Reduced virulence of a pseudorabies virus isolate from wild boar origin in domestic pigs correlates with hampered visceral spread and age-dependent reduced neuroinvasive capacity

Abstract

Morbidity and mortality associated with pseudorabies virus (PRV) infection are dependent on the age of the pig and the virulence of the strain. PRV strains circulating in wild boar are considered to be low virulent, but no mechanistic explanation for their reduced virulence is available. Here infection of 2- and 15-week-old domestic pigs with the PRV wild boar strain BEL24043 did not induce clinical symptoms in 15-week-old pigs, but resulted in important neurological and respiratory disease in 2-week-old piglets. A detailed study of the (neuro) pathogenesis and associated cytokine mRNA expression showed that the reduced virulence of the wild boar strain, compared to what was previously reported for the virulent domestic NIA3 strain, is due to a severely hampered spread to visceral organs in pigs of both age categories and to an efficient suppression of viral replication at primary replication sites of 15-week-old pigs and to a lesser extent in those of 2-week-old piglets. The age-dependent difference in induced symptoms seems to be due to an immature development state of the immune and/or nervous system in 2-week-old pigs. An extensive viral replication associated with a robust expression of cytokine-related mRNA was found in the olfactory bulb of 2-week-old piglets, correlating with observed neurological disease. Neuroinvasion also occurred via the trigeminal route in 2-week-old pigs, but viral replication was efficiently suppressed in the trigeminal ganglion in the presence of a moderate induction of cytokine-related mRNA. Viral replication in the peripheral and central nervous system of 15-week-old pigs was limited and efficiently suppressed.

Pathologic changes in pig organs, infected with the Aujeszkys disease

“…(Guan et al, 2018;Sorooshyari et al, 2018), this is due to the fact that the virus rarely penetrate the blood-brain barrier (Miller et al, 2019). Because of that clinical symptoms indicating severe damage to the nervous system and itching were usually not observed (Verpoest et al, 2018). Scientists who are studying Aujeszky's disease have described in detail the pathological and anatomical changes during the course of this disease in pigs (Caruso et al, 2018;Wu et al, 2018;Zhao et al, 1996), but there is little data on microscopic changes of internal organs of suckling piglets that died from Aujeszky's disease, therefore we studied microscopic changes in the lungs, Ukrainian Journal of Ecology, 10(5), 2020 stomach, intestines, liver, pancreas, kidneys, thymus, lymph nodes, spleen, brain and spinal cord of sucking piglets that died from Aujeszky's disease.…”

Effects of Intranasal Pseudorabies Virus AH02LA Infection on Microbial Community and Immune Status in the Ileum and Colon of Piglets

“…Infected pigs, particularly weaning and starter piglets showed various clinical symptoms, including high fever, respiratory distress, systemic neurological symptoms, and diarrhea [3,4,5]. Previous studies have shown that respiratory and neurological symptoms induced by intranasal PRV infection are related to extensive viral replication and immune response in the respiratory tract and the central nervous system of piglets [6,7]. However, it is not known whether direct infection of the intestine with PRV leads to diarrhea.…”

Latent pseudorabies virus infection in medulla oblongata from quarantined pigs

“…

Pseudorabies virus (PRV; also known as Aujeszky's disease virus), a member of the family Herpesviridae, can cause severe respiratory, reproductive and neurological symptoms in pigs. Although it has been eradicated in domesticated pigs in North America, it is still a major pathogen for pig husbandry in many other countries and has caused huge economic losses around the world (Verpoest, Redant, Cay, Favoreel, & De Regge, 2018). As a typical α-herpesvirus, PRV is often used as a research tool or model for gene therapy and tumour therapy, as well as neuronal circuit tracing (Tombácz et al, 2018).

…”