Atypical Porcine Pestivirus (APPV) as a New Species of Pestivirus in Pig Production

Abstract

The genus Pestivirus , which belongs to the family Flaviviridae , includes ssRNA+ viruses responsible for infectious diseases in swine, cattle, sheep, goats, and other domestic and wild animals. Recently, several putative pestiviruses species have been discovered and characterized in mammalian species (giraffe pestivirus, antelope pestivirus, HoBi virus, Bungowannah virus, and Linda virus); one of these is a genetically distinct pestivirus, named atypical porcine pestivirus (APPV), discovered using the next-generation sequencing technology. APPV has been detected in piglets with congenital tremor (CT) from four different continents, including North America, South America, Europe, and Asia. There is strong evidence that experimental inoculation and in field outbreaks involving APPV induce CT in piglets. Additionally, splay leg (SL) syndrome has been observed concurrently with CT, and it was induced by APPV in experimental studies and some field cases. Animals with a persistent and/or chronic infection condition can shed the virus over time. Viral-RNA is frequently detected in different tissues from CT-piglets; however, high loads of APPV are detected most consistently in central nervous tissue. Moreover, the APPV genome has been recently detected in semen and preputial swabs from boar studs, as well as in serum and tissue samples from wild boars and domestic adult pigs, all known to be clinically healthy. Phylogenetic analysis revealed that the APPV sequence (complete or partial polyprotein) exhibits high genetic diversity between viral strains detected in different countries and formed independent clusters according to geographic location. Additional studies are needed to evaluate the molecular detection and sero-prevalence of APPV around the world. Lastly, more research is needed to understand clinical presentations associated with APPV infection, as well as the economic losses related to the virus in pig production worldwide.

Seroprevalences of Newly Discovered Porcine Pestiviruses in German Pig Farms

“…However, in contrast to the generally comparable results of the two time periods, results on state level are quite diverse, which might be related to the described wave-like outbreaks of CT type II [20]. Since there is still only limited information available about the route of transmission, infection dynamics, spread, and pathogenesis of APPV [33] the reason for this certain outbreak pattern remains unknown.…”

Evolution and genetic diversity of atypical porcine pestivirus (APPV) from piglets with congenital tremor in Guangxi province, Southern China

“…Sequence analysis revealed that six APPV strains from Guangxi province shared 83. 3 among the APPV isolates, and shared 88.2% nucleotide identity with the APPV sequences from USA [6,33]. The genomic sequence of APPVs from Austria shared 90% nucleotide identity with those from USA and 92% nucleotide identity with those from Germany [7].…”

“…CT in newborn piglets was first reported in 1922, but the causative agent has always been a mystery. Viral agents responsible for type A-Ⅱ CT had been seeking for decades until APPV was identified in USA and other countries in 2015 [3][4][5][6][7][8][9][10][11][12][13][14][15][16][17]. APPV have been detected in serum, thymus, peripheral lymphoid organs (spleen, tonsil, submaxillary lymph node and inguinal lymph node), nervous system (brain stem, brain, and cerebellum), digestive system (duodenum) and semen [1,8,29,30,31,32], which indicated that this virus has widespread tissue tropism.…”

“…sequencing (NGS) from clinical samples in the United States in 2015 [1]. Since then, the presence of APPV in new born piglets with congenital tremor (CT) has been reported in many countries worldwide [2,3], such as USA [4], the Netherlands [5], Germany [6], Austria [7], Spain [8], Brazil [9], Hungary [10], England [11], Canada [12], Sweden [13], China [14], Korea [15], Switzerland [16], Italy [17] and so on, showing that APPV has wide geographical distribution around the world. Two independent studies have been reported that congenital tremor (CT) was reproduced following experimental inoculation with serum or tissue-homogenate-pools containing APPV, demonstrating that APPV could be a very likely causative agent of CT in piglets [4,5].…”

Detection of Atypical porcine pestivirus in Swedish piglets with congenital tremor type A-II

“…Atypical porcine pestivirus is a ssRNA+ virus that belongs to the species Pestivirus K in the genus Pestivirus within the family Flaviviridae (9, 10). The genome of APPV is ~10.8-11.5 kb and up until now about 20 complete genomes have been published (11). Interestingly, the genetic variability of the APPV isolates is very high also within the same geographic region (6,12).…”