Mosquito-borne disease transmission in a changing world

Background

In recent decades, arthropod-borne viruses (arboviruses) have emerged or re-emerged as human and animal pathogens with important implications for public health. These include dengue, Zika and chikungunya viruses, which circulate between humans and the urban mosquitoes, Aedes aegypti and Aedes albopictus, as well as zoonoses with complex transmission pathways that involving multiple vectors and vertebrate hosts. These include Japanese encephalitis virus (JEV), Murray Valley encephalitis virus (MVEV) and Ross River virus (RRV).

We are particularly interested in incriminating transmission pathways, and the factors that drive human spill-over for JEV, MVEV and RRV. The former is vaccine preventable, but in Australia we do not know where and when to target vaccination campaigns because the disease is highly unpredictable in its spatial and temporal prevalence. MVEV is endemic to Australia and Papua New Guinea, but in this case there are no vaccines or therapeutants for a disease whose appearance is also impossible to predict across regions or years. Both MVEV and JEV are deadly and untreatable in a small proportion of human cases. RRV is Australia’s commonest mosquito-borne disease (ca 5000 cases per annum) causing debilitating arthritogenic symptoms. It has caused explosive epidemics in the Pacific countries and territories, involving > 100,000 human cases. Recent sero-surveys suggest that it may now be endemic across the Pacific and that transmission is becoming more common in urban Australia.

Globally, anthropogenic and ecological changes, particularly those related to climate and extreme weather events, may increase vector and host prevalence, expose new reservoirs to infection or induce arboviruses to adapt to new maintenance cycles. These factors may favour the emergence and spread of human zoonotic infectious diseases. Detailed studies on JEV, MVEV, RRV, and their vectors and its hosts are required to 1) track the diversity and evolution of viruses across habitats, 2) understand their key transmission dynamics, and 3) determine the risks of human spill-over.

Objectives

• Demonstrate how new surveillance technologies (mosquito trapping,  and molecular xeno-monitoring) can incriminate vectors and vertebrate reservoirs of disease.
• Identify key pathways of arbovirus transmission and human spill-over in urban and rural environments in Australia.
• Apply these new insights to prioritise future research and to target interventions (i.e. health communication, insecticidal control, and vaccines).

Sub-objectives

• Gain a fine-scale understanding of how specific virus variants emerge, spread and dominate particular habitats.
• Support the longitudinal collection and identification of mosquitoes (including blood-fed individuals) and vertebrates around areas associated with virus transmission.
• Employ a range of diagnostic tools (serology of mosquito blood meals, metabarcoding and virus sequencing of trap collections) to identify transmission pathways.
• Application of modelling techniques (SIR or matrix models) to explore the impacts of different vectors and hosts on transmission.

Project Potential

• This work will draw on recent developments in arbovirus surveillance, molecular xeno-diagnostics, and risk mapping to define key transmission pathways (virus variants, habitat, vectors and reservoirs) for mosquito-borne zoonoses.
• The resulting “toolbox” of methods, and their interpretation, will have relevance for risk prediction and control campaigns.
• The project is pertinent, not only for Australia, but for the emergence of zoonotic arboviruses in the Pacific.