Question

Dropsy in fish is caused by

• A. Viruses
• B. Bacteria
• C. Protozoa
• D. Fungus

Hint:

Bacterial Fish Diseases:
Dropsy Motile Aeromonad Septicemia = BACTERIA (Aeromonas hydrophila).
Columnaris Disease = Flavobacterium columnare.
Fin/Tail Rot = Aeromonas Pseudomonas.

Answer 1

The Correct Option is B

Step 1: Understanding the Concept:
Systemic bacterial septicemia in freshwater fishes: infectious dropsy is caused by motile aeromonads (Aeromonas hydrophila Pseudomonas) inducing capillary endothelial damage and severe ascitic abdominal fluid distension.
Key Formula or Approach:
\[ \text{Pathogen: } \textit{Aeromonas hydrophila} \xrightarrow{\text{Endotoxins}} \text{Capillary Damage \& Renal Failure} \implies \text{Ascites (Abdominal Dropsy)} + \text{Exophthalmos} + \text{Pinecone Scales} \]

Step 2: Detailed Explanation:
Pathogenesis of Infectious Dropsy (Ascites Abdominal Dropsy) in carps:
- A major systemic infectious disease of freshwater carps (Rohu, Catla, Mrigal, Common Carp) and ornamental aquarium fishes.
- The primary etiological agents are opportunistic Bacteria, predominantly {Aeromonas hydrophila (Motile Aeromonad Septicemia MAS) and Pseudomonas fluorescens.
- Bacterial hemolysins and enterotoxins cause systemic vascular endothelial necrosis and acute renal tubular failure, resulting in massive accumulation of straw-colored ascitic fluid in the peritoneal cavity (abdominal swelling/dropsy), bilateral bulging eyes (exophthalmos), and protruding 'pinecone' scales.

Step 3: Final Answer:
Therefore, Dropsy in fish is caused by Bacteria, corresponding to option (B).