Infectious Diseases Practice Questions

Q: Animal to man transmission (zoonosis) is seen in -

Rabies. ***Rabies*** - **Rabies** is a classic zoonotic disease, primarily transmitted to humans through the bite or scratch of an infected animal, most commonly **dogs, bats, or other wild carnivores**. - The virus travels from the site of infection to the central nervous system, leading to characteristic neurological symptoms. *Tuberculosis* - While certain strains of **Mycobacterium bovis** can cause zoonotic tuberculosis, the question implies common human tuberculosis (**Mycobacterium tuberculosis**), which is primarily transmitted person-to-person via airborne droplets. - While bovine TB is zoonotic, general "Tuberculosis" in this context usually refers to the human-to-human transmitted form. *Measles* - **Measles** is a highly contagious disease caused by the **measles virus**, which is a **human paramyxovirus**. - It is spread exclusively from **person to person** through respiratory droplets and has no known animal reservoir. *HIV* - **HIV (Human Immunodeficiency Virus)** is thought to have originated from **simian immunodeficiency virus (SIV)** in non-human primates, thus representing a historic zoonotic jump. - However, current and continued transmission of HIV is almost exclusively through **human-to-human contact**, not ongoing animal-to-human transmission.

Q: Elimination of leprosy is defined as prevalence rate of:

< 1 per 10000. ***< 1 per 10,000*** - The World Health Organization (WHO) defines **elimination of leprosy as a public health problem** as achieving a prevalence rate of **less than 1 case per 10,000 population** at the national level. - This target was set to highlight significant progress in disease control and public health efforts. - India achieved this milestone in December 2005. *< 1 per 1 lakh (100,000)* - This rate is significantly lower than the internationally accepted threshold for leprosy elimination and is not the standard definition. - A prevalence rate of less than 1 per 100,000 population indicates a level beyond elimination, often nearing eradication. *< 1 per 100* - A prevalence rate of less than 1 per 100 population (1%) is still a high prevalence and does not constitute elimination of leprosy. - This level would indicate a substantial burden of disease within the population. *< 1 per 1,000* - While a reduction from higher prevalence, a rate of less than 1 per 1,000 population is not the defined threshold for leprosy elimination. - This rate still suggests an ongoing public health concern that has not met the global elimination target.

Q: According to WHO, leprosy is considered a major public health problem when the prevalence is:

0.01%. ***0.01% or more (≥ 1 case per 10,000 population)*** - The World Health Organization (WHO) defines **elimination of leprosy as a public health problem** when prevalence falls **below 1 case per 10,000 population** (< 0.01%). - Conversely, leprosy **remains a public health problem** when prevalence is **≥ 1 case per 10,000 population** (≥ 0.01%). - This threshold is used for global monitoring to assess disease control and elimination targets. *1%* - A prevalence of 1% (100 cases per 10,000 population) would indicate a **severe hyperendemic** situation, far exceeding the WHO threshold. - This represents **uncontrolled transmission** and would be seen in areas with no leprosy control programs. *0.50%* - A prevalence of 0.50% (50 cases per 10,000 population) is significantly high, indicating a **major endemic burden**. - This is **50 times higher** than the WHO elimination threshold and represents poor disease control. *0.10%* - A prevalence of 0.10% (10 cases per 10,000 population) is **10 times higher** than the WHO threshold. - While indicating substantial burden requiring intervention, it is not the specific WHO-defined threshold for public health problem status.

Q: World Malaria Day is observed in which month?

April. ***April*** - **World Malaria Day** is observed annually on **April 25th**. - Its purpose is to raise awareness about malaria and celebrate the efforts made globally to control and eradicate this disease. *September* - While September hosts various health observances, it is not the month for **World Malaria Day**. - Other public health campaigns, such as **World Alzheimer's Month**, are observed in September. *May* - May is recognized for several health-related days, but not specifically for **World Malaria Day**. - For example, **World Hypertension Day** is observed in May. *June* - June includes observances like **World Blood Donor Day**, but it is not the month designated for **World Malaria Day**. - Public health calendars indicate April 25th for this specific event.

Q: White death is

TB. ***TB*** - **Tuberculosis (TB)**, particularly the pulmonary form, has historically been known as the **"White Death"** due to the characteristic pallor, weight loss, and widespread prevalence it caused, leading to death. - This term reflects the devastating impact of the disease, which left victims looking pale and wasted due to chronic illness and cachexia. *Plague* - The **Plague** is famously known as the **"Black Death"** due to the development of **gangrene** and **hemorrhages** that turned the skin black. - It is caused by the bacterium *Yersinia pestis* and is characterized by rapidly progressing, severe symptoms, often in the form of bubonic, pneumonic, or septicemic plague. *Yellow fever* - **Yellow fever** is named for the **jaundice (yellowing of the skin and eyes)** that affects some patients due to liver damage. - It is a viral hemorrhagic disease transmitted by mosquitoes and is not associated with the term "White Death." *HIV* - **HIV (Human Immunodeficiency Virus)** infection leads to **AIDS (Acquired Immunodeficiency Syndrome)**, which was historically known as the **"slim disease"** due to the severe weight loss and wasting it caused, but not specifically the "White Death." - HIV primarily targets the immune system, leading to opportunistic infections and cancers, rather than the pallor associated with chronic lung disease.

Q: The following statements are true regarding leptospirosis, except -

Lice act as reservoirs of infection. ***Lice act as reservoirs of infection*** - **Lice** are not known reservoirs or vectors for leptospirosis; the infection is primarily spread through the urine of infected animals. - The main reservoirs are **rodents**, **livestock**, and **wild animals**, which excrete bacteria in their urine. *It is zoonosis* - **Leptospirosis** is indeed a **zoonotic disease**, meaning it is transmitted from animals to humans. - Humans typically acquire the infection through contact with the urine of infected animals or contaminated water/soil. *Man is the dead end host* - Humans are considered **dead-end hosts** for leptospirosis, meaning they typically do not transmit the infection to others. - While humans can become severely ill, their role in maintaining the natural cycle of the disease is minimal. *Man is an accidental host* - Humans are also considered an **accidental host**, as they contract the disease incidentally from the environment rather than being a natural part of the pathogen's life cycle. - The primary cycle of transmission occurs between infected animals and the environment.

Q: All of the following statements about tetanus are true except:

Uterine tetanus is the least severe.. ***Uterine tetanus is the least severe.*** - Uterine tetanus (or **puerperal tetanus**) is actually a severe form of tetanus, often leading to high morbidity and mortality in mothers and neonates due to complications associated with childbirth. - The severity of tetanus is generally related to the **amount of toxin produced** and disseminated, and uterine infections can lead to significant toxin production due to anaerobic conditions. *Soil and intestines of infected humans and animals act as chief reservoirs.* - **Clostridium tetani** spores are widely distributed in the environment, especially in **soil contaminated with feces** from humans and animals. This makes soil a primary reservoir. - The gastrointestinal tracts of humans and animals can harbor the bacterium without causing disease, thus serving as an additional reservoir. *Incubation period is 6-12 days.* - The typical incubation period for tetanus is generally reported to be **3 to 21 days**, with a common range of **6 to 12 days**. - A shorter incubation period is often associated with more severe disease and a worse prognosis due to greater toxin load or closer proximity to the central nervous system. *Tetanospasmin is the neurotoxin responsible for clinical manifestations* - **Tetanospasmin** is indeed the potent neurotoxin produced by *Clostridium tetani* that is responsible for all the clinical manifestations of tetanus. - This toxin acts by blocking the release of **inhibitory neurotransmitters** (glycine and GABA) in the spinal cord, leading to uncontrolled muscle spasms and rigidity.

Q: The most practical way of treating typhoid carrier is -

Cholecystectomy. ***Correct Option: Cholecystectomy*** - **Cholecystectomy** (surgical removal of the gallbladder) is the **most practical and definitive treatment** for chronic typhoid carriers - Chronic carriers harbor *Salmonella typhi* in the **gallbladder**, especially when **gallstones** are present, where bacteria form biofilms - **Success rate >90%** in eliminating the carrier state permanently - Particularly important for **food handlers** and healthcare workers where definitive cure is essential - While surgical, it provides a **permanent solution** unlike antibiotics which have high failure/relapse rates *Incorrect Option: Chemotherapy* - Antibiotic therapy alone has a **poor success rate** (~80% failure) in chronic typhoid carriers - Bacteria in the gallbladder are protected by **biofilms** on gallstones and poor antibiotic penetration - High **relapse rates** even after prolonged courses of ciprofloxacin or ampicillin - May be attempted first but is not the most practical definitive treatment *Incorrect Option: Isolation* - **Isolation** is a public health measure to prevent transmission, not a treatment - Does not eliminate the bacteria from the carrier's body - Only controls spread to others, not a therapeutic intervention *Incorrect Option: Vaccination* - Provides **prophylactic immunity** against future infection but does not treat existing carrier state - Does not eliminate *Salmonella typhi* bacteria already colonizing the gallbladder - Used for prevention, not treatment of carriers

Q: All of the following statements about plague are wrong except -

Bubonic is the most common variety. ***Bubonic is the most common variety*** - **Bubonic plague** is indeed the most frequent clinical form of plague, accounting for 80-95% of cases. - It results from the bite of an infected flea, leading to the development of **buboes** (swollen, tender lymph nodes). *Incubation period for pneumonic plague is 10-14 days* - The incubation period for **pneumonic plague** is typically much shorter, usually 1 to 3 days, not 10-14 days. - A longer incubation period would be atypical for such an aggressive and rapidly progressing disease. *The causative bacillus can survive up to 10 years in the soil of rodent burrows* - While *Yersinia pestis* can survive in the environment, its survival in soil is typically for days to weeks, not years. - The primary survival mechanism is within infected animals and fleas, not as dormant free-living bacteria for a prolonged period in soil. *Domestic rat is main reservoir* - While domestic rats (Rattus species) can be involved in urban plague cycles, the main reservoirs of *Yersinia pestis* are wild rodents such as **ground squirrels, marmots, and prairie dogs**. - These wild rodents maintain the enzootic cycle in nature, and fleas often transmit the bacteria between them.

Q: Amplifier host in Japanese encephalitis is:

Pigs. ***Pigs*** - **Pigs** are the primary **amplifier hosts** for Japanese encephalitis virus, meaning they develop high viremia and can efficiently transmit the virus to mosquitoes. - This high viral load in pigs plays a crucial role in maintaining and intensifying the **transmission cycle** of the disease. *Monkey* - While **monkeys** can be infected with Japanese encephalitis, they are generally considered **dead-end hosts** or have a minor role in amplification. - They do not typically develop a high enough viremia to efficiently transmit the virus back to mosquitoes. *Dogs* - **Dogs** are not known to be significant **reservoir hosts** or **amplifier hosts** for Japanese encephalitis. - They are generally considered refractory to infection or develop only mild, subclinical disease. *Horse* - **Horses** can be infected with Japanese encephalitis and may develop neurological symptoms, including fatal encephalitis. - However, they are considered **dead-end hosts** as they do not develop sufficient viremia to transmit the virus back to mosquitoes.

Question 1

Animal to man transmission (zoonosis) is seen in -

Accepted Answer

Rabies

Answer

Tuberculosis

Answer

Measles

Answer

HIV

Question 2

Elimination of leprosy is defined as prevalence rate of:

Accepted Answer

< 1 per 10000

Answer

< 1 per 1 lakh

Answer

< 1 per 100

Answer

< 1 per 1000

Question 3

According to WHO, leprosy is considered a major public health problem when the prevalence is:

Accepted Answer

0.01%

Answer

1%

Answer

0.50%

Answer

0.10%

Question 4

World Malaria Day is observed in which month?

Accepted Answer

April

Answer

September

Answer

May

Answer

June

Question 5

White death is

Accepted Answer

TB

Answer

Plague

Answer

Yellow fever

Answer

HIV

Question 6

The following statements are true regarding leptospirosis, except -

Accepted Answer

Lice act as reservoirs of infection

Answer

It is zoonosis

Answer

Man is the dead end host

Answer

Man is an accidental host

Question 7

All of the following statements about tetanus are true except:

Accepted Answer

Uterine tetanus is the least severe.

Answer

Soil and intestines of infected humans and animals act as chief reservoirs.

Answer

Incubation period is 6-12 days.

Answer

Tetanospasmin is the neurotoxin responsible for clinical manifestations

Question 8

The most practical way of treating typhoid carrier is -

Accepted Answer

Cholecystectomy

Answer

Chemotherapy

Answer

Vaccination

Answer

Isolation

Question 9

All of the following statements about plague are wrong except -

Accepted Answer

Bubonic is the most common variety

Answer

Incubation period for pneumonic plague is 10-14 days

Answer

The causative bacillus can survive up to 10 years in the soil of rodent burrows

Answer

Domestic rat is main reservoir

Question 10

Amplifier host in Japanese encephalitis is:

Accepted Answer

Pigs

Answer

Monkey

Answer

Dogs

Answer

Horse

Infectious Diseases — MCQs

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