engleski

Vertical transmission and possible role of viral infections in hatchability problems of duck embryos

Diagnostic investigation of viruses infecting ducks was conducted to reveal the possible role of viruses in pre-hatching mortality of duck embryos and to discuss correlation between virus infection and hatchabilty problems. Dead duck embryos were collected from 32 flocks and were tested by polymerase chain reaction (PCR) for the presence of avian astroviruses (avian nephritis virus, chicken astrovirus, duck astrovirus, turkey astrovirus type 1 and 2), avian reovirus, duck circovirus, duck enteritis virus, Derzsy's disease virus and duck hepatitis B virus. The rate of unhatched ducklings varied between the flocks, and although some flocks had slightly higher level of embryo mortality, none of tested flocks suffered from excessive mortality. PCR assays confirmed virus infection in 25 flocks, and mixed infections (avian nephritis virus and chicken astrovirus ; turkey astrovirus-2 and duck hepatitis B virus) were detected in two flocks. The most common infection found in duck embryos was with avian nephritis virus (12/34), while infections with other types of astrovirus were less frequently detected (1 flock was postive to chicken astrovirus, turkey astrovirus-1 was detected in 2, while turkey astrovirus-2 in 3 flocks). Duck hepatitis B virus was identified in 5 and duck circovirus in 4 flocks, while no other viruses were found to infect tested embryos. Viral infections occured naturally, by vertical transmission. Embryos were slightly to moderate underdeveloped, which was prominent finding in astrovirus positive flocks. Beside other possible infections and conditions in the hatchery that could have caused death of embryos, it is possible that developing immune system of duck embryos was affected with several factors, including identified viruses, which resulted in death before hatching. Considering that astroviral infection can be found in sick and healthy poultry flocks, we believe that synergy of unfavorable factors is crucial for developing clinical disease and death. Because circovirus infection is associated with immunosuppression and growth problems, it is likely that it had negative impact on development of duck embryos. Further research of vertically transmitted viruses and testing of apparently healthy and hatched ducklings is needed to get more relevant data regarding pre-hatching mortality of duck embryos.

duck embryos; viruses; hatchability

nije evidentirano