Density of Vibrios in Hemolymph and Hepatopancreas of Diseased Pacific White Shrimp, Litopenaeus vannamei, from Northwestern Mexico

Vibriosis is one of the most widespread infectious diseases of cultured shrimp in Mexico; as a result, the Research Centre for Food and Development (CIAD, for the Spanish wording) offers a diagnostic service to the shrimp farmers where they bring samples of diseased shrimp as judged by themselves. Hemolymph (HL) and hepatopancreas (HP) of diseased Litopenaeus vannamei were analyzed from five regions of Northwestern Mexico (from 2001 to 2006) in tiosulphate citrate bile sacharose (TCBS) agar; a total of 5912 shrimp were examined. The results showed a mean vibrios density of 6.45 x 103, SD = 6.90 x 104 CFU/mL for HL and 1.40 x 105, SD = 3.20 x 105 CFU/g for HP (n = 5912). HL samples had 12% (SD = 26%) of green colonies (GCs) in TCBS, and 23% (SD = 34%) of GCs in HP samples. Of the total shrimp analyzed, 46% were not found to possess vibrios in HL, whereas 60% of the shrimp examined contained more than 105 CFU/g of HP. More than 60 and 40% of the shrimp did not have GC in HL and HP, respectively. The highest Pearson coefficient correlation was observed between vibrios HL and GCs in HL for 2006 (r = 0.611, n = 712, P < 0.001).