Avaliação do uso de Crassostrea sp. como bioindicador do vírus da mionecrose infecciosa em estuários de fazendas de engorda de Litopenaeus vannamei em Pernambuco

Abstract

Infectious Myonecrosis is a disease caused by the Infectious Myonecrosis Virus (IMNV), and its main characteristic is skeletal muscle necrosis and cumulative mortality of 70% throughout the Litopenaeus vannamei cycle. Thus, aiming at preventing outbreaks and detecting subclinical infections of IMNV for L. vannamei, an action that can be adopted is the development of a monitoring plan for the virus in the environment, through the use of sentinel organisms. However, to date, there are no protocols that apply these organisms, such as bivalves, to monitor IMNV. For this reason, the objective of this work is to evaluate the use of wild oysters (Crassostrea sp.) as sentinels/bioindicators for the detection of IMNV in areas close to L. vannamei producing units located in the estuaries of the Botafogo and Passos rivers, both located in Pernambuco. The collections of the specimens were carried out during the summer and winter, in the North and South coasts of the state. Each coast had 3 collection points, and each point had a total of 25 animals sampled, thus totaling 75 animals per coast and 150 per season of the year. These animals were evaluated for the presence of IMNV through real-time PCR and histopathological analysis. For statistical analysis, the nonparametric Mann-Whitney U and Kruskal-Wallis tests were used, followed by Dunn's post-hoc test. There were no statistical differences in the percentage of Crassostrea sp. infected by IMNV by collection site and season of the year, with positive detection of animals on both coasts and stations analyzed. As for viral load, the mean values determined on the north coast did not differ statistically in the summer, with the highest mean viral load (1.47x104 viral copies of IMNV/μl of total RNA) at point A, for the winter. On the south coast, for the summer, the lowest mean value of viral load was found at point C, with 5.22x103 viral copies of IMNV/μl of total RNA. On the other hand, during winter, no differences in viral loads were detected. No histopathological lesions were found to suggest infection of oysters by IMNV. It is concluded that the oysters Crassostrea sp. wild species, can be efficiently used as a bioindicator of IMNV for monitoring this pathogen in estuaries of L. vannamei shrimp production units, without the need to collect shrimp on farms, being, therefore, candidate organisms for the development and implementation of programs of sanitary surveillance of aquatic animals.