Two novel porcine teschovirus strains as the causative agents of encephalomyelitis in the Netherlands

Abstract

Background: Porcine teschovirus (PTV) circulates among wild and domesticated pig populations without causing clinical disease, however neuroinvasive strains have caused high morbidity and mortality in the past. In recent years, several reports appeared with viral agents as a cause for neurologic signs in weanling and growing pigs among which PTV and new strains of PTV were described.

Case presentation: On two unrelated pig farms in the Netherlands the weanling pig population showed a staggering gate, which developed progressively to paresis or paralysis of the hind legs with a morbidity up to 5%. After necropsy we diagnosed a non-suppurative encephalomyelitis on both farms, which was most consistent with a viral infection. PTV was detected within the central nervous system by qPCR. From both farms PTV full-length genomes were sequenced, which clustered closely with PTV-3 (98%) or PTV-11 (85%). Other common swine viruses were excluded by qPCR and sequencing of the virus.

Conclusion: Our results show that new neuroinvasive PTV strains still emerge in pigs in the Netherlands. Further research is needed to investigate the impact of PTV and other viral agents causing encephalomyelitis within wild and domestic pig populations supported by the awareness of veterinarians.

Keywords: Non-suppurative encephalomyelitis; Porcine teschovirus; Weanling pigs.

Fig. 1

Sections of the central nervous system and trigeminal ganglion. Tissue sections from one animal from farm A stained with hematoxylin and eosin (H&E). a Trigeminal ganglion with infiltration of a large number of macrophages and lymphocytes (asterisk) (Bar = 100 μm); (b) Proximal spinal cord (gray matter) with perivascular infiltrates (perivascular cuffing; arrow) of mainly macrophages, lymphocytes and a lesser number of plasma cells, extending into the neuropil (Bar = 200 μm); (c) Cerebrum (gray matter) with perivascular cuffing, gliosis and neuronal degeneration and necrosis (arrow) (Bar = 100 μm); (d) Cerebellum with infiltration of a large number of lymphocytes and macrophages into the meninges (asterisk), and perivascular cuffing in the parenchyma (arrow) (Bar = 200 μm)

Fig. 2

The maximum likelihood (ML) phylogeny of Porcine teschovirus (PTV) VP1. The gene of the three isolates (red and blue) and 40 references sequences with bootstrap values. The 40 reference sequences are labeled by name, GenBank accession number and serotype. The three PTV strains of interest are colored blue (PTV_strain_GD_v06) and red (PTV_WBVR_197_v01 and 199)