Infectious Diseases Practice Questions

Q: Two students from a university dormitory building have contracted meningitis due to Neisseria meningitides. Which of the following students in the dormitory are most likely to benefit from chemoprophylaxis?

close contacts only, with oral rifampin. ***close contacts only, with oral rifampin*** - **Chemoprophylaxis** for *Neisseria meningitidis* is primarily recommended for **close contacts** due to the direct person-to-person transmission mode [1]. - **Oral rifampin** is an effective antibiotic for prophylaxis as it penetrates pharyngeal secretions and eliminates carriage of the bacteria [1]. *everybody in the dormitory, with oral rifampin* - Administering chemoprophylaxis to **everyone** in the dormitory is **excessive** and not indicated, as the risk of transmission is highest among close contacts [1]. - Widespread indiscriminate use of antibiotics like rifampin can contribute to **antibiotic resistance**. *close contacts only, with oral amoxicillin* - While prophylaxis is correctly targeted at **close contacts**, **amoxicillin** is generally **not recommended** for *N. meningitidis* chemoprophylaxis. - Amoxicillin does not reliably eradicate meningococcal carriage from the nasopharynx and is therefore **ineffective** for prophylaxis. *everybody in the dormitory, with oral amoxicillin* - This option is incorrect because both the scope of administration (**everybody in the dormitory**) and the choice of antibiotic (**amoxicillin**) are inappropriate. - **Amoxicillin** is not effective for clearing *N. meningitidis* carriage, and widespread use is not justified for prophylaxis.

Q: In a case of meningitis, Neisseria meningitides was grown in culture after 48 hours. Which measure is to be taken immediately ?

Antibiotic treatment of contacts. ***Correct: Antibiotic treatment of contacts*** - **Chemoprophylaxis is the immediate priority** for close contacts of confirmed *Neisseria meningitidis* cases - Should be administered **within 24 hours** of case identification to prevent secondary cases - **Recommended antibiotics**: Rifampicin (2 days), Ciprofloxacin (single dose), or Ceftriaxone (single dose) - **Close contacts include**: household members, daycare contacts, anyone directly exposed to patient's oral secretions, healthcare workers exposed to respiratory secretions - This is the **most effective immediate measure** to prevent transmission as meningococcal disease has a 2-10 day incubation period *Incorrect: Isolation of contacts* - **Contacts do NOT require isolation** according to WHO and CDC guidelines - Only the **index patient** requires droplet precautions for 24 hours after starting appropriate antibiotics - Contacts can continue normal activities while on chemoprophylaxis and should monitor for symptoms - Isolating healthy contacts is not evidence-based and creates unnecessary social disruption *Incorrect: Vaccination of contacts* - Meningococcal vaccination is important for **long-term prevention** but not immediate post-exposure prophylaxis - Vaccines take **7-14 days** to develop protective immunity, too slow for immediate protection - Recommended in **outbreak settings** or for high-risk groups as an adjunct to chemoprophylaxis - Does not replace the need for immediate antibiotic prophylaxis *Incorrect: All of the options* - **Only antibiotic chemoprophylaxis** is the immediate measure required - Isolation of contacts is not standard practice for meningococcal disease - Vaccination is a secondary/long-term measure, not immediate - The question asks for the **immediate** measure, which is unequivocally chemoprophylaxis

Q: Which of the following is Amphixenoses?

Trypanosoma cruzi. ***Trypanosoma cruzi*** - **Amphixenoses** refers to infections that are naturally maintained in both wild (sylvatic) and domestic animal populations, with transmission occurring between these populations. - ***Trypanosoma cruzi***, the causative agent of **Chagas disease**, is a classic example of amphixenosis. - It cycles between **wild animals** (opossums, armadillos, rodents), **domestic animals** (dogs, cats), and **humans**, transmitted by **triatomine bugs (kissing bugs)**. - The disease is maintained in both wild and domestic cycles, making it a true amphixenosis. *Salmonella* - While **Salmonella** can infect both humans and animals, it is primarily classified as a **zoonosis** or **anthropozoonosis**. - It follows a fecal-oral transmission route and is not considered an **amphixenosis** in the classical epidemiological sense. *Anthrax* - **Anthrax (Bacillus anthracis)** is a classic **saprozoonosis** (or sapronosis). - The organism survives in soil (non-living reservoir) and infects herbivores through environmental spores. - Its epidemiology is linked to environmental contamination rather than sustained cycles in both wild and domestic animal populations. *Rabies* - **Rabies** is classified as a **zoonosis**, maintained primarily in wild carnivores (foxes, bats, raccoons) and domestic animals (dogs). - While it affects both wild and domestic animals, transmission is predominantly unidirectional (animal to human via bites), not bidirectional between wild and domestic animal populations as required for amphixenosis classification.

Q: Which of the following diseases is transmitted by Mansonia?

Bancroftian filariasis. ***Bancroftian filariasis*** - **Bancroftian filariasis** (caused by *Wuchereria bancrofti*) is commonly transmitted by three mosquito genera: *Culex*, *Anopheles*, and *Mansonia*. - *Mansonia* mosquitoes are known vectors for the larvae of *Wuchereria bancrofti*, which mature into adult worms in the human lymphatic system. *Chikungunya* - Chikungunya virus is primarily transmitted by mosquitoes of the genus *Aedes*, particularly **_Aedes aegypti_** and **_Aedes albopictus_**. - *Mansonia* mosquitoes are not considered primary or significant vectors for the transmission of Chikungunya. *Japanese encephalitis* - Japanese encephalitis virus is mainly transmitted by mosquitoes of the genus _Culex_, specifically **_Culex tritaeniorhynchus_**. - While *Mansonia* mosquitoes may occasionally carry the virus, they are not primary vectors for its transmission to humans. *Dengue* - Dengue virus is primarily transmitted by **_Aedes aegypti_** and **_Aedes albopictus_** mosquitoes. - *Mansonia* mosquitoes are not implicated in the transmission cycle of Dengue fever.

Q: Where did the last case of Smallpox occur?

Somalia. ***Somalia*** - The **last naturally occurring case** of **variola major** (a more severe form of smallpox) was reported in **Ali Maow Maalin** in **Somalia** in 1977. - This case marked a significant milestone in the global eradication campaign, as subsequent cases were either laboratory-related or variola minor (a milder form). *Uganda* - While smallpox was endemic in many African countries, **Uganda** was not the site of the last naturally occurring case. - The last outbreaks in Uganda preceded the final eradication efforts in other regions. *Sudan* - **Sudan** did experience smallpox outbreaks in the past, but it was not the location of the very last case. - Eradication efforts were extensive across Africa, with the final focus shifting to specific regions. *Libya* - **Libya** also had experience with smallpox, but it was not the country where the last naturally transmitted case was identified. - The global eradication strategy systematically targeted remaining pockets of disease.

Q: Spread of which disease cannot be controlled by isolation -

Neonatal tetanus. ***Neonatal tetanus*** - **Neonatal tetanus** is caused by spores of *Clostridium tetani* entering the umbilical stump, particularly in unhygienic birth practices. - Its spread is primarily through **environmental contamination** and unsterile wound care, not person-to-person transmission, making isolation ineffective. *Diphtheria* - **Diphtheria** is a highly contagious bacterial infection spread through respiratory droplets, making **isolation of infected individuals** crucial to prevent transmission. - Strict isolation and prompt antitoxin treatment are essential for controlling outbreaks. *Mumps* - **Mumps** is a viral infection that spreads easily through respiratory droplets from infected individuals. - **Isolation measures** and vaccination are highly effective in controlling its spread within communities. *Cholera* - **Cholera** is an acute diarrheal illness caused by ingestion of food or water contaminated with *Vibrio cholerae*. - While isolation can help prevent spread through direct contact in exceptional circumstances, primary control relies on **sanitation, safe water, and hygiene**, as well as careful management of bodily fluids.

Q: Not true about measles

Carriers are the source of infection. ***Carriers are the source of infection*** - Measles is transmitted through **respiratory droplets** from infected individuals during the **prodromal phase** and early rash, not through asymptomatic carriers. - While individuals can transmit the virus before symptoms fully develop, they are not considered **asymptomatic carriers** in the sense of long-term, symptom-free transmission. *Koplik spots are pathognomonic* - **Koplik spots** are indeed considered **pathognomonic** for measles, appearing as small, white, or bluish-white spots on the buccal mucosa. - Their presence helps in the **early clinical diagnosis** of measles, often before the characteristic rash appears. *Edmonston zagreb strain used for vaccine* - The **Edmonston-Zagreb strain** is one of the attenuated live virus strains used in some measles vaccines (e.g., in some MMR formulations), demonstrating its relevance in immunization. - Other attenuated strains, such as the **Schwarz** and **Moraten** strains, are also used in measles vaccines globally. *Incubation period is 2 weeks* - The typical incubation period for measles is around **10-14 days** (approximately 2 weeks) from exposure to the onset of symptoms like fever and rash. - This period allows for viral replication before the characteristic clinical signs of the disease become apparent.

Q: Relapsing fever is transmitted by -

Soft tick. ***Soft tick*** - **Relapsing fever** (especially endemic/spirochetal relapsing fever) is primarily transmitted by the bite of infected **soft ticks** (*Ornithodoros* species). - These ticks are often nocturnal feeders and brief, painless bites, making them difficult to detect. *Hard tick* - **Hard ticks** (families Ixodidae) are vectors for diseases such as **Lyme disease**, **Rocky Mountain spotted fever**, and **Babesiosis**, but not typically relapsing fever. - They tend to attach for longer periods (hours to days) to feed. *Sandfly* - **Sandflies** are vectors for diseases like **leishmaniasis** and **sandfly fever**, which are caused by protozoa or viruses, respectively. - They are not associated with the transmission of spirochetes causing relapsing fever. *Tsetse fly* - The **tsetse fly** is the primary vector for **African trypanosomiasis** (sleeping sickness), caused by parasitic protozoa. - Its transmission mechanism and the pathogens it carries are different from those involved in relapsing fever.

Question 1

Two students from a university dormitory building have contracted meningitis due to Neisseria meningitides. Which of the following students in the dormitory are most likely to benefit from chemoprophylaxis?

Accepted Answer

close contacts only, with oral rifampin

Answer

everybody in the dormitory, with oral rifampin

Answer

close contacts only, with oral amoxicillin

Answer

everybody in the dormitory, with oral amoxicillin

Question 2

In a case of meningitis, Neisseria meningitides was grown in culture after 48 hours. Which measure is to be taken immediately ?

Accepted Answer

Antibiotic treatment of contacts

Answer

All of the options

Answer

Isolation of contacts

Answer

Vaccination of contacts

Question 3

Which of the following is Amphixenoses?

Accepted Answer

Trypanosoma cruzi

Answer

Salmonella

Answer

Anthrax

Answer

Rabies

Question 4

Which of the following diseases is transmitted by Mansonia?

Accepted Answer

Bancroftian filariasis

Answer

Chikungunya

Answer

Japanese encephalitis

Answer

Dengue

Question 5

Where did the last case of Smallpox occur?

Accepted Answer

Somalia

Answer

Uganda

Answer

Sudan

Answer

Libya

Question 6

Spread of which disease cannot be controlled by isolation -

Accepted Answer

Neonatal tetanus

Answer

Diphtheria

Answer

Mumps

Answer

Cholera

Question 7

Not true about measles

Accepted Answer

Carriers are the source of infection

Answer

Koplik spots are pathognomonic

Answer

Edmonston zagreb strain used for vaccine

Answer

Incubation period is 2 weeks

Question 8

‘Accompanied MDT’ in NLEP implies

Accepted Answer

Any responsible person from family or village can collect MDT, if patient is unable to come

Answer

MDT should be accompanied with Steroids/ Clofazimine to help fight Reversal reactions

Answer

MDT prescription should be accompanied by all the precautions to be observed by the patient

Answer

A patient will be given MDT only in the presence of a MDT provider

Question 9

Relapsing fever is transmitted by -

Accepted Answer

Soft tick

Answer

Hard tick

Answer

Sandfly

Answer

Tsetse fly

Question 10

All the following are true regarding Dracunculiasis, EXCEPT:

Accepted Answer

Mebendazole and niridazole are effective in preventing the transmission of the disease

Answer

Control of cyclops helps prevent the spread of the disease

Answer

No effective vaccines are available to prevent the disease

Answer

The parasites reach adulthood by 10-14 months

Infectious Diseases — MCQs

Infectious Diseases — MCQs

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