A new entomopoxvirus from a cockroach: light and electron microscopy

The cockroach entomopoxvirus caused a chronic infection in cultures of the German cockroach Blattella germanica. Heavily infected specimens showed a reduced mobility. Ellipsoid virus occlusion bodies (8 x 5 to 19 x 12 microm) were found intracellularly in tracheole cells, in the hypodermis, in fat body cells, and in muscles. Several hundred virus particles were integrated in a single occlusion body (OB), their long axis being oriented axially. Ovoid viroids measured 320 x 190 nm and possessed a unilateral, concave core and one lateral body. Starting occlusion, small granules attached to the virus particles which later transformed to a beaded, wavy envelope. An initial halo around the occluded virions disappeared in more central regions of the OB. Virus particles were formed either in a dense cytoplasmic area containing electron-dense viroids, or in a loosely aggregated viroplasm. In the latter, developmental stages were mainly represented by spheres with double membranes enclosing granular material. Spindles and larger crystal-like virus-free inclusion bodies occurred in the cytoplasm. The cytoplasm of infected cells appeared degenerated and the chromatin of the nuclei condensed at the periphery or disintegrated. Taxonomically, the described virus exhibits features of both EPV genus A and EPV genus B. Provisory it is named Blattella germanica EPV (BgEPV). A possible use of the cockroach EPV as a biological control agent is discussed.