Seroprevalence in Arbovirus and metagenomic characterization of Orbivirus in Sloths of Western Panama

Arthropod-borne viruses (arboviruses) pose a growing public health threat, particularly in tropical and subtropical regions, influenced by human activities, urbanization, and environmental factors. This study explores the seroprevalence of arboviruses in sloths (Choloepus hoffmanni and Bradypus variegatus) in rural areas of Western Panama (Capira and Chorrera). Blood samples from 60 sloths were analyzed using plaque reduction neutralization tests (PRNTs) to detect antibodies against nine arboviruses (CHIKV, VEEV, MADV, UNAV, MAYV, DENV-2, PTV, OROV, Changuinola (CGLV): Pansloth 149 and D50). In addition, genetic and phylogenetic analyses were performed on viral strains using sequences obtained from culture supernatants of Pan-Sloth 149 isolates and D50. Viral RNA was extracted, amplified, and sequenced using Illumina technology, and sequences were aligned using MAFFT software. Phylogenetic trees were constructed using IQ-TREE, employing the GTR+F+I+R3 nucleotide substitution model, revealing close genetic relationships among Panamanian viral strains. While antibodies against DENV, ZIKV, CHIKV, and PTV were undetected, 6.7% of sloths had antibodies against neurological alphaviruses (VEEV and MADV) and OROV 3.4 %, and high seroprevalence for orbiviruses Pan-Sloth 149 (23.3%) and Pan-Sloth D50 (53.3%) was noted. These Orbiviruses, closely related to CGLV, exhibited high genetic variability and segment-specific clustering with Panamanian strains identified in earlier studies. VP1, VP3, VP4, VP7, NS2, and NS3 segments showed low mutation frequencies, while VP2, involved in host attachment, demonstrated high variability likely driven by selective pressures and ecological adaptations. Phylogenetic analyses confirmed that Pan-Sloth Orbivirus strains form a monophyletic group with close genetic ties to other CGLV strains, highlighting potential host-specific adaptations and evolutionary divergence. These findings underscore the role of sloths as potential reservoirs for arboviruses in Panama, with implications for spillover risks to humans. They highlight the importance of integrating genetic and phylogenetic approaches to understanding virus-host relationships, while emphasizing the need for enhanced surveillance and One Health strategies. Ongoing efforts to monitor arbovirus transmission in wildlife and human populations are critical to mitigating their public health impact.