Shrimp is the second most valuable global aquaculture product after carp. Penaeus vannamei (Pacific whiteleg shrimp) and Penaeus monodon (giant tiger prawn) are the most common farmed species, which account for roughly 80% of all farmed shrimp worldwide. Infectious diseases, however, often cause havoc in shrimp farms. Microbes, including Vibrio bacteria, are omnipresent in shrimp farms and can lead to disease outbreaks in favorable conditions, including Acute Hepatopancreatic Necrosis Disease (AHPND) caused by Vibrio parahaemolyticus. Disease control in shrimp farming currently relies upon preventative measures. The lack of commercially available therapeutics for shrimp urged urgent development of orally delivered vaccines/therapeutics, which can be adapted widely for farm application.
Immunomodulating proteins were produced in microalgae and incorporated into shrimp diets. Experiments were conducted in aquariums and cages-in-pond to evaluate the effects on shrimp morphometric changes, survival percentage, and level of Vibrios loads, followed by the histological and pathological analysis of hepatopancreas, immune parameters quantification and feed conversion ratio. In a laboratory experiment, 15 juvenile shrimps (5 gm each) were assigned to three 40-liter aquariums per test diet. Animals were fed 8 times a day for 14 days. In the cages-in-pond experiment, shrimp post larvae (PL 18-24) were stocked in the density of 1000 animals/m2 in 3 cages per test diet. Animals were fed 6 times a day for 7 days. The experimental results indicate an increase in the survival rate compared to controls fed with a commercial diet and high immunity as indicated by elevated superoxide dismutase (SOD) levels in the hemolymph. Moreover, growth performance parameters such as the average weight of animals and feed conversion ratio (FCR) were positively impacted. Test diets also decreased the level of V. parahaemolyticus loads in the hepatopancreas resulting in healthier hepatopancreas tissues