Molecular characterization of equine rotaviruses circulating in Argentinean foals during a 17-year surveillance period (1992-2008).

This research study investigated the types and evolution of equine rotaviruses (ERVs) present in foal populations in Argentina over a 17-year period (1992-2008) for a better understanding of the incidence and distribution of different ERV strains and their implications on vaccine design.

Objective and Methodology

• The intention of the study was to track and compare data on ERV strains in foals in Argentina throughout a lengthy time frame. This would allow for a more comprehensive understanding of ERV epidemiology in the area.
• The specific genes of these ERVs (VP7, VP4, NSP4) were analysed to determine their sequences and to perform phylogenetic analyses. These are essentially genetic studies to classify and understand the relationships between different strains of ERVs.
• In this case, foal stool samples were monitored for the presence of ERVs and these viruses were then characterised by their G (glycoprotein) and P (protease-sensitive protein) type, two key molecular types in rotaviruses.

Findings

• Out of 771 diarrheic stool samples, ERVs were found in 21% of them, which corresponded to almost 39% of the 116 outbreaks on the surveyed thoroughbred horse farms.
• Of the positive cases, the breakdown of G types was as follows: 51% were G3, 33% were G14, 4% had a mixed G3 and G14 infection, and 11% of the cases could not be categorized.
• Throughout the 17 years of the study, the G3 ERV was identified consistently, while G14 ERVs were first detected in 2000 and increasingly became more common, especially in 2006 and 2007.
• Moreover, all analyzed strains belonged to the P[12] genotype except for one G3 case which belonged to the P[3] genotype. This was the first reported instance of a P[3]G3 ERV strain.

Phylogenetic Analysis and Implications

• The genetic sequences of the ERVs were studied to understand their evolutionary relationships. The G3 Argentinean ERV strains were similar to ERVs from Ireland, while the G14 Argentinean ERV strains formed a distinct cluster, grouped within the G14 genotype.
• Furthermore, the VP4 gene (part of the P[12] genotype) in the ERV strains shared similarities with strains from Ireland and France.
• The study also found that the NSP4 gene, of the E12 genotype, in Argentinean ERVs, was closely related to those in guanaco and bovine strains in Argentina, suggesting a close evolutionary relationship.
• The increase in the frequency of G14 ERV, which is not included in currently available vaccines, may necessitate a change in vaccine design for better protection against ERVs in future.