Infectious Diseases — MCQs

Infectious Diseases Indian Medical PG Practice Questions and MCQs

Question 651: 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 652: 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 653: All following are at-risk group adults meriting Hepatitis B vaccination in low endemic areas except for which of the following?

A. Medical/nursing personnel
B. Patients with chronic liver disease
C. Diabetics on insulin (Correct Answer)
D. Patients on chronic hemodialysis

Explanation: ***Diabetics on insulin*** - This is the correct answer as the exception based on **guidelines at the time of this exam (2012)**. - At that time, diabetics were **not routinely listed** as a standard at-risk group for hepatitis B vaccination in low endemic areas, though the ACIP was beginning to recognize increased risk in this population. - **Current Update (Post-2012):** The **CDC/ACIP now recommends** hepatitis B vaccination for all previously unvaccinated adults with diabetes aged 19-59 years, due to documented increased risk of HBV infection associated with: - Shared blood glucose monitoring devices - Assisted blood glucose monitoring in healthcare settings - Outbreak investigations showing higher transmission rates - For the purpose of this historical exam question, diabetics were the exception among the listed groups. *Medical/nursing personnel* - Healthcare workers are at **high occupational risk** due to frequent exposure to blood and body fluids. - This has been a **standard, long-standing recommendation** for HBV vaccination regardless of endemic status. - The risk remains present even in low endemic areas due to potential exposure to infected patients. *Patients with chronic liver disease* - Individuals with pre-existing chronic liver disease are at risk of **severe outcomes** if they acquire hepatitis B infection. - Superimposed acute HBV infection can lead to: - Rapid progression to cirrhosis - Acute-on-chronic liver failure - Hepatocellular carcinoma - Vaccination is **crucial for prevention** and has been a standard recommendation. *Patients on chronic hemodialysis* - Hemodialysis patients face **elevated risk** of HBV acquisition due to: - Frequent vascular access procedures - Prolonged time in healthcare settings - Potential for nosocomial transmission in dialysis units - Their **immunocompromised state** increases risk of chronic infection and complications. - Vaccination is a **standard preventive measure** in this population.

Question 654: National Leprosy Eradication Programme was started in -

A. 1949
B. 1955
C. 1973
D. 1983 (Correct Answer)

Explanation: **Correct: 1983** - The **National Leprosy Eradication Programme (NLEP)** was launched in India in **1983** - Its goal was to eliminate leprosy as a public health problem by reducing its prevalence rate to less than 1 case per 10,000 population - This marked the shift from control to eradication strategy with the introduction of **Multi-Drug Therapy (MDT)** *Incorrect: 1949* - This year is not associated with the inception of a national leprosy eradication program in India - While efforts against leprosy existed, a comprehensive national program was not established at this time *Incorrect: 1955* - The **National Leprosy Control Programme (NLCP)** was launched in India in **1955** - This was a control program, preceding the eradication program, focusing on diagnosis and treatment with Dapsone monotherapy - NLCP was later upgraded to NLEP in 1983 *Incorrect: 1973* - This year is not cited as the start date for the national leprosy eradication program in India - The focus shifted from control to eradication in 1983 with the adoption of WHO-recommended MDT

Question 655: Schistosomiasis is transmitted by?

A. Fish
B. Snail (Correct Answer)
C. Cattle
D. Cyclops

Explanation: ***Snail*** - **Snails** act as the **intermediate host** for all species of Schistosoma, where the parasite undergoes asexual reproduction. - Humans become infected when they come into contact with water contaminated with **cercariae**, which are released from infected snails. *Cyclops* - **Cyclops** (a type of freshwater crustacean) are the intermediate hosts for parasites like **Dracunculus medinensis** (guinea worm) and **Diphyllobothrium latum** (fish tapeworm). - They are not involved in the life cycle or transmission of Schistosoma. *Fish* - Various fish can be intermediate hosts for parasites such as **Clonorchis sinensis** (Chinese liver fluke) or **Diphyllobothrium latum**. - Fish do not play a role in the transmission of schistosomiasis. *Cattle* - **Cattle** can serve as definitive hosts for certain parasites, such as **Taenia saginata** (beef tapeworm), where the larval stage (cysticerci) is found in their muscle tissue. - They are not involved in the life cycle or transmission of Schistosoma.

Question 656: Schistosomiasis is an example of which type of zoonosis that requires an intermediate host?

A. Meta-zoonoses (Correct Answer)
B. Cyclo-zoonoses
C. Direct-zoonoses
D. Sporo-zoonoses

Explanation: ***Meta-zoonoses*** - **Meta-zoonoses** are defined as zoonotic diseases that require an **intermediate invertebrate host** for the completion of the parasite's life cycle. - **Schistosomiasis** fits this definition as it involves fresh water snails acting as an intermediate host, where the parasite undergoes essential developmental stages. *Cyclo-zoonoses* - **Cyclo-zoonoses** require **more than one vertebrate host species** but no invertebrate host for the completion of the infectious agent's life cycle. - An example would be **Taeniasis**, which involves humans and cattle or pigs, but not an invertebrate. *Direct-zoonoses* - **Direct-zoonoses** are transmitted directly from an **infected vertebrate host to a susceptible vertebrate host** without the need for an intermediate host or vector. - Examples include **rabies** or **brucellosis**, which are passed directly from animals to humans. *Sporo-zoonoses* - **Sporo-zoonoses** are zoonoses where the infectious agent undergoes **sporogonic development in an invertebrate host**, but this term is not a standard or widely recognized category in the same way as direct, cyclo-, or meta-zoonoses. - The more appropriate term for diseases involving an invertebrate intermediate host is **meta-zoonoses**.

Question 657: Pediculosis is caused by?

A. Louse (Correct Answer)
B. Mite
C. Tick
D. Black Fly

Explanation: ***Louse*** - **Pediculosis** is a parasitic infestation of the skin by blood-feeding insects called **lice**. - There are different types of lice, including head lice (Pediculus humanus capitis), body lice (Pediculus humanus humanus), and pubic lice (Pthirus pubis), all of which cause pediculosis. *Mite* - **Mites** are responsible for infestations like **scabies**, which is caused by Sarcoptes scabiei. - While both lice and mites are arthropods, they cause distinct parasitic conditions with different clinical presentations and treatments. *Tick* - **Ticks** are known vectors for various diseases, including **Lyme disease** (Borrelia burgdorferi), **Rocky Mountain spotted fever** (Rickettsia rickettsii), and **tick-borne encephalitis**. - Ticks are arachnids, not insects, and their bites can cause localized reactions but not pediculosis. *Black Fly* - **Black flies** (Simulium species) are vectors for **onchocerciasis** (river blindness), caused by the parasitic nematode Onchocerca volvulus. - Their bites are typically painful and can cause localized swelling and allergic reactions, but they do not transmit pediculosis.

Question 658: Transovarian transmission is seen in which of the following infections?

A. Plague
B. Ebola fever
C. Yellow fever (Correct Answer)
D. None of the options

Explanation: ***Yellow fever*** - **Transovarian transmission** refers to the passage of a pathogen from an adult female arthropod (like a mosquito) to her offspring via the eggs. This mechanism allows the virus to persist in the **vector population** even in the absence of infected vertebrate hosts. - **Yellow fever virus** is known to undergo transovarian transmission in its mosquito vectors, particularly *Aedes aegypti* and other *Aedes* species. *Plague* - Plague is caused by the bacterium *Yersinia pestis* and is primarily transmitted by **flea bites** from infected rodents to humans. - It does not involve transovarian transmission; the fleas acquire the bacteria during a **blood meal** from an infected host. *Ebola fever* - Ebola virus is transmitted through **direct contact** with blood or bodily fluids of infected humans or animals. - It is not an **arthropod-borne disease** and therefore does not exhibit transovarian transmission. *None of the options* - This option is incorrect because **Yellow Fever** clearly demonstrates transovarian transmission within its mosquito vector.

Question 659: Vector of scrub typhus in man?

A. O. tsutsugamushi
B. Leptotrombidium deliense (Correct Answer)
C. Lice
D. Pediculus humanus

Explanation: ***Leptotrombidium deliense*** - This is the **chigger mite** species primarily responsible for transmitting **scrub typhus** to humans. - **Larval mites (chiggers)** of this species feed on human skin and transmit the bacterium *Orientia tsutsugamushi*. *O. tsutsugamushi* - This is the **causative agent** of scrub typhus, not the vector. - It is a **rickettsial bacterium** transmitted by infected chiggers. *Lice* - **Lice** (e.g., *Pediculus humanus corporis*) are vectors for diseases like **epidemic typhus** (caused by *Rickettsia prowazekii*) and **relapsing fever**, but not scrub typhus. - They are **blood-sucking insects** distinct from mites. *Pediculus humanus* - This refers to **human lice**, specifically *Pediculus humanus capitis* (head louse) or *Pediculus humanus corporis* (body louse). - As mentioned, lice transmit diseases like epidemic typhus, not **scrub typhus**.

Question 660: Botulism is most commonly due to -

A. Egg
B. Milk
C. Meat
D. Home-canned vegetables (Correct Answer)

Explanation: ***Home-canned vegetables*** - **Home-canned vegetables** are the **most common** source of botulism, particularly improperly processed low-acid vegetables like beans, corn, and asparagus - *Clostridium botulinum* spores survive inadequate heat treatment and germinate in the **anaerobic, low-acid environment** of improperly canned foods - The **lack of sufficient heat sterilization** (pressure canning at 121°C/250°F is required) allows spore survival and subsequent toxin production - Most foodborne botulism outbreaks are traced to **home-canned vegetables** rather than commercially processed foods *Meat* - While improperly preserved meats can cause botulism, they are **not the most common source** in epidemiological data - Commercial meat processing standards and refrigeration significantly reduce this risk - Meat-associated botulism is more common in certain cultural practices involving fermented or preserved meats *Egg* - **Eggs** are not associated with botulism as they do not provide the anaerobic environment necessary for *Clostridium botulinum* toxin production - Eggs are more commonly linked to **Salmonella infections** if improperly handled or undercooked *Milk* - **Milk** and dairy products are not typical sources of botulism - **Pasteurization** and refrigeration prevent conditions favorable for *C. botulinum* growth - Dairy products are more associated with **Listeria** or **Campylobacter** if contaminated

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