Question

White tail disease in freshwater prawn is caused by

• A. Vibrio sp
• B. Mrnv and xsv
• C. Yellow head virus
• D. WSSV

Hint:

Remember: White Tail = Water Prawn (Macrobrachium).
Causative duo: MrNV + XSV.
This is a critical disease in freshwater prawn hatcheries worldwide.

Answer 1

The Correct Option is B

Step 1: Understanding the Question:
The question asks for the causative agents of White Tail Disease (WTD), which specifically affects the Giant Freshwater Prawn (Macrobrachium rosenbergii).
Detailed Explanation:

• WTD Symptoms: The disease is characterized by a whitish, opaque appearance of the abdominal muscles (tail) of the post-larvae and early juveniles of freshwater prawns. It leads to very high mortality.

• Causative Agents: WTD is caused by a co-infection of two viruses:
• Macrobrachium rosenbergii Nodavirus (MrNV): A small, non-enveloped RNA virus.

• Extra Small Virus (XSV): A satellite virus that is often associated with MrNV.

• Impact: The combination of these two agents leads to severe muscular necrosis. While MrNV is considered the primary pathogen, XSV often co-occurs and may enhance the pathology. Other options like Vibrio (bacteria) or WSSV (mostly penaeid shrimp) are not the primary causes of WTD in freshwater prawns.

Step 3: Final Answer:
White Tail Disease is caused by MrNV and XSV.