Abstract
Contaminated vaccine is one unexpected and potential origin of virus infection. In order to investigate the most likely cause of disease in a broiler breeder company of Shandong Province, all 17 batches of live-virus vaccines used in the affected flocks and 478 tissue samples were tested by dot-blot hybridization, nested PCR, and IFA. The results suggested the outbreak of disease was most probably due to the vaccination of REV-contaminated MD-CVI988/Rispens vaccines and ND-LaSota+IB-H120 vaccines. Furthermore, the REV was probably transmitted to the commercial chickens through congenital transmission.
Highlights
The avian reticuloendotheliosis virus (REV), classified as a gamma-retrovirus, causes runting, immunosuppression, and lymphoma in a variety of avian hosts including chicken, turkey, duck, goose, pheasant, and peafowl [1,2]
Sensitivity examination showed that the probe with the final concentration of 50 ng/mL could be hybridized with serially diluted polymerase chain reaction (PCR) product of REV env gene, and REV env gene was still sensitive to the probe when PCR product quantity reached 10 pg (Fig. 1B)
The results showed the REVpositive rates of the affected flocks were between 26.5% and 32.8%
Summary
The avian reticuloendotheliosis virus (REV), classified as a gamma-retrovirus, causes runting, immunosuppression, and lymphoma in a variety of avian hosts including chicken, turkey, duck, goose, pheasant, and peafowl [1,2]. Cheng et al [3] performed serosurvey on broiler breeders in China during the period from September 2008 to November 2009, and discovered the antibody positive rate of REV was 42.6%. In September 2010, three flocks (Flocks 2, 3, and 5; 25– 30 weeks old) of a broiler breeder company in Shandong Province of China suffered emaciation and sporadic death with the death rate of around 0.8% in a week. Further investigation revealed that commercial chickens bred by the three broiler breeder flocks suffered poor and irregular growth, and demonstrated a poor immunological response to vaccination with Newcastle disease vaccines and avian influenza vaccines. The 30 days old commercial chickens had a livability of about 93% All of these respects corresponded to the typical characteristics of REV-infection. When the source of infection could not be determined, we suspected the possible target-vaccine
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