Neutralising antibodies for West Nile virus in horses from Brazilian Pantanal

Abstract

The Pantanal is a tropical, seasonal wetland of approximately 140,000 km 2 that is fed by tributaries of the upper Paraguay River in the centre of South America, which covers mainly Brazilian but also Paraguayan and Bolivian territories and is classified as one of the largest freshwater wetland ecosystems in the world (Alho 2005). The Brazilian Pantanal, which represents 85% of the total Pantanal area, is located within the states of Mato Grosso do Sul and Mato Grosso in Central-West Brazil, which are recognised as South and North Pantanal, respectively (Alho et al. 1988). This region is ecologically classified into sub-regions according to vegetation, flooding and physiography (Silva & Abdon 1988). The Nhecolândia sub-region that is situated in South Pantanal is one of the largest, comprising approximately one fifth of the total area, and is characterised by hundreds of shallow lakes that display varying degrees of salinity and coalescence with the system during floods (Adámoli 1982).Recent studies have demonstrated that some crocodilian species may be infected by WNV (Steinman et al. 2003, Jacobson et al. 2005 and that Alligator mississippiensis may also have a viremic load that affords the infection of blood-feeding Culicidae vectors, which suggests that in areas with high population densities of these alligators, juvenile individuals could play an important role in WNV transmission (Klenk et al. 2004). Taking these data into account, the unsuccessful efforts to detect WNV circulation in the avian hosts in Brazil and the widespread, high prevalence of the Crocodilia species, Caiman crocodilus yacare, in the Brazilian Pantanal (Campos et al. 2005), our strategy was to investigate the WNV circulation in the potential vectors, dead-end hosts and natural secondary amplifying hosts through the collection and testing of mosquitoes and serum samples of horses and wild caimans from the Nhecolândia sub-region. No morbidity was observed during the sampling period and only apparently healthy horses and caimans were sampled in the present study. MATERiALS AND METHoDSStudy area -In February 2009, mosquitoes and blood samples from horses and wild caimans were collected in six different cattle ranches of the Nhecolândia sub-region (18º20' 19º40'S and 57º14' 55º00'W) during the rainy season. Considering the free circulation of mosquitoes, horses and wild caimans in large ranches, sample collections for the study were undertaken in a 700-square-kilometre (70,000 ha) area (Figure). The collections for this study were authorised by the Brazilian Institute of Environment and Natural Resources (license IBAMA 18363-1/2009).Samples collections -Adult mosquitoes were captured at sites that were randomly selected using CDC automatic light traps and manual aspirators while landing to blood-feed on horses and research team members as routinely reported. Living mosquito specimens were transported to a field laboratory where they were immobilised by chilling and the species were identified through direct observation of the morphological ...

Serologic survey of West Nile virus in horses from Central-West, Northeast and Southeast Brazil

“…In light of this, we considered only the serum samples that reacted in both the rDIII-WNV ELISA and WNV-NT as positives. Our results corroborate a report from 2011 showing that WNV-neutralising antibodies were found in 3% of the horses sampled in MS (Pauvolid-Corrêa et al 2011). Recently, WNV-neutralising antibodies were found in horses and chickens sampled in the state of Mato Grosso (Melandri et al 2012).…”

“…In 2006, WNV was isolated from the brains of two dead horses in Argentina (Morales et al 2006). In Brazil, WNV-specific neutralising antibodies were reported for the first time in horses from Nhecolândia, which is in the Pantanal region of the state of Mato Grosso do Sul (Pauvolid-Corrêa et al 2011). Recently, serological evidence of WNV activity in horses and chickens has also been reported in the Brazilian Pantanal (Melandri et al 2012).…”

“…It is well established that birds from North and South American countries migrate to certain Brazilian regions, including the Pantanal, each winter. Due to the large diversity of flora and fauna, as well as the high density of mosquitoes found in the Pantanal, this region may support the establishment and spread of WNV into other regions of the country (Pauvolid-Corrêa et al 2011). …”

Arboviral diseases in the Western Brazilian Amazon: a perspective and analysis from a tertiary health & research center in Manaus, State of Amazonas

“…The virus has spread through North America and towards Latin America (26) . There have been recent reports of WNV activity in Colombia, Venezuela and especially Argentina, where anti-WNV antibodies have been detected in birds (26) and the virus was isolated from the brains of horses that had died of encephalitis (27) . Human infections by WNV have never been reported in Brazil, but there is serological evidence of WNV activity in the Pantanal region (27) .…”

“…There have been recent reports of WNV activity in Colombia, Venezuela and especially Argentina, where anti-WNV antibodies have been detected in birds (26) and the virus was isolated from the brains of horses that had died of encephalitis (27) . Human infections by WNV have never been reported in Brazil, but there is serological evidence of WNV activity in the Pantanal region (27) . When the sera of 168 horses were tested for fl avivirus-reactive antibodies and the positive samples were further tested using a plaque-reduction neutralization test (PRNT90) for WNV, 5 animals had specifi c virus-neutralizing antibodies, which suggests that this virus has infected horses in Pantanal region.…”