Molecular epidemiology and characterization of porcine adenoviruses in pigs with diarrhea in Thailand.

Pigs have been assumed as a source of human viral infections. Surveillance of viruses in animals is essential to evaluate the risk to human and animal health and to determine economic impact. A number of studies focused mainly on well- known enteritis viruses such as porcine epidemic diarrhea virus (PEDV), transmissible gastroenteritis virus (TGEV), and porcine group A rotavirus (PRVA), however, little data is available for porcine adenovirus (PAdV). In this study, the presence of PAdV was investigated in fecal samples collected from piglets with and without diarrhea from 31 commercial pig farms in northern Thailand. A total of 781 fecal specimens (516 from diarrheic piglets and 265 from non-diarrheic piglets) were screened for adenovirus using nested-PCR. Initial screening both in diarrheic and non-diarrheic piglets showed the overall prevalence of PAdV infection in piglets at 16.9% (132/781). Co-infection with PRVA was found in 24 out of 132 (18.2%) PAdV positive cases whereas PAdV mono-infection was observed at 81.8% (108/132). The prevalence of PAdV infection in diarrheic piglets (24.2%, 102/516) was significantly higher than those detected in non-diarrheic piglets (2.6%, 7/265). Most of PAdV detected in this study (97%, 128/132) were genotype 3 while the other 4 PAdV positive samples were non identifiable genotype. Phylogenetic analysis revealed that the viruses detected in diarrheic and non-diarrheic piglets displayed a closely related (95.4 to 100%) nucleotide sequence identity. To our knowledge, this is the first report on the epidemiology and molecular characterization of PAdV in piglets in Thailand.

Detection and genetic characterization of porcine astroviruses in piglets with and without diarrhea in Thailand.

Porcine astrovirus (PAstV) is widely distributed and highly prevalent among pigs, nevertheless its clinical significance remains unclear as it can be detected in both diarrheic and in healthy pigs. Information about the prevalence, clinical significance and molecular characterization of PAstV in Thailand is not available. This study investigated the prevalence of PAstV in 488 fecal samples collected from piglets with and without diarrhea in 28 pig farms in northern and central parts of Thailand using RT-PCR. The overall prevalence of PAstV infection was 6.5% (32/488), of which 21/251 (8.4%) were in diarrheic and 11/237 (4.6%) were in healthy pigs. Of 32 positive samples, 46.9% were positive for PAstV alone whereas 53.1% were co-infected with porcine group A rotavirus (PRVA). A phylogenetic analysis of the partial RNA-dependent RNA polymerase/capsid genes revealed two lineages of PAstV strains detected in this study. PAstV4 was the most dominant genotype (92%), followed by PAstV2 (8%). This study revealed for the first time that PAstV4 and PAstV2 were circulating in Thailand with PAstV4 as the most dominant genotype in pig herds in northern and central parts of Thailand.

Detection and molecular characterization of porcine kobuvirus in piglets in 2009-2013 in northern Thailand.

A total of 636 fecal samples collected from piglets with and without diarrhea during 2009 to 2013 were tested for porcine kobuvirus by RT-PCR. From a total of 528 fecal samples collected from piglets with diarrhea and 108 from healthy controls, 505 (95.6%) and 104 (96.3%) were positive for porcine kobuvirus, respectively. The detection rates of porcine kobuvirus were remarkable equally high in both diarrheic and healthy piglets. Phylogenetic analysis revealed that porcine kobuvirus strains detected in both symptomatic and asymptomatic piglets were genetically closely related to each other and also to other porcine kobuviruses reported worldwide. It was interesting to point out that one of the porcine kobuvirus strains isolated from piglet in our study was similar to a porcine-like bovine kobuvirus reference strain isolated previously in South Korea. This finding provided the evidence to support the interspecies transmission of kobuviruses between cattle and swine.

Analysis of complete genome sequences of G9P[19] rotavirus strains from human and piglet with diarrhea provides evidence for whole-genome interspecies transmission of nonreassorted porcine rotavirus.

Whole genomes of G9P[19] human (RVA/Human-wt/THA/CMH-S070-13/2013/G9P[19]) and porcine (RVA/Pig-wt/THA/CMP-015-12/2012/G9P[19]) rotaviruses concurrently detected in the same geographical area in northern Thailand were sequenced and analyzed for their genetic relationships using bioinformatic tools. The complete genome sequence of human rotavirus RVA/Human-wt/THA/CMH-S070-13/2013/G9P[19] was most closely related to those of porcine rotavirus RVA/Pig-wt/THA/CMP-015-12/2012/G9P[19] and to those of porcine-like human and porcine rotaviruses reference strains than to those of human rotavirus reference strains. The genotype constellation of G9P[19] detected in human and piglet were identical and displayed as the G9-P[19]-I5-R1-C1-M1-A8-N1-T1-E1-H1 genotypes with the nucleotide sequence identities of VP7, VP4, VP6, VP1, VP2, VP3, NSP1, NSP2, NSP3, NSP4, and NSP5 at 99.0%, 99.5%, 93.2%, 97.7%, 97.7%, 85.6%, 89.5%, 93.2%, 92.9%, 94.0%, and 98.1%, respectively. The findings indicate that human rotavirus strain RVA/Human-wt/THA/CMH-S070-13/2013/G9P[19] containing the genome segments of porcine genetic backbone is most likely a human rotavirus of porcine origin. Our data provide an evidence of interspecies transmission and whole-genome transmission of nonreassorted G9P[19] porcine RVA to human occurring in nature in northern Thailand.

Great genetic diversity of rotaviruses detected in piglets with diarrhea in Thailand.

A total of 491 fecal specimens collected from diarrheic piglets in Thailand from January 2011 to March 2014 were screened for group A rotavirus by RT-PCR assay. The G and P genotypes of the detected rotaviruses were determined by multiplex PCR or nucleotide sequencing. Group A rotaviruses were detected in 113 out of 491 (23.0 %) fecal specimens. A wide variety of G-P genotype combinations were identified, and G4P[13] was the most prevalent genotype combination (29.2 %), followed by G4P[23] (14.1 %), G5P[23] (11.5 %), G4P[6] (9.7 %), G3P[23] (7.0 %), G5P[13] (6.1 %), G3P[13] (4.4 %), G3P[6] (2.7 %), and G5P[6] (2.7 %). In addition, the other G-P combinations were also detected at a low percentage, including G3P[19], G4P[7], G9P[19], G9P[23], G9P[7], G4P[19], and G11P[13] strains. This study indicated that group A rotaviruses are a common causes of diarrhea in piglets and a great diversity of G and P genotype combinations are circulating in piglets in Thailand.