Caracterização molecular de rotavírus genotipo P[6] de origem humana em um foco de diarreia neonatal suína

AUTOR(ES)
DATA DE PUBLICAÇÃO

2010

RESUMO

Neonatal diarrhea is the major piglet health problem in swine production systems worldwide.In intensive production the porcine serogroup A rotaviruses (PoRV-A) are common cause of diarrhea in suckling and recently weaned piglets. The VP4 and VP7 proteins of the outer layer viral capsid of RV-A are relevant for immunity against rotavirus infection by inducing neutralizing antibodies. According to the antigenic and molecular characteristics of the genes that encode VP4 and VP7 proteins, the RV-A strains can be classified in genotypes P and G, respectively. In the modern swine production the main health management to control the PoRV-A infections is the sows vaccination. However, the diversity of G (VP7) and P (VP4) genotypes identified in wild-type PoRV-A strains can be responsible for vaccine failures. Despite of several P genotypes identified in PoRV-A strains, the P[6] genotype is considered important for the frequency and for the great antigenic diversity. So far, have been described 5 lineages (I-V) and 8 sublineages (Ia-If; Va-Vb) of P[6] genotype in RV-A strains of human and porcine origin. The present study was developed to detect P genotype (VP4 gene) in PoRV-A strains identified during an outbreak of diarrhea in piglets. The outbreak occurred in a pig farm located in the state of Santa Catarina, South area of Brazil that presented good management practices and regular vaccination against porcine rotaviruses. Were collected 80 fecal samples being 49 diarrheic and 31 with normal consistency (control group). Were evaluated 57 stool samples of suckling (≤ 3-week-old) and 23 of recently-weaned (4-weekold) piglets. PoRV-A diagnosis was carried out by silver-stained polyacrylamide gel electrophoresis and RT-PCR assay. Positive samples were genotyping by multiplex-nested- PCR with genotype-specific primers and four PoRV-A strains were sequenced to define the molecular epidemiology of the infection. During this study were identified 22 (27.5%) PoRVA positive stool samples of which 16 (72.7%) were from symptomatic and 6 (27.3%) from asymptomatic piglets. PoRV-A was detected in fecal samples either from suckling as weaned piglets. In all the 20 wild-type PoRV-A strains included in this study were only amplified a PCR products with 267 bp length that belong to the P[6] genotype present in RV-A strains of human origin (M37-like strains). The sequencing and phylogenetic analysis carried out in a 586 bp length product of the VP4 gene (VP8*) of four Brazilian wild-type PoRV-A strains allowed to classify two P[6] strains (BRA838/07-Po and BRA844/07-Po) as P[6]-Ie genotype and the other two P[6] strains (BRA843/07-Po and BRA898/07-Po) as P[6]-If genotype. The genotype sublineages P[6]-Ie and If were recently described in RV-A strains of human origin.This is the first description of P[6]-Ie and If genotypes in RV-A strains of porcine origin. These findings suggest that the neonatal diarrhea outbreak might have been resulted of interspecies transmission of RV-A. The regularly vaccination of the sows with a rotavirus commercial vaccine containing P[6] genotype of porcine origin (Gottfried strain) might have provide the disappearance of the genotype P[6]-II (Gottfried-like) of porcine origin and the selection of RV-A strains with VP4 gene described only in RV-A strains of human origin such as P[6]-Ie and If. Heterologous infections are described in rotavirus infections in human beings and in animals. Rotavirus vaccination fails can occur in RV-A infections with virus strains carrying P and/or G genotypes different from those presents in the vaccine. The neonatal diarrhea outbreak in a regularly vaccinated pig herd and the characterization of PoRV-A strains with atypical P genotypes described in this study highlight the importance of the epidemiological studies of human and animal rotaviruses.

ASSUNTO(S)

leitão (suíno) - doenças diarréia em suínos rotavírus virologia veterinária swine diseases diarrhea in swines

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