After the insect larvae infects the nuclear polyhedrosis virus, there is no obvious abnormality at the initial stage; as the inclusion body is digested in the insect body to release virus particles, the virus particles proliferate in the insect host cells, the host insect larvae show anorexia, dull movement, blood The lymph is gradually changed from milky white to normal, and the body becomes pale or shiny; then the body softens, the body tissue liquefies, the body segments swell, the epidermis is fragile and easily cracked, and after the break, a white or brown thick liquid flows out, containing a large amount of newly formed Polyhedrons, which have no special odor before they invade the liquid, are not invaded by saprophytic bacteria. The dying larvae of infected animals often climb to the heights of the plants. They often hang their branches and tails to hang on the branches of plants and die. The liquefaction of the larvae falls and the bottom of the body expands. This is the typical characteristic for finding infected worms. Sometimes the amount of virus infected by larvae is not enough to make it die in the larval stage. Some larvae only have the characteristic of infection with slightly hemolymph at the last age, and the infected larvae can die in the flood season. The incubation period after the larvae have been infected until symptoms and symptoms occur is affected by various factors. If the inoculum size is small, the incubation period is long, and the susceptibility to juvenile infestation is generally smaller, and the incubation period is also prolonged. Higher temperatures and higher relative humidity can easily induce insect-borne viral diseases.
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