Rocio virus was isolated and fully sequenced for the first time from a clinical encephalitis case in a horse in Brazil after nearly 40 years, indicating sustained virus circulation and evolution.
Case Report (n=1)
No
The isolation and sequencing of Rocio virus from a horse with encephalitis confirms its sustained cryptic circulation in Brazil and highlights the potential of horses as sentinels for arbovirus surveillance.
Rocio virus (ROCV), a neurotropic arbovirus of the Orthoflavivirus genus, caused Brazil’s largest encephalitis outbreak in the 1970s but has since been rarely detected. We report the first ROCV encephalitis clinical case after nearly 40 years and isolated and sequenced the virus from CNS tissue of a horse. Metatranscriptomics enabled full-genome sequencing, revealing divergence from the reference sequence at an evolutionary rate of 5.8–7.0 × 10⁻⁴, consistent with Orthoflavivirus. Thirty-one non-synonymous substitutions were identified, with the envelope protein most affected. Findings indicate ROCV cryptic circulation and ongoing evolution. Horses may act as sentinels, underscoring the need for strengthened ROCV genomic surveillance.
Gräf et al. (Sat,) conducted a case report in A 5-year-old Quarter Horse mare in Paraná state, Brazil, presenting with neurological symptoms including hindlimb paralysis and seizures consistent with Rocio virus encephalitis (n=1). Virus isolation and metatranscriptomic sequencing of Rocio virus from CNS tissue was evaluated on Identification and full genome sequencing of Rocio virus from CNS tissue of an infected horse with neurological symptoms. Rocio virus was isolated and fully sequenced for the first time from a clinical encephalitis case in a horse in Brazil after nearly 40 years, indicating sustained virus circulation and evolution.