URV researchers have managed to halt the white spot virus that prevents prawns from growing and then kills them in prawn farms

For many years now, the farms where prawns are raised for human consumption (Litopenaeus vannamei) have been attacked by the so-called white-spot virus, a disease that stops them growing and can even be lethal. As a result, the breeding of these crustaceans has been significantly impaired, and almost all of the production has been lost. This problem has particularly affected some areas in Brazil, China and various countries in Latin America, where prawns are farmed on such a massive scale that the virus spreads easily. Aware of the situation, researchers from the FoodIE research group, from the URV’s Department of Chemical Engineering, took up the challenge and found a solution to the problem by encapsulating thymus extract and adding it to the prawns’ food.

The research team, headed by Sílvia de Lamo and Osmar Tomazelli decided to use a natural product like thyme because it is suitable for animal and human consumption and because its antimicrobial properties were already known. What they did not know, however, was whether it could be effective as an antiviral agent. Using thyme oil, the researchers made a simple emulsion, which they subsequently encapsulated using the technique of atomization, which turns a substance from liquid into powder. To do this, they needed a carrier material – a polysaccharide known as maltodextrina – which is widely used in the food industry.

The prawns are fed with pellets – compressed food – that float on the water of the tanks in which they are raised. The researchers gave different concentrations of thyme oil encapsulated in these pellets to prawns that had been inoculated with the virus. They also used a control group of healthy prawns that ate the pellets without the essential oil.

The results of this study showed that adding 1% of essential thyme oil to the pellets consumed by the prawns meant that even though they were carriers of the virus they did not develop the disease. The prawns grew to their ideal size in the adult stage and were then commercialized and consumed, since humans are not affected by the virus.

The microencapsulation of essential oils with antimicrobial and antiviral properties paves the way to using this technique to prevent diseases in other farm animals by modifying what they eat.

Bibliographical reference: Tomazelli Júnior, O., Kuhn, F., Mendonça Padilha, P.J., Nunes Nesi, C., Mestres, M., Dal Magro, J., De Lamo Castellví, S. Effect of microencapsulated thyme essential oil on white spot virus-infected Litopenaeus vannamei. Aquaculture International. DOI: 10.1007/s10499-018-0296-5.