Roadmap for Vector Transmission Control (VTC)

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

Identify how hematophagous vectors find their hosts and how they feed on them and use the knowledge to disrupt their infestations as well as pathogen transmission:

• What are the various naturally occurring behavioural or physiological mechanisms that regulate host preferences of parasitic, hematophagous arthropods,
• What are the hosts’ innate and acquired immune responses,
• What drugs or other chemicals target the vector, or
• What other biological interventions are effective, such as microbes that disrupt the vector’s habitat or its host
  preference and thus their ability to find and infest the host and/or transmit pathogens
• Can animal nutrition affect immunity to vectors and VBDs?

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

• Identifying naturally occurring physiological or anatomical vector resistance mechanisms among hosts, i.e., differences between host species and breeds regarding levels of vector infestation and pathogen transmission and whether it is possible to select for animals with the protective traits or otherwise co-opt these differences in other technological solutions (e.g., repellents).
• Determining how different target livestock and poultry species or breeds respond to vector bites by inflammation and innate and adaptive immune responses to limit infestation or infection so that this can be
  genetically selected for or induced by prophylactics such as vaccines or other technologies. (E.g., while much of the research on mosquito feeding has been conducted in mice, there is a need for more studies
  on how other host species respond.)
• Furthering understanding of vector pathways that can be targeted by chemical intervention to control infestation or identifying biologics that limit vectors on the host or in the environment.

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

These are outlined individually below in 2a, 2b and 2c.

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

• Improved understanding of host-vector interaction, especially vector attraction to specific hosts and subsequent feeding
• Identification of naturally more resistant and susceptible animals within livestock and poultry breeds to be used to study the mechanisms of resistance
• Understanding vector biology and physiology to develop new chemical targets

Existing knowledge including successes and failures

• Several publications examine individual hosts and host breeds that present contrasting phenotypes of vector infestations and vector-transmitted pathogen infections (e.g., ticks, mosquitos or biting flies and greater vs lesser attraction to particular individual hosts; Trypanosoma brucei,; greater or lesser parasitemia and pathology in different breeds of cattle).
• No genetic improvement through breeding or gene-editing or transgenesis are available yet because neither SNPs or specific genes that correlate with resistance have been identified.
• A commercial vaccine is available for only one tick species despite decades of research. Vaccines for other vectors such as tsetse flies or mosquitos are not available.
• Different ways to administer chemical controls are known but are dependent upon the type of host and are particularly concerning for food animals.
• Resistance to chemical acaricides for vector control, particularly ticks, is of enormous concern worldwide thus having animals that are naturally resistant or vaccines to protect against vectors is of substantial importance.