Comparative Pathology of Domestic Pigs and Wild Boar Infected with the Moderately Virulent African Swine Fever Virus Strain “Estonia 2014”

Abstract

Endemically infected European wild boar are considered a major reservoir of African swine fever virus in Europe. While high lethality was observed in the majority of field cases, strains of moderate virulence occurred in the Baltic States. One of these, “Estonia 2014”, led to a higher number of clinically healthy, antibody-positive animals in the hunting bag of North-Eastern Estonia. Experimental characterization showed high virulence in wild boar but moderate virulence in domestic pigs. Putative pathogenic differences between wild boar and domestic pigs are unresolved and comparative pathological studies are limited. We here report on a kinetic experiment in both subspecies. Three animals each were euthanized at 4, 7 and 10 days post infection (dpi). Clinical data confirmed higher virulence in wild boar although macroscopy and viral genome load in blood and tissues were comparable in both subspecies. The percentage of viral antigen positive myeloid cells tested by flow cytometry did not differ significantly in most tissues. Only immunohistochemistry revealed consistently higher viral antigen loads in wild boar tissues in particular 7 dpi, whereas domestic pigs already eliminated the virus. The moderate virulence in domestic pigs could be explained by a more effective viral clearance.

The Male Reproductive Organs in African Swine Fever–Implications for Transmission

“…In line with our previous studies [6,9], and irrespective of the virus strain or host type involved, ASF viral genome and infectious virus were detected in all organs of the male reproductive tract and in epididymal sperm.…”

“…Upon termination of the study, the animals were sacrificed by exsanguination in deep anesthesia with a combination of tiletamine/ zolazepam (Zoletil®, Virbac), xylazine (Xylazin 20 mg/ml, medistar), and ketamine (Ketamin 100 mg/ml, cp-pharma). Subsequently, all animals were subjected to a full necropsy and macroscopic findings were assessed following the protocol by Galindo-Cardiel [8] with slight modifications [9]. Blood as well as the following tissues were sampled for subsequent investigations and reference material acquisition: spleen, lung, lymph nodes, liver, kidney, skin, tonsil, testis, epididymis, epididymal sperm, vesicular gland, bulbourethral gland, and prostate.…”

“…Viral antigen detection was performed following the protocol published recently [9] using an in-house rabbit polyclonal primary antibody against the major capsid protein p72 of ASFV. Cells were evaluated positive when showing a fine granular cytoplasmic signal.…”

“…Pathomorphological changes were assessed on hematoxylin and eosin stained tissue sections following a standard protocol as described earlier [9]. Pathohistological changes scored on a 0-3 scale (normal (0), mild (1), moderate (2), severe (3)) are shown in Table 1.…”

Dynamic Variations in Infrared Skin Temperature of Weaned Pigs Experimentally Inoculated with the African Swine Fever Virus: A Pilot Study

“…African swine fever (ASF) is a fatal disease causing serious economic losses in the pig industry [ 7 ]. Previous studies revealed that the incubation period of the African swine fever virus (ASFV) was approximately 3–5 days, and infected pigs died within 7–13 days post inoculation (dpi) [ 8 , 9 , 10 , 11 ]. Due to the short incubation period and immediate death, ASFV gives a short window for the disease to be reported by pig farms [ 8 ].…”