Infectious Diseases Practice Questions

Q: The life cycle of the malaria parasite in the mosquito is described as?

Cyclopropagative. ### Explanation In epidemiology, the relationship between a pathogen and its vector is classified based on whether the pathogen undergoes changes in form (development) or increases in number (multiplication) within the vector. **1. Why "Cyclopropagative" is Correct:** The malaria parasite (*Plasmodium*) undergoes **Cyclopropagative** transmission within the female *Anopheles* mosquito. * **Cyclo-:** Refers to a change in form (developmental cycle). The parasite transforms from gametocytes into ookinetes, oocysts, and finally sporozoites. * **Propagative:** Refers to multiplication. A single oocyst ruptures to release thousands of sporozoites, significantly increasing the parasite count. Since both development and multiplication occur, it is termed cyclopropagative. **2. Analysis of Incorrect Options:** * **Propagative (Option A):** The organism multiplies in number but does not change its form or undergo a developmental cycle. *Example: Plague bacilli in the rat flea.* * **Cyclodevelopmental (Option B):** The organism undergoes developmental changes (morphological stages) but does not multiply in number. *Example: Filarial parasite (Wuchereria bancrofti) in the Culex mosquito or Guinea worm in Cyclops.* **3. NEET-PG High-Yield Pearls:** * **Biological Transmission:** This includes all three types (Propagative, Cyclopropagative, Cyclodevelopmental). It is characterized by an **extrinsic incubation period** (the time required for the parasite to complete its cycle in the vector before it becomes infective). * **Mechanical Transmission:** The vector simply carries the pathogen on its body parts (e.g., Housefly carrying Typhoid or Cholera) without any biological interaction. * **Malaria Vector:** Only the female *Anopheles* mosquito is the vector because it requires a blood meal for egg production; the male mosquito feeds on plant juices.

Q: Which statement is not true regarding Yellow Fever?

The vaccine is valid for 6 years.. **Explanation:** The correct answer is **D** because the validity of the Yellow Fever vaccine certificate has been updated by the WHO under the International Health Regulations (IHR). 1. **Why Option D is the correct answer (False statement):** Previously, the Yellow Fever vaccination certificate was valid for 10 years. However, since **July 11, 2016**, the WHO has mandated that a single dose of the Yellow Fever vaccine provides **life-long protection**. Therefore, the certificate is now valid for the duration of the life of the person vaccinated, starting 10 days after vaccination. 2. **Analysis of other options (True statements):** * **Option A:** It is an **exotic disease** in India. While the vector (*Aedes aegypti*) is present, the disease itself is not endemic, and strict quarantine laws are in place to prevent its entry. * **Option B:** The intrinsic incubation period in humans is typically **3 to 6 days**, making the "2-6 days" range accurate. * **Option C:** The vaccine is a **live attenuated** preparation using the **17D strain** (grown in chick embryos). It is highly effective and safe. **High-Yield Clinical Pearls for NEET-PG:** * **Vector:** *Aedes aegypti* (Urban cycle) and *Haemagogus* (Sylvan/Jungle cycle). * **Vaccination Dose:** 0.5 ml, subcutaneous. * **Contraindications:** Infants <6 months, egg allergy, and symptomatic HIV/immunocompromised states. * **Quarantine:** The Indian Aircraft Public Health Rules specify a quarantine period of **6 days** for unvaccinated travelers coming from endemic zones. * **Cold Chain:** The vaccine is highly heat-sensitive and must be stored between **-30°C and +5°C**.

Q: The GET strategy is used for the management of which disease?

Trachoma. **Explanation:** The **GET 2020** (Global Elimination of Trachoma by 2020) strategy was launched by the WHO to eliminate blinding trachoma as a public health problem. The core of this strategy is the **SAFE** acronym, which is a high-yield concept for NEET-PG: * **S:** Surgery (for Trichiasis) * **A:** Antibiotics (Azithromycin 20mg/kg single dose) * **F:** Facial cleanliness * **E:** Environmental improvement (water and sanitation) **Analysis of Options:** * **Trachoma (Correct):** Caused by *Chlamydia trachomatis* (Serotypes A, B, Ba, C). It is the leading infectious cause of blindness worldwide. The GET strategy focuses on community-wide interventions to break the transmission cycle. * **Onchocerciasis:** Managed primarily through the **APOC** (African Programme for Onchocerciasis Control) using annual mass drug administration of **Ivermectin** (Mectizan). * **Cataract:** Addressed under **Vision 2020: The Right to Sight**. The focus is on increasing the Cataract Surgical Rate (CSR) and utilizing IOL implantations. * **Vitamin A Supplementation:** Part of the **National Prophylaxis Programme against Nutritional Blindness**, involving periodic high-dose Vitamin A (2 lakh IU) for children aged 6–60 months. **High-Yield Clinical Pearls:** * **WHO Grading (FISTO):** Follicular, Intense, Scarring, Trichiasis, Opacity. * **Drug of Choice:** Oral **Azithromycin** is preferred over Tetracycline eye ointment for mass treatment due to better compliance. * **Vector:** The common housefly (*Musca sorbens*) acts as a mechanical vector. * **India Status:** India was declared free from infective trachoma in 2017, but surveillance for chronic stages (Trichiasis) continues.

Q: Dracunculiasis was historically more common in which of the following states of India?

Rajasthan. **Explanation:** **Dracunculiasis (Guinea Worm Disease)** was a major public health problem in India until its official eradication in 2000. The disease is caused by the nematode *Dracunculus medinensis* and is transmitted through the ingestion of water containing infected cyclops (intermediate host). **Why Rajasthan is Correct:** Historically, Dracunculiasis was highly endemic in the **arid and semi-arid regions** of North-West and Central India. **Rajasthan** was the most severely affected state due to the traditional use of **step-wells (Baoris)**. In these wells, people would step into the water to collect it, allowing the female worm to discharge larvae directly into the water source where cyclops were present, thus completing the life cycle. **Analysis of Incorrect Options:** * **Orissa & Uttar Pradesh:** While these states had sporadic cases, they were not the primary epicenters compared to the high-burden states of Rajasthan and Madhya Pradesh. * **Tamil Nadu:** Southern states had a significantly lower prevalence. The disease was primarily concentrated in 7 states: Rajasthan, Madhya Pradesh, Gujarat, Maharashtra, Andhra Pradesh, and Karnataka. **High-Yield Clinical Pearls for NEET-PG:** * **Eradication Status:** India was declared Guinea Worm free by the WHO on **February 25, 2000**. * **Last Case:** The last case in India was reported in **July 1996** in the Jodhpur district of Rajasthan. * **Intermediate Host:** *Cyclops* (Water flea). * **Definitive Host:** Humans. * **Prevention:** The primary intervention was the conversion of step-wells into draw-wells and the use of nylon mesh filters.

Q: Which of the following diseases is cyclopropagative?

Malaria. In vector-borne diseases, the transmission depends on the biological development of the pathogen within the vector. This is categorized into three main types: **1. Cyclopropagative (Correct Answer: Malaria)** In this type, the parasite undergoes both **multiplication** (increase in number) and **change in form** (developmental stages) within the vector. In Malaria, the *Plasmodium* parasite undergoes sexual reproduction (sporogony) in the mosquito, changing from a gametocyte to a sporozoite while multiplying significantly. **2. Cyclo-developmental (Option C: Filaria)** Here, the parasite undergoes **change in form** (development) but **no multiplication** occurs. In Filariasis, one microfilaria ingested by the *Culex* mosquito develops into exactly one infective third-stage larva (L3). Guinea worm (*Dracunculus*) also follows this pattern. **3. Propagative (Option B: Plague)** In this type, the pathogen only **multiplies** in number but undergoes **no change in form**. Examples include the Plague bacilli (*Yersinia pestis*) in rat fleas and most viral diseases like Yellow Fever or Dengue in *Aedes* mosquitoes. **High-Yield Clinical Pearls for NEET-PG:** * **Extrinsic Incubation Period:** The time required for the pathogen to complete its biological cycle within the vector before it becomes infective. * **Transovarial Transmission:** When the pathogen is passed to the next generation of vectors via eggs (e.g., Scrub Typhus in mites, Kyasanur Forest Disease in ticks). * **Mechanical Transmission:** No biological development occurs; the vector acts as a simple carrier (e.g., Housefly carrying Typhoid or Cholera).

Q: What is the insecticide of choice for Phlebotomus argentipes?

DDT. **Explanation:** The correct answer is **DDT (Dichloro-Diphenyl-Trichloroethane)**. *Phlebotomus argentipes* is the primary vector for **Kala-azar (Visceral Leishmaniasis)** in the Indian subcontinent. The insecticide of choice for its control is DDT, administered via **Indoor Residual Spraying (IRS)**. **1. Why DDT is the Correct Answer:** *Phlebotomus* sandflies are highly susceptible to DDT. They are "exophilic" (rest outdoors) but "endophagic" (feed indoors) or rest on indoor walls after feeding. DDT is used in two rounds of IRS annually (at a dosage of 0.25–0.5 $g/m^2$) to cover the walls up to a height of 6 feet. Despite resistance in mosquitoes, sandflies in India remain largely sensitive to DDT, making it the mainstay of the National Vector Borne Disease Control Programme (NVBDCP) for Kala-azar. **2. Why Other Options are Incorrect:** * **Malathion:** This is an organophosphate used primarily for **chemical fogging** during outbreaks of Dengue or Malaria, or as an alternative where DDT resistance is documented in mosquitoes. It is not the primary choice for sandflies. * **BHC (Benzene Hexachloride):** While used in the past for various pests, it has been largely phased out due to environmental persistence and toxicity. * **Pyrethrum:** This is a **space spray** (knock-down agent) used for immediate relief in indoor settings. It does not provide the long-lasting residual effect required for sustained sandfly control. **High-Yield Clinical Pearls for NEET-PG:** * **Vector Habitat:** Sandflies breed in damp soil, cracks in walls, and dark corners with high organic content. * **Control Strategy:** IRS must cover cattle sheds and human dwellings, as *P. argentipes* is often zoophilic. * **Drug of Choice for Kala-azar:** Liposomal Amphotericin B (single dose) is currently the preferred treatment. * **Post-Kala-azar Dermal Leishmaniasis (PKDL):** Occurs in 5-10% of cases; these patients act as a major reservoir for the parasite.

Q: Which of the following statements about meningococcal meningitis is false?

The source of infection is mainly clinical cases.. **Explanation:** **1. Why Option B is the Correct (False) Statement:** In Meningococcal meningitis (caused by *Neisseria meningitidis*), the primary source of infection is **asymptomatic carriers**, not clinical cases. For every one clinical case, there are typically 10 to 100 carriers in the community. The bacteria colonize the nasopharynx; while cases are infectious, they are usually isolated quickly, whereas carriers remain the hidden reservoir responsible for the continued transmission and endemicity of the disease. **2. Analysis of Other Options:** * **Option A (True):** The traditional **unconjugated polysaccharide vaccines** (targeting groups A, C, Y, W-135) are poorly immunogenic in children under 2 years because their immune systems do not respond well to T-cell independent antigens. (Note: Newer conjugate vaccines are effective in infants). * **Option C (True):** Meningococcal disease shows distinct seasonality. It is more common in **dry and cold months** (winter and spring). Dry weather irritates the nasopharyngeal mucosa, facilitating bacterial invasion. * **Option D (True):** Chemoprophylaxis is mandatory for **close contacts** (household members, daycare contacts) to eliminate the carrier state. **Rifampicin** is the drug of choice; alternatives include Ciprofloxacin or Ceftriaxone. **Clinical Pearls for NEET-PG:** * **Reservoir:** Humans are the only known reservoir. * **Portal of Entry:** Nasopharynx. * **Most common Serogroup in India:** Historically Serogroup A. * **Drug of Choice for Treatment:** Intravenous Ceftriaxone or Penicillin G. * **Waterhouse-Friderichsen Syndrome:** Severe complication involving adrenal hemorrhage and septicemia.

Q: A 27-year-old sexually active woman presents with copious vaginal discharge of 2 days duration. According to the syndromal management of vaginal discharge, which of the following would be given to her?

Metronidazole + Fluconazole. ### Explanation **1. Why Option C is Correct:** Under the **Syndromal Management of Sexually Transmitted Infections (STIs)** guidelines provided by NACO (National AIDS Control Organisation), a patient presenting with **vaginal discharge** is treated using **Kit 2 (Green Kit)**. The most common causes of vaginal discharge are **Bacterial Vaginosis (BV)**, **Trichomoniasis**, and **Candidiasis**. * **Metronidazole (2g single dose)** is used to cover both Bacterial Vaginosis and Trichomoniasis. * **Fluconazole (150mg single dose)** is used to treat Candidiasis (yeast infection). Therefore, the combination of Metronidazole and Fluconazole addresses the most likely pathogens in this syndrome. **2. Why Other Options are Incorrect:** * **Option A:** This combination (Kit 1/Grey Kit) includes Azithromycin, which is used for **Urethral/Cervical discharge** to cover *Chlamydia trachomatis* and *Neisseria gonorrhoeae*. While this patient is sexually active, the primary complaint is vaginal discharge, not cervicitis. * **Option B:** Azithromycin alone is insufficient as it does not cover the anaerobic bacteria or fungi responsible for vaginal discharge. * **Option D:** Fluconazole alone only treats Candidiasis, leaving Bacterial Vaginosis and Trichomoniasis (the most common causes) untreated. **3. Clinical Pearls for NEET-PG:** * **Kit 1 (Grey):** Urethral/Cervical discharge (Azithromycin 1g + Cefixime 400mg). * **Kit 2 (Green):** Vaginal discharge (Metronidazole 2g + Fluconazole 150mg). * **Kit 3 (White):** Non-herpetic Genital Ulcer (Benzathine Penicillin + Azithromycin). * **Kit 6 (Yellow):** Lower Abdominal Pain/PID (Cefixime + Metronidazole + Doxycycline). * **Whiff Test:** Positive (fishy odor) in Bacterial Vaginosis. * **Strawberry Cervix:** Characteristic of *Trichomonas vaginalis*.

Question 1

The life cycle of the malaria parasite in the mosquito is described as?

Accepted Answer

Cyclopropagative

Answer

Propagative

Answer

Cyclodevelopmental

Answer

None of the above

Question 2

Which statement is not true regarding Yellow Fever?

Accepted Answer

The vaccine is valid for 6 years.

Answer

It is an exotic disease.

Answer

The incubation period is 2-6 days.

Answer

The vaccine is a live attenuated 17D strain.

Question 3

The GET strategy is used for the management of which disease?

Accepted Answer

Trachoma

Answer

Onchocerciasis

Answer

Cataract

Answer

Vitamin A supplementation

Question 4

Dracunculiasis was historically more common in which of the following states of India?

Accepted Answer

Rajasthan

Answer

Orissa

Answer

Tamil Nadu

Answer

Uttar Pradesh

Question 5

An adult male patient presented with cough and fever for 3 months and intermittent haemoptysis. His sputum was positive for AFB. He had previously received 3 weeks of RHZE treatment from a nearby hospital and discontinued. How will you categorize and manage this patient?

Accepted Answer

Category I, Category 2 (RHZ)3

Answer

Category III, Category 2 (RHZ)3

Answer

Category II, Category 2 (RHZ)3

Answer

Category II, Category 2 (RHZ)3

Question 6

For controlling an outbreak of cholera, which of the following measures is NOT recommended?

Accepted Answer

Mass chemoprophylaxis

Answer

Proper disposal of excreta

Answer

Chlorination of water

Answer

Early detection and management of cases

Question 7

Which of the following diseases is cyclopropagative?

Accepted Answer

Malaria

Answer

Plague

Answer

Filaria

Answer

None

Question 8

What is the insecticide of choice for Phlebotomus argentipes?

Accepted Answer

DDT

Answer

Malathion

Answer

BHC

Answer

Pyrethrum

Question 9

Which of the following statements about meningococcal meningitis is false?

Accepted Answer

The source of infection is mainly clinical cases.

Answer

The vaccine is not effective in children below 2 years of age.

Answer

The disease is more common in dry and cold months of the year.

Answer

Chemoprophylaxis of close contacts of cases is recommended.

Question 10

A 27-year-old sexually active woman presents with copious vaginal discharge of 2 days duration. According to the syndromal management of vaginal discharge, which of the following would be given to her?

Accepted Answer

Metronidazole + Fluconazole

Answer

Azithromycin + Metronidazole + Fluconazole

Answer

Azithromycin

Answer

Fluconazole

Infectious Diseases — MCQs

Infectious Diseases — MCQs

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