Detection of avipoxvirus in a cutaneous lesion of a swallow tanager (Tersina viridis) by transmission electron microscopy / Detecção de avipoxvírus em lesões cutâneas de saí-andorinha (Tersina viridis) por microscopia eletrônica de transmissão

Abstract

Avianpox is a highly contagious disease that affects worldwide both commercial and wild birds. The etiologic agent is a poxvirus, belonging to the Poxviridae family and Avipoxvirus genus. The disease manifests itself in three ways, cutaneous, diphtheric and septicemic. In June 2007, during the illegal commercialization of birds, a Swallow tanager (Tersina viridis) was apprehended by the Forestry Police, among other birds, which was sent to the Tietê Ecological Park, São Paulo, SP, Brazil. After one month, the bird presented skin lesions on its legs, anorexia, emaciation, mobility difficulties, diarrhea, dehydration and death, and was sent to the Electron Microscopy Laboratory of the Biological Institute, São Paulo, SP, Brazil, to search for viral agents. Fragments of skin lesions and crusts were collected and processed for transmission electron microscopy using the techniques of negative staining (rapid preparation) and immunocytochemistry (immunollabelling with colloidal gold particles). Under the transmission electron microscope using the negative staining technique, a large number of typical poxvirus particles ovoid in shape, showing irregular arrangement of the tubules on the outer membrane, some enveloped, measuring an average of 240 nm in length x 200 nm in diameter, were seen in suspension of skin lesions or crusts. . In the immunocytochemistry technique the antigen-antibody reaction was strongly enhanced by the dense particles of colloidal gold on poxviruses.