Studies on Porcine Circovirus Infections in Bulgaria

Svetoslav Martinov^1*, Reneta Petrova¹, Raiko Peshev¹ & Ivo Sirakov²

¹National Diagnostic and Research Veterinary Medical Institute-Sofia, Bulgaria
²Medical University-Sofia, Bulgaria

Dr. Svetoslav Martinov, National Diagnostic and Research Veterinary Medical Institute-Sofia, Bulgaria.

Keywords: Porcine Circovirus; Infections; Immunohistochemistry

Abstract

Circovirus infections are a current and significant veterinary and economic problem in a number of countries with developed pig breeding. Clinical manifestations of the disease caused by Porcine Circovirus Type 2 (PCV 2) include Postweaning Multisystemic Wasting Syndrome (PMWS), Porcine Dermatitis and Nephropathy Syndrome (PDNS), respiratory, reproductive or intestinal disorders, subclinical infections (PCV 2 SI). Circovirus Type 3 (PCV 3) is responsible for cardiac and multisystemic infections, PDNS, febrile conditions, pneumonia and reproductive failure. In the present study are presented data for etiology, the spread of infection among the populations and categories of pigs in Bulgaria and its clinical manifestations and histopathology, as well as the applied modern approaches for diagnostics and research. Employed were serological methods (indirect ?LISA with recombinant antigen and monoclonal antibodies), immunohistochemistry (IHC), in situ hybridization (ISH), PCR techniques, sequencing of isolates. High seropositivity was found among different categories pigs (domestic, Eastern Balkan breed, wild), which shows a wide prevalence of PCV 2 infection among pigs in the country. Most susceptible group was adolescent pigs at 12-14 weeks of age. The incidence varied from 30 to 60% and mortality - from 3 to 20%. IHC detected viral antigen in lymph nodes, spleen, tonsils and lungs. The application of ISH method is effective. By conventional PCR of blood samples from pigs were obtained DNA amplicons of 656 bp and in the study of specimens from lymph nodes - amplification products with size of 494 bp were found. By sequencing the PCV 2 isolates were received data for difference in nucleotide and amino acid sequences of the capsid gene of Bulgarian isolates and reference strains. The Bulgarian PCV 2 isolates Han Asparuh 4 and 19 belong to PCV 2b genotype and represent a separate branch from the referent isolates. Te third Bulgarian PCV 2b isolate Rousse also is separate branch based on its differences with the mentioned Bulgarian PCV 2 isolates, as well as with reference isolates from Spain, Netherlands and Scotland. Most typical histological changes for circovirus infections were found in lymph nodes characterized by different degrees of granulomatous inflammation. Frequent findings in the lungs were purulent, interstitial or fibrinous pneumonia.

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