| In recent years, DRV infections has been found frequently in muscovy duck's feed section of the province. DRV infections is also known as "the liver white-spots" and "colored liver disease". The percentage of the disease was 30% to 90% and the death rate was from 60% to 80%. If the muscovy ducks were stimulated badly or with mixed infection, the mortality rate could be gone up to 90%. So it would cause serious economic problems to the business of the muscovy duck .During the period of positive illness, mixed infection took place in large numbers, and symptoms of immunodepression were found on muscovy ducks. We examined the infected muscovy ducks' immune enginery by many means and researched into the effect of muscovy ducks' immunodepression, thus, providing important theory gist for prevention of DRV infections.Then we have researched to the immunodepression with DRV YB4 strain.After infection with DRV, the primary symptom of muscovy ducks were piling together, weak feet, some of them were crouching and were drawing back their heads. The course of diseases was between 2 days to 20 days and the death pinnacle was from 10 to 17 days. Moreover, the main pathological changes were white putrescence spots on the liver and spleen and liver infection,pericardities were also discovered later. LD50... |
