Analysis of diagnostic cases of turkey viral enteritis in commercial turkey poults in California

Abstract

Poult enteritis complex is a multifactorial intestinal disease of young turkeys, which results in considerable economic losses for commercial turkey producers. The objectives of this study were to determine the current prevalence of viral enteritis in California turkeys, assess the methods of detection and the gross and histological presentations of laboratory case submissions. The electronic database at the California Animal Health and Food Safety ( CAHFS ) system was searched for necropsy cases in which intestinal content from commercial turkey poults was submitted for transmission electron microscopy ( TEM ) and/or quantitative reverse transcriptase ( qRT )-PCR for enteric viruses for the period February 1, 2020 to February 1, 2021. Based on these search parameters, the study identified and analyzed a total of 66 poult necropsy cases originating from 22 commercial turkey premises. A diagnosis of viral enteritis was made in 43 of the 66 cases (65.1%) screened for enteric viruses by TEM and/or qRT-PCR. The viruses detected in this study included turkey astroviruses, avian rotavirus, avian reovirus, avian enteric picornavirus, and avian parvovirus. Turkey astroviruses species (32/43, 74.4%) were the most frequently detected viruses, with turkey astrovirus-2 (24/43, 55.8%) being the most common species detected amongst all enteric viruses. A single enteric virus was detected in 44.2% (19/43) of cases submissions, while 2 or more enteric viruses were detected in 55.8% (24/43) of submissions. The age at which enteric viruses were detected ranged from one to 7 wk of age, with the highest frequency of detection occurring in the first 3 wk of life (38/43, 88.4%, 95% CI: 1.2–13.3, odds ratio [ OR ] = 4.1). Within the first 3 wk, the majority (24/43, 55.8%) of poults positive for enteric viruses ranged between 1 and 7 d of age. Our assessment of the different diagnostic methods used at CAHFS indicates that the use of TEM in conjunction with qRT-PCR improved our ability to detect viruses in cases where 2 or more enteric viruses were present. The most common macroscopic findings included pale, thin-walled, fluid-filled small intestines (76.7%); thin, dilated, fluid-filled ceca (69.7%), and primarily litter in the gizzard (60.4%). The most common microscopic findings included villi changes (atrophy, fusion, blunting) (72%), infiltration of the lamina propria with mixed inflammatory cells (51%), hyperplasia of crypt epithelial cells (16%), and increase in the number of goblet cells (16%). This study provides an update on the prevalence of turkey viral enteritis in California commercial turkeys operations and discussed production practices which impact the occurrence of the disease complex. It also identified the current presentation of this disease condition in California and discussed the best approach for diagnosing turkey viral enteritis.