Effectiveness of oral Elancoban™ and Avimix-ST™ against Nematopsis (Apicomplexa: Porosporidae) gametocyts infecting the shrimp Litopenaeus vannamei

Gregarines from Nematopsis genus are a common intestinal parasite infection in the white shrimp, Litopenaeus vannamei, that is cultured on the Pacific coast of Mexico. Slow growth and mortalities of white shrimp have been associated with gregarine infections. Control of gregarine infections in Mexican shrimp farms with antibiotics by empirical methods is becoming increasingly important. However, no effective chemotherapeutic control has been demonstrated. The objective of the present study was to evaluate the effectiveness of oral administration of sodium monensin, Elancoban™ and sulfachloropyrazine, Avimix-ST™ in removing Nematopsis gametocysts from the intestine of naturally infested cultured white shrimp (L. vannamei). Four experiments were carried out where different concentrations of antibiotics were administered to naturally infested shrimp through medicated feed for 5 consecutive days. The experimental system consisted of glass aquaria containing 8-10 shrimp. Concentrations of antibiotic varied from 2 to 8 g kg−1 for Elancoban™ and from 1.5 to 7 g kg−1 for Avimix-ST™. After 5 days of treatment, both products significantly reduced the mean intensity of Nematopsis gametocysts when compared to the control. Elancoban™ treatment reduced Nematopsis gametocysts by 92% and 94% at 5.5 and 6 g kg−1, respectively, and Avimix-ST™ reduced the numbers of gametocysts by 85% and 83% at 2.5 and 3.5 g kg−1, respectively. No mortalities were recorded for these treatments. The study demonstrates the effectiveness of Elancoban™ and Avimix-ST™ used in medicated feed as a gregarinostats in the control of Nematopsis gametocysts in the white shrimp L. vannamei.