Serodiagnosis of asymptomatic dengue infection

Dengue virus (DENV) is a mosquito-transmitted virus that is expanding across the world. The incidence of dengue infection, especially severe disease, has been increasing. DENV consist of 4 serotypes of single stranded RNA viruses (D1–D4) in the genus Flavivirus, family Flaviviridae. Majority of dengue infections are asymptomatic cases, which cause difficulty in disease control and are important in dengue surveillance. There is still no gold standard to diagnose asymptomatic dengue infection. Plaque reduction neutralization test (PRNT) has been developed for many purposes such as immunological study, clinical study, vaccine trial and is currently the most sensitive and specific method for serological surveillance. However, PRNT shows some degree of cross reaction among different dengue serotypes especially secondary dengue infection cases and to other flaviviruses. Moreover, various modification since the beginning make PRNT lack of inter-laboratory standardization which is an important issue. This paper discusses the important of asymptomatic dengue infection and its diagnostic method.

Serodiagnosis of asymptomatic dengue infection

Dengue virus (DENV) is a mosquito-transmitted virus that is expanding across the world. The incidence of dengue infection, especially severe disease, has been increasing. DENV consist of 4 serotypes of single stranded RNA viruses (D1-D4) in the genus Flavivirus, family Flaviviridae. Majority of dengue infections are asymptomatic cases, which cause difficulty in disease control and are important in dengue surveillance. There is still no gold standard to diagnose asymptomatic dengue infection. Plaque reduction neutralization test (PRNT) has been developed for many purposes such as immunological study, clinical study, vaccine trial and is currently the most sensitive and specific method for serological surveillance. However, PRNT shows some degree of cross reaction among different dengue serotypes especially secondary dengue infection cases and to other flaviviruses. Moreover, various modification since the beginning make PRNT lack of inter-laboratory standardization which is an important issue. This paper discusses the important of asymptomatic dengue infection and its diagnostic method.

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.

Antibodies to West Nile virus in equines of Antioquia and Meta, Colombia, 2005-2008 / Anticuerpos contra el virus del Oeste del Nilo en equinos de Antioquia y Meta, Colombia, 2005-2008 / Anticorpos contra o Vírus do Nilo Ocidental em eqüinos da Antioquia e do Meta, Colômbia 2005-2008

West Nile Virus (WNV) is an arthropod-borne agent classified in the Flavivirus genus. Infection has been demonstrated in many vertebrate species including birds, mammals and reptiles. WNV can affect the nervous system of humans, horses and birds causing mild to severe illness and sometimes death. In 1999 WNV was introduced into the Americas causing a small outbreak in New York City. In the following years, the virus spread across North America and later into Central America, the Caribbean and parts of South America. Serological evidence of WNV in Colombia was first documented in 2005 in equines from the Atlantic coast; however clinical cases in humans or animals have not been reported. We extended these studies searching for WNV antibodies in sera of equines of two other provinces in Colombia: Antioquia and El Meta. IgG and IgM antibodies were first determined and reactive sera were processed by plaque reduction neutralization test (PRNT) to confirm the specificity of results. Four horses from Antioquia but none from El Meta tested positive for WNV antibodies. These results suggest that WNV has spread across the Atlantic coast and is now invading the Andean region in Colombia.

El virus del Oeste del Nilo (WNV) es un agente del género Flavivirus transmitido por artrópodos. La infección con WNV ha sido demostrada en muchas especies de aves, mamíferos y reptiles. El WNV puede afectar el sistema nervioso de humanos, caballos y aves causando enfermedad de leve a severa, ocasionando la muerte en algunos casos. En 1999, el virus fue introducido en Norteamérica causando un brote en la ciudad de New York. En los siguientes años, el virus se extendió por Norteamérica, y posteriormente fue encontrado en el Caribe, Centro y Suramérica. El primer reporte de anticuerpos para WNV en Colombia se hizo en 2005, en equinos de la costa Atlántica. En el presente estudio se extendió la búsqueda de anticuerpos a otros dos Departamentos de Colombia: Antioquia y El Meta. Primero se determinó la presencia de anticuerpos IgM e IgG, y los sueros reactivos fueron procesados para anticuerpos neutralizantes por la técnica de reduccion de placas para confirmar los resultados. Cuatro equinos de Antioquia y ninguno de El Meta fueron positivos para anticuerpos anti-WNV. Los resultados sugieren que el WNV está ampliamente distribuido en la costa Atlántica de Colombia y ha iniciado su dispersión por la zona andina.

O vírus do Nilo Ocidental é um agente transmitido por artrópodes e pertence ao género Flavivirus. A infecção tem sido demonstrada em várias espécies de vertebrados incluindo pássaros, mamíferos e répteis. O vírus do Nilo Ocidental pode afectar o sistema nervoso de humanos, eqüinos e pássaros, causando doença de severidade média à grave a qual pode causar a morte em alguns casos. Em 1999, o vírus do Nilo Ocidental foi introduzido no continente americano, causando um surto na cidade de Nova York. Posteriormente, o vírus se disseminou pela América do Norte e mais tarde pela América Central, Caribe e parte da América do Sul. Os primeiros relatos do vírus do Nilo Ocidental na Colômbia surgiram em 2005 afectando eqüinos na costa atlântica. O objectivo desse trabalho foi buscar anticorpos contra o vírus do Nilo Ocidental no soro de equinos de dois estados da Colômbia: Antioquia e Meta. Anticorpos da classe IgG e IgM foram primeiramente determinados e soros reactivos foram analisados pela técnica de neutralização por redução em placa (PRNT) para confirmar a especificidade dos resultados. Quatro equinos provindos da Antioquia apresentaram resultados positivos para anticorpos contra o vírus do Nilo Ocidental; entretanto não foram detectados anticorpos nos animas provindos do Meta. Estes resultados sugerem que o vírus do Nilo Ocidental tem se disseminado através da costa atlântica e está agora invadindo a região andina na Colômbia.