DNA from dead shrimp tissues is suitable for white spot syndrome virus detection by the polymerase chain reaction

The growth of the shrimp industry has been accompanied by an increased incidence of infectious diseases (Bachere 2000). Among them, the White Spot Syndrome Virus (WSSV) has been responsible for high mortality rates worldwide. Currently, there is no specific treatment to control this viral agent, restricting its management to prophylaxis. In fact, the production of a WSSV free stock is one of these measures. To achieve that, it is imperative to monitor the maturation laboratories as well as other stages of the culture cycle. Although Colombian laboratories are performing the complex routine testing of broodstock, additional information could be obtained from animals that are found dead in the maturation tanks. Inasmuch as these animals cannot be studied by histopathology due to rapid tissue autolysis, DNA diagnostic tests are a conceivable alternative. It is known that DNA is susceptible to degradation by hydrolytic and oxidative endogenous nucleases (Dessauer 1995). These enzymes can break down highly informative long strands of DNA into small fragments, and consequently, they might interfere with the Polymerase Chain Reaction (PCR) amplification (Seutin 1991). However, DNA analysis of postmortem samples is a widely used method in forensic sciences and other fields (Turner 1993, Ferreira 2000). Taking into account the value of employing postmortem samples for WSSV diagnosis and the possibility that DNA degradation might interfere with the amplification of viral DNA, we investigated the reliability of tissue DNA extracted at different time points postmortem, for PCR based WSSV diagnosis.