Evidence for current circulation of an ancient West Nile virus strain (NY99) in Brazil

Abstract INTRODUCTION: In Brazil, West Nile virus (WNV) was first detected, in 2018, in horses with neurological disease. AIM: We report the first case of WNV infection in a horse from Ceará state and the complete genome sequence of an isolate from Espírito Santo state. Both infections occurred in 2019. METHODS: WNV was isolated from the tissues of a horse with neurological signs in Espírito Santo and sequenced by MiSeq. RESULTS: Phylogenetic analysis revealed that the isolate belongs to lineage 1a, clustering with the NY99 strain, a strain that has not circulated in the USA since 2005. CONCLUSIONS: Our findings reinforce the hypothesis that WNV has been silently circulating in Brazil for many years.

Serological detection of West Nile virus in horses and chicken from Pantanal, Brazil

In an effort to detect West Nile virus (WNV) in Brazil, we sampled serum from horses and chickens from the Pantanal region of the state of Mato Grosso and tested for flavivirus-reactive antibodies by blocking ELISA. The positive samples were further confirmed for serological evidence of WNV infection in three (8%) of the 38 horses and one (3.2%) of the 31 chickens using an 80% plaque-reduction neutralisation test (PRNT80). These results provide evidence of the circulation of WNV in chickens and horses in Pantanal.

Serological detection of St. Louis encephalitis virus and West Nile virus in equines from Santa Fe, Argentina

St. Louis encephalitis virus (SLEV) and West Nile virus (WNV) present ecological and antigenic similarities and are responsible for serious human diseases. In addition, WNV is a significant pathogen in terms of equine health. The purpose of our study was to analyse the seroprevalence of SLEV and WNV in equine sera collected in Santa Fe Province, Argentina. The seroprevalence determined using the plaque reduction neutralisation test was 12.2% for SLEV, 16.2% for WNV and 48.6% for a combination of both viruses. These results provide evidence of the co-circulation of SLEV and WNV in equines in Santa Fe.

Seroconversion for west Nile and St. Louis encephalitis viruses among sentinel horses in Colombia

We prospectively sampled flavivirus-naïve horses in northern Colombia to detect West Nile virus (WNV) and St. Louis encephalitis virus (SLEV) seroconversion events, which would indicate the current circulation of these viruses. Overall, 331 (34.1 percent) of the 971 horses screened were positive for past infection with flaviviruses upon initial sampling in July 2006. During the 12-month study from July 2006-June 2007, 33 WNV seroconversions and 14 SLEV seroconversions were detected, most of which occurred in the department of Bolivar. The seroconversion rates of horses in Bolivar for the period of March-June 2007 reached 12.4 percent for WNV and 6.7 percent for SLEV. These results comprise the first serologic evidence of SLEV circulation in Colombia. None of the horses sampled developed symptoms of encephalitis within three years of initial sampling. Using seroconversions in sentinel horses, we demonstrated an active circulation of WNV and SLEV in northern Colombia, particularly in the department of Bolivar. The absence of WNV-attributed equine or human disease in Colombia and elsewhere in the Caribbean Basin remains a topic of debate and speculation.

Neutralising antibodies for West Nile virus in horses from Brazilian Pantanal

Despite evidence of West Nile virus (WNV) activity in Colombia, Venezuela and Argentina, this virus has not been reported in most South American countries. In February 2009, we commenced an investigation for WNV in mosquitoes, horses and caimans from the Pantanal, Central-West Brazil. The sera of 168 horses and 30 caimans were initially tested using a flaviviruses-specific epitope-blocking enzyme-linked immunosorbent assay (blocking ELISA) for the detection of flavivirus-reactive antibodies. The seropositive samples were further tested using a plaque-reduction neutralisation test (PRNT90) for WNV and its most closely-related flaviviruses that circulate in Brazil to confirm the detection of specific virus-neutralising antibodies. Of the 93 (55.4 percent) blocking ELISA-seropositive horse serum samples, five (3 percent) were seropositive for WNV, nine (5.4 percent) were seropositive for St. Louis encephalitis virus, 18 (10.7 percent) were seropositive for Ilheus virus, three (1.8 percent) were seropositive for Cacipacore virus and none were seropositive for Rocio virus using PRNT90, with a criteria of > four-fold antibody titre difference. All caimans were negative for flaviviruses-specific antibodies using the blocking ELISA. No virus genome was detected from caiman blood or mosquito samples. The present study is the first report of confirmed serological evidence of WNV activity in Brazil.

O vírus do Nilo Ocidental: [revisão] / West Nile virus: [review]

O vírus do Nilo Ocidental (WNV) é um flavivírus que se mantém na natureza em ciclos alternados de infecção, em pássaros e mosquitos hematófagos, principalmente do gênero Culex. A infecção natural já foi demonstrada em mais de 200 espécies de aves, sendo que a susceptibilidade à infecção e à doença varia amplamente. Os corvídeos e os passeriformes são particularmente susceptíveis, desenvolvendo altos níveis de viremia e também elevada mortalidade. Ocasionalmente, a infecção pode ser transmitida para mamíferos pela picada de mosquitos que realizaram o repasto sangüíneo em aves virêmicas. Os humanos e os eqüinos estão entre os mamíferos mais susceptíveis e freqüentemente desenvolvem um quadro febril, que pode ser acompanhado de infecção neurológica e meningoencefalite fatal. A infecção pelo WNV, inicialmente identificada em Uganda (1937), durante décadas ficou restrita ao Norte da África, ao Oeste da Ásia, ao Oriente Médio e à Europa Mediterrânea, com relatos de casos isolados ou pequenos surtos de doença em humanos e eqüinos. Em 1999, o vírus foi introduzido em Nova Iorque, nos Estados Unidos, onde causou mortalidade de milhares de aves e infectou centenas de pessoas, levando 21 a óbito. A partir de então, a infecção se disseminou por praticamente todos os Estados norte-americanos, causando infecção e/ou doença em mais de 27 mil pessoas (1100 mortes), eqüinos (mais de 25.000 casos) e provocando mortalidade e redução da população de algumas espécies de aves silvestres. Evidências da infecção têm sido progressivamente detectadas em várias espécies animais no México, na América Central, no Caribe e no Norte da América do Sul, indicando a sua disseminação na direção sul. O WNV foi identificado como o agente de meningoencefalite fatal em três eqüinos na Argentina (2006), onde parece estar presente em pássaros nativos pelo menos desde 2005. Pesquisadores e autoridades sanitárias brasileiras da área humana e animal temem que a infecção seja introduzida...

West Nile virus (WNV) is a Flavivirus maintained in nature through alternate cycles of infection in wild birds and haematophagus mosquitoes, mainly Culex sp. Natural infection by WNV has been demonstrated in more than 200 bird species, which present variable susceptibility to infection and disease. Corvids and passeriformes are particularly susceptible and develop high levels of viremia and mortality. Occasionally, the virus may be transmitted to mammals by mosquitoes feeding previously on viremic birds. Human and horses are highly susceptible to WNV infection and often develop fever, which may be followed by neurological infection and fatal meningoencephalitis. Originally identified in Uganda (1937), WNV infection remained for decades restricted to North Africa, East Asia, Middle East and Mediterranean Europe. In these areas, isolated cases of human and horse disease, or small outbreaks were occasionally reported. In 1999, the virus was introduced in New York, USA, where it caused mortality in thousands of wild and captive birds and infected hundreds of people, killing 21. Thereafter, the infection rapidly spread out over the US territory, causing thousands of human infections (more than 27.000 - around 1100 deaths) and equine infections (more than 25.000 cases). WNV infection has also been detected in wild and domestic birds, horses and other mammals across Mexico, Central America and the Caribbean, and northern South America, indicating its dissemination southwards. In 2006, WNV was first identified as the agent of fatal neurological disease in three horses in Argentina, where it has been shown to be circulating in wild birds at least since 2005. Brazilian's human and animal health authorities are concerned with a possible introduction of the virus in the country, where it would find ideal ecological conditions for transmission and spread. This article presents a brief review on the main epidemiological and clinico-pathological...

Prevalencia de infección por el virus del Nilo Occidental en dos zoológicos del estado de Tabasco / Prevalence of West Nile Virus infection in animals from two state zoos Tabasco

OBJETIVO: Determinar la prevalencia de infección por el virus del Nilo Occidental (VNO) en animales, mosquitos y personal que labora en dos zoológicos del estado de Tabasco, en México. MATERIAL Y MÉTODOS: Con la utilización de ELISA de bloqueo se detectaron anticuerpos en sueros de animales: se buscó un fragmento del genoma del VNO por RT-PCR en el suero de animales, empleados y mosquitos. RESULTADOS: En el zoológico "La Venta" se encontró una seroprevalencia de 25.67 por ciento (19/74) en aves y de 85.71 por ciento (6/7) en reptiles. En el zoológico "Yum-Ká", 31.25 por ciento (50/160) de las aves y 34.48 por ciento (16/29,) de los mamíferos, tuvieron anticuerpos contra el VNO. En un grupo de mosquitos (Culex quinquefasciatus) se detectó el genoma del virus. CONCLUSIONES: La detección de anticuerpos contra el VNO en animales de ambos zoológicos y del genoma viral en mosquitos demuestra la presencia del virus, lo cual representa un riesgo potencial de infección para animales y humanos.

OBJECTIVE: To determine the prevalence of West Nile Virus (WNV) infection in animals, mosquitoes and employees from two zoos of Tabasco state, Mexico. MATERIAL AND METHODS: WNV antibodies were detected by blocking ELISA in serum samples from animals. Viral RNA was detected by RT-PCR from mosquitoes and serum samples from employees at "Yum-Ká" zoo. RESULTS: Seroprevalence in birds was 25.65 percent (19/74) and 85 percent (6/7) in reptiles from "La Venta" zoo. Thirty-one percent of birds (50/160) and 34.48 percent mammals (16/29) at the "Yum-Ká" zoo, were seropositive. All human serum samples from Yum-ká zoo were negative by RT-PCR. A pool of mosquitoes (Culex quinquefasciatus) was positive for WNV. CONCLUSIONS: The presence of WNV antibodies in animals from both zoos and the detection of viral genome in mosquitoes demonstrate the presence of WNV in this region and indicates a potential risk of infection in animals and humans.