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by Fabián Jijón, Global Species Manager Aquaculture and International Sales Manager in LATAM, Dostofarm GmbH and Francisca Veinat G, Product Manager, Dostofarm GmbH


Gregarines are common gut parasites that affects shrimp populations around the world. This parasite can affect shrimp in any of its life cycle stage. Some of the negative effects of the gregarine presence in shrimp aquaculture are low daily weight gain and high feed intake, leading to a high FCR, and secondary bacterial infections (Vibrio spp.). Earth ponds, which are the most widespread building practice for commercial shrimp operations, living vectors (ie clams), low pond soil bottom management, high feeding rates or low feed quality are some of the factors that increase the risk of having Gregarines present in shrimp aquaculture systems.

Feed additives have been used for years to support performance and animal health. The positive effects of essential oils are well-known from human medicine and can also contribute to increase performance and health in livestock and aquaculture. Essential oregano oil is characterised by its antimicrobial and antiparasitic properties. The effectiveness depends on the chemical composition of the oregano oil. This is influenced by the origin, plant species, growth stage and processing method. Important here is a consistent quality of the essential oil in order to achieve a constant effect at the recommended dosage.

Origin of oregano oil

In a commercial shrimp operation in Ecuador with a recurring gregarine problem was tested the potential of DOSTO® Concentrate 500 to control the infection. DOSTO® Concentrate 500, contains 50 percent oregano oil from a specific subspecies of Origanum vulgare var. hirtum. After harvesting, the essential oregano oil is extracted from the plant by gentle steam distillation.

The content of phytochemicals in the essential oil is determined after each production in order to ensure a consistent standardised composition. Oregano oil can be used in all livestock and aquaculture species both conventional and organic production systems.

Experimental Setup

Three infected shrimp ponds, diagnosed using Wet Mount analysis, were uses in this study. The gregarine load in the gut is measured using a scale that indicates the number of gregarine individuals present in gastrointestinal tract.

The effect of DOSTO® Oregano was evaluated by comparing the infection load before and after the application of the product DOSTO® Concentrate 500 at a dosage of 200 grams-per-tonne of feed during five days.


Before the application of DOSTO® Concentrate 500 in the feed all three ponds showed level infections between two and three in the mid gut and three in the hindgut.

Figure 1 observes the gut of a shrimp with a level 3 infection (more than 20 gregarines per visual). After five days of feeding the shrimp DOSTO® Concentrate 500 their gregarine load was reduced to safe levels.

DOSTO® Concentrate 500 is an effective tool to control gregarine in shrimp operations. Natural and standardised, DOSTO® Oregano oil has antiparasitic properties, especially in gregarines, which showed a high sensitivity to its components. Five days' treatment is enough to reduce gregarine load to a safe level. To avoid reinfection and reactivation of the parasite's life cycle, it is recommended to feed DOSTO® Concentrate 500 continuously.

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