2.5. Some common diseases and treatments

2.5.1. Diseases caused by Vibrio bacteria

* Signs:

– Vibrio diseases, also known as Vibriosis, can cause broken antennae, black gill, rotten tail, or black spots in shrimp.
– Shrimp looks unclean and weak. Shrimp has dirty gill. The color of shrimp body converts into red pink. Shrimp stops eating and dies.
– Shrimp deaths can occur when Vibrio diseases are in acute phases. If these diseases are chronic, shrimp grows slowly, has soft shell and separates from their groups.

* Pathogens:

– The main agents causing Vibrio diseases are bacteria in the genus Vibrio. Different Vibrio bacteria cause different types of diseases in shrimp.
– Vibrio bacteria enter farming ponds through water, breed, and feed from pond bottoms if pond cleaning and preparation are not effective.

* Preventions – treatments: Depending on types of Vibrio diseases, apply the following solutions:

– Implement synthetic methods to inhibit the growth of bacteria:
+ Keep good water quality in ponds.
+ Shrimp density should not be not too high.
+ Avoid vulnerable factors to shrimp.
+ Periodically use microbial products to reduce the amount of organic matters in ponds.
+ Reduce salinity down to 15-20 parts per thousand (ppt) to restrict the development of Vibrio bacteria.
+ Increase shrimp resistance with good environmental management and feed shrimp vitamins C, A, E.

– Vibrio diseases often occur when water in ponds is dirty and shrimp is weak. Apply simultaneously these solutions:
+ Improve environmental conditions and kill bacteria in shrimp body: implement siphon techniques to pond bottoms; change water to reduce bacteria density; use products permitted to treat diseases. The use of medicines must follow manufacturers’ instructions.
+ Increase shrimp resistance by mixingn vitamin C in shrimp feed.
+ Use squid oil combined with feed: 5-10ml/kg of feed.
+ Stimulate molting by Saponin 10-15g/m3.

Source: Temporary process for safe brackish-water shrimp farming in areas affected by diseases in Vietnam. According to The Official Dispatch No. 10/TCTS-NTTS. January 6th, 2015. Vietnamese Directorate of Fisheries

Viet Linh 2015. Translated by Sonia Linh V.