A Coronavirus Associated with Runting Stunting Syndrome in Broiler Chickens

Abstract

Runting stunting syndrome (RSS) is a disease condition that affects broilers and causes impaired growth and poor feed conversion because of enteritis characterized by pale and distended small intestines with watery contents. The etiology of the disease is multifactorial, and a large variety of viral agents have been implicated. Here we describe the detection and isolation of an infectious bronchitis virus (IBV) -like coronavirus from the intestines of a flock of 60,000 14-day-old brown/red broiler chicks. The birds showed typical clinical signs of RSS including stunting and uneven growth. At necropsy, the small intestines were pale and distended with watery contents. Histopathology of the intestines revealed increased cellularity of the lamina propria, blunting of villi, and cystic changes in the crypts. Negative stain electron microscopy of the intestinal contents revealed coronavirus particles. Transmission electron microscopy of the intestine confirmed coronavirus in the cytoplasm of enterocytes. Using immunohistochemistry (IHC), IBV antigen was detected in the intestinal epithelial cells as well as in the proventriculus and pancreas. There were no lesions in the respiratory system, and no IBV antigen was detected in trachea, lung, air sac, conjunctiva, and cecal tonsils. A coronavirus was isolated from the intestine of chicken embryos but not from the allantoic sac inoculated with the intestinal contents of the broiler chicks. Sequencing of the S1 gene showed nucleic acid sequence identities of 93.8% to the corresponding region of IBV California 99 and of 85.7% to IBV Arkansas. Nucleic acid sequence identities to other IBV genotypes were lower. The histopathologic lesions in the intestines were reproduced after experimental infection of specific-pathogen-free chickens inoculated in the conjunctiva and nares. Five days after infection, six of nine investigated birds showed enteritis associated with IBV antigen as detected by IHC. In contrast to the field infection, birds in the experimental group showed clear respiratory signs and lesions in the upper respiratory tract. The results suggest a broader tissue tropism of this isolate, which might be related to the mutations in the S1 gene.

Runting and Stunting Syndrome in Broiler Chickens: Histopathology and Association With a Novel Picornavirus

“…14,30,35,46 The cause of RSS is not well understood and many viruses have been described in association with this syndrome including chicken astrovirus, 10,13,14 avian nephritis virus (ANV), 7,10,34,38 chicken parvovirus, 10,15,33,48 avian reovirus, 10,34 avian rotavirus (AvRV), 31,34 and infectious bronchitis virus. 10,12 Recently, other viruses have been detected as possible agents of cystic enteritis, such as birnavirus, 19,21,27 calicivirus, 10,19,45 fowl adenovirus group-I, 8,19,24,38 and other members of the families Picornaviridae, 10,19 Siphoviridae, Myoviridae, 10 Anelloviridae, and Circoviridae as well as CRESS-DNA virus. 19 It is suggested that RSS may be caused by one or more viruses.…”

Molecular Biology and Pathological Process of an Infectious Bronchitis Virus With Enteric Tropism in Commercial Broilers

“…When CalEnt was replicated in SPF embryonated eggs, the virus was retrieved from embryo intestines, but not from allantoic fluid or the chorioallantoic membrane. After an in vivo challenge experiment with IBV CalEnt, the enteritis and stunting was successifully reproduced in a laboratory setting, suggesting an enteric tropism [14]. Despite all the efforts in characterizing the pathobiology of IBV strains with supposed enteric tropism, information on the molecular aspects of such strains are scarce.…”

“…These results suggest that CalEnt is an IBV variant that arose from continued virus mutations in the presence of vaccine strains. The emergence of IBV variants such as CalEnt in 2012 [14] and Cal 99 in 1999 [26,27] likely resulted from vaccine mishandling in the field, either by poor application techniques or by usage of vaccines at a lower dosage than the recommended by the manufacturer. Vaccination issues may lead to rolling reactions and back-passaging of vaccine viruses within the flock, providing opportunities for mutations and recombination events that generate novel variants over time that might circumvent vaccine immunity [28].…”

The ocular surface, coronaviruses and COVID‐19

“…More recently, coronaviruses which can cause fatal infections in humans -SARS-CoV in 2002-2003, MERS-CoV in 2012 10 and of course SARS-CoV-2 in 2019have emerged. Coronaviruses also cause large economic losses as they can cause severe diseases in farm animals such as cows 11 and chickens 12,13 as well as domestic animals such as cats. 14,15 All viruses need to bind (adhere) to host cells, as the first step in their invasion of cells and subsequent replication.…”