Comparative Pathogenicity Studies on Avian Reoviruses.

Abstract

Poult enteritis and mortality syndrome (PEMS), a condition with multifactorial etiology is characterized by an acute, contagious enteric disease of turkey poults between the ages of 2-4 weeks. The current study was conducted to define the role of PEMS-associated agents on poult performance. In the first study, the 'novel' Cornell virus, defined as the reovirus ARVCU98, a small round virus (SRV or ARVCU98) and a turkey astrovirus, Ohio State University isolate (TastOSU), were gavaged orally into the crop of turkey poults. Reduced body weights and reduced relative weights of the bursa of Fabricius, thymus, and liver were observed in virus-challenged poults. The reduced body weight gain and tissue atrophy was exacerbated by the presence of E. coli. In study number two, the possibility of vertical transmission of reovirus via the egg was tested. In ovo inoculation resulted in pathogenic and metabolic alterations in broilers challenged in ovo at day 9 of embryonation with ARVCU98 and the field isolated S1733 (1:100 and 1:500 dilution). In a third study, hyperimmunization of turkey breeder hens against the ARVCU98 reovirus provided limited protection to progeny as indicated by decreased weight gain and loss of lymphoid organ integrity in post hatch ARVCU98-challenged poults. Overall these studies demonstrated that PEMS-associated astrovirus and reovirus affected poult performance by decreasing body weight and altering lymphoid organ integrity, and the addition of E. coli further exacerbated these signs under a controlled environment. Additionally, ARVCU98 reovirus is a turkey isolate, and the evidence presented herein clearly demonstrated that it can infect broilers and that vertical transmission via the egg is a strong possibility.