Vectorial capacity of Aedes aegypti for Chikungunya and Dengue viruses

MICIELI, M. V.; CHIN, PAM; BALSALOBRE, A.; MUTTIS, E.; EHRBAR, DYLAN D; CIOTA, ALEXANDER T; KRAMER, LAURA D

Manaos

Seminario; NIH Fiocruz Arbovirus Seminar: Global Health Challenges and Collaborative Opportunities in Arbovirus Research; 2015

NIH

Introduction. Chikungunya virus (Togaviridae; Alphavirus) was introduced into the Caribbean in October 2013 and subsequently expanded its range to Central and South America as well as the United States. The virus is indigenous now in Brazil, along with two other mosquito-borne viruses, Dengue virus and the newly introduced Zika virus (Flaviviridae; Flavivirus). Dengue has been endemic in Brazil since its re-emergence in 1981. The Brazilian Ministry of Health has reported 746,000 registered cases of Dengue fever since January 2015, a 234% increase in cases since 2014. Brazil confirmed autochthonous transmission of Zika virus in the northeastern part of the country in May 2015.The predominant vector implicated in the transmission of these three viruses in the western hemisphere is Aedes aegypti, although Aedes albopictus are present and may be serve as vectors as well.This presentation will address the importance of vector competence and more importantly vectorial capacity of Aedes aegypti in determining intensity of transmission of arboviruses. Methods. As a model for the types of studies that need to be conducted, a comprehensive study beginning in 2014 on Ae. aegypti in Argentina over the extent of its geographic range will be presented. The project focuses on how local cycling temperatures and genetic variation in natural populations of Ae. Aegypti impact life history traits of this mosquito, as well as its ability to become infected with and transmit CHIKV and DENVviruses. Ae. Aegypti is known to have considerable genetic, behavioral, and ecological variation that is often spatially and/or temporally heterogeneous. We collected Ae. Aegypti from four reported genetically distinct populations in Argentina, ranging from tropical Iguazu and Posadas in the north to temperate Buenos Aires in the south, and Salta in the northwest. The mosquitoes were reared to the first generation of adults in the laboratory at the appropriate natural cycling temperatures, then blood fed for F1- F2 eggs, which were hatched to determine life table characteristics and vector competence for each of the study sites.Genetic analyses also were conducted. Results. Ae aegypti originating from Posadas had the highest transmission potential for CHIKV, Salta had the highest potential for DENV, but Salta had the highest vectorial capacity for both viruses. Genetic analyses are pending.Conclusions. These results confirm components other than vector competence may be more important when determining vectorial capacity, i.e., when determining where the greatest risk lies, although they may align as with DENV. They also reaffirm that populations of a mosquito vector may differ, and response to different viruses differ, re-emphasizing the complexity of vector-borne pathogen transmission.