Infectious Diseases Practice Questions

Q: Under the National Malaria Eradication Programme (NMEP), what is the minimum annual blood examination rate that should be achieved?

10%. **Explanation:** The **Annual Blood Examination Rate (ABER)** is a critical process indicator used to monitor the efficiency and operational coverage of malaria surveillance activities. It represents the percentage of the total population from which blood smears (thick and thin) are collected and examined for malaria parasites over one year. **1. Why 10% is Correct:** Under the National Malaria Eradication Programme (now integrated into the National Center for Vector Borne Diseases Control - NCVBDC), a **minimum ABER of 10%** is required to ensure adequate surveillance. This threshold is based on the epidemiological assumption that approximately 10% of the population in a malarious area will suffer from fever at least once a year. If the ABER falls below 10%, it indicates "poor surveillance," meaning cases are likely being missed, which could lead to an undetected outbreak. **2. Analysis of Incorrect Options:** * **B (12%) & C (14%):** While achieving a higher ABER (e.g., 15% or more) is encouraged in high-endemic areas to ensure no cases are missed, these are not the "minimum" statutory requirement set by the national guidelines. * **D (18%):** This value is significantly higher than the standard requirement and does not correspond to any specific surveillance target under the NMEP/NVBDCP. **3. High-Yield Clinical Pearls for NEET-PG:** * **ABER Formula:** (Number of blood slides examined in a year / Total population) × 100. * **API (Annual Parasite Incidence):** The most sensitive index to measure the malaria burden in a community. Formula: (Total confirmed cases in a year / Total population) × 1000. * **Surveillance Types:** ABER includes both **Active Case Detection (ACD)** (health workers visiting houses) and **Passive Case Detection (PCD)** (patients reporting to clinics). * **SPR (Slide Positivity Rate):** (Total slides positive / Total slides examined) × 100. This measures the validity of the surveillance.

Q: Safe injection practices can prevent which of the following diseases?

Hepatitis B. **Explanation:** The core concept behind this question is the **mode of transmission** of viral hepatitis. Safe injection practices are designed to prevent the transmission of **blood-borne pathogens** (infections spread through blood and body fluids). **Why Hepatitis B is correct:** Hepatitis B Virus (HBV) is primarily transmitted through parenteral routes, including contaminated needles, syringes, and medical equipment. Safe injection practices—such as using a sterile needle for every patient, preventing needle-stick injuries, and avoiding the reuse of multidose vials—directly interrupt this chain of transmission. Other blood-borne diseases prevented by these practices include Hepatitis C and HIV. **Why the other options are incorrect:** * **Hepatitis A and Hepatitis E:** These viruses are transmitted via the **fecal-oral route**, usually through contaminated food or water. While they are types of hepatitis, they are not typically associated with percutaneous (injection) exposure. * **Typhoid (Enteric Fever):** Caused by *Salmonella typhi*, this is also a water-borne/food-borne disease transmitted via the fecal-oral route. **High-Yield Clinical Pearls for NEET-PG:** * **HBV Infectivity:** HBV is highly infectious; the risk of transmission after a needle-stick injury from an HBeAg-positive source is approximately **30%** (compared to 3% for HCV and 0.3% for HIV). * **WHO Definition:** A safe injection is one that does not harm the recipient, does not expose the provider to any avoidable risk, and does not result in waste that is dangerous to the community. * **Injection Safety:** The use of **Auto-Disable (AD) syringes** is the gold standard recommended by the WHO to prevent reuse.

Q: A freshly prepared oral rehydration solution should not be used after how many hours?

24 hours. **Explanation:** The correct answer is **24 hours (Option D)**. **Why it is correct:** Oral Rehydration Solution (ORS) is a glucose-electrolyte solution used to prevent and treat dehydration. Once the ORS powder is dissolved in water, it becomes a potential medium for bacterial growth. The glucose in the solution acts as a substrate for microorganisms, and since the solution is often kept at room temperature in domestic settings, the risk of contamination increases over time. According to WHO and UNICEF guidelines, any unused portion of the prepared solution must be discarded after 24 hours to ensure safety and prevent secondary gastrointestinal infections. **Why other options are incorrect:** * **4, 6, and 12 hours (Options A, B, C):** While the solution is certainly safe during these intervals, discarding it this early would be wasteful, especially in resource-limited settings. The 24-hour mark is the standardized clinical threshold where the risk of microbial contamination outweighs the benefit of the solution. **High-Yield Clinical Pearls for NEET-PG:** * **Composition of WHO Reduced Osmolarity ORS:** Total osmolarity is **245 mOsm/L**. (Sodium: 75, Glucose: 75, Chloride: 65, Potassium: 20, Citrate: 10 mmol/L). * **Trisodium Citrate:** It is added to ORS to increase shelf life and help in the correction of acidosis. * **Zinc Supplementation:** Always given alongside ORS in diarrhea (20 mg/day for 14 days; 10 mg for infants <6 months) to reduce the duration and severity of the episode. * **Home-made ORS:** If commercial packets are unavailable, a solution of 6 teaspoons of sugar and 1/2 teaspoon of salt in 1 liter of water is recommended.

Q: Which of the following are vector-borne diseases?

Japanese encephalitis. **Explanation:** Vector-borne diseases are illnesses caused by pathogens (viruses, bacteria, or parasites) transmitted to humans by organisms like mosquitoes, ticks, or lice. **Japanese Encephalitis (JE)** is a classic vector-borne viral disease caused by a Flavivirus. It is transmitted to humans through the bite of infected **Culex mosquitoes** (primarily *Culex tritaeniorhynchus*). The virus cycles between vertebrate hosts (pigs and water birds) and mosquitoes, with humans acting as "dead-end" hosts. **Analysis of Options:** * **Epidemic Typhus (Option A):** While this is technically vector-borne (transmitted by the human body louse, *Pediculus humanus corporis*), in the context of standard NEET-PG questions, JE is often the prioritized answer for "vector-borne" unless multiple selections are allowed. However, if this were a single-choice question where JE is marked correct, it highlights JE's higher prevalence in the Indian public health context. * **Tetanus (Option C):** This is **not** vector-borne. It is caused by the contamination of wounds with spores of *Clostridium tetani*, typically found in soil or manure. * **Kyasanur Forest Disease (Option D):** KFD is also a vector-borne disease (transmitted by **Hard Ticks**, *Haemaphysalis spinigera*). If the question allows only one answer and JE is marked, it may be due to JE's status as a major National Health Program priority. **High-Yield Clinical Pearls for NEET-PG:** * **JE Vector:** *Culex* mosquitoes breed in stagnant water, specifically **irrigated rice fields**. * **JE Host:** Pigs are "amplifier hosts"; Ardeid birds are "reservoir hosts." * **KFD:** Known as "Monkey Fever"; localized to Karnataka and surrounding Western Ghats. * **Epidemic Typhus:** Caused by *Rickettsia prowazekii*; transmitted by lice (Brill-Zinsser disease is the recrudescent form).

Q: Diethyltoluamide is an effective agent against which of the following?

Repellent. **Explanation:** **Diethyltoluamide (DEET)** is the most widely used chemical **insect repellent** worldwide. It works by interfering with the chemoreceptors on the antennae of biting insects (such as mosquitoes, ticks, and fleas), effectively "masking" the host's scent or acting as an irritant that prevents the insect from landing or biting. * **Why Option C is Correct:** DEET is the gold standard for personal protection against vector-borne diseases. It is applied topically to skin or clothing. It does not kill the insect but prevents contact between the vector and the human host. * **Why Options A & B are Incorrect:** Larvicides (e.g., Temephos, Abate) and agents targeting pupae (e.g., Paris Green or mineral oils) are used for **source reduction** in water bodies. DEET has no efficacy in killing the immature stages of the mosquito life cycle. * **Why Option D is Incorrect:** Space sprays (e.g., Pyrethrum extract) are used for "knock-down" effects in indoor or outdoor environments to kill adult mosquitoes instantly. DEET is a personal protective measure, not an environmental spray. **High-Yield Facts for NEET-PG:** * **Duration of Action:** A 30% concentration of DEET typically provides protection for about 6 hours. * **Safety:** It is generally safe for adults and children over 2 months of age, but high concentrations should be avoided in infants due to the risk of neurotoxicity (encephalopathy). * **Other Repellents:** Dimethyl phthalate (DMP), Dibutyl phthalate, and Picaridin are other examples. * **Chemoprophylaxis vs. Repellent:** While DEET prevents the bite (mechanical), drugs like Doxycycline or Mefloquine provide pharmacological prophylaxis against the pathogen itself.

Q: Mites are known to transmit which of the following diseases?

Scabies. **Explanation:** **Correct Option: A. Scabies** Scabies is a contagious skin infestation caused by the itch mite, ***Sarcoptes scabiei* var. *hominis***. The female mite burrows into the stratum corneum of the skin to deposit eggs, leading to a delayed type IV hypersensitivity reaction. This results in the characteristic intense nocturnal pruritus and polymorphic lesions (vesicles, pustules, and burrows). **Analysis of Incorrect Options:** * **B. Relapsing Fever:** Louse-borne relapsing fever is transmitted by the **Body Louse** (*Pediculus humanus corporis*), while tick-borne relapsing fever is transmitted by **Soft Ticks** (*Ornithodoros*). * **C. Kyasanur Forest Disease (KFD):** This viral hemorrhagic fever is transmitted to humans via the bite of infected **Hard Ticks** (*Haemaphysalis spinigera*). * **D. Human Babesiosis:** This malaria-like parasitic disease is transmitted by the bite of **Hard Ticks** (specifically *Ixodes scapularis*). **High-Yield Clinical Pearls for NEET-PG:** * **Mite-borne diseases:** Apart from Scabies, mites are vectors for **Scrub Typhus** (transmitted by the *Leptotrombidium* chigger mite) and **Rickettsialpox** (*Liponyssoid sanguineus*). * **Scabies Treatment:** The drug of choice is **Permethrin 5% cream** (applied neck down overnight). Oral **Ivermectin** (200 µg/kg) is an alternative, especially for crusted (Norwegian) scabies. * **Vector Distinction:** Always distinguish between **Mites** (Scabies, Scrub Typhus) and **Ticks** (KFD, Babesiosis, Indian Tick Typhus) as they are frequently confused in exams.

Q: Hookworm infestation is associated with which of the following findings?

Chandler's index. **Explanation:** **Chandler’s Index** is the correct answer as it is a standard epidemiological measure used to assess the severity of hookworm infestation (primarily *Ancylostoma duodenale* and *Necator americanus*) in a community. It is calculated by taking the average number of eggs per gram (EPG) of stool across a sampled population. An index of less than 2000-2500 is generally considered low, while higher values indicate a significant public health problem and a higher risk of iron-deficiency anemia among the population. **Analysis of Incorrect Options:** * **Metafren index:** This is a distractor and not a recognized clinical or epidemiological scoring system in parasitology. * **MELD score (Model for End-Stage Liver Disease):** This is a scoring system used to predict the 3-month mortality risk in patients with chronic liver disease and is primarily used for prioritizing patients for liver transplantation. * **Burrows in skin:** This is the classic clinical finding of **Scabies** (*Sarcoptes scabiei*), where the female mite tunnels into the stratum corneum. While hookworms cause "creeping eruption" (Cutaneous Larva Migrans), they do not form permanent burrows in the same manner as scabies. **High-Yield Clinical Pearls for NEET-PG:** * **Hookworm Anemia:** The primary morbidity is microcytic hypochromic anemia due to chronic blood loss (0.03–0.2 ml/day/worm). * **Ground Itch:** An allergic reaction at the site of larval entry (usually the feet). * **Loeffler’s Syndrome:** Transient pulmonary eosinophilia occurring during the larval migration phase through the lungs. * **Treatment:** Albendazole (400 mg single dose) is the drug of choice.

Question 1

Filaria elimination is possible in the South-East Asian region due to all of the following reasons EXCEPT:

Accepted Answer

Humans are the only reservoir.

Answer

The parasite does not multiply in the intermediate host mosquito.

Answer

Larvae multiply in the human reservoir only.

Answer

Infectious larvae are deposited on the skin but most of them die before penetrating.

Question 2

Under the National Malaria Eradication Programme (NMEP), what is the minimum annual blood examination rate that should be achieved?

Accepted Answer

10%

Answer

12%

Answer

14%

Answer

18%

Question 3

Which of the following is NOT a mosquito-borne disease?

Accepted Answer

Tularemia

Answer

Yellow fever

Answer

Kala-azar

Answer

Dengue fever

Question 4

Safe injection practices can prevent which of the following diseases?

Accepted Answer

Hepatitis B

Answer

Hepatitis A

Answer

Typhoid

Answer

Hepatitis E

Question 5

A freshly prepared oral rehydration solution should not be used after how many hours?

Accepted Answer

24 hours

Answer

4 hours

Answer

6 hours

Answer

12 hours

Question 6

Which of the following are vector-borne diseases?

Accepted Answer

Japanese encephalitis

Answer

Epidemic typhus

Answer

Tetanus

Answer

Kyasanur Forest Disease (KFD)

Question 7

Diethyltoluamide is an effective agent against which of the following?

Accepted Answer

Repellent

Answer

Larvicidal

Answer

Agent against pupae of Anopheles

Answer

Space spray

Question 8

Which of the following is true for Directly Observed Treatment, Short-course (DOTS)?

Accepted Answer

Treatment is provided under direct supervision

Answer

All patients receive the exact same treatment regimen

Answer

Streptomycin is administered to every patient

Answer

The treatment regimen is administered daily

Question 9

Mites are known to transmit which of the following diseases?

Accepted Answer

Scabies

Answer

Relapsing fever

Answer

Kyasanur Forest Disease (KFD)

Answer

Human babesiosis

Question 10

Hookworm infestation is associated with which of the following findings?

Accepted Answer

Chandler's index

Answer

Metafren index

Answer

MELD score

Answer

Burrows in skin

Infectious Diseases — MCQs

Infectious Diseases — MCQs

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