Etiological And Serological Investigations Of Immunosuppressive Viruses In White Meat-type Chickens In Shandong Province

Marek's disease virus, avian Reticuloendotheliosis virus, Chicken anemia virus and avian reovirus are common immunosuppressive viruses in chicken flocks. They may not only cause their own particular disease (such as cancer, anemia or acute death) but also often infect chickens in the form of subclinical infection and caused varying degrees of immune suppression, so, resulting in growth retardation or a secondary bacterial infection or a serious disturbance on Newcastle Disease and avian flu vaccine effect. It's difficult to control these diseases, severely limits the potential exports of broiler in our province. It is necessary to adopt comprehensive measures to control immunosuppressive disease virus. In order to master the popular rule with immunosuppressive disease and offer reasonable measures of prevention, serum and pathogen are tested from the breeder and broiler.Antibodies against avian reticuloendotheliosis virus (REV), Chicken anemia virus (CAV) and Avian leucosis virus (ALV) in serums collected from meat-type breeding chickens at different ages were tested with ELISA kit. Among 212 serums, no matter whether the flocks were vaccinated with CAV vaccine or not, their positive rate to CAV was 100% except for one 15-week-old flock, whose positive rates were 75%. The positive rates to REV and ALV (A and B subtype) were from 16.7%to 62.5%or from 0 to 75% respectively.The DNA and RNA were extracted for hybridization in Dot blot with dig-labeled probes for Marek′s disease virus (MDV) , Reticuloendotheliosis virus (REV), Chicken anemia virus and avian reovirus in the commercial broiler chickens eliminated through selection or competition and died from disease and the white meat-type parent breeders eliminated through selection or competition. The results indicated that the infection rate of ARV is the highest of the four virus in the three type chickens,and ARV mainly infect in the form of a single infection. The infection rate of ARV (18.60%) in the commercial broiler chickens died from disease is the highest. So, we speculated that ARV is the most severe immunosuppressive virus; The rate of Co-infection in the parent breeders was 10.25% and was more serious than any other flocks. Followed by commercial broiler chickens died from disease, the positive rate is 7.0%.Based on the above, in order to obtain a more complete epidemiological information pathogenic and serological survey on the REV and CAV were did with chickens at different ages throughout the breeding cycle of broilers in a new large-scale commercial broiler farms in Shandong Province. The results indicated that the REV infection percentage(2.19%)is higher than the CAV infection percentage (1.46%) in 137samples. The positive rate of antibody against REVwas respectively 40%, 20%, 45%, 25% and the positive rate of CAV was 100%, 30%, 85%, 30% in 1d, 14d, 21d, 28d. The positive rate of REV (50%) was higer than the rate of CAV in 42d. The results are analyzed comprehensively and we found that chicken are easily infected the REV and CAV before 21-day period, feeding and management should be strengthened, REV is likely to be vertical transmission, parent breeding chickens should be vaccined before egg producing period to raise the level of maternal antibody to prevent early infection. Because there is no REV commercial vaccine, it's necessary to eliminate the positive parent breeders. Feeding and management and strengthening environmental disinfection are important to prevent and control CAV. The investigation can lay the foundation for the next comprehensive prevention and control.