Possible non-sylvatic transmission of yellow fever between non-human primates in São Paulo city, Brazil, 2017-2018

Abstract

Yellow Fever (YF) is a severe disease caused by Yellow Fever Virus (YFV), endemic in some parts of Africa and America. In Brazil, YFV is maintained by a sylvatic transmission cycle involving non-human primates (NHP) and forest canopy-dwelling mosquitoes, mainly Haemagogus-spp and Sabethes-spp. Beginning in 2016, Brazil faced one of the largest Yellow Fever (YF) outbreaks in recent decades, mainly in the southeastern region. In São Paulo city, YFV was detected in October 2017 in Aloutta monkeys in an Atlantic Forest area. From 542 NHP, a total of 162 NHP were YFV positive by RT-qPCR and/or immunohistochemistry, being 22 Callithrix-spp. most from urban areas. Entomological collections executed did not detect the presence of strictly sylvatic mosquitoes. Three mosquito pools were positive for YFV, 2 Haemagogus leucocelaenus, and 1 Aedes scapularis. In summary, YFV in the São Paulo urban area was detected mainly in resident marmosets, and synanthropic mosquitoes were likely involved in viral transmission.

Figure 1

Map of São Paulo city with sites of Culicidae captures after confirmed epizootic events, 2017–2018. Districts represent the administrative divisions of the city. Reservoir represents the city water dams. Forest represents the Atlantic Forest protections area. Urban Green Areas (UGA) consists of urban parks and squares. Map was generated using QGIS version 2.14.9 ( available at https://www.qgis.org/pt_BR/site/).

Figure 2

Positive Callithrix monkeys and Aedes scapularis from Santo Amaro district. The buffer indicates a medium flight range of most Culicidae species (radius = 6Km).