H. L. Shivaprasad

Novel Borna Virus in Psittacine Birds with Proventricular Dilatation Disease

Pyrosequencing of cDNA from brains of parrots with proventricular dilatation disease (PDD), an unexplained fatal inflammatory central, autonomic, and peripheral nervous system disease, showed 2 strains of a novel Borna virus. Real-time PCR confirmed virus presence in brain, proventriculus, and adrenal gland of 3 birds with PDD but not in 4 unaffected birds.

The putative capsid protein of the newly identified avian hepatitis E virus shares antigenic epitopes with that of swine and human hepatitis E viruses and chicken big liver and spleen disease virus.

We recently identified a novel virus, designated avian hepatitis E virus (avian HEV), from chickens with hepatitis-splenomegaly (HS) syndrome in the USA. We showed that avian HEV is genetically related to swine and human HEVs. Here we report the antigenic cross-reactivity of the putative open reading frame 2 (ORF2) capsid protein of avian HEV with those of swine and human HEVs and the Australian chicken big liver and spleen disease virus (BLSV). The region encoding the C-terminal 268 amino acid residues of avian HEV ORF2 was cloned into expression vector pRSET-C. The truncated ORF2 protein was expressed in E. coli as a fusion protein and purified by affinity chromatography. Western blot analysis revealed that the avian HEV ORF2 protein reacted with antisera against the Sar-55 strain of human HEV and with convalescent antisera against swine HEV and the US2 strain of human HEV, as well as with antiserum against BLSV. Convalescent sera from specific-pathogen-free chickens experimentally infected with avian HEV also reacted with the recombinant capsid proteins of swine HEV and Sar-55 human HEV. Antisera against the US2 human HEV also reacted with recombinant ORF2 proteins of both swine HEV and Sar-55 human HEV. The antigenic cross-reactivity of the avian HEV putative capsid protein with those of swine and human HEVs was further confirmed, for the most part, by ELISA assays. The data indicate that avian HEV shares certain antigenic epitopes in its putative capsid protein with swine and human HEVs, as well as with BLSV. The results have implications for HEV diagnosis and taxonomy.

Use of avian bornavirus isolates to induce proventricular dilatation disease in conures

The fulfillment of Koch’s postulates shows that the virus causes proventricular dilatation disease in parrots.

Unusual and severe lesions of proventricular dilatation disease in cockatiels (Nymphicus hollandicus) acting as healthy carriers of avian bornavirus (ABV) and subsequently infected with a virulent strain of ABV

A flock of 14 apparently healthy cockatiels, purchased from a single aviary, was tested for the presence of avian bornavirus (ABV). Twelve birds were found to be intermittently shedding ABV, predominantly genotype 4. Four of the cockatiels known to be shedding ABV4 were subsequently challenged with the tissue culture derived, virulent M24 strain of ABV4. The challenged birds remained in apparent good health until day 92 when one was found dead. The remaining three birds began to exhibit severe neurologic signs, ataxia and convulsions on day 110 and were euthanized. On necropsy, all four birds showed mild proventricular enlargement. In contrast, histopathological examination showed unusually severe and widespread tissue lesions. These included massive lymphocytic infiltration and lymphoid nodule formation within and around the ganglia throughout the gastrointestinal tract. There were similar lesions in the medullary cords of the adrenal gland, heart, spleen, liver, kidney, lungs, pancreas, testes and ovary. Immunohistochemistry demonstrated ABV P antigen not only in the cells of the central and autonomic nervous systems, but also within the mononuclear cells infiltrating the various organs. Two healthy cockatiels, one of which was a known ABV carrier, were inoculated with uninfected tissue culture cells and euthanized on day 150. These birds showed no gross lesions of proventricular dilatation disease but had a mild lymphocytic infiltration in their liver, spleen, and kidneys. Prior infection with ABV did not therefore confer significant immunity on these birds, and may have resulted in increased disease severity following challenge.

Novel Picornavirus in Turkey Poults with Hepatitis, California, USA

To identify a candidate etiologic agent for turkey viral hepatitis, we analyzed samples from diseased turkey poults from 8 commercial flocks in California, USA, that were collected during 2008–2010. High-throughput pyrosequencing of RNA from livers of poults with turkey viral hepatitis (TVH) revealed picornavirus sequences. Subsequent cloning of the ≈9-kb genome showed an organization similar to that of picornaviruses with conservation of motifs within the P1, P2, and P3 genome regions, but also unique features, including a 1.2-kb sequence of unknown function at the junction of P1 and P2 regions. Real-time PCR confirmed viral RNA in liver, bile, intestine, serum, and cloacal swab specimens from diseased poults. Analysis of liver by in situ hybridization with viral probes and immunohistochemical testing of serum demonstrated viral nucleic acid and protein in livers of diseased poults. Molecular, anatomic, and immunologic evidence suggests that TVH is caused by a novel picornavirus, tentatively named turkey hepatitis virus.

The Isolation, Pathogenesis, Diagnosis, Transmission, and Control of Avian Bornavirus and Proventricular Dilatation Disease

Proventricular dilatation disease (PDD) is a common infectious neurologic disease of birds comprising a dilatation of the proventriculus by ingested food as a result of defects in intestinal motility, which affects more than 50 species of psittacines, and is also known as Macaw wasting disease, neuropathic ganglioneuritis, or lymphoplasmacytic ganglioneuritis. Definitive diagnosis of PDD has been problematic due to the inconsistent distribution of lesions. Since its discovery, avian bornavirus (ABV) has been successfully cultured from the brains of psittacines diagnosed with PDD, providing a source of antigen for serologic assays and nucleic acid for molecular assays. This article provides evidence that ABV is the etiologic agent of PDD. Recent findings on the transmission, epidemiology, pathogenesis, diagnosis, and control of ABV infection and PDD are also reviewed.

Advanced diagnostic approaches and current management of proventricular dilatation disease.

Proventricular dilatation disease (PDD) is a fatal inflammatory disease that affects mainly, but not exclusively, psittacine birds (Order: Psittaciformes). PDD has long been suspected to be a viral disease, but its causative agent, a novel Bornavirus, was only identified in 2008.

Electron Microscopic Identification of Viruses Associated With Poult Enteritis In Turkeys Grown In California 1993–2003

Abstract Poult enteritis (PE) is one of the most common diseases seen in young turkey flocks. Since 1993, more than 1800 cases of suspected PE have been submitted for examination by negative stain electron microscopy; this has involved more than 2400 individual results, because in many cases more than one virus was identified; at least 1500 individual results were positive for viruses. Viruses have been identified in poults as young as 3 days and up to 9 wk of age. The most commonly found viruses are rotavirus-like viruses and small round viruses ranging from 15 nm to 30 nm, either alone or in combination. Reovirus, birnavirus, and adenovirus have also been detected. There has been no evidence to suggest the presence of coronaviruses. This report summarizes our findings.

Proventricular Dilatation Disease in Cockatiels (Nymphicus hollandicus) After Infection With a Genotype 2 Avian Bornavirus

Abstract An isolate of genotype 2 avian bornavirus (ABV) was recovered from a cockatiel (Nymphicus hollandicus) that was euthanatized for an unrelated lesion and showing no clinical evidence of proventricular dilatation disease (PDD). On histopathologic examination, mild inflammatory lesions were present in the heart and brain, but gastrointestinal lesions characteristic of classic PDD were not observed. To investigate if this ABV2 isolate had reduced virulence, the virus was propagated in duck embryo fibroblasts and inoculated into 2 adult cockatiels by the oral and intramuscular routes. One bird developed clinical signs on day 33 and was euthanatized on day 36. The second challenged bird developed clinical signs on day 41 and was euthanatized on day 45. At necropsy, the proventriculus of both birds was slightly enlarged. Histopathologic examination showed lesions typical of PDD in the brain, spinal cord, heart, adrenal gland, and intestine. A control, uninoculated cockatiel was apparently healthy when euthanatized on day 50. These results show that ABV2 is now the second ABV genotype to be formally shown to cause PDD.

Pathogenicity of Salmonella Enteritidis Phage Types 4, 8, and 23 in Broiler Chicks

Four hundred fifty day-old Hubbard broiler chicks were subdivided into 15 groups of 30 chicks each. Six groups of chicks received 0.5 ml of broth culture containing 5 x 10(6) colony-forming units (CFU) of Salmonella enteritidis (SE) phage types (PTs) 4, 8, and 23 by crop gavage. Similarly, six other groups received 0.5 ml containing 5 x 10(8) CFU of SE. One group was inoculated with 0.5 ml containing 5 x 10(6) CFU of Salmonella pullorum, and another group received 0.5 ml containing 5 x 10(8) CFU of S. pullorum. A group of 30 chicks were kept as uninoculated controls. Chicks were observed daily for clinical signs and mortality. All birds were weighed at 7, 14, and 21 days postinoculation 21 (DPI). Four chicks were randomly selected from each treatment group, euthanatized, and necropsied at 7 and 14 DPI. Gross lesions were recorded and selected tissues were collected for histopathology. The higher rates of illness and mortality were observed in chicks inoculated with 5 x 10(6) and 5 x 10(8) CFU of S. pullorum, followed by SE PT4 of human origin and SE PT4 of chicken origin. Moderate to high mortality was observed in chicks inoculated with the higher dose of SE isolates that belonged to PT8 and one SE of PT23. Variable mortality was evident in groups inoculated with the lower dose of salmonella. The most consistent gross and histopathologic changes, including fibrinous pericarditis and perihepatitis, were seen in the dead birds from various treatment groups. The lower mean body weights were present in all treatment groups compared with uninoculated controls. No illness or mortality was observed in uninoculated control groups.