Poster Presentation 9th Australasian Virology Society Meeting 2017

Vector Competence of Australian Aedes aegypti for a Highly Divergent Dengue Virus Type 2 (#119)

Paul A Pickering 1 , Leon Hugo 2 , John Aaskov 1 3 , Wenjun Liu 1
  1. Australian Army Malaria Research Institute, Enoggera, QLD, Australia
  2. Mosquito Control Laboratory, QIMR Berghofer Medical Research Institute, Brisbane, Queensland, Australia
  3. Institute of Health and Biomedical Innovation, Queensland University of Technology, Brisbane, Queensland, Australia

In 2015, we recovered a strain of dengue virus (DENV) type-2 from a tourist returning to Australia. Phylogenetic analysis of this strain (QML22/2015) determined it to be a highly divergent member of DENV2 with a phylogenetically basal position to all previously isolated human and sylvatic DENV2 sequences. Here we evaluate the competence of local strains of Aedes aegypti to become infected with, and to transmit this virus. Mosquitoes (5-day old) were exposed to blood meals containing 107pfu/ml of either QML22/2015, or an endemic strain of DENV2 (QML16). The infection, dissemination and transmission rates were assessed by assaying virus in mosquito bodies, legs and saliva at different times post infection. The infection rates of Ae. aegypti with QML22/2015 were 36% (day-7), 44% (day-10) and 36% (day-14) which was less than those for the endemic strain, QML16, (84%, 68% and 72%) at the same intervals post-infection. However, the mean titres of virus (TCID50/body) in mosquitoes infected with either virus were similar (QML22/2015; 1.9x107, day-7; 2.1x106, day-10; 2.5x107, day-14) (QML16; 1.9x107, day-7; 1.6x107, day-10; 5.4x106, day-14). Dissemination rates and virus titres in legs were lower in mosquitoes infected with the divergent strain QML22/2015 than in those infected with the endemic strain, QML16. Dissemination rates of QML22/2015 were 0% (day-7), 46% (day-10) and 78% (day-14) whereas dissemination rates for QML16 were 71% (day-7), 88% (day-10) and 89% (day-14). Virus titres in mosquito legs for QML22/2015 were <25 at day-7, 4.1x103 at day-10 and 3.4x105 at day-14. For QML16, leg titres were 3.7x106 at day-7, 9.6x105 at day-10 and 3.3x106 at day-14. These preliminary data suggest that although the infection and dissemination of this highly divergent strain of DENV2 (QML22/2015) in Ae. aegypti is less efficient than conventional strains, it still has potential to enter cycles of transmission involving humans in urban settings in Australia.

  1. Wenjun Liu, Paul Pickering, Sebastián Duchêne, Edward C. Holmes, and John G. Aaskov. Highly Divergent Dengue Virus Type 2 in Traveler Returning from Borneo to Australia. Emerg Infect Dis. 2016, 22(12):2146-2148