Molecular prevalence of equine parvovirus hepatitis in healthy horses from the Northern region of the state of Rio Grande do Sul, Brazil.

Overview

• This study investigated the presence of equine parvovirus hepatitis (EqPV-H) in healthy horses from the northern region of Rio Grande do Sul, Brazil.
• Researchers found that EqPV-H is common among these horses and identified genetic similarities and some regional differences in virus strains compared to those found in other countries.

Background

• Equine parvovirus hepatitis (EqPV-H) was first linked to fatal cases of equine serum hepatitis, a serious liver disease in horses.
• More recently, EqPV-H has been detected in both sick and asymptomatic horses worldwide, including a few cases reported in southeastern Brazil.
• Despite knowledge of the virus’s presence, its spread and genetic diversity in southern Brazil had not been extensively studied prior to this research.

Study Objective

• The goal was to determine the molecular prevalence (presence of viral DNA) of EqPV-H in healthy horses from the northern region of Rio Grande do Sul state.
• Researchers also aimed to analyze the genetic characteristics of the virus strains found in this region.

Methodology

• Sample Collection:
  • 1000 serum samples were collected from healthy horses across 40 different municipalities in the target region.
  • Samples were grouped into 200 pools, each containing five samples, organized according to the horse’s origin and age to optimize testing.
• Viral Detection:
  • A nested polymerase chain reaction (nPCR) technique was used to detect EqPV-H DNA in serum pools.
  • This method is sensitive for detecting low amounts of viral DNA.
• Genetic and Phylogenetic Analysis:
  • Partial NS1 gene sequences from five positive serum pools were analyzed to assess genetic similarities and differences.
  • Comparisons were made to worldwide EqPV-H isolates to understand genetic conservation and regional specificity.

Results

• Prevalence:
  • EqPV-H DNA was found in 69 pooled samples, representing 34.5% of all pools tested.
  • Positive cases were identified in 26 out of 40 municipalities, indicating wide distribution (65%).
  • No significant difference in viral prevalence was observed across different age groups (p = 0.52), suggesting infection is widespread regardless of age.
• Genetic Findings:
  • Partial NS1 sequences showed strong genetic conservation among the viruses found, similar to strains identified worldwide.
  • However, specific nucleotide variations were detected in strains from Brazil and Argentina that were not present in strains from other countries, suggesting regional genetic diversity.

Conclusions

• This study provides the first comprehensive evidence that EqPV-H is widespread among healthy horses in the northern Rio Grande do Sul region.
• The presence of the virus in asymptomatic horses indicates it may be circulating silently in the horse population.
• Given the potential link between EqPV-H and clinical hepatitis cases, this virus should be considered in the diagnosis of liver disease in horses.
• The identification of region-specific genetic variations may inform future research on viral evolution and epidemiology in South America.

Implications and Future Directions

• Veterinarians and horse owners in the region should be aware of EqPV-H infection risk even in apparently healthy animals.
• Further studies are needed to understand the clinical impact of EqPV-H in the local equine population, including potential transmission pathways.
• Expanded surveillance and genetic sequencing can help track virus evolution and spread within Brazil and neighboring countries.
• Development of diagnostic protocols and preventive measures may improve equine health management related to hepatitis-associated viruses.