Haemagogus leucocelaenus and Haemagogus janthinomys are the primary vectors in the major yellow fever outbreak in Brazil, 2016–2018

Abstract

The yellow fever virus (YFV) caused a severe outbreak in Brazil in 2016–2018 that rapidly spread across the Atlantic Forest in its most populated region without viral circulation for almost 80 years. A comprehensive entomological survey combining analysis of distribution, abundance and YFV natural infection in mosquitoes captured before and during the outbreak was conducted in 44 municipalities of five Brazilian states. In total, 17,662 mosquitoes of 89 species were collected. Before evidence of virus circulation, mosquitoes were tested negative but traditional vectors were alarmingly detected in 82% of municipalities, revealing high receptivity to sylvatic transmission. During the outbreak, five species were found positive in 42% of municipalities. Haemagogus janthinomys and Hg. leucocelaenus are considered the primary vectors due to their large distribution combined with high abundance and natural infection rates, concurring together for the rapid spread and severity of this outbreak. Aedes taeniorhynchus was found infected for the first time, but like Sabethes chloropterus and Aedes scapularis , it appears to have a potential local or secondary role because of their low abundance, distribution and infection rates. There was no evidence of YFV transmission by Aedes albopictus and Aedes aegypti, although the former was the most widespread species across affected municipalities, presenting an important overlap between the niches of the sylvatic vectors and the anthropic ones. The definition of receptive areas, expansion of vaccination in the most affected age group and exposed populations and the adoption of universal vaccination to the entire Brazilian population need to be urgently implemented.

Recent sylvatic yellow fever virus transmission in Brazil: the news from an old disease

“…Unlike NHP and humans, which succumb to the disease or heal by developing long-term immunity, mosquitoes are considered reservoirs of YFV since they remain infected and can transmit the virus throughout life [2,74]. In Brazil, species within the genera Haemagogus (H. janthinomys, H. albomaculatus, H. leucocelaenus, H. capricornii, and H. spegazzinii) and Sabethes (S. chloropterus, S. soperi, S. cyaneus, S. glaucodaemon, and S. albiprivus) are the primary sylvatic YFV vectors [2,33,75]. YFV-naturally infected specimens of Aedes scapularis, Aedes taeniorhynchus, Aedes serratus, and Psorophora ferox have been reported in Brazil, however, these mosquitoes are not considered primary YFV vectors [75][76][77][78][79].…”

Genomic Surveillance of Yellow Fever Virus Epizootic in São Paulo, Brazil, 2016 – 2018

“…In the Americas, YFV transmission is thought to occur through two main transmission cycles: (i) a sylvatic cycle that involves transmission between tree-dwelling mosquitoes (e.g. Haemagogus janthinomys, Haemagogus leucocelaenus and in some local areas, mosquitoes of the Sabethes genus) and non-human primates in forested areas ([6–8]); and (ii) an urban cycle, undetected since the 1940s with transmission between humans and Aedes aegypti mosquitoes in heavily populated areas [1, 9]. Alongside the urban and sylvatic cycles, in Africa, YFV transmission also occurs through (iii) an intermediary cycle, in which semi-domestic mosquitos that inhabit both urban and forested environment scan transmit YFV to both humans and non-human primates [1].…”

Natural infection and vertical transmission of two flaviviruses (Yellow fever and Zika) in mosquitoes in primary forests in the Brazilian state of Rio de Janeiro (Diptera: Culicidae)

“…It should be emphasized that the presence of Hg. janthinomys , the other highly suspected species [13] in an urban forest (Parque Dois Irmãos) in Recife, Pernambuco state [53], a city highly endemic to ZIKV and other viruses (DENV and CHIKV) [54] should be studied for natural infection.…”