Roadmap for Vector Transmission Control (VTC)

What are we trying to achieve and why? What is the problem we are trying to solve?

To establish which vector species are capable of transmitting any particular pathogen and the necessary conditions for cyclical transmission

What are the scientific and technological challenges (knowledge gaps needing to be addressed)?

• Determine if there are variations in time and temperature requirements where cyclical transmission occurs
• Need to identify differences in competence between vector species/strains, recognising there are wider variation between both different species and different populations of the same species with respect to susceptibility to infection and transmission.
• Need to identify vector factors that define pathogen acceptance and proliferation. E.g., determine why some species of mosquito are susceptible to a particular virus and others are not. That is, define the molecular determinants of vector infection. Need a system biology approach (understanding the molecular, cellular and physiological interactions between vector and pathogen)
• Increase our knowledge about host co-infections and their impact on tick-borne diseases. Ticks are known to transmit multiple pathogens, but our understanding of how co-infection impacts disease transmission and host immune responses is still limited. Further research is needed to identify the specific mechanisms behind co-infection and develop more effective treatments for these diseases.
• Have knowledge gaps about the vector midgut microbiome: While it is known that the tick midgut is relatively empty compared to the ovaries in terms of microbiome composition, our understanding of the role of this microbiome in tick biology and disease transmission is still limited. Further research is needed to identify the specific functions of the tick midgut microbiome and how it interacts with host cells. Where is the microbiome present/identify real microbiota in ticks and mosquitos (ovaries) – could be strategy for poultry mites, vector control and transmission control in general
• Determine why infected ticks live for shorter periods than non-infected ticks but still feed normally, including considering immune upregulation and energy expenditure
• Bacterial and viral microbiota/infection can alter the pathogen transmission of the vector

What approaches could/should be taken to address the research question?

• Has feeding on uninfected blood an influence on infected ticks? Feeding on infected animals followed by “clean” animals. Artificial feeding on “spiked” blood followed by feeding on clean animals.
• Identification of receptors for pathogen entry into vector cells or body compartments
• The Ig binding protein in ticks is another area of research that could provide new insights into tick biology and control. This protein is involved in the tick’s immune response and could be a potential target for vaccines or other control measures.

What else needs to be done before we can solve this need?

Determine how the host-vector interaction affects transmission so that this effect can be negated when trying to elucidate the vector-pathogen interaction including pathogen survival in the vector and successful transmission to the host

Existing knowledge including successes and failures

This includes discussion of Wolbachia and transgenic approaches.
Higgs, S. (2013). Alternative approaches to control dengue and chikungunya: transgenic mosquitoes. Public Health. 24: 35-42.
Shi et al. 2022 Bidirectional interactions between Arbovirusses and the bacterial and viral microbiota in Aedes aegypti and Culex quinquefqsciatus. mBIO13, 5.
Hobson-Peters et al. 2013 A new insect-specific flavivirus from northern Australia suppresses replication of West Nile Virus and Murray Valley Encephalitis Virus in Co-infected mosquito cells. PLOSone 2013, 8,2 e56534
Hall-Mendelin et al. 2016 The insect-specific Palm Creek virus modulates West Nile virus infection in and transmission by Australian mosquitoes. Parasites and Vectors 9, 414.
Schutz et al 2018 Dual insect specific virus infection limits Arbovirus replication in Aedes mosquito cells. Virology 518, 406-413.