Evaluation the Correlation Between Pathogenic Microorganisms on Cultured Clam Meretrix SP. and Disease Incidence

The study was carried out to determine the density of Vibrio sp. and Vibrio sp. in cultured clams and evaluate the correlation between pathogenic microorganisms and disease incidence of white clams (Meretrix Lyrata) in Mekong Delta from March to May 2019. Clam samples were collected in different four regions (Ben Tre, Tra Vinh, Bac Lieu, and Tien Giang provinces) and there was mass mortality of clam in Tra Vinh province in May. In this assay, determination of the Vibrio sp. density was performed using Vibrio sp. selective Thiosulfate Citrate Bile Salt agar plates. Also, the Vibrio sp. was cultured in Fluid thioglycollate medium to isolating the spore that effect to harmful for cultured clam. Then, T-test and one-way ANOVA analysis were used to access the impacts of those parameters on the clam health. Clams did not show specific clinical signs, and histological results showed minor injuries on their shells and gills. Correlation analysis revealed some biotic components related to clam health status; they were several Vibrio bacteria in clams were in the range of 0-2.23 x 105 (CFU/g). The presence of Vibrio sp. was detected in the clam tissue with a prevalence of 53% of the ratio of infection and the infection intensity of 4.08-57.43 (spores/g). However, the density of Vibrio sp. and the ratio of infection of Vibrio sp. on clam was no significant difference on outbreak disease and non-outbreak disease factor on clam samples (P>0.05) in the clam samples. Thus, dead clams can be caused by several other factors.