The intensification of pig farming has led to serious health implication. In modern production systems health is impaired due to multifactorial diseases and the identification of the causal agent cannot be based exclusively on the result of a single diagnostic tool. Most pathogens are ubiquitous, so the identification of an infectious agent suggests only a possible diagnosis.
Pathology plays a key role in determining causality in the diagnosis of infectious diseases. Histopathology allows to correlate the presence of the infectious agent with the characteristic microscopic lesions: based on the availability of antibodies or probes to detect respectively the presence of antigens or the genome of viruses or bacteria in histological sections, histopathology is useful for determining the causal link with the disease.
The introduction of this thesis is focused on the role of pathology in infectious diseases of swine followed by a discussion on the proper sampling for histopathological examination in the diagnosis of respiratory, enteric and reproductive diseases.
The experimental section reports the results of diagnostic investigations in porcine pathology conducted to define the role of PCV2 and PRRSV in Porcine respiratory disease complex (PRDC) (chapter 2) and to define a diagnostic pathway for porcine proliferative enteropathy caused by Lawsonia intracellularis to improve the diagnostic accuracy (chapter 3).
Chapter 4 describes the use of histopathology as an essential methodological component to evaluate the protective efficacy of vaccines in vaccine challenge studies. The chapter describes the results obtained in two subsequent trials to evaluate the efficacy of two experimental vaccines for PCV2, the first formulated with inactivated PCV2b strain administered at different doses of antigen; the second formulated with recombinant “Cap” antigen not assembled in virus-like particles (VLP).