Shrimp aquaculture is a major animal production activity worldwide, producing 5,717 million tons in 2020 (FAO 2020). In Mexico, Sinaloa produced 96,606 tons (45% of the national farmed shrimp volume) in 2020 (CONAPESCA 2022). Nonetheless, disease is a major constraint for shrimp farming worldwide. Acute hepatopancreas necrosis disease (AHPND) causes severe mortalities and production losses. The pathogenicity of isolates is related to the severity of the disease. Hence, the aim of this study was to evaluate the pathogenicity of two AHPND isolates from Guasave Sinaloa.
Bacterial isolates from shrimp farms with AHPND disease outbreaks were obtained, characterized by growth on TCBS and Chromagar Vibrio. PCR analyses were done to detect PirA (AP3) and PirB (VpIT) genes. Cell counts (CFUml-1) were done at a 10-6 concentration of cultures with OD600=1. Afterwards, two bioassays were done using different CFU ml-1 concentrations (Table 1) in groups of 10 juvenile shrimp (n= 120; MBW = 0.48 ± 0.28 g).
Bacteria on TCBS displayed green or yellow colonies on TCBS, but on Chromagar Vibrio, green, white or mauve colonies indicated that not all isolates were V. parahaemolyticus. Two isolates (HP1 and HP5) were V. parahaemolyticus and AHPND. Cell counts of these isolates were 107.97 and 108.04 CFU ml-1, respectively. Inoculation of shrimp with 350,000 CFU ml-1 of each of these isolates showed slight differences in pathogenicity (Table 1; Figure 1). It is concluded that differences in pathogenicity may exist in AHPND isolates in Northern Sinaloa, and this feature should be further studied.
CONAPESCA (2022) Anuario Estadístico de Acuacultura y Pesca 2020. Mazatlan, Mexico, pp. 293.
FAO (2020) The State of World Fisheries and Aquaculture 2020. Sustainability in action, Rome, Italy, pp. 206.