Abundance of potentially pathogenic micro-organisms in Penaeus monodon larvae rearing systems in India

Area of Science:

• Aquaculture microbiology
• Shrimp pathology
• Marine biology

Background:

• Monodon baculovirus (MBV) and Vibrio species are significant threats in Penaeus monodon aquaculture.
• Hatchery environments can harbor external fouling organisms (EFO) and diverse bacterial populations.

Purpose of the Study:

• To monitor Monodon baculovirus (MBV), external fouling organisms (EFO), and bacteria, especially Vibrio species, in Indian Penaeus monodon hatcheries.
• To identify sources and quantify Vibrio-like bacteria in relation to post-larvae health and mortality.

Main Methods:

• Bacterial counts (total heterotrophic, Vibrio-like, presumptive V. harveyi, V. anguillarum, V. vulnificus) were performed on shrimp eggs, post-larvae, water, and feed (Artemia nauplii, microencapsulated feed).
• Monitoring occurred across nine Penaeus monodon rearing hatcheries in India from 1996-1997.
• Comparison of bacterial loads between MBV-infected and uninfected post-larvae and their environments.

Main Results:

• MBV-infected post-larvae and their environment exhibited higher Vibrio-like bacteria counts than uninfected ones.
• Presumptive Vibrio harveyi and Vibrio anguillarum predominated in rearing water and post-larvae.
• Vibrio-like bacteria in Artemia nauplii were identified as a likely source of hatchery contamination.
• Post-larvae mortality occurred when Vibrio-like bacteria counts reached 2 x 10(2) CFU.

Conclusions:

• Artemia nauplii can serve as a vector for pathogenic Vibrio species into shrimp hatcheries.
• Elevated Vibrio-like bacteria counts are directly linked to post-larvae mortality.
• These bacteria act as opportunistic pathogens, causing disease in stressed post-larvae.