Infectious Diseases Practice Questions

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

Anopheles culicifacies. ***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.

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

Relapsing fever. ***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.

Q: In which condition is a night blood survey performed?

Lymphatic filariasis. ***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.

Q: What is the annual infection rate of tuberculosis?

Percentage of new patients positive for tuberculin test. ***Percentage of new patients positive for tuberculin test*** - The **annual infection rate of tuberculosis (AIRT)** is defined as the percentage of individuals (typically children aged 1-9 years) who show **tuberculin conversion** (from negative to positive) in a given year. - Among the given options, this is the **closest representation** as it focuses on **newly infected individuals** rather than prevalent cases. - AIRT is a key epidemiological indicator reflecting **ongoing transmission** and the **annual risk of tuberculous infection** in a community. - This measure helps assess TB control program effectiveness and disease burden. *Percentage of total patients positive for tuberculin test* - This represents the **prevalence of tuberculosis infection** in the population, including both old and new infections. - It does not specifically measure the **annual rate of acquiring new infections**, which is what AIRT captures. *Percentage of sputum positive total patients* - This indicates the **prevalence of active, infectious pulmonary tuberculosis** in a population. - It refers to individuals with **active TB disease** who are shedding bacteria in sputum, not latent infection detected by tuberculin testing. *Percentage of sputum positive new patients* - This represents the **incidence of new, active, infectious tuberculosis cases** (case detection rate). - While important for TB surveillance, it measures **active disease** rather than **infection rate** detected by tuberculin skin test.

Q: Most common mode of transmission of nosocomial infection is -

Hand contact. ***Hand contact*** - **Direct contact** with healthcare workers' contaminated hands is the primary way pathogens are transferred between patients in a healthcare setting. - Failure to perform adequate **hand hygiene** between patient contacts is the single most important factor contributing to nosocomial infection transmission. *Droplet infection* - While droplet transmission can cause nosocomial infections, especially for respiratory viruses, it is not the most common mode of transmission for the overall burden of healthcare-associated infections. - **Droplets** usually travel short distances and deposit on mucous membranes of the nose, mouth, or eyes of a susceptible host. *Blood and blood products* - Transmission through **blood and blood products** is a significant concern for specific infections (e.g., HIV, hepatitis B/C), but the incidence is relatively low due to stringent screening and safety protocols. - This mode accounts for a small fraction of overall nosocomial infections compared to contact transmission. *Contaminated water* - **Contaminated water** can lead to outbreaks (e.g., *Legionella*, *Pseudomonas*), especially in immunocompromised patients, but it is not the most frequent mode of transmission on a day-to-day basis across all types of nosocomial infections. - Healthcare facilities implement measures to ensure water safety, limiting this as the primary route.

Q: Transovarian transmission is seen in-

Rickettsial diseases. ***Rickettsial diseases*** - **Transovarian transmission** is a key mechanism for the maintenance and spread of **rickettsiae** in arthropod vectors. The bacteria can pass from an infected female arthropod (like a tick or mite) to her offspring via the eggs. - This ensures that the next generation of vectors is already infected and can transmit the disease, even without needing to acquire the pathogen from an infected vertebrate host. *Malaria* - Malaria is transmitted via the bite of an infected **Anopheles mosquito**, which acquires parasites from an infected human. - **Transovarian transmission** does not occur in malaria; mosquitoes are not born with the ability to transmit the parasite. *Filaria* - Filariasis is spread by various **mosquito vectors** (e.g., *Culex*, *Anopheles*, *Aedes*) or **black flies**, which acquire microfilariae from an infected host during a blood meal. - The parasite undergoes development within the insect, but **transovarian transmission** to the insect's offspring does not occur. *None of the options* - This option is incorrect because **rickettsial diseases** do exhibit transovarian transmission, making it a valid answer. - The phenomenon of passing pathogens directly from a female parent to her offspring via the egg is a specific mechanism seen in certain vector-borne diseases.

Q: All of the following are anthropozoonosis except

Schistosomiasis. ***Schistosomiasis*** - This is a **human-to-human** disease, even though it involves an intermediate **snail host**. - Its life cycle does not involve transmission of pathogens from vertebrate animals to humans. *Rabies* - Rabies is a classic **anthropozoonosis**, transmitted to humans primarily through the saliva of infected animals, most commonly **dogs** and **bats**. - It involves a pathogen (rabies virus) that cycles between animals and can be transmitted to humans. *Plague* - Plague is an **anthropozoonosis** caused by *Yersinia pestis*, typically transmitted from **rodents** (e.g., rats) to humans via flea bites. - The disease maintains a natural reservoir in wild rodent populations, making it a prime example of animal-to-human transmission. *Anthrax* - Anthrax is an **anthropozoonosis** caused by *Bacillus anthracis*, transmitted to humans from infected **livestock** (e.g., cattle, sheep). - Humans usually acquire the infection through contact with infected animals or their products, or by inhaling spores.

Q: What is the recommended concentration of diethylcarbamazine in DEC medicated salt for the treatment of endemic filariasis?

0.1-0.2 gm/kg. ***0.1-0.2 gm/kg*** - The recommended concentration of **diethylcarbamazine (DEC)** in medicated salt for the treatment of endemic filariasis is typically 0.1-0.2 gm/kg of salt. - This low, sustained dose helps to gradually eliminate microfilariae and prevent transmission without causing severe adverse reactions. *0.5-1.0 gm/kg* - This concentration is significantly higher than the standard recommendation for mass drug administration using DEC medicated salt. - Such a higher dose would increase the risk of adverse drug reactions, making it unsuitable for community-wide use. *2-4 gm/kg* - This concentration is far too high for safe and effective use in DEC medicated salt programs. - Administering DEC at this level would likely lead to widespread and potentially severe side effects among the treated population. *5-10 gm/kg* - Concentrations in this range are excessively high and would be toxic if used in medicated salt for filariasis treatment. - This would result in widespread and severe adverse events, making it an unacceptable option.

Question 1

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

Accepted Answer

Anopheles culicifacies

Answer

Anopheles stephensi

Answer

Anopheles subpictus

Answer

Anopheles fluviatilis

Question 2

Which of the following diseases is NOT transmitted by sandflies?

Accepted Answer

Relapsing fever

Answer

Visceral Leishmaniasis

Answer

Oriental sore

Answer

Cutaneous Leishmaniasis

Question 3

In which condition is a night blood survey performed?

Accepted Answer

Lymphatic filariasis

Answer

Typhoid fever

Answer

Malaria infection

Answer

Visceral leishmaniasis

Question 4

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

Accepted Answer

Transmission of O. volvulus has been reduced to a level where it cannot sustain itself in the population.

Answer

All interventions have been successfully implemented.

Answer

There is no recrudescence of the disease after a defined period.

Answer

All of the options are true.

Question 5

What is the annual infection rate of tuberculosis?

Accepted Answer

Percentage of new patients positive for tuberculin test

Answer

Percentage of total patients positive for tuberculin test

Answer

Percentage of sputum positive total patients

Answer

Percentage of sputum positive new patients

Question 6

All are features of yellow fever except?

Accepted Answer

Validity of vaccination begins immediately after vaccination

Answer

Caused by vector aedes

Answer

IP 3-6 days

Answer

1 attack gives life long immunity

Question 7

Most common mode of transmission of nosocomial infection is -

Accepted Answer

Hand contact

Answer

Droplet infection

Answer

Blood and blood products

Answer

Contaminated water

Question 8

Transovarian transmission is seen in-

Accepted Answer

Rickettsial diseases

Answer

Malaria

Answer

Filaria

Answer

None of the options

Question 9

All of the following are anthropozoonosis except

Accepted Answer

Schistosomiasis

Answer

Rabies

Answer

Plague

Answer

Anthrax

Question 10

What is the recommended concentration of diethylcarbamazine in DEC medicated salt for the treatment of endemic filariasis?

Accepted Answer

0.1-0.2 gm/kg

Answer

5-10 gm/kg

Answer

0.5-1.0 gm/kg

Answer

2-4 gm/kg

Infectious Diseases — MCQs

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