Sunday, November 13, 2016

14/11/2016: EMS in shrimp aqua feeds decreasing the mortality in early mortality syndrome

by Dr Ron Cravens and Dr San “Chris” Ching, Amlan

Research shows Calibrin products decrease the effects of biotoxins. 

For example biotoxins produced by Clostridium perfringens that are the cause of necrotic enteritis in poultry. Similarly, Early Mortality Syndrome (EMS) in shrimp is caused by biotoxins from Vibrio parahaemolyticus.

Therefore, research was conducted to determine if Calibrin products would decrease the effects of this disease.

Studies done in Thailand and the University of Arizona in the USA showed Calibrin products reduced mortality of shrimp challenged with V. parahaemolyticus or the toxins it produces.

Rapid move across SE Asia

The devastating disease soon to be known as Early Mortality Syndrome was first seen by Chinese shrimp producers in 2009.

It rapidly moved to Vietnam, Malaysia and Thailand and in 2013 was first reported across the ocean in Mexico. The name Early Mortality Syndrome is very descriptive as its symptom is a high percentage of dead shrimp before 30 days of age.

In 2013, a team of researchers at the University of Arizona found that the cause of EMS was the bacteria V. parahaemolyticus. Soon researchers in Thailand isolated, and researchers in Taiwan purified, biotoxins from V parahaemolyticus which are responsible for the damage to the hepatopancreas of the shrimp, causing the high levels of mortality.

Research shows Calibrin products decrease the effects of biotoxins. An example would be biotoxins produced from Clostridium perfringens, the cause of necrotic enteritis in poultry.

Therefore, when it was resolved that EMS in shrimp was caused by biotoxins from V parahaemolyticus it was anticipated that Calibrin products might be able to help decrease the effects of this disease that was devastating the shrimp industry around the world. Experiments were conducted to determine the effects of Calibrin products on challenged shrimp.

In vitro / in vivo Toxin Binding – Thailand

These studies looked at how Calibrin products would interact directly with the V. parahaemolyticus toxins: ToxA and ToxB. Biotoxin binding and toxicity studies were performed by incubating increasing amounts of Calibrin (0, 31.3, 62.5, 250, and 500 mg) with 1mg of ToxA and ToxB.

The biotoxins were taken from a strain of V. parahaemolyticus known to produce EMS. The mixture of toxin and Calibrin was shaken gently for 30 minutes at room temperature. It was then centrifuged and the supernatant, which would contain the toxin that had not been bound by the Calibrin product, was divided into two portions.

If Calibrin bound the toxin it should no longer be in the supernatant, and thus no longer have toxic effects. The first part of the supernatant was used in gel electrophoresis (see Figure 1). Gel electrophoresis shows a heavier band at a specific area when there is more of a substance in the sample.

In this case the sample contained the biotoxin remaining after the Calibrin product had a chance to remove it. The bands indicating ToxA and ToxB get smaller as the amount of Calibrin in the mixture increases, this indicates that adding Calibrin removed the toxin from the supernatant.

If this is true, injecting the supernatant into shrimp should show decreasing toxicity as the Calibrin: toxin ratio increased. Therefore, the part of the supernatant that had been set aside was injected into shrimp (2-4g) using a reverse gavage method.

The shrimp were observed until almost 100 percent of the shrimp on the control (using no Calibrin) were dead. In that time shrimp mortality decreased as Calibrin in the original mixture increased (see Figure 2). Only five percent of the shrimp that had 500mg of Calibrin in the mixture died.

These experiments showed that Calibrin can bind ToxA and ToxB from V. parahaemolyticus.

Read the full article HERE.

The Aquaculturists
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