Evaluation the Correlation Between Pathogenic Microorganisms on Cultured Clam &amp;lt;i&amp;gt;Meretrix SP.&amp;lt;/i&amp;gt; and Disease Incidence

Nguyen Duc Minh,Le Ngoc Hanh,Nguyen Thuy Linh

doi:10.11648/j.aff.20200904.11

Abstract

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.

Highlights

Besides there was research by Ngo Thi Thu Thao et al (2008), that study some clam pathogens in Ben Tre province and the results show that there were bacteria of Vibrio sp. and Perkinsus sp. parasite caused disease
In Bac Lieu and Tra Vinh provinces, the highest density of Vibrio is in March
In March, dead clam occurred in Tra Vinh as a rate of 50% but no significant difference in outbreak disease and non-outbreak disease factor on clam samples (P>0.05)

Summary

Introduction

Meretrix have long been commonly cultivated in Vietnam and provide an important protein source for the local population. They are endemic to Vietnam’s estuaries and coastal areas and can be found all over the country, from the Northern provinces to Ca Mau Cape in the South. The clam which originates from Ben Tre is an important commercial species in the coastal areas for domestic and export markets (Directorate of Fisheries, 2011). Meretrix Lyrata is widely distributed in southern provinces such as Go Cong (Tien Giang), Binh Dai, Ba Tri, Thanh Phu (Ben Tre), Cau Ngang, Duyen Hai (Tra Vinh), Vinh Chau (Soc Trang), Vinh Loi (Bac Lieu), Ngoc Hien (Ca Mau) and Can Gio (Ho Chi Minh city). Lyrata has been introduced to aquaculture in the North of Vietnam because of the decline in Northern indigenous clam production

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