Genetic Diversity of Bovine Group A Rotavirus Strains Circulating in Korean Calves during 2014 and 2018

Abstract

The purpose of this study was to investigate annual changes in BoRVA strains by examining the VP4 and VP7 genes of rotaviruses in Korean calves. Between 2014 and 2018, 35 out of 138 samples of calf diarrhea feces collected nationwide were positive for BoRVA. Further genetic characterization of the VP7 and VP4 genes of 35 BoRVA isolates identified three different G-genotypes (G6, G8, and G10) and two different P genotypes (P[5] and P[11]). The G6 genotype was most common (94.3%) in BoRVA-positive calves, followed by the P[5] genotype (82.9%). Four genotypes comprised combinations of VP4 and VP7: 80% were G6P[5], 14.2% were G6P[11], 2.9% were G8P[5], and 2.9% were G10P[11]. Susceptibility to infection was highest in calves aged < 10 days (35%) and lowest in calves aged 30–50 days (15.4%). The data presented herein suggest that the G6P[5] genotype is the main causative agent of diarrhea in Korean calves. In addition, it is predicted that G6P[5] will continue to act as a major cause of diarrhea in Korean calves.

Phylogenetic Analysis of G and P Genotypes of Bovine Group A Rotavirus Strains Isolated from Diarrheic Vietnam Cows in 2017 and 2018

“…For example, BoRVAs circulated widely among dairy calves in 2018, with G6P [1] being the dominant genotype in China [7]. A recent study from South Korea suggests that the G6P [5] genotype circulating among calves was most prevalent between 2014 and 2022 [8,22]. In Japan, BoRVAs circulating from 2018 to 2020 were predominantly G10P [11] (41.8%), with other genotypes (G6P [11], G6P [5], G6P [1], G8P [11], and G8P [1]) being detected at low rates [9].…”

“…In Japan, China, and Korea, there have been changes in the prevalence of dominant Gand P-genotype combinations [7,9,[22][23][24][25]. The predominant genotype of Japanese BoRVAs changed from G6P [5] to G10P [11] [9,26], that of Chinese BoRVAs changed from G6P [5] to G6P [1] [7,24,25], and that of Korean BoRVAs changed from G8P [7] to G6P [5] [22,23].…”

“…In Japan, China, and Korea, there have been changes in the prevalence of dominant Gand P-genotype combinations [7,9,[22][23][24][25]. The predominant genotype of Japanese BoRVAs changed from G6P [5] to G10P [11] [9,26], that of Chinese BoRVAs changed from G6P [5] to G6P [1] [7,24,25], and that of Korean BoRVAs changed from G8P [7] to G6P [5] [22,23]. Unfortunately, because the present study is the first to investigate the genetics of BoRVA VP7 and VP4 genes in Vietnam, our data cannot be compared with those from past studies of Vietnamese BoRVAs.…”

“…In particular, BoRVA infection is estimated to affect 27-36% of newborn calves [32], and, in some cases, BoRVA infection of newborn calves has a mortality rate of up to 80%; however, the mortality rate is usually around 5-20% [37]. Other studies from South Korea suggest that BoRVAs are an important cause of diarrhea in young calves (aged < 10 days) [8,22]. We found that the incidence of BoRVA infection in Vietnamese calves aged less than 2 months was twice that in adult cows; however, the prevalence of BoRVAs across 8 Vietnamese regions was 1.9%, which is very low when compared with data from other countries.…”