Molecular Characterization and Zoonotic Potential Analysis of Rotaviruses Detected in Pediatric Patients and Piglets with Acute Gastroenteritis

Abstract

Rotaviruses are the major cause of severe acute gastroenteritis in infants, young children, and in young animals of many species, especially in pigs. Close contact between humans and pigs may facilitate interspecies transmission and genetic reassortment during co-infection in the same cell and result in the generation of novel progeny virus strains. Moreover, several epidemiological studies revealed the increasing detections of porcine-human group A rotavirus reassortant strains. These findings indicate that interspecies transmission among humans and porcine rotaviruses may have been occurred in nature. The objectives of the present study aimed to assess the prevalence and to perform molecular characterization of human and porcine rotaviruses with diarrhea. After that, the human rotavirus strains detected were analyzed for their genetic relationships with porcine rotaviruses in order to elucidate the possibility of interspecies transmission and reassortment of these viruses circulating in Chiang Mai and Lamphun provinces. A total of 401 stool specimens were collected from children hospitalized with diarrhea in Chiang Mai, Thailand during January 2013 through February 2014. In addition, 491 stool samples were collected from diarrheic piglets in several pig farms in Chiang Mai and Lamphun provinces during January 2011 to March 2014. All stool samples were screened for group A rotavirus by reverse transcription-polymerase chain reaction (RT-PCR). The detected group A rotaviruses were identified for their G and P genotypes by multiplex PCR method using genotype-specific primers or nucleotide sequencing. The sequences were analyzed for the genetic relationship between human and porcine rotaviruses by phylogenetic analysis. Group A rotaviruses were detected in 137 out of 401 (34.2%) and 113 out of 491 (23.0%) stool specimens collected from children hospitalized with diarrhea and diarrheic piglets, respectively. The identification of rotavirus genotypes revealed wide variety of G-P genotype combinations. For human rotaviruses, G3P[8] was the most predominant genotype (49.6%), followed by G1P[8] (23.4%), G2P[4] (13.9%), G1P[4] (4.4%), G8P[8] (2.9%), G2P[8] and G9P[8] (each of 2.2%), and mix-infection of G3 in combination with P[8] and P[4] (0.7%). Interestingly, the uncommon strain of human rotavirus G9P[19], was detected in a child with diarrhea in this study. For porcine rotaviruses, G4P[13] was the most prevalent genotype (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] and G5P[6] (each of 2.7%). In addition, the other G-P combinations were detected at less than 2.0% in each of the following G-P combination, including G3P[19], G4P[7], G9P[19], G9P[23], G9P[7], G4P[19], and G11P[13] strains. However, G4 and G11 in combination with P nontypeable strains were also detected at each of 0.9%. The genetic sequence analysis of VP7 and VP4 genes of G9P[19] rotavirus demonstrated that the virus isolated from human was more closely related to the porcine rotavirus than to human rotaviruses detected in the same study. It was interesting to point out that additional full-length nucleotide sequence analysis of VP7, VP4, VP6, NSP4, and NSP5 genes of those G9P[19] rotavirus strains revealed high nucleotide sequence identity of those genes between human and porcine rotavirus strains detected in the same study period. The genotype constellation of G (VP7), P (VP4), I (VP6), E (NSP4), and H (NSP5) genotypes by nucleotide sequence analysis of these G9P[19] strains were assigned as the G9-P[19]-I5-E1-H1 genotypes for both human and piglet rotavirus isolates. The finding implies that interspecies transmission among human and porcine rotaviruses could be occurred in nature.

In conclusion, the present study provides valuable epidemiological information and molecular characteristics of rotavirus strains circulating in pediatric patients and in piglets with acute gastroenteritis in Chiang Mai and Lamphun provinces. In addition, the evidence of interspecies transmission and reassortment events between rotaviruses of human and pig origins were occurred in nature.