Vector-Borne Zoonoses — MCQs
KFD is transmitted by:
A man presents with fever and chills 2 weeks after a louse bite. There was a maculo-papular rash on the trunk which spread peripherally. The cause of this infection can be
True about Arboviruses is -
A patient hailing from Delhi presents with fever, arthralgia, and extensive petechial rash for 3 days. Lab investigations revealed a hemoglobin of 9 g/ dL, a white blood cell count of 9000 cells/mm3, a platelet count of 20000 cells/mm3, and a prolonged bleeding time. The clotting time was normal. What is the most likely diagnosis?
A woman traveling from Bihar to Delhi is suspected to have Kala-azar. Suitable investigation is?
A patient presents with fever and retro-orbital pain. Which investigation should be conducted next for confirmation of dengue fever?
Animal to man transmission (zoonosis) is seen in -
In scrub typhus all are true except:
Japanese encephalitis is caused by which virus?
A militant presents with rashes all over his body sparing the palms and soles. On examination, he was febrile and lice were noted. Which of the following is responsible for his condition?
Vector-Borne Zoonoses Indian Medical PG Practice Questions and MCQs
Question 1: KFD is transmitted by:
- A. Sandfly
- B. Mosquito
- C. Tick (Correct Answer)
- D. Mite
Explanation: ***Tick*** - KFD, or **Kyasanur Forest Disease**, is a viral hemorrhagic fever endemic to India that is primarily transmitted by infected **ticks**, specifically *Haemaphysalis spinigera*. - Humans can contract the disease through a **tick bite** or contact with an **infected animal**, such as monkeys, which are reservoirs for the virus. *Sandfly* - **Sandflies** are vectors for diseases such as **leishmaniasis** and **bartonellosis**, not Kyasanur Forest Disease. - These insects transmit parasites or bacteria, whereas KFD is a **viral infection** transmitted by ticks. *Mosquito* - **Mosquitoes** are common vectors for many viral diseases, including **dengue**, **malaria**, and **chikungunya**, but they do not transmit Kyasanur Forest Disease. - KFD is exclusively associated with **tick transmission** in its endemic regions. *Mite* - **Mites** can transmit diseases like **scrub typhus** (via chiggers) or cause conditions like **scabies**, but they are not vectors for Kyasanur Forest Disease. - The primary vector for KFD is the **hard tick**.
Question 2: A man presents with fever and chills 2 weeks after a louse bite. There was a maculo-papular rash on the trunk which spread peripherally. The cause of this infection can be
- A. Epidemic typhus (Correct Answer)
- B. Scrub typhus
- C. Endemic typhus
- D. Rickettsial pox
Explanation: ***Epidemic typhus*** - This condition is characterized by **fever**, **chills**, and a **maculopapular rash** that spreads centrally to peripherally, often following a **louse bite**. - It is caused by **Rickettsia prowazekii** and transmitted by the human body louse (Pediculus humanus corporis), making it common in crowded, unhygienic conditions. *Scrub typhus* - Scrub typhus is typically transmitted by the bite of **chiggers (larval mites)** and is caused by **Orientia tsutsugamushi**. - A characteristic feature is an **eschar** at the site of the bite, which is not mentioned in the patient's presentation. *Endemic typhus* - Also known as **murine typhus**, this disease is caused by **Rickettsia typhi** and transmitted by the **rat flea**. - While it causes fever and rash, its transmission vector (**flea**) and typical epidemiology (associated with rodents) differ from the louse bite described. *Rickettsial pox* - Rickettsial pox is caused by **Rickettsia akari** and transmitted by the **house mouse mite**. - It presents with an initial **papule** at the bite site that develops into an eschar, followed by fever and a **vesicular rash**, which is different from the maculopapular rash described.
Question 3: True about Arboviruses is -
- A. Yellow fever is endemic in India
- B. Chikungunya is transmitted by Aedes aegypti (Correct Answer)
- C. Dengue has only one serotype
- D. KFD was first identified in West Bengal
Explanation: ***Chikungunya is transmitted by Aedes aegypti*** - **Chikungunya virus** is primarily transmitted to humans by **Aedes aegypti** and **Aedes albopictus** mosquitoes. - This transmission vector is well-established and critically important for understanding the epidemiology and control of the disease. *Yellow fever is endemic in India* - **Yellow fever** is primarily endemic in **tropical and subtropical regions of Africa and South America**, not India. - There have been no reported indigenous cases of yellow fever in India, although it remains a concern due to potential importation. *Dengue has only one serotype* - **Dengue virus** has **four distinct serotypes (DENV-1, DENV-2, DENV-3, and DENV-4)**, not just one. - Infection with one serotype provides lifelong immunity to that specific serotype but only temporary and partial immunity against the others, increasing the risk of more severe disease (DHF/DSS) if a second infection with a different serotype occurs. *KFD was first identified in West Bengal* - **Kyasanur Forest Disease (KFD)**, a tick-borne viral hemorrhagic fever, was first identified in the **Kyasanur Forest of Karnataka, India**, in 1957. - It derived its name from the location of its initial discovery, not West Bengal.
Question 4: A patient hailing from Delhi presents with fever, arthralgia, and extensive petechial rash for 3 days. Lab investigations revealed a hemoglobin of 9 g/ dL, a white blood cell count of 9000 cells/mm3, a platelet count of 20000 cells/mm3, and a prolonged bleeding time. The clotting time was normal. What is the most likely diagnosis?
- A. Dengue (Correct Answer)
- B. Malaria
- C. Scrub typhus
- D. Typhoid
Explanation: Dengue - The combination of **fever, arthralgia, extensive petechial rash**, and severe **thrombocytopenia** (platelet count 20,000/mm³) with **prolonged bleeding time** is highly characteristic of severe dengue infection, especially in an endemic area like Delhi [1]. - While leukocytosis (WBC 9000/mm³) is not typical for dengue (usually causes leukopenia), the other features strongly point to dengue hemorrhagic fever [1]. *Malaria* - Typically presents with **intermittent high fever**, chills, and sweats. While it can cause some thrombocytopenia and anemia, the **extensive petechial rash** is not a characteristic feature. - **Thrombocytopenia** in malaria is usually milder than observed here, and prolonged bleeding time is less common [2]. *Scrub typhus* - Caused by Orientia tsutsugamushi, it is characterized by **fever, headache, myalgia, and a characteristic eschar** (necrotic ulcer) at the bite site, which is not mentioned. - While it can cause rash and some thrombocytopenia, the **petechial rash** and such severe thrombocytopenia with prolonged bleeding time are less typical. *Typhoid* - Presents with **sustained high fever**, headache, bradycardia, and sometimes a **rose spot rash** (maculopapular), which is different from a petechial rash. - Typhoid typically causes **leukopenia** and can lead to gastrointestinal complications like intestinal bleeding, but severe thrombocytopenia and extensive petechiae are not common presenting features.
Question 5: A woman traveling from Bihar to Delhi is suspected to have Kala-azar. Suitable investigation is?
- A. P24 antigen
- B. Rk-39 test (Correct Answer)
- C. Combo RDT
- D. HRP-2 antigen
Explanation: ***Rk-39 test*** - The **Rk-39 test** is a rapid diagnostic test highly sensitive and specific for detecting antibodies against the **kinesin-related protein K39** of *Leishmania donovani*, the causative agent of **Kala-azar (visceral leishmaniasis)**. - It is particularly useful in **endemic regions** like Bihar for quick and accurate diagnosis, especially in patients with suspected Kala-azar presenting with fever, splenomegaly, and pancytopenia. *P24 antigen* - **P24 antigen** testing is primarily used for the diagnosis of **HIV infection**. - It detects the **core protein p24** of the HIV virus, which is not relevant for the diagnosis of Kala-azar. *Combo RDT* - A **Combo RDT** (Rapid Diagnostic Test), without further specification, typically refers to tests for **malaria**, which detect antigens like **HRP-2** and **aldolase**. - While RDTs are used for parasitic diseases, this general term does not specifically refer to a test for **Kala-azar**. *HRP-2 antigen* - **HRP-2 (Histidine-rich protein 2) antigen** is a specific marker for **Plasmodium falciparum**, used in the diagnosis of **malaria**. - It is not associated with the diagnosis of **Kala-azar**, which is caused by *Leishmania donovani*.
Question 6: A patient presents with fever and retro-orbital pain. Which investigation should be conducted next for confirmation of dengue fever?
- A. Viral culture
- B. NS1 antigen test (Correct Answer)
- C. IgM ELISA
- D. PCR
Explanation: ***NS1 antigen test*** - The **NS1 antigen test** is highly sensitive and specific for dengue in the **early stages** of infection (typically 0-7 days after symptom onset), which is when a patient with fever and retro-orbital pain would likely present. - It detects a non-structural protein of the dengue virus, indicating **active viral replication**. *Viral culture* - **Viral culture** for dengue is time-consuming and technically demanding, making it impractical for rapid diagnosis in clinical settings, especially when an urgent confirmation is needed for patient management. - It is primarily used for research purposes rather than routine clinical diagnosis [2]. *IgM ELISA* - **IgM ELISA** detects antibodies produced in response to dengue infection, which typically become detectable **5-7 days after symptom onset**. - While useful for confirming dengue in later stages of illness, it may yield a **false negative** result if performed too early in the course of the disease [2]. *PCR* - **PCR (Polymerase Chain Reaction)** detects dengue viral RNA and is highly sensitive and specific in the **early acute phase** of infection (first 5 days) [1]. - However, it is generally more expensive, requires specialized laboratory equipment, and has a longer turnaround time compared to the NS1 antigen test, making NS1 a more accessible initial diagnostic choice.
Question 7: Animal to man transmission (zoonosis) is seen in -
- A. Tuberculosis
- B. Measles
- C. Rabies (Correct Answer)
- D. HIV
Explanation: ***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.
Question 8: In scrub typhus all are true except:
- A. Maculopapular rash
- B. Lymphadenopathy
- C. Fever
- D. Icterus (Correct Answer)
Explanation: ***Icterus*** - While **scrub typhus** can cause **hepatic dysfunction** and abnormal liver enzymes, **frank icterus** (jaundice) is an uncommon and non-specific finding, making it the least likely "always" true symptom among the options. - Severe liver involvement causing jaundice is rare and usually indicates a **complicated** or severe disease course. *Maculopapular rash* - A **maculopapular rash** is a common dermatological manifestation in **scrub typhus**, often appearing a few days after fever onset. - It results from widespread **vasculitis** caused by the obligate intracellular bacterium *Orientia tsutsugamushi* [1]. *Lymphadenopathy* - **Regional lymphadenopathy** is a very common finding, particularly in the lymphatic drainage area corresponding to the eschar [1]. - This symptom is a direct response to the **local bacterial infection** spreading via the lymphatic system [1]. *Fever* - **Fever** is a hallmark symptom of **scrub typhus**, typically high-grade and persistent [1]. - It is one of the earliest and most consistent clinical signs, indicating a systemic inflammatory response to the infection [1].
Question 9: Japanese encephalitis is caused by which virus?
- A. Human retrovirus
- B. Arboviruses (Correct Answer)
- C. Enteroviruses
- D. Cytomegalovirus
Explanation: ***Arboviruses*** - Japanese encephalitis virus is a **flavivirus**, which belongs to the larger group of **arboviruses**. - **Arboviruses** are viruses transmitted by arthropod vectors, such as mosquitoes, which is how Japanese encephalitis spreads. *Human retrovirus* - **Retroviruses** include viruses like HIV, which are characterized by their ability to reverse-transcribe RNA into DNA. - They are not associated with encephalitis transmitted by insect vectors. *Enteroviruses* - **Enteroviruses** primarily replicate in the gastrointestinal tract and can cause a range of illnesses, including meningitis and hand-foot-and-mouth disease. - They are typically spread via the fecal-oral route, not through mosquito bites. *Cytomegalovirus* - **Cytomegalovirus (CMV)** is a herpesvirus that can cause infections in people of all ages, often asymptomatic but particularly severe in immunocompromised individuals and neonates. - CMV is transmitted through close contact, not via arthropod vectors.
Question 10: A militant presents with rashes all over his body sparing the palms and soles. On examination, he was febrile and lice were noted. Which of the following is responsible for his condition?
- A. Rickettsia typhi
- B. Rickettsia prowazekii (Correct Answer)
- C. Rickettsia akari
- D. Rickettsia conorii
Explanation: ***Rickettsia prowazekii*** - This bacterium is the causative agent of **epidemic typhus**, which is transmitted by the **body louse** (Pediculus humanus corporis), consistent with the presence of lice. - The characteristic rash of epidemic typhus **spares the palms and soles** and often begins on the trunk, spreading centrifugally. *Rickettsia typhi* - This organism causes **murine typhus**, which is transmitted by **fleas**, particularly those found on rodents. - While it can cause a rash that typically spares the palms and soles, the transmission vector and typical setting (exposure to rodents) do not fit the clinical scenario as well as **body lice**. *Rickettsia akari* - This bacterium causes **rickettsialpox**, transmitted by **mites**. - The rash of rickettsialpox is typically papulovesicular, and a characteristic **eschar** (or black scab) is usually present at the site of the mite bite, which is not mentioned in the case. *Rickettsia conorii* - This organism causes **Mediterranean spotted fever** (also known as Boutonneuse fever), transmitted by **ticks**. - A distinguishing feature of this infection is the presence of a **tache noire** (eschar) at the site of the tick bite, which is absent in the patient's presentation.
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