Abstract. An immunohistochemical method for the detection of type 2 porcine circovirus (PCV2) in paraffin-embedded tissue was developed. Rabbits were inoculated with purified PCV2 to obtain a polyclonal antiserum. Antiserum was applied to sections of porcine tissue that contained lesions consistent with postweaning multisystemic wasting syndrome and in which PCV2 genome had been demonstrated by in situ hybridization. In all cases (18/18), the density and distribution of positive cells detected by in situ hybridization or immunohistochemistry were identical. The immunohistochemical method is more rapid and less expensive than in situ hybridization and is thus more suitable for routine diagnostic use.A newly emerged porcine disease syndrome, postweaning multisystemic wasting syndrome (PMWS), has been reported throughout North America and Europe and is associated with infection by a novel strain of porcine circovirus (PCV). 2,3,5,7-10 PMWS is characterized clinically by progressive dyspnea, emaciation, and occasionally icterus and pathologically by a wide range of inflammatory lesions that most often include lymphohistiocytic to granulomatous lymphadenitis, interstitial pneumonia, hepatitis, and interstitial nephritis. 2,3 The hallmark of PMWS is depletion of lymphoid tissues and the consistent presence in those tissues of a newly identified strain of PCV. 2,3,5,[7][8][9][10] The genotype and serotype of the PCV isolated from PMWS lesions (PCV2) is markedly different from that of PCV1, an apparently ubiquitous, nonpathogenic virus initially identified over 20 years ago as a contaminant of the PK15 cell line. 1,6,11,12 Although pigs with PMWS are consistently infected with PCV2, it remains uncertain whether PCV2 infection alone is sufficient to induce PMWS. 4 Detection of PCV2 in tissues has been achieved by 1) identification of macrophages with large basophilic to amphophilic intracytoplasmic inclusion bodies that ultrastructurally correspond to arrays of PCV particles, 7 2) demonstration of viral genome via in situ hybridization (ISH), 2,9 or 3) demonstration of viral antigen via immunohistochemistry. 3,4,7 Because characteristic inclusion bodies are an inconsistent feature of PCV2 infection, reliable methods for the detection of PCV2 genome or antigen are highly desirable. Compared with immunohistochemistry, ISH is more complex and less suited to a busy diagnostic laboratory. Others have reported the immunohistochemical detection of PCV in tissues using rabbit antisera raised against PCV1 3,4 or monoclonal antibodies to PCV1. 4 Immunohistochemistry using rabbit antisera to a presumptive PCV2 isolate was previously reported, 7 but detailed methodology was not presented. Herein, the production of polyclonal Received for publication April 19, 1999. rabbit antiserum to purified PCV2 and utilization of this antiserum in an immunohistochemical assay suitable for routine diagnostic use is described. A well-characterized PCV2 isolate (ISU-31) was propagated in glucosamine-treated PCV-free PK15 cells. 9 When an indirec...

No abstract

Abstract. Out of 45 cases of fatal chronic pneumonia in calves examined for Mycoplasma bovis infection from February to July 1994, 11 cases with pulmonary abscesses that were culture positive for M. bovis were encountered. The cases were studied in detail using a recently developed monoclonal antibody-based immunoperoxidase technique. Mycoplasma bovis organisms were detected in specific locations at all stages of abscessation observed. In bronchioles or terminal airways within which abscesses developed, M. bovis was located at the epithelial surface and in close association with infiltrating neutrophils and macrophages. Abscessed airways that had lost the epithelium were encapsulated and were seen as coagulative necrotic foci that stained intensely for M. bovis, especially at the periphery. Some foci stained weakly and such might have been resolving lesions. Mycoplasma bovis was also demonstrated at sites of mild mononuclear cell infiltration in the livers and kidneys of 2 calves. The mycoplasma was detected within bile ducts in the liver and in the tubular epithelium of the kidney. Abscesses not staining for M. bovis, presumably caused by other pathogens, were seen concurrently with M. bovis-associated abscesses in some lungs. Thirteen other M. bovis-positive cases showed no abscesses, possibly indicating heterogeneity among M. bovis strains. Three other cases with abscesses were negative for M. bovis by culture and immunoperoxidase staining. The monoclonal antibody-based immunohistochemical technique is efficient for specific detection of M. bovis in cases of enzootic pneumonia of calves with or without abscessation. Mycoplasma bovis is implicated in the pathogenesis of lung abscesses in some calves.Naturally occurring infectious pneumonias of clinical significance usually have complex causes, often requiring the interaction of two or more organisms and predisposing environmental factors.2 Calf pneumonia resistant to antibiotic therapy is frequently encountered in the United States of America and Canada. 10 In areas where calves dying of chronic pneumonia would normally have been treated for bacterial agents, diagnostic effort is necessarily geared towards elucidating the role of viruses and mycoplasmas. Viral agents often cause acute pneumonia in calves, with a histological picture of bronchointerstitial pneumonia. 2Among bovine mycoplasmas recognized in the USA, Canada, and Europe, Mycoplasma bovis stands out as the most invasive and destructive. This mycoplasma can cause pneumonia and arthritis in calves and mastitis in adult cattle .2,7 Mycoplasma bovis has also been cultured from blood.11 There are studies in which M. Received for publication October 7, 1994. bovis was inoculated into calves concurrently with Pasteurella hemolytica, 3 respiratory syncytial virus, 11 and bovine viral diarrhea virus and P. hemolytica. 8 Lesions produced by M. bovis alone were described as focal areas of coagulative necrosis surrounded by mononuclear cells and suppurative bronchiolitis with varying degrees of lympho...