Spatial Repellency Flashcards
What component of blood is essential for mosquito egg production?
Proteins
Name intrinsic factors for host preference.
Physiologic and learning
Genetics
Name extrinsic factors for host preference.
Odorants (most important); Sex; Defensive behaviour; Parasites and pathogens; Blood quality; Colour; Body heat; Humidity; Body mass; Climate
What odorants are factors for host preference?
Octenol, L-lactic acid, carbon dioxide
What experiments can be used to test for host preference?
Dual choice tests, traps, wind tunnels, experimental huts
Genetic factors influence of host preference.
The most important for determining host preference which is usually dominant. An example of this is the development of behavioural resistance in mosquito populations.
How may mosquito infection influence host preference?
A mosquito infected with parasites/pathogens of human or animal origin may experience behavioural changes, increasing bite number and therefore infection rate.
(Batista et al. Parasites and Vectors 2013) - finding
Malaria infected humans are more attractive to mosquitoes than non-infected individuals.
Define spatial repellency - (Guidelines for efficacy testing of spatial repellents. WHO, 2013)
A range of insect behaviours induced by airborne chemicals, resulting in reduction in human/vector contact and therefore provide personal protection.
Behaviours include: Movement away from a chemical stimulus; interference with host detection; feeding response.
Define spatial repellency - (Nolen et al., US Patent Office 2002)
An inhibiting compound dispensed into the atmosphere of a 3D space, inhibiting mosquito ability to locate and track a target such as humans or livestock.
How does a wind tunnel test host preference?
By testing mosquito responses to odour cues by releasing said cues in air streams and analysing vector response
How do experimental huts test host preference?
They create a natural host biting environment and analyse insect response to certain stimuli.
What are the order of chemical actions in an experimental hut test? (image on slide 11)
- Prevent the vector from entering (spatial repellency); 2. Cause escape response before biting (contact irritancy); 3. Kill upon contact before leaving (toxicity, LLIN); 4. Kill folowing a blood meal (delayed toxicity, rest wall); 5. No effect (boooo)
Spatial repellency tools.
Y-maze olfactometer; Modfied two-port Gouck olfactometer; Free - flight testing room; Semi - field repellent evaluation
Y-maze olfactometer
Insect released on right, stimulus influence where vector flies and how quickly. On the left arm are different repellents.
Free-flight room
A less artificial environment, observe where flies go depending on their stimulus
Modified two-port Gouck olfactometer
Similar to Y-maze but can attach a mosquito cage. Mosquitoes are able to interact with one another before they make a decision to fly towards a source.
Semi-field environments
A person is placed in a room with an intervention, and another in a room with a control. Mosquitoes are tracked to see whether they are more attracted to human in intervention or control room. Climate can be adjusted.
Define attraction
For insects, something that causes insects to make oriented movements towards its source.
Define inhibition
Activity inhibitors that cause a neutral reaction (neither attraction or repulsion) whereby an insect stops questing purposefully, but is not anaesthetised or narcotised
Advantages of attraction/inhibition methods
To create protective spaces for people, and for the trapping of insects.
Mosquito magnet
Emits a plume of CO2, heat and moisture to attract mosquitoes. Mainly used for monitoring. >£500, 10 kg
Define insect repellent
A compound applied to surfaces, discouraging insects from climbing or landing on that surface. Generally divided by olfactory or irritation.
Examples of irritant repellence (toxicity)
DDT, permethrin, lambdacyhalothrin
Examples of olfactory repellents.
DEET, Icaridin, PMD, IR3535 (biopesticide), citronella, essential oils, VUAA1 (developed by Zwiebel and colleagues, 2011. It is a super-repellent(?): 1000x stronger than DEET)
How does a ThermaCELL mosquito repellent work?
Butane-fuelled generator that heats a metal plate to volatilize cis or trans-allethrin (synthetic pyrethroid) from a impregnated paper
Problems with DEET
Damages clothes, unpleasant odour
DEET alternatives. Disadvantages
citronella, eucalyptus oils
more volatile and less effective
DEET MoA
Little is known about mechanism, two hypotheses:
- Odour repellent (Walter Leal and collaborators, PNAS, 2008 and 2014) receptor evolved from plant defences.
- ‘Confusant’ that scrambles the insect odour code. (Vosshall and collaborators, Nature, 2011) Odour enters fluid around neurons
What is ORCO in regards to olfactory reception?
A co-receptor which is stimulated by different odours through different signalling pathways
Why do most odours require a OBP transporter?
Majority hydrophobic so don’t diffuse across liquid
Three processes of olfactory reception.
Peri-recpetor process, reception, olfactory transduction
1-methylpiperzine and and mosquito repellency
Renders humans ‘invisible’ to mosquito senses. On skin either from secretions or surface bacterial activity.
Common insect repellent side effect (not for DEET)
Eye irritation.
What compound is also known as ‘mushroom alcohol’?
1-octen-3-ol
Chemical in human sweat/breath thought to attract mosquitos. Used with CO2 in traps.
