Step 1: Understanding the Concept:
Epizootic Ulcerative Syndrome (EUS) is a severe seasonal panzootic disease affecting wild and farmed freshwater finfishes across Asia and Australia.
Step 2: Detailed Explanation:
EUS is caused by the invasive, oomycete water mold Aphanomyces invadans.
The disease is characterized by large, deep, necrotic red ulcers on the skin and muscle tissues of fishes.
In India, EUS outbreaks have historically devastated freshwater wild and farmed fish resources, showing high pathogenicity in carps (Indian Major Carps and snakeheads).
Crustaceans like shrimps and prawns are completely immune to this fungal infection.
Step 3: Final Answer:
EUS is predominantly seen in the Carp group, which corresponds to option (A).