Rotavirus A Associated with Clinical Disease and Hepatic Necrosis in California Pigeons (Columba livia domestica).

Retrospective analysis of pigeon necropsy submissions to the California Animal Health and Food Safety Laboratory System from 2000 to 2018 revealed 14 submissions diagnosed with rotavirus A hepatic necrosis or "reoviruslike" viral hepatitis. Nine of the 14 submissions (64%) occurred in 2018. Submissions were racing pigeons and squab breeders from flocks with increased mortality. Juvenile and adult pigeons were submitted with a history of depression, diarrhea, regurgitation, labored breathing, and weakness. Flock morbidity peaked at 80% and mortality at 28%. The most consistent findings on postmortem examination were variably congested, mottled, and enlarged livers and spleens. Microscopically, mild to severe hepatic necrosis was observed with variable bile duct hyperplasia, sinusoidal congestion, hemosiderosis, and portal lymphoplasmacytic inflammation. Rotavirus A was detected in hepatocytes and inflammatory cells by immunohistochemistry. Negative-stain electron microscopy identified viral particles consistent with a member of Reoviridae in all negatively stained liver homogenates. Eleven cases were analyzed by reverse transcriptase-PCR targeting rotavirus A viral protein (VP) 6 and VP7 genes. Subsequent phylogenetic analysis of the VP6 and VP7 sequences compared to published Chinese, Nigerian, and German rotavirus A VP6 and VP7 sequences demonstrated the formation of two and three distinct clades, respectively. To the authors' knowledge, rotavirus A hepatic necrosis in pigeons has not been previously reported in the United States and represents a significant emerging disease for the pigeon industry due to the potential for high flock mortality and lost production.

Rotavirus A asociado con enfermedad clínica y necrosis hepática en palomas de California (Columba livia domestica). El análisis retrospectivo de los casos de necropsias de palomas remitidos al Sistema de Laboratorio de Salud Animal y Seguridad Alimentaria del Estado de California entre los años 2000 a 2018 reveló 14 casos con diagnóstico de necrosis hepática por rotavirus A, o hepatitis viral ocasionada por "virus similares a reovirus". Nueve de los 14 casos (64%) ocurrieron en el año 2018. Los casos fueron de palomas de competencia y de criadores de pichones de parvadas con aumento en la mortalidad. Se presentaron palomas jóvenes y adultas con antecedentes de depresión, diarrea, regurgitación, dificultad para respirar y debilidad. La morbilidad mayor fue de un 80% como máximo y la mortalidad fue de un 28%. Los hallazgos más consistentes en el examen post mortem incluyeron hígados y bazos con congestión, apariencia moteada y aumento de tamaño de forma variable. Microscópicamente, se observó necrosis hepática de leve a severa con hiperplasia variable de los conductos biliares, congestión de sinusoides, hemosiderosis e inflamación linfoplasmocítica portal. Se detectó rotavirus A en hepatocitos y células inflamatorias por inmunohistoquímica. La microscopía electrónica de tinción negativa identificó partículas virales consistentes con virus posiblemente miembros de la familia Reoviridae en todos los homogenizados de hígado teñidos negativamente. Se analizaron once casos mediante transcripción reversa y PCR dirigida a los genes de la proteína viral (VP) 6 y VP7 del rotavirus A. El análisis filogenético posterior de las secuencias de los genes VP6 y VP7 cuando se compararon con secuencias de genes VP6 y VP7 de rotavirus A de China, Nigeria y de Alemania previamente publicadas demostró la formación de dos y tres clados distintos, respectivamente. De acuerdo con el conocimiento de los autores, la necrosis hepática por rotavirus A en palomas no se había reportado previamente en los Estados Unidos y representa una enfermedad emergente importante para la industria de las palomas debido a su potencial de alta mortalidad de la parvada y a las pérdidas en la producción.

Characterization of the antigenic, immunogenic, and pathogenic variation of infectious bursal disease virus due to propagation in different host systems (bursa, embryo, and cell culture). I. Antigenicity and immunogenicity.

In vitro and in ovo virus neutralization assays were conducted to assess the role of different host systems in infectious bursal disease virus (IBDV) antigenic and immunogenic variation. Four different strains, two variant (1084 E and GLS) and two standard (Edgar and STC), were propagated separately in the bursa of Fabricius and embryos, and were compared with cell culture-adapted preparations of the homologous strains. Chicken polyclonal antisera were prepared against each IBDV and neutralizing antibody titres were determined. Normalized IBDV antibody concentrations were used in neutralization assays against homologous and heterologous IBDVs in 10-day-old specific pathogen free embryos. Both antigenic and immunogenic changes occurred in IBDVs evaluated, as evidenced by differences in the ability of normalized antibody to neutralize IBDV propagated in different host systems. Antibody induced by bursal-derived IBDV neutralized all isolates equally well, whereas antibody induced by cell culture-derived virus neutralized bursal-derived IBDV much less effectively.

Characterization of the antigenic, immunogenic, and pathogenic variation of infectious bursal disease virus due to propagation in different host systems (bursa, embryo, and cell culture). II. Antigenicity at the epitope level.

Antigenic variation of infectious bursal disease virus (IBDV) due to propagation in different host systems (bursa of Fabricius, embryos, or cell cultures) was determined by enzyme-linked immunosorbent assay (indirect and antigen capture) and western blot analysis. To conduct this study, we used 27 non-neutralizing anti-VP(2) monoclonal antibodies, a reference panel of nine neutralizing monoclonal antibodies, and 13 neutralizing anti-IBDV chicken polyclonal antibodies. Changes occurred in neutralizing, cross-reactive, conformation-dependent epitopes on the VP(2) protein of IBDV. Interestingly, non-neutralizing, cross-reactive, conformation-dependent and confirmation-independent epitopes also changed on VP(2). These epitope changes were directly associated with the method used to propagate IBDV. These results demonstrate that different host systems may play an important role in the antigenicity of IBDV.

Characterization of the antigenic, immunogenic, and pathogenic variation of infectious bursal disease virus due to propagation in different host systems (bursa, embryo, and cell culture). III. Pathogenicity.

Differences in the relative pathogenicity of variant (1084 E and GLS) and standard (Edgar and STC) infectious bursal disease virus (IBDV) strains were observed after propagation in the bursa of Fabricius, embryos, or cell cultures. Bursa-derived IBDV induced the most severe lesions in the bursa of Fabricius when compared with strains propagated in embryos or cell cultures. Embryo-derived IBDV induced moderate gross bursal lesions, whereas cell culture-derived IBDV did not damage the bursa grossly. A high frequency of virus re-isolations was obtained from bursal, spleen, and thymic samples collected from birds inoculated with bursa-derived or embryo-derived IBDV. Virus re-isolation occurred much less frequently from birds inoculated with cell culture-adapted IBDV. Serological evaluations demonstrated that bursa-derived IBDV strains induced a higher neutralizing antibody response than did embryo-derived or cell culture-derived strains. These results document that the relative pathogenicity and immunogenicity of IBDV is reduced following propagation in embryos or cell cultures.