Neutralising antibodies for Mayaro virus in Pantanal, Brazil.

Alex Pauvolid-Corrêa,Rita Maria Ribeiro Nogueira,Raquel Soares Juliano,Nicholas Komar,Jason Velez,Zilca Campos

doi:10.1590/0074-02760140383

Abstract

The Pantanal hosts diverse wildlife species and therefore is a hotspot for arbovirus studies in South America. A serosurvey for Mayaro virus (MAYV), eastern (EEEV), western (WEEV) and Venezuelan (VEEV) equine encephalitis viruses was conducted with 237 sheep, 87 free-ranging caimans and 748 equids, including 37 collected from a ranch where a neurologic disorder outbreak had been recently reported. Sera were tested for specific viral antibodies using plaque-reduction neutralisation test. From a total of 748 equids, of which 264 were immunised with vaccine composed of EEEV and WEEV and 484 had no history of immunisation, 10 (1.3%) were seropositive for MAYV and two (0.3%) for VEEV using criteria of a ≥ 4-fold antibody titre difference. Among the 484 equids without history of immunisation, 48 (9.9%) were seropositive for EEEV and four (0.8%) for WEEV using the same criteria. Among the sheep, five were sero- positive for equine encephalitis alphaviruses, with one (0.4%) for EEEV, one (0.4%) for WEEV and three (1.3%) for VEEV. Regarding free-ranging caimans, one (1.1%) and three (3.4%), respectively, had low titres for neutralising antibodies to VEEV and undetermined alphaviruses. The neurological disorder outbreak could not be linked to the alphaviruses tested. Our findings represent strong evidence that MAYV and all equine encephalitis alphaviruses circulated in the Pantanal.

Highlights

Ten alphaviruses have been reported in Brazil: Mayaro virus (MAYV), eastern equine encephalitis virus (EEEV), Venezuelan equine encephalitis virus (VEEV), western equine encephalitis virus (WEEV), Una virus, Trocara virus, Aura virus, Mucambo virus (MUCV), Pixuna virus (PIXV) and most recently chikungunya virus (CHIKV) (Vasconcelos et al 1998, PAHO/WHO 2015)
MAYV, EEEV, VEEV, MUCV, PIXV and CHIKV have been reported as the cause of human disease in Brazil (Alice 1956, Pinheiro et al 1986, Iversson et al 1990, Vasconcelos et al 1998, PAHO/WHO 2015)
Considering the caiman is abundantly distributed throughout the Pantanal, reaching densities of more than 60 caiman/km2 in the Nhecolândia subregion (Mourão et al 2000) and that sporadic cases of EEEV have been reported in sheep elsewhere (Bauer et al 2005), these species as well as equids may serve as useful indicators for detecting alphavirus activity

Summary

Introduction

Ten alphaviruses have been reported in Brazil: Mayaro virus (MAYV), eastern equine encephalitis virus (EEEV), Venezuelan equine encephalitis virus (VEEV), western equine encephalitis virus (WEEV), Una virus, Trocara virus, Aura virus, Mucambo virus (MUCV), Pixuna virus (PIXV) and most recently chikungunya virus (CHIKV) (Vasconcelos et al 1998, PAHO/WHO 2015). MAYV, EEEV, VEEV, MUCV, PIXV and CHIKV have been reported as the cause of human disease in Brazil (Alice 1956, Pinheiro et al 1986, Iversson et al 1990, Vasconcelos et al 1998, PAHO/WHO 2015). Despite serological evidence of its circulation (Melo et al 2012), VEEV has not been reported as a disease agent of equids in Brazil, but has caused equine epizootics in other South American countries (Navarro et al 2005). Considering the caiman is abundantly distributed throughout the Pantanal, reaching densities of more than 60 caiman/km in the Nhecolândia subregion (Mourão et al 2000) and that sporadic cases of EEEV have been reported in sheep elsewhere (Bauer et al 2005), these species as well as equids may serve as useful indicators for detecting alphavirus activity. We investigated the prevalence of infection of equine encephalitis alphaviruses and MAYV in equids, sheep and free-ranging caimans in the Pantanal

Methods

Results

Conclusion