KY

Entomology

Public Health

Barrier Applications for Mosquito Suppression in the Suburban Landscape

Dr. Grayson Brown

Public Health Entomology Laboratory

Department of Entomology

University of Kentucky

Lexington KY

Mosquitoes are top health concern among Americans

62

38

30

26

11

14

Mosquitoes

Stinging Insects

Ticks

Spiders

Bed Bugs

Other

Source: NPMA 2013 Summer Survey reported in PCT Online, Sept. 2013

Of those concerned, disease topped the list

Source: NPMA 2013 Summer Survey reported in PCT Online, Sept. 2013

54

43

35

11

5

Disease

Pain, sting/bite

Infestation in home

Allergy

Disease history

Recent mosquito-borne disease outbreaks in N. America

� West Nile Virus: 1999 – 2006

� Dengue: 2005 – 20011

� Chikungunya: 2011 – 2015

� Zika: 2016 – Present

� More to come

Zika Symptoms

Eye Redness Mild Viral Conjunctivas

Flu-like symptoms Joint aches, particularly in wrists and ankles

Mild rash

•  Self-limiting, 3 days – week •  Not typically neuroinvasive, few complications, deaths extremely rare

and only in immune-compromised individuals

Most people don’t need to worry about Zika

It’s only a serious threat to one

group

Result of decreased brain size

Microcephalic Births in Brazil

0

500

1000

1500

2000

2500

3000

3500

4000

4500

2007 2008 2009 2010 2011 2012 2013 2014 2015 2016

Ann

ual

Cas

es

Year

Before Zika

April 2015

Post Zika

Extensive public concern at all levels

How do mosquitoes transmit disease?

�  Mosquitoes are not “flying syringes”

�  In order for a pathogen to be transmitted by a mosquito: �  It has to infect the mosquito in a specific way �  The mosquito must have the biological, behavioral

and ecological traits to enable transmission �  The pathogen must have a pathogenic cycle inside its

human host that enables a return to the mosquito (optional)

�  We can’t do anything about the first & last of these. Our mosquito control efforts are targeted at the 2nd one.

Feeding

•  Once the mosquito lands, the labium slides back, exposing mandibles & maxillae (stylets)

•  Stylets pierce the skin and probe until sensors on the tip detect a capillary

•  Saliva continues to be injected during feeding as an anticoagulant.

•  Full blood meal is half to a couple of microliters (0.001 ml).

Sensory Setae

Human Hair

Blood Capillary

Sensors

Lower “Lip” (labium)

Palp

Mandibles & Maxillae

Compound Eye

Choumet V, Attout T, Chartier L, Khun H, Sautereau J, et al. (2012) Visualizing Non Infectious and Infectious Anopheles gambiae Blood Feedings in Naive and Saliva-Immunized Mice. PLoS ONE 7(12): e50464. doi:10.1371/journal.pone.0050464

Mosquito Life Cycle �  Larvae are wigglers

�  Pupae are tumblers (quite active)

�  Both breath air

�  Eggs are laid on the surface of water in rafts (Culex) or singly (Anopheles) or near water (Aedes)

Eggs

Anopheles (note floats)

Culex egg raft

Aedes eggs are laid near water

Mosquito Diet � Most Larvae feed on

algae & bacteria but a few are predaceous and feed on other mosquito larvae

�  Only females are blood sucking

� Males and females feed on nectar and other plant juices

Mosquito Lifestyle

� Most mosquitoes do not travel far from the water from which they emerged

�  Adults are active at night or twilight

� Many spend the day in hollow trees, culverts, and dense shaded areas

Mosquitoes in the N. American Suburban Landscape

�  About 150 spp. of mosquitoes in N. America in 8 genera. Of these: �  < 10 are serious disease transmission threats

�  About 10 more are less serious threats �  Another 20 or so are seasonal nuisance pests

�  Most problems are confined to a few species in only 2 genera: Aedes and Culex.

�  These two genera differ in very important ways.

Two  Generic  Biologies  

Aedes/Ochlerotatus Culex

Dengue, EEE, LaCrosse West Nile, SLE, other encephalitis

Attacks mammals Attacks birds, few human bites Daytime – early evening Late night – early morning Prefers cleaner water Prefers stagnant water Few gens/year, OW as eggs Many gens/year, OW as adult Daytime resting sites < 10 ft (bushes)

Daytime resting sites > 10 ft (trees)

Municipal Control Vs. Backyard Control

Municipal ULV Backyard Perimeter

AI Sumithrin Lambda cyhalothrin, bifenthrin, deltamethrin

Application Time Late PM/Early AM Daytime

Residual activity Hours Weeks/months

Spatial Scale Area Code Single Backyard

Most effective against Culex spp, some Anopheles

Aedes, Ochlerotatus

Diseases Controlled West Nile, other encephalitis

Zika, Dengue, Chikungunya

The two are compatible and complementary

Suburban backyard as a mosquito habitat

Need Aedes Culex

Water Clean Stagnant

Hosts Mammals Birds

Resting sites Low, dark, humid sites

Trees

Air movement Minimal Minimal

Overwintering Areas that will be covered with water

Crevices in tree bark, siding, etc.

How to they move about, What are their stimuli

1.  They have a simple stimulus response

2.  First day or so post-eclosion, they just sit

3.  Then they search for nectar (carbohydrate source) so they orient toward flowers

4.  Next they search for a blood meal. �  If no olfactory stimuli, they move toward light �  CO2 is a long distance stimulus �  Body heat for short range �  Other volatile chemicals for individual selection

5.  After a blood meal, they search for oviposition site �  Volatiles emitted by microfauna and other larvae are stimuli.

This completes a gonotropic cycle. Next cycle begins with a return to step 3.

How do they move toward people?

Direction of air movement

CO2 Plume

CO2 Plume

How do they move toward people?

Direction of air movement

This is the basis for how perimeter applications for

mosquito control work.

Objective is to treat mosquito adults’ daytime resting sites and work FROM the house

Start with vegetation near home

Then vegetation in the yard

Finally treat the perimeter

Objective is to flush the mosquitoes from the yard

Technique and properties are important

�  Bad Things:

�  Properties with little to no perimeter vegetation

�  Properties whose predominate vegetation is grass and flower/vegetable/herb gardens

�  Treating grass/flowers/vegetables

�  Treating in a haphazard pattern

�  Failing to use proper PPE

Bad Property, Bad Technique

Good Property, Good Technique

Dense non-flowering ground vegetation

Dense Canopies

Underneath decks, crawlspaces or other raised structures

Objective is to treat any location that is dark, cool and moist.

Home’s Perimeter

Objective is to treat any location that is dark, cool and moist.

Yard’s Perimeter

Use a vertical or circular motion to coat the undersides of the leaves

What results should you expect?

0

3

6

9

12

-2 -1 0 1 2 3 4 5 6 7 8 Mos

quito

es/T

rap/

Nig

ht

Weeks Post Treatment

Demand CS Water Placebo

Excellent control of Aedes

Avg. 75% reduction after 1 week

Avg. 60% reduction over 6 weeks

96% Aedes

Before Treatment

After Treatment

96% Aedes species

Greatly reduced mosquito bites

0

2

4

6

8

-2 -1 0 1 2 3 4 5 6 7 8

Mos

quito

Bite

s/10

min

Weeks Post Treatment

Demand CS Water Placebo

85% reduction after 1 week

73% reduction over 6 weeks

98% Aedes

98% Aedes species

No effect on Culex mosquitoes

0

15

30

45

60

-1 0 1 2 3 4 5 6 7 8 Mos

quito

es/T

rap/

Nig

ht

Weeks Post Treatment

Demand CS Water Placebo

No Effect

96% Culex (Principal WNV vector)

Season-­‐long  Summary  (Totals  7/7/14  –  9/10/14)  

Post-­‐Treatment  Totals  

Demand  CS   Demand  +  Archer   Control  

CDC  Mosquitoes   102 68 763

Gravid  Trap  Mosquitoes  

133 96 489

HLR  Counts   59 84 224

Larvae  in  Egg  Traps   89 35 1,788

2014  Season-­‐Long  Summary    %  ReducNon    of  Selected  Species  RelaNve  to  Control  

Species   Demand  CS   Demand  +  Archer  

Aedes  albopictus   87 % 78

Culex  pipiens   34 61

Aedes  vexans   72 79

Anopheles  spp.   16 44

2014 Aedes Trap Results

0  

10  

20  

30  

40  

50  

60  

70  

1   2   3   4   5   6   7   8   9   10   11   12  

Total  m

osqu

itoes/trap/night  

Week  

Demand  +  Archer   Demand  Alone   Control  

Most recent work is showing significant suppression for 2 months (2015 data)

0  

10  

20  

30  

40  

50  

60  

70  

1   2   3   4   5   6   7   8   9  

Mosqu

itoes  

Weeks  Post-­‐Treatment  

Mean  (±SE)  -­‐  CDC  Trap  

Demand   Demand  +  Archer   Control  

Mosquito bites on humans (2015 data)

0  

2  

4  

6  

8  

10  

12  

14  

16  

18  

2   3   4   5   6   7   8   9  Average  #  Mosqu

itoes/5  m

inutes

 

Weeks  Post-­‐Treatment  

Mean  (±SE)  -­‐  Human  Landing  Rate  Count    

Demand   Demand  +  Archer   Control  

Barrier treatments are only one part of a

comprehensive management program

Homeowners �  They have responsibility too

�  Source Reduction

�  Avoiding pruning/removal of treated foliage

�  Ideally removing harborage sites prior to treatment

�  Gutter repair

�  Expectations �  Suppression is not elimination

�  May reduce some disease risk but not all

Problems �  Problems that can arise with these management

programs and how to avoid/resolve them.

�  Non-target effects

�  Chemical trespass

�  Resistance management and its importance

�  Mosquito species not well controlled by these programs and their significance (Culex)

Non-Target Effects

�  Some can be avoided �  Pollinators

�  Aquatic organisms

�  Plants

�  Other beneficials

�  Some cannot �  Lady beetles �  Fireflies

�  Some spiders

Chemical Trespass

Main method of avoiding chemical trespass is to keep the spray low on low

wind days

Insecticide layer & Aedes resting sites

Culex resting sites

8 – 10 feet

Resistance Management �  Growing problem with resistance to synthetic

pyrethroids in mosquitoes �  Greatest problem is with sumithrin

�  Great variability between species �  Residuals have relatively little problem right now

�  Typical neighborhoods have ~ 10% of homes treated so 90% of mosquitoes are not exposed

�  We need to keep an eye on this and use resistance management strategies as much as possible.

�  Backyard perimeter applications will provide effective suppression of Zika vectors

�  They should be used as part of a comprehensive program

�  Consider printing a homeowner pamphlet on what they can do (cf. CDC, your Pub. Health Dept. sites)

�  Consider products that minimize treatment frequency.

�  Don’t forget that you are part of an overall mosquito management effort

Tips for this coming year

KY

Entomology

Public Health

Thank You