Abstract
Porcine circovirus 3 (PCV-3) is a recently described virus belonging to the family Circoviridae. It represents the third member of genus Circovirus able to infect swine, together with PCV-1, considered non-pathogenic, and PCV-2, one of the most economically relevant viruses for the swine worldwide industry. PCV-3 was originally found by metagenomics analyses in 2015 in tissues of pigs suffering from porcine dermatitis and nephropathy syndrome, reproductive failure, myocarditis and multisystemic inflammation. The lack of other common pathogens as potential infectious agents of these conditions prompted the suspicion that PCV-3 might etiologically be involved in disease occurrence. Subsequently, viral genome was detected in apparently healthy pigs, and retrospective studies indicated that PCV-3 was already present in pigs by early 1990s. In fact, current evidence suggests that PCV-3 is a rather widespread virus worldwide. Recently, the virus DNA has also been found in wild boar, expanding the scope of infection susceptibility among the Suidae family; also, the potential reservoir role of this species for the domestic pig has been proposed. Phylogenetic studies with available PCV-3 partial and complete sequences from around the world have revealed high nucleotide identity (>96%), although two main groups and several subclusters have been described as well. Moreover, it has been proposed the existence of a most common ancestor dated around 50 years ago. Taking into account the economic importance and the well-known effects of PCV-2 on the swine industry, a new member of the same family like PCV-3 should not be neglected. Studies on epidemiology, pathogenesis, immunity and diagnosis are guaranteed in the next few years. Therefore, the present review will update the current knowledge and future trends of research on PCV-3.
Highlights
The evolution of emerging diseases is associated with factors embedded in the concept “host-agent-environment triangle” [1]
Pathogenesis, immunity and diagnosis are guaranteed in the few years, but the scientific community is still in its very beginning on the knowledge of this new infectious agent
Viral DNA sequences retrieved from wild boar showed more than 98% similarity with the available sequences from domestic pigs [95, 96]
Summary
The evolution of emerging diseases is associated with factors embedded in the concept “host-agent-environment triangle” [1]. Genetic uniformity generated through genetic selection of the host [3] and the fact that demographic changes, intensification of farming, and international commerce have occurred markedly over the last decades, must be considered as essential factors for the development of emerging diseases [4,5,6]. Livestock production in large communities (i.e., pig farms or poultry flocks) represents an excellent environment to facilitate the transmission and maintenance of huge viral populations, contributing to the pathogen evolution (through mutation, recombination and reassortment, followed by natural selection) [7,8,9]. The intensification of livestock during the last four decades has probably been one of the main factors that contributed to the emergence of new pathogens and/or pathogen variants, leading to changes in the epidemiology and presentation of diseases [10]
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