Abstract
The cytoplasmic polyhedrosis virus (CPV, Family Reoviridae) is an entomopathogen with a very wide host range, affecting mainly lepidopterous insects. The virus often causes chronic infections in insects, infecting mainly the midgut epithelium. Detailed studies of the effects of CPV on silkworm, Bombyx mori, have been done by Japanese workers , but there is very little information on the histopathology of CPV on other insects.In this study, 5-day old corn earworm (H. zea) larvae were infected per os with CPV. Control larvae were fed sterile water. The midgut was dissected out at 20, 48 and 72h post-treatment for both SEM and TEM studies. In the SEM study the midgut was fixed in 2.5% glutaraldehyde in phosphate buffer at pH 7.2, postfixed in buffered 2% osmium tetroxide at room temperature, dehydrated in ethanol, cryofractured in liquid nitrogen, critical-point dried, mounted, coated with gold-palladium and examined in a Hitachi HHS-2R scanning electron microscope at 20 kV. In the TEM study, the tissues were fixed in half-strength Karnovsky's fixative, postfixed in buffered cold 2% osmium tetroxide, en bloc stained in aqueous 0.5% uranyl acetate, dehydrated in ethanol and embedded in Spurr resin. Ultrathin sections were cut with glass knives, sequentially stained in aqueous uranyl acetate and lead citrate, and observed in a Zeiss 109 transmission electron microscope at 50 kV or a Siemens 101 at 80 kV.
Published Version
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