Comportamento como indicador de saúde em camarões infectados por Vibrio parahaemolyticus

Abstract

World shrimp culture suffers large economic losses for viral and bacterial diseases, so it is important that studies and actions be encouraged to minimise the damage caused by these diseases in all areas - economy, animal and human health and environment. The present study evaluated the effect of a) presence of the substrate on the behaviour of juvenile shrimp Litopenaeus vannamei in the laboratory (manuscript I); b) behavioral activities of juvenile shrimp L. vannamei infected by Vibrio parahaemolyticus (ATCC 17802) and subjected to veterinary treatments in laboratory (manuscript II); c) identified the pathogenic agents associated to diseases with high mortality in shrimp culture farms (manuscript III). The study was conducted in three stages. In the first stage (manuscript I), the animals were subjected to two treatments, the absence or presence of sand as substrate, and were divided into two groups, placed in 30 plastic aquariums with capacity for four liters, half of them with sand on the bottom as substrate and the other half without sand. Burying behavior was evaluated only for the group whose aquariums had sand as substrate; inactivity, swimming, food intake, cleaning and crawling, survival and weight gain were measured in both groups. In the second stage (manuscript II), the animals were divided into five groups: 1) control, 2) infected animals with no veterinary treatment; 3) infected animals treated with isopathic medicine; 4) infected animals treated with antibiotics (florfenicol); 5) infected animals treated with isopathic medicine plus antibiotics (florfenicol). Then, the behaviors and survival and weight gain of the animals were analysed. In the third stage, we visited a shrimp farm with high rates of mortality in Obregón city, Sonora, Mexico. Thirty animals collected in the ponds were taken to presumptive (fresh smear analysis and bacteriology) and confirmatory (Biochemistry and qPCR) analyses for identification of viral and/or bacterial pathogens. The results in Manuscript 1 showed that for juvenile prawns maintained in aquariums with or without sand as substrate for up to three weeks, behavior, survival and weight gain were not significantly different, which demonstrates that lack of sand on the substrate did not modify behavioral responses of the animals. So, in the next stage, sand was not used as substrate anymore. In Manuscript 2, the infected prawns that were treated with isopathy plus antibiotics showed behavioral performance similar to the control group, indicating that their behavior is compatible with healthy individuals. And in Manuscript 3, concerning the high mortality of juvenile prawns in the ponds, besides the pathogenous that causes AHPND, Vibrio parahaemolyticus, other species of bacteria of the genus Vibrio and Aeromonas were associated to the pathology of the prawns.