Epidemiological surveillance of West Nile virus in the world and Brazil

Abstract

<jats:p>West Nile virus (WNV) is a neurovirulent mosquito-borne Flavivirus that is maintained in nature by a zoonotic transmissioncycle between avian hosts and ornithophilic mosquito vectors, mostly from the Culex genus. Until the 1990s, WNV wasconsidered to be an old-world arbovirus, but in 1999, WNV emerged in the United States (US) and spread rapidly, becoming amajor threat to public health. WNV adapted to the transmission cycle involving American mosquitoes and birds and reachedCentral and South America in subsequent years. In 2003, the National West Nile Fever Surveillance System was created in Brazilbased on serological screening of animals and sentinel vectors, as recommended by the Pan American Health Organization(PAHO) and the World Health Organization (WHO). Since 2008, serological evidence of WNV infection in Brazilian horseshas been reported, and the circulation of WNV has been monitored through the regular serological screening of sentinel horsesand reporting of encephalomyelitis cases. Horses are highly susceptible to WNV infection, and outbreaks of neurologicaldisease among horses often precede human cases. In this regard, equine surveillance has been essential in providing earlywarning to public and animal health authorities in several countries, including Brazil. This demonstrates the need for animaland public health intervention programs to allocate resources to make veterinarians aware of the role they can play in thehuman surveillance processes by monitoring horses. This review discusses the importance of equine surveillance and the gapthat veterinarians can fill on the front line in human surveillance, in Brazil and worldwide, in the context of “One Health”</jats:p>

Retrospective Investigation in Horses with Encephalitis Reveals Unnoticed Circulation of West Nile Virus in Brazil

“…Our data suggest that the first importation events, likely related to the North America outbreak, occurred in early March 2013, whereas the second introduction, likely related to the circulation of WNV in South America (potentially in Colombia), occurred in early September 2017. Despite our data suggesting the earliest introduction may have occurred in 2013, the reporting of WNV circulation in mammals and birds since 2004, as shown in several serological studies [ 10 , 14 , 15 , 16 , 17 , 18 , 19 , 20 , 40 , 41 , 42 ], might reflect a possible cryptic transmission of this virus in the region. This hypothesis is also corroborated by the detection of WNV in an equid sampled in Boa Viagem, Ceará in 2019.…”

“…In this study, using portable nanopore sequencing, we generated three new WNV-1a genomes collected between 2017 and 2019 from the northeastern region of Brazil. Among the zoonotic arboviruses detected in Brazil [ 14 , 30 , 31 , 32 , 33 , 34 , 35 , 36 , 37 , 38 , 39 ], since 2004, several studies have provided serological evidence regarding the circulation of West Nile virus (WNV) in mammal and bird reservoirs [ 10 , 14 , 15 , 16 , 17 , 18 , 19 , 20 , 40 , 41 , 42 ]. Even though the circulation of WNV has been documented since 2004, the short period of infection, followed by a low viremia and the difficulty of accessing the possible infected animals reduced the possibility of molecular confirmation and sequencing [ 9 , 10 , 14 , 15 , 16 , 17 , 18 , 20 , 40 , 41 , 42 ].…”

“…Among the zoonotic arboviruses detected in Brazil [ 14 , 30 , 31 , 32 , 33 , 34 , 35 , 36 , 37 , 38 , 39 ], since 2004, several studies have provided serological evidence regarding the circulation of West Nile virus (WNV) in mammal and bird reservoirs [ 10 , 14 , 15 , 16 , 17 , 18 , 19 , 20 , 40 , 41 , 42 ]. Even though the circulation of WNV has been documented since 2004, the short period of infection, followed by a low viremia and the difficulty of accessing the possible infected animals reduced the possibility of molecular confirmation and sequencing [ 9 , 10 , 14 , 15 , 16 , 17 , 18 , 20 , 40 , 41 , 42 ]. The lack of genomic data and viral surveillance decreases the possibility of reconstructing the dispersal routes of this pathogen and monitoring sources of new introductions.…”