animals like monkeys. *Rickettsialpox* - Rickettsialpox is caused by *Rickettsia akari* and transmitted by the **house mouse mite** (*Liponyssoides sanguineus*). - The mite serves as both the reservoir and vector for this disease. *Scabies* - Scabies is a skin infestation caused by the **human itch mite** (*Sarcoptes scabiei* var. *hominis*). - The mites burrow into the skin to lay eggs, leading to intense itching and rash. *Scrub typhus* - Scrub typhus is caused by *Orientia tsutsugamushi* and is transmitted to humans by the bite of infected **chiggers** (larval mites) of the family Trombiculidae. - These mites are often found in areas with scrub vegetation, hence the name.

Question 378: Sodium content in mmol/L in WHO oral rehydration solution is

A. 90
B. 75 (Correct Answer)
C. 20
D. 111

Explanation: ***75*** - The **WHO oral rehydration solution (ORS)** has been reformulated to a lower osmolarity to improve efficacy, with a sodium content of **75 mmol/L**. - This lower sodium concentration helps reduce the risk of **hypernatremia** and is effective in managing dehydration due to diarrhea. *90* - An ORS with **90 mmol/L** sodium content was part of the **original WHO ORS formula**. - While effective, this higher sodium concentration was associated with a greater risk of **hypernatremia** in some patients. *20* - A sodium content of **20 mmol/L** is significantly lower than recommended for effective rehydration in most diarrheal diseases. - This concentration would be insufficient to replace the **sodium losses** typically experienced during dehydration. *111* - A sodium content of **111 mmol/L** is considerably higher than the current WHO recommendation. - Such a high concentration would increase the risk of **hypernatremia** and potentially worsen dehydration at the cellular level due to high osmolarity.

Question 379: For the prevention of human rabies, immediate flushing and washing the wound(s) in animal bite cases, with plenty of soap and water, under running tap should be carried out for how much time?

A. 15 minutes (Correct Answer)
B. 5 minutes
C. 2 minutes
D. 1 minute

Explanation: ***15 minutes*** - **Immediate and thorough wound cleansing** with soap and water for at least 15 minutes is crucial for reducing the risk of rabies infection after an animal bite. - This physical removal of the *rabies virus* from the wound site is the **most effective first-aid measure** in preventing the disease. *5 minutes* - While some cleansing is better than none, five minutes may not be sufficient for **maximal removal of viral particles**, especially from deeper or more contaminated wounds. - The extended duration of 15 minutes ensures a more **thorough decontamination** and increased safety margin. *2 minutes* - This short duration of washing is **inadequate** for effective removal of the rabies virus from the wound. - It significantly increases the **risk of viral persistence** in the wound, undermining the primary goal of immediate first aid. *1 minute* - Washing for only one minute is **grossly insufficient** and offers minimal protective benefit against rabies transmission following an animal bite. - **Thorough mechanical scrubbing** and flushing for a longer period are essential.

Question 380: All of the following are helminthic waterborne disease except?

A. Hydatid cyst
B. Roundworm
C. Giardiasis (Correct Answer)
D. Threadworm

Explanation: ***Giardiasis*** - **Giardiasis** is caused by the **protozoan parasite** *Giardia lamblia*, not a helminth. - It is a true waterborne disease, transmitted through contaminated water. - This is the correct answer as it is NOT a helminthic infection. *Hydatid cyst* - **Hydatid cyst disease** is caused by the larval stage of the **tapeworm** *Echinococcus granulosus*, a helminth. - Primarily transmitted through ingestion of eggs from dog feces (zoonotic), though contaminated water can occasionally serve as a vehicle. *Roundworm* - **Roundworm infection** (ascariasis) is caused by the nematode *Ascaris lumbricoides*, a helminth. - Classified as a soil-transmitted helminth (STH), acquired through ingestion of eggs from contaminated soil; water can occasionally act as a transmission vehicle. *Threadworm* - **Threadworm infection** (enterobiasis/pinworm) is caused by the nematode *Enterobius vermicularis*, a helminth. - Primarily transmitted person-to-person via the fecal-oral route through contaminated hands and fomites; water transmission is uncommon but possible in poor sanitation conditions.

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Communicable Disease Control Principles

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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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