Estudo sobre o potencial de infecção da cepa brasileira de West Nile virus em Culex quinquefasciatus Say, 1823 (Diptera: Culicidae) da Região Amazônica.

Abstract

West Nile Fever is an arboviruss caused by the West Nile virus (WNV), whose main vectors are mosquitoes of the Culex spp. genus, including Culex quinquefasciatus. The species has crepuscular, ornithophilical and antropophilic habits, with preference for oviposition in collections containing stagnant water with a high content of decomposing organic matter, it is very well adapted to urban environments, being considered in Brazil the main vector of Wuchereria bancrofti causing Filariasis Lymphatic and secondary vector of the Oropouche orthobunyavirus (OROV). Females of Culex quinquefasciatus, when performing the blood meal, ingesting blood containing several nutrients for egg maturation, as well as being vulnerable to various pathogens. Therefore, it is noteworthy that an important characteristic for the dissemination of arboviruses is a high vector competence, which is defined as the ability of the arthropod to be susceptible to infection, with multiplication and dissemination of pathogens through tissues to saliva, where it can be transmitted in a new blood meal. Thus, the present study aimed to evaluate the vector competence of females of Culex quinquefasciatus from the Ananindeua city (Amazon Region) orally infected with WNV (strain BE AN 854747) to verify the viability of infection in this population, to determine the viral titer in the body and head regions and also saliva, in order to calculate WNV infection, dissemination and transmission rates. For this purpose, the mosquitoes were artificially fed with 4mL of defibrinated sheep blood containing 2mL of infected Vero cell suspension, then, on the 7th, 14th and 21st day of post-infection (dpi) the saliva extraction and segmentation of the engorged females was performed to verify the presence of the virus using the techniques of Viral Isolation and Viral Titration in plates. High infection rates were observed in the three dpi's analyzed (100%), with titers ranging from 1,1x104 to 7x105 PFU/mL on the 7th dpi, 1,3x104 to 4,3x104 PFU/mL on the 14th dpi and 1,9x108 to 5,1x108 PFU/mL at 21st dpi, demonstrating high susceptibility of the species to infection. The dissemination rate was higher at 21st dpi with 100% of the positive samples and titers between 1,8x107 and 4,2x108 PFU/mL. The transmission rate was also higher in samples from the 21st dpi, with 100% of positive saliva, with titers between 1,3x104 and 4x102 PFU/mL. We concluded that the population of Culex quinquefasciatus studied has a high susceptibility to WNV infection with high vector competence and probability of the species becoming an important vector of the virus, since the Brazilian strain studied was able to overcome anatomical barriers, with constant viral dissemination over the 21 days evaluated, thus allowing its transmission to animals and humans.