Propagation of an Avirulent Turkey Hemorrhagic Enteritis Virus Isolate in Chickens

A series of studies were undertaken to optimize the propagation of hemorrhagic enteritis virus (HEV) in specific-pathogen-free (SPF) chickens. A total of 562 SPF chickens were orally inoculated with an Australian avirulent HEV isolate of turkey origin at 9, 14, 21, or 28 days of age with 5, 6, 7, or 8 log 10 genomic copies (GC), while 102 chickens served as uninfected controls. No clinical signs were observed in infected chickens. There was an inoculum-dose-dependent increase in the relative spleen and liver weight (P < 0.01). Relative spleen weight 7 days post-HEV inoculation was up to 85% higher in chickens that were inoculated with 6 to 7 GC compared with controls, with no further increase at higher doses. Relative liver weight increased up to 14% in chickens inoculated with 6 GC, with no further increase. Birds inoculated with a 7 GC dose had a higher frequency of HEV DNA-positive birds (77% to 86%) than birds inoculated with lower doses (33% to 59%; P < 0.01). The most efficient dose for live passage propagation was 7 GC inoculated in 9-to-14-day-old birds, yielding an infection rate of 81%. Livers and spleens from infected birds at all doses were processed to produce a putative vaccine with a final GC recovery in the vaccine material of 8.6 GC/bird. In summary, HEV of turkey origin can be readily propagated in SPF chickens, and conditions to maximize viral retrieval were established.