The
Picornavirus
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| Turkey entero-like virus
(Reynolds et al., 1987; Swayne et al., 1990;
Hayhow and Saif, 1993; Hayhow et al., 1993a,b);
picornavirus or astrovirus? Abstract from Reynolds et al. (1987)... Intestinal samples from 91 turkey flocks between 1 day and 5 weeks of age were examined for enteric viruses using electron microscopy and electropherotyping. These flocks originated from eight operations in six states. Individual flocks were sampled only once. At the time of sampling, 31 flocks were considered normal/healthy and 60 were considered to have enteric disease. The most frequently identified viruses from diseased flocks were astroviruses (78%) and rotavirus-like viruses (RVLVs) (67%). Far less frequent were rotaviruses (22%), atypical rotaviruses (12%), enteroviruses (5%), and reoviruses (2%). Only 10% of the samples from diseased flocks were negative, but 48% of the samples from normal/healthy flocks were negative. Astroviruses and RVLVs were far less frequent in normal/healthy flocks than in diseased flocks, but rotaviruses were identified slightly more often. No viruses were detected from flocks sampled within the first few days of life. Astrovirus infections seemed to occur at an earlier age than other virus infections. Seldom was only one type of virus identified. Astrovirus + RVLV was the most frequently identified combination in diseased flocks. Abstract from Swayne et al. (1990)... Four- and 5-day-old specific-pathogen-free turkey poults were inoculated orally or by contact exposure to a small round turkey-origin enteric virus. At days 4 and 8 postinoculation (PI), the orally inoculated poults had significantly lower body weight gains than control poults. Poults at day 4 (orally inoculated) and 5 (contact-exposed) PI had watery droppings, dilated thin-walled ceca filled with yellow foamy fluid, catarrhal small intestinal secretions, pale intestinal serosa, and mild lymphocytic enteritis. In addition, at day 4 PI, poults were lymphopenic, had intracytoplasmic crystalline arrays of 17.1 +/- 1.1 nm viral particles in the jejunal villar enterocytes, and had an 18-to-24-nm virus in intestinal contents. Analysis of morphometric data revealed mild shortening of villi in the duodenum and elongation of crypts in the duodenum and ileum during the late stage of the syndrome (day 8 PI). These findings suggest that the 18-to-24-nm virus can produce an enteric disease syndrome and that the acute clinical manifestation of this syndrome is not the result of morphologic change such as intestinal villus atrophy. The definitive identity of this 18-to-24-nm virus is not known; however, based on size and intracytoplasmic arrays of virus, it is most probably an enterovirus. Abstract from Hayhow and Saif (1993)... Diagnosis of enterovirus infection in turkey poults is currently done using electron microscopy. We have developed an antigen-capture enzyme-linked immunosorbent assay (ELISA) for use in diagnosis of enterovirus infection in turkey intestinal contents. Intestinal contents from naturally and experimentally infected turkey poults were evaluated for the presence of astrovirus and enterovirus by immune electron microscopy (IEM). The results were compared with the findings obtained using the ELISA for the presence of enterovirus. The ELISA, using the samples from the naturally infected poults, had a sensitivity of 0.963 and a specificity of 0.879. The Kappa value of 0.834 for the naturally infected samples and 0.97 for the experimentally infected samples showed excellent agreement between the ELISA and IEM for detection of enterovirus. Our results indicate that the ELISA is a rapid, sensitive, and specific method for diagnosis of turkey enterovirus infection. Abstract from Hayhow et al. (1993a)... Previously, we described a disease syndrome in young turkeys caused by an enterovirus-like virus. The virus was designated an enterovirus-like virus based on size, morphology, and intracytoplasmic crystalline arrays of virus. In the present study, further characterization of the virus was performed to ascertain its classification. The virus has a buoyant density of 1.33 g/ml in CsCl and single-stranded RNA genome of approximately 7.5 kilobases. These combined characteristics indicate that this agent is an enterovirus. Abstract from Hayhow et al. (1993b)... To evaluate sites of enterovirus replication and to characterize the resulting lesions, twenty 4-day-old specific-pathogen-free (SPF) turkey poults were orally inoculated with an enterovirus. Twenty uninoculated SPF poults served as controls. Inoculated poults were depressed, had ruffled feathers, watery droppings, and pasted vents. Gross lesions were dilated thin-walled ceca with foamy yellow fluid. Immune electron microscopy of the gastrointestinal tract contents revealed an enterovirus with an average diameter of 23.5 nm. Immunoperoxidase and indirect immunofluorescent antibody assays revealed intracytoplasmic staining in enterocytes of the duodenum, jejunum, and ileum. This correlated with the scanning electron microscopy findings, which showed the most lesions in the jejunum and ileum. The ileum had prominent cell outlines because of rounded, distinct, bulging epithelial cells. Histopathology revealed slight shortening of villi and increased crypt depth in the intestines of inoculated poults. Our findings indicate that the small intestine is the site of turkey enterovirus replication, and the gross and microscopic changes observed are determined to result from viral damage to the enterocytes. References Hayhow, C.S. and Saif, Y.M. (1993). Development of an antigen-capture enzyme-linked immunosorbent assay for detection of enterovirus in commercial turkeys. Avian Dis. 37: 375-379. Hayhow, C.S., Parwani, A.V. and Saif, Y.M. (1993a). Single-stranded genomic RNA from turkey enterovirus-like virus Avian Diseases 37: 558-560. Hayhow, C.S., Saif, Y.M., Kerr, K.M. and Whitmoyer, R.E. (1993b). Further observations on enterovirus infection in specific-pathogen-free turkey poults. Avian Dis. 37: 124-134. Reynolds, D.L., Saif, Y.M. and Theil, K.W. (1987). A survey of enteric viruses of turkey poults. Avian Dis. 31: 89-98. Swayne, D.E., Radin, M.J. and Saif, Y.M. (1990). Enteric disease in specific-pathogen-free turkey poults inoculated with a small round turkey-origin enteric virus. Avian Dis. 34: 683-692. |