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Difficulty: Very hardHuman Physiology, Health, and Diseases

Consider the following statements regarding major infectious human diseases, their causative pathogens, and vectors of public health importance:

1. Scrub Typhus is a bacterial disease caused by *Orientia tsutsugamushi* and is transmitted to humans through the bite of infected larval trombiculid mites (chiggers).
2. Japanese Encephalitis is a viral disease caused by a Flavivirus and is transmitted primarily by mosquitoes of the *Culex* genus, with pigs and wading birds acting as amplifying hosts.
3. Lymphatic Filariasis is a protozoan disease caused by *Wuchereria bancrofti* and is transmitted primarily by the bite of female *Phlebotomus* sandflies.

Which of the statements given above is/are correct?

  1. 1 and 2 onlyAnswer
  2. B
    2 and 3 only
  3. C
    1 and 3 only
  4. D
    1, 2 and 3

Answer

Statements 1 and 2 are correct, whereas Statement 3 is incorrect.
Scrub Typhus is caused by the bacterium Orientia tsutsugamushi and is transmitted by chigger mites. Japanese Encephalitis is caused by a mosquito-borne Flavivirus with pigs and ardeid birds serving as key amplifying hosts. Both Statements 1 and 2 are completely accurate. Statement 3 is false because Wuchereria bancrofti is a filarial nematode (helminth), not a protozoan, and its primary vector in India is the Culex quinquefasciatus mosquito rather than the sandfly.

Step-by-Step Solution

1
Evaluate Statement 1 regarding Scrub Typhus.
Scrub Typhus is caused by Orientia tsutsugamushi (an obligate intracellular bacterium) and transmitted by larval trombiculid mites (chiggers). Statement 1 is factually correct.
Verify the pathogen category (bacterium) and vector (chigger mite) for Scrub Typhus.
2
Evaluate Statement 2 regarding Japanese Encephalitis.
Japanese Encephalitis is caused by the Japanese Encephalitis Virus (a single-stranded RNA virus of the genus Flavivirus) and transmitted principally by Culex tritaeniorhynchus mosquitoes, with pigs and water birds serving as amplifying reservoirs. Statement 2 is factually correct.
Verify the viral nature, mosquito vector family, and host reservoirs of Japanese Encephalitis.
3
Evaluate Statement 3 regarding Lymphatic Filariasis.
Lymphatic Filariasis is caused by parasitic filarial nematodes (roundworms/helminths) such as Wuchereria bancrofti and Brugia malayi. In India, its principal vector is the Culex quinquefasciatus mosquito. Sandflies (Phlebotomus species) transmit Visceral Leishmaniasis (Kala-azar), not filariasis. Thus, Statement 3 is incorrect.
Identify taxonomic misclassifications of the pathogen (helminth vs protozoan) and vector misattribution (mosquito vs sandfly).
4
Synthesize the statement evaluations to select the correct choice.
Only Statements 1 and 2 are correct.
Combine verified truth values of all three statements.

Key Concept

Classification of infectious human diseases by pathogen type (bacterial, viral, helminthic) and specific vector-host transmission dynamics.
Estimated Time:2m 0s
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Topics

Human Physiology, Health, and Diseases

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