Abstract We report a case of encephalitis associated with Zika virus infection and reactivation of varicella-zoster virus in the central nervous system of a Brazilian child. This case raises the possibility that reactivation of the latent varicella-zoster virus may be a mechanism of neurological impairment induced by acquired Zika virus infection.

This study showed that laboratory markers of recent infection by dengue, Zika or chikungunya arboviruses were detected in the biological samples of approximately one-third of patients with encephalitis, myelitis, encephalomyelitis or Guillain-Barré syndrome, in a surveillance programme in Piauí state, Brazil, between 2015-2016. Fever and myalgia had been associated with these cases. Since in non-tropical countries most infections or parainfectious diseases associated with the nervous system are attributed to herpesviruses, enteroviruses, and Campylobacter jejuni, the present findings indicate that in tropical countries, arboviruses may now play a more important role and reinforce the need for their surveillance and systematic investigation in the tropics.

RESUMO: O estado do Pará corresponde a 26% da Amazônia brasileira, onde uma grande diversidade de arbovírus foi descrita. Este estudo procurou avaliar a prevalência e a distribuição de anticorpos inibidores da hemaglutinação (IH) contra antígenos de quatro alfavirus (Togaviridae: Alphavirus ), das espécies: Vírus da encefalite equina do leste (EEEV), Vírus da encefalite equina do oeste (WEEV), Vírus mayaro (MAYV) e Vírus mucambo (MUCV), de 753 amostras de soro de equinos no estado do Pará, Brasil. Todos os arbovirus pesquisados foram detectados, indicando que os equinos são suscetíveis a esses Alphavirus e mostrando evidências de sua circulação ativa em animais de fazenda na Amazônia brasileira.

ABSTRACT: The State of Pará comprises 26% of Brazilian Amazon region, where a large diversity of arboviruses has been described. This study sought to assess the prevalence and distribution of hemagglutination inhibition (HI) antibodies against antigens of four alphaviruses (Togaviridae: Alphavirus ) from the species: Eastern equine encephalitis (EEEV), Western equine encephalitis (WEEV), Mayaro virus (MAYV), and Mucambo virus (MUCV) in 753 serum samples of horses in Pará State, Brazil. All investigated arboviruses were detected and indicate that horses are susceptible to these alphaviruses, and show evidences of their active circulation in farm animals in the Brazilian Amazon.

Rocio virus (ROCV) is an encephalitic flavivirus endemic to Brazil. Experimental flavivirus infections have previously demonstrated a persistent infection and, in this study, we investigated the persistence of ROCV infection in golden hamsters (Mesocricetus auratus). The hamsters were infected intraperitoneally with 9.8 LD50/0.02 mL of ROCV and later anaesthetised and sacrificed at various time points over a 120-day period to collect of blood, urine and organ samples. The viral titres were quantified by real-time-polymerase chain reaction (qRT-PCR). The specimens were used to infect Vero cells and ROCV antigens in the cells were detected by immunefluorescence assay. The levels of antibodies were determined by the haemagglutination inhibition technique. A histopathological examination was performed on the tissues by staining with haematoxylin-eosin and detecting viral antigens by immunohistochemistry (IHC). ROCV induced a strong immune response and was pathogenic in hamsters through neuroinvasion. ROCV was recovered from Vero cells exposed to samples from the viscera, brain, blood, serum and urine and was detected by qRT-PCR in the brain, liver and blood for three months after infection. ROCV induced histopathological changes and the expression of viral antigens, which were detected by IHC in the liver, kidney, lung and brain up to four months after infection. These findings show that ROCV is pathogenic to golden hamsters and has the capacity to cause persistent infection in animals after intraperitoneal infection.