Nuclear polyhedrosis virus isolated from mulburry silkworm bombyx mori in Thailand
1988
Tipvadee Attathom | Neungpanich Sinchaisri (Kasetsart Univ., Bangkok (Thailand). Faculty of Agriculture. Dept. of Entomology)
Diseased silkworm larvae, Bombyx mori, were collected from several sericultural farms in the Northeast of Thailand. Light and electron microsocopic observations revealed that the causal pathogen was the nuclear polyhedrosis virus (NPV) of single-embedded type. In addition, virions of multiple-embedded type were observed in the polyhedra and in the infected nuclei. Polyhedra of 2.7 microm were primary tetragonal in shape although globular and hexagonal polyhedra were also found. The virus has a rod shaped nucleocapsid, measuring 340 x 45 nm. The isolated NPV was highly pathogenic to silkworm larvae and exhibitied a pronounced characteristic symptom in the 5th instar larvae or at the time of cocoon forming. Pathological study revealed that this virus infected the nuclei of fat tissue, hypodermis, tracheal matrix, silkgland and the testicular sheath. Some ultrastructural changes observed in infected cells indicated that the NPV found in this study was different from those previously reported from other lepidopterous insects. It is also concluded that this virus is one of the major factors inflicting economic damage to the silkworm industry in Thailand.
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