Yellow fever epizootics in non-human primates, Southeast and Northeast Brazil (2017 and 2018)

Abstract

Background: Yellow fever (YF) is a severe, infectious, but non-communicable arboviral hemorrhagic disease. In the last decades, yellow fever virus (YFV) infections have been prevalent in endemic areas in Brazil, affecting human and non-human primate (NHP) populations. Monitoring of NHP infection started in 1999, and reports of epizootic diseases are considered important indicators of viral transmission, particularly in relation to the sylvatic cycle. This study presents the monitoring of YFV by real-time RT-PCR and the epidemiological findings related to the deaths of NHPs in the southeastern states and in the northeastern state of Bahia, during the outbreak of YF in Brazil during 2017 and 2018. Methods: A total of 4198 samples from 2099 NHPs from southeastern and northeastern Brazilian states were analyzed by real-time reverse transcription polymerase chain reaction (rtRT-PCR). Results: A total of 4198 samples from 2099 NHPs from southeastern and northeastern Brazilian states were collected between 2017 and 2018. The samples were subjected to molecular diagnostics for YFV detection using realtime reverse transcription polymerase chain reaction (rtRT-PCR) techniques. Epizootics were coincident with human YF cases. Furthermore, our results showed that the YF frequency was higher among marmosets (Callithrix sp.) than in previous reports. Viremia in species of the genus Alouatta and Callithrix differed greatly. Discussion: Our results indicate a need for further investigation of the role of Callithrix spp. in the transmission cycles of YFV in Brazil. In particular, YFV transmission was observed in a region where viral circulation has not been recorded for decades and thus vaccination has not been previously recommended. Conclusions: This highlights the need to straighten epizootic surveillance and evaluate the extent of vaccination programmes in Brazil in previously considered "YFV-free" areas of the country.

Neighbor danger: Yellow fever virus epizootics in urban and urban-rural transition areas of Minas Gerais state, during 2017-2018 yellow fever outbreaks in Brazil

“…However, we observed a strong negative correlation for detection of YFV in urban marmosets and higher median Cqs compared to Callicebus and Alouatta, suggesting lower genomic viral loads in those urban marmosets. Previous studies showed similar data when Callithrix presented higher Cqs (lower viral loads) than Alouatta during the recent YFV epizootics in Brazil [33]. On the other hand, we did not observe a difference among rural NHP (Callithrix, Alouatta, and Callicebus), which presented median estimates of genomic viral loads of 10E+6 times higher than Callithrix from urban and urban-rural transition areas.…”

“…However, the high infestation of Brazilian urban areas by Aedes aegypti poses a risk for YFV urban/ Aedes transmission [4,34,37,38]. Concerning Aedes, previous studies in Brazil have confirmed the competence of Aedes aegypti and Aedes albopictus, although the latter has shown low transmission competency to YFV [33].…”

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

“…In São Paulo, marmosets are found in city centers close to humans, and sometimes are even used as pets. However, unlike Alouatta monkeys, which are highly susceptible to YFV 23,24 , marmosets may not be efficient YFV amplifier hosts due to low viral loads, as previously reported 25,26 . As our results demonstrate, Alouatta monkeys were restricted to forest areas, mainly in Atlantic Forest preserved areas, while most marmosets were found in squares and other green areas, in close proximity to humans.…”

Vaccination and Therapeutics: Responding to the Changing Epidemiology of Yellow Fever

“…This led to an exponential increase in transmission leading to over 2000 confirmed cases and over 600 deaths. Molecular analysis confirmed that the 2016-2017 epidemic strain was within the South American (SA) 1 genotype and that the epidemic resulted from direct sylvatic spill over to humans with the absence of sustained YFV transmission within the urban cycle [19,32,33]. Some studies have attributed the 2016 YF epidemic in YF non-endemic regions of Brazil to increased virulence of the new virus strain [31,32,34], others have blamed changing aspects of population and ecology, such as the rise in population density [34], the geographical expansion of the peri-urban mosquito Aedes albopictus [35], human encroachment into NHP habitats [36], and global warming [37].…”

“…Due to slow evolutionary rates and constant spillover, the phylogeny of YFV isolates from NHP are genetically similar to isolates from human outbreaks [12,17,18]. Consequently, in South America, regular surveillance of YFV outbreaks in NHP populations can be used as an epidemic preparedness strategy [12,19]. In addition to active surveillance, elimination of future YF outbreaks requires a comprehensive understanding of the current epidemiology and the influence of control and prevention methods, such as vaccination.…”