PCV2-DNA in formalin-fixed and paraffin embedded lymph nodes of wild boar (Sus scrofa ssp. scrofa): one sampling approach for two laboratory techniques

Since 1998, Porcine Circovirus type 2 (PCV2) has been recognized to play an important role in postweaning multisystemic wasting syndrome (PMWS), as well as in many other pathologies in pig [1] defined as PCVD (PCV2 Diseases), causing huge economic losses to swine husbandry in all affected countries. The host spectrum is limited to the genus Sus [1] and numerous studies report in wild boar both PCV2 infection and associated diseases [2-5]. The wide spread of the infection and the absence of a close correlation between this and the pathological description made in situ tests (immunohistochemistry-IHC and in situ hybridization-ISH) the gold standard for the diagnosis of PCVD [1], whereby the causative agent is highlighted in the lesion. Despite this, it is also true that the greater sensitivity of PCR based methods [6] can provide more accurate information in assessing the infection prevalence in wild boar [3,7,8]. In many cases, paraffin embedded material is available as well as frozen serum samples [9,10].In the light of that, some studies have developed sophisticated techniques to extract viral nucleic acid, from formalin-fixed and paraffin-embedded (FFPE) specimens, sufficiently preserved to be submitted for biomolecular investigations [10,11]. The objectives of the present study were: 1) to carry out PCV2-DNA extraction and a subsequent investigation on FFPE with PCR in wild boar; 2) to compare the PCR results with those obtained on the same samples by IHC.In a previous study [2], 148 superficial inguinal lymph nodes, from as many wild boar shot in the Bologna Province (44°00'N, 11°00'E) and in the Colli Euganei Regional Park (45°14'N, 11°45'E), were examined with an IHC technique. Within the total amount, 72 lymph nodes were selected according to the following criteria: PCV2-IHC strongly positive lymph nodes with PMWS histological lesions (4 samples; outcome 1); weak to mild PCV2-IHC positivity without PMWS histological lesions (6 samples; outcome 2); randomly ch