This Ph.D. thesis presents different aspects of porcine circovirus diseases (PCVDs), based upon
work performed at The Faculty of Life Sciences, University of Copenhagen, Denmark and at The
National Veterinary Institute, Technical University of Denmark.
The introduction, chapter 1, briefly presents the background and objectives of this study.
Chapter 2 describes different aspects of porcine circovirus type 2 (PCV2), including molecular
biology, genotypes, other closely related circoviruses and also the pathogenesis of PCV2 infections.
Furthermore, the different porcine circovirus diseases (PCVDs) and experimental models of PCVDs
In chapter 3, the results achieved by the research are presented as four manuscripts (I-IV):
Manuscript I is focussed on the presence of PCV2 and viral replication, in the bone marrow
and thymus of experimentally infected pigs and pigs naturally affected by postweaning
multisystemic wasting syndrome (PMWS). By in situ hybridization (ISH) virus and viral
replication was detected, mainly in histiocyte-like cells, in both organs of the PMWSaffected
pigs. However, there was no evidence that bone marrow or thymus is especially
important in regard of PCV2 replication.
In manuscript II the occurrence and tissue distribution of PCV2 is examined, by
immunohistochemistry (IHC) of lungs, kidneys, lymph nodes and spleen from slaughtered
Danish finishing pigs with or without bronchopneumonia. Detection of PCV2 could not be
related to lesions or PCVD. The virus was mainly detected in lymph nodes in association
with follicular dendritic cells, which were identified by IHC. Whether this finding represents
subclinical or persistent infection, or a status after PCV2 infection with innocent storage of
antigen, remains unclear.
Manuscript III focuses on the progression and diagnostics of an outbreak of naturally
occurring PCV2 associated reproductive failure in a Danish herd. In stillborn and
mummified foetuses PCV2 was detected mainly in the heart and bone marrow, by IHC, and
replication was detected in myocardiocytes, by ISH. The study showed that measurements
of total immunoglobulin G in foetuses are not very reliable as indication of intrauterine
infection with PCV2. Furthermore, real-time polymerase chain reaction proved to be better
for the detection of PCV2 in infected foetuses, compared to IHC, as PCV2 only was
detected early in the outbreak by the latter method.
• Manuscript IV is an update on the pathology and pathogens present in porcine respiratory
disease complex (PRDC) in Danish finishing pigs. Multiple pathogens were detected,
including PCV2, confirming the previously reported pathogen profile and multifactorial
aetiology of PRDC. The histopathology was very variable and no clear-cut associations
were detected between specific pathogens and histological lesions.
In chapter 4, the achieved results are discussed and the future perspectives are addressed, and the
thesis is closed with a summary of the drawn conclusions.