Comparative study of two Rift Valley fever virus field strains originating from Mauritania

Area of Science:

• Virology
• Epidemiology
• Molecular Biology

Background:

• Rift Valley fever (RVF) is a significant arthropod-borne viral disease in Africa.
• Recent Rift Valley fever virus (RVFV) outbreaks in West Africa, particularly in Mauritania and Senegal, have impacted human and animal health.
• Specific outbreaks in Mauritania in 2010 and 2013-2014 prompted investigations into circulating RVFV strains.

Purpose of the Study:

• To characterize two RVFV field strains isolated from dromedary camels and goats during Mauritanian outbreaks in 2010 and 2013-2014.
• To compare the genetic makeup, replication efficiency, and virulence of these field strains against a reference strain.
• To identify potential viral determinants influencing RVFV replication and virulence.

Main Methods:

• Isolation and deep sequencing of RVFV strains MRU25010-30 (camel, 2010) and MRU2687-3 (goat, 2013).
• Whole-genome sequencing of field strains and the reference strain ZH548.
• Phylogenetic analysis to determine genetic lineages.
• In vitro replication assays in cell culture models.
• In vivo virulence studies in BALB/c mice via subcutaneous and intranasal inoculation.

Main Results:

• Phylogenetic analysis revealed that the two field strains belong to distinct RVFV genetic lineages.
• RVFV strain MRU25010-30 demonstrated significantly higher replication efficiency in vitro compared to MRU2687-3 and ZH548.
• In vivo, MRU25010-30 exhibited greater virulence, causing rapid death in mice with high viral loads in the liver and serum.
• MRU2687-3 and ZH548 infections led to mouse death correlated with high viral loads in the brain.

Conclusions:

• The study successfully characterized two distinct RVFV strains from Mauritanian outbreaks.
• Significant differences in replication capacity and virulence were observed between the field strains and the reference strain.
• Findings provide a foundation for investigating molecular mechanisms underlying RVFV virulence and replication.