Analysis of morphological changes, expression and distribution of viral antigen in the brain of foxes naturally infected with canine distemper virus

Abstract

In this doctoral dissertation brain samples of red foxes (Vulpes vulpes) naturally infected with canine distemper virus (CDV) were examined. After exclusion of animals positive for rabies using direct immunofluorescence test, red foxes' blood serum samples were examined using enzyme-linked immunosorbent assay to detect CDV antibodies. Gross and microscopic examinations of samples of serologically positive animals were performed. The viral antigen expression and distribution in the brain of affected animals were revealed immunohistochemically, as well as the nature of perivascular inflammatory infiltrate. The degree of demyelination was visualized using luxol fast blue staining. Molecular studies were performed to detect the presence of viral RNA. Patomorphological changes were statistically evaluated. Animals positive for rabies were not detected. Presence of CDV antibodies was detected in 36.8% of examined animals with no link between the antibody titer and the amount of pathological changes. Although no gross changes were observed, numerous changes consistent with non-purulent panencephalitis and demyelinating leukoencephalitis were evident microscopically. Immunohistochemical staining revealed moderate to strong positive reaction against viral nucleoprotein (CDV-NP), as well as the presence of T cells in the perivascular inflammatory infiltrate. Demyelination was the most pronounced in the cerebellar white matter. Using the molecular method (RT-PCR) viral RNA was not detected. Statistical evaluation, comparing the mean values of histopathological changes, showed a significant difference between various brain segments.

U ovoj doktorskoj disertaciji ispitivani su uzorci mozga crvenih lisica (Vulpes vulpes) prirodno inficiranih virusom štenećaka. Nakon isključivanja životinja pozitivnih na besnilo metodom direktne imunofluorescencije, vršena su ispitivanja uzoraka seruma crvenih lisica imunoenzimskom metodom u cilju utvrđivanja prisustva antitela protiv virusa štenećaka. Rađena su makroskopska i mikroskopska ispitivanja uzoraka mozga serološki pozitivnih jedinki. Ekspresija i distribucija virusnog antigena u mozgu inficiranih lisica utvrđena je imunohistohemijski, kao i ispitivanje prirode inflamatornog ćelijskog infiltrata. Histohemijskim bojenjem LFB metodom određen je stepen demijelinizacije bele moždane mase. Molekularno-genetička ispitivanja korišćena su za dokazivanje virusne RNK. Izvršena je statistička obrada rezultata utvrđenih patomorfoloških promena. Nije utvrđeno prisustvo jedinki pozitivnih na besnilo. Prisustvo antitela utvrđeno je kod 36,8% životinja i nije utvrđen uticaj visine titra antitela na izraženost patomorfoloških promena. Iako nisu utvrđene makroskopske promene, mikroskopski su se uočavale brojne promene u tipu negnojnog panencefalitisa i demijelinizujućeg leukoencefalitisa. Imunohistohemijski, utvrđena je pozitivna reakcija umerenog do jakog intenziteta protiv virusnog nukleoproteina (CDV-NP), kao i prisustvo T ćelija u perivaskularnom infiltratu. Demijelinizacija je bila najizraženija u beloj masi malog mozga. Upotrebom molekularno-genetičke metode (RT-PCR) nije utvrđeno prisustvo virusne RNK. Poređenjem srednjih vrednosti histopatoloških promena statističkom obradom podataka utvrđena je signifikantna razlika između pojedinih segmenata mozga.