Presence of herpesvirus in diseased fishes
Abstract
Herpesviruses that infect fishes belong to the Herpesvirales order and Alloherpesvirus family. In these species, the different types of herpesvirus can cause tumors, adenocarcinoma and skin lesions. This study aims detect to presence of herpesvirus in fishes from commercial, recreation or experimental creations of the States of São Paulo and Minas Gerais, Brazil. Organ fragments and lesions of 53 fish species coming of mortality cases were forwarded at Biological Institute for examination by transmission electron microscopy by research of etiological agent. By transmission electron microscopy through negative staining technique, were observed herpes virus -like particles in 46 fishes and through embedding res in technique, in ultrathin sections were visualized herpes virus immature particles, measuring 90 -110nm in diameter, located in the nuclei and complete particles measuring 160nm. In the histopathology technique, lesions associated with the virus as corpuscles inclusion, papillomas, and dermal lesions and in the gills were observed in 27 fishes. The evaluated techniques of TEM and the histopathology were effective for the rapid detection of herpesvirus in the examined samples.
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Introduction
Aquaculture, in full development, is becoming more important as livestock activity, although it is still considered by many a s an appendage of the fishing industry. Practiced in all Brazilia n states, aquaculture mainly covers the following creations of fish, shrimp, frogs, shellfish, oysters and mussels and other aquatic crops such as growing algae are practiced on a smaller scale [1].
According to Toranzo et al. (2004) [2], infectious diseas es caused by viruses can cause damage to the economic viability of aquaculture activities. These diseases occur mostly confined animals, and can develop serious infectious processes affecting the development of animals and even cause death.
Herpesviruses belong to Herpesvirales order, divided into three families, Alloherpesvirus , Herpesviridae and Malacoherpesvirus , encompassing viruses that occur in several animal species such as molluscs, fish, amphibians, reptiles, birds and mammals [3]. The Herpesvirid ae family keeps viruses of mammals, birds and reptiles, the Alloherpesviridae family includes fish and frogs viruses, and Malacoherpesviridae family contains the virus from bivalves [4].
The virus mainly affecting the early stages of fish life and therefor e eggs, larvae and young fish are more susceptible. The infected eggs can produce larvae, newly hatched, with clinical signs of illness, while the infected adult fish may or may not present any symptoms [5]. Within the family of herpesviruses, can highlight herpesvirus papilloma of cyprinids [6], channel catfish herpesvirus and herpesvirus salmon [7].
The need for a more detailed and thorough knowledge of the damage caused by herpesviruses in aquaculture, especially in fish farming, has led us to this research. The pathological relationship between etiologic agent s involving these animals is not well established, since in Brazil there is no survey of the pisces herpesviroses, and the reports are sporadic and opportunistic, depending on the shipment of samples to a diagnostic center. In this way, all studies in the area are important because the virus can remain latent in healthy animals or decimate entire flocks in a breeding, unfeasible a production.
Page | 8 This study aimed to detect the presence of herpes virus in organs fragments of fishes from the states of São Paulo and Minas Gerais, using transmission electron microscopy techniques (negative staining and resin embedding) and associating viral presence with indicative lesions observed by optical microscopy, u sing histological technique hematoxylin -eosin (H&E) .
Conclusion
From these findings it was concluded that electron microscopy techniques used in this study were effective in diagnosing the presence of herpesvirus, allowing the visualization of agent, and should be spread widely.
Routine histopathological technique was also effective in the visualization of lesions suggestive of the viral agent, as the presence of inclusion bodies. Moreover, enabled to perform the analysis of the animals overall condition, indicating that the quality of creation can make it susceptible to infection by herpesvirus. Histopathology and electron microscopy tests must be complementary.
We cannot here say that the disease, followed by mortality, are directly caused by herpesvirus, however, serious condition s predisposing to poor water quality, unsuitable managements, high density and poor nutritional quality must have contributed to viral replication. The viral presence, of course, contributed to the worsening of the picture, intensifying clinical symptoms followed of mortality. Studies to assess what are the fish herpesvirus subtypes that are circulating in our country and its real impact on mortality should be conducted.
