ABSTRACT
The term wasting refers to a clinical sign used to describe a physical condition characterized by growth retardation, usually of multifactorial origin. The objective of the present study was to describe for the first time a pathological process characterized by forebrain neuropil vacuolization in pigs showing wasting without conspicuous neurological signs. To characterize the lesions pathologically, affected and non-affected pigs from eight of these farms were investigated. Histologically, the most consistent lesion was neuropil vacuolization of the prosencephalon, mainly located in the thalamic nuclei and in the transition between the white and grey matter of the neocortex (40/56 in sick and 4/30 in healthy pigs). In the most severe cases, the vacuolation also involved the midbrain, cerebellar nuclei and, to a lesser extent, the medulla oblongata. Vacuolization of the forebrain was associated with pigs experiencing marked emaciation and growth retardation. Although the specific cause of the present case remained unknown, the preventive use of multivitamin and mineral complexes in drinking water ameliorated the condition, strongly suggesting a metabolic origin of the observed condition.
ABSTRACT
This study aimed to provide information regarding viral pathogenesis and molecular epidemiology linked with recently reported atypical porcine pestivirus (APPV) strains and to determine the circulation of APPV in Spain from 1997 to 2016. Two-day-old piglets with moderate-severe congenital tremor (CT) from a Spanish farm were received for diagnostic purposes. Sera, nasal and rectal swabs and tissue samples were collected. qRT-PCR was performed in these samples, and a retrospective study to detect APPV RNA was carried out using a serum collection from 1997 to 2016. APPV genome was identified with high and moderate RNA loads in different tissues of the CT affected pigs. High APPV RNA load was detected in lymphoid organs, suggesting that these constitute a target for APPV replication. In 89 of the 642 retrospectively analysed samples (13.9%), APPV genome was detected. CT cases were related to the presence of APPV in viraemic piglets below 1 week of age, in which the viral RNA load was the highest. A considerable number of animals between 4 and 14 weeks of age and some 1-week-old piglets were viraemic in the absence of CT, which can act as carriers of the virus. The relative risk of APPV and CT was 8.5 (CI 95% 5.8-12.5). Thus, our data show that APPV infection is epidemiologically related to CT. Phylogenetic analysis from 1615 NS2-3 nucleotides showed only one defined APPV clade, grouping the most phylogenetically related strains from Europe and China. Of this clade, there are other strains from Europe, USA and China. This data confirm the high APPV genetic diversity, not being able to cluster this virus according to the geographic area. Our result showed that APPV has been circulating in Spain at least since 1997, being the earliest date of detection of this virus worldwide and suggesting that APPV may be widespread.
