Control of Aedes aegypti from the Perspective of a Mosquito Control District
Christopher Lesser and Mark LathamManatee County MCD
Palmetto, FL
Aedes aegypti + Ae. albopictus
• Container breeding mosquitoes that develop in a variety of water-holding containers, both natural and artificial
• Vectors of pathogens that can cause disease in humans and animals
• High nuisance spp; generate large amount of public discomfort
• Daytime active and live in very close proximity to humans making control difficult
Methods of “Traditional” Mosquito Control
“Traditional” Habitat: -Isolated -Concentrated breeding - Adults have long flight range -Easily accessible - Remote/rural
Methods of “Traditional” Mosquito Control
“Traditional” Habitat: -Isolated -Concentrated breeding - Adults have long flight range -Easily accessible - Remote/rural
Ae. aegypti/albopictus Habitat: - Amongst human residents - Larval and adults are diffuse -Adults have very short flight range = area of larval breeding - Breeding habitat is difficult to access -Urban, but can endo- or exophilic
Sanitation is the Most Effective Means of Domestic Mosquito Control!
• But relies on homeowner to voluntarily perform (ie “cleanup own yard”)……. but simply doesn’t happen; forced-sanitation is unpopular in US and only successful in Countries where mandated by laws/fines
• Access to individual properties is difficult (sometime impossible)
• Scope of Problem: 2-person teams; 20min/home; 6hr field day = 18homes per day = 6 acres/day
•25,000 acre block•Team of 2 cover 6 acres/day •Need 4,200 days for to make a complete sanitation (11.5 yrs)•Or need 140 employees to make the complete inspection every 30-days•Cost - $7.0 million in direct/indirect employee costs
What Else is Available?
• Larvicides and Adulticides• Delivered through both truck and aerial
applications platforms
• Not considering any “hand-application” (backpack sprayers) platforms or ATSB since these techniques are VERY labor intensive, don’t cover enough areas in timely manner and generally aren’t applicable to wide-area population control
5/2 5/9 5/16 5/23 5/31 6/6 6/13 6/20 6/27 7/5 7/11 7/18 7/25 8/1 8/8 8/15 8/22 8/29 9/6 9/12 9/19 9/26 10/3 10/100
20
40
60
80
100
120
140
160
180
24.1
32.8 31.1
53.5 51.6
27.2
48.240.7
30.5
53.8
70.2
60.555.7
52.1
62.3 59.8
64.6
64.160.6
51.9
60.0
29.9
23.3
34.9
66.9
161.5167.2
107.1 110.1
78.2
104.3
88.7
62.2 63.6
99.4
91.2
57.0
69.7
130.8
94.7
52.1
25.2 26.1 23.131.4
18.1
9.6
2011: Efficacy of Aerial Larviciding upon Ae. aegypti/albopictus Populations(Values Indicate Average # of Eggs & Larvae at 15 Sampling Sites within each
group)
Control
Polynomial (Control)
Treatment
Date of Collection
Aerial Larvicide - Methoprene on 8/16, 8/31 and 9/14; Midnight - 2am128-acres
Num
ber of Eggs and L
arvae
5/2 5/9 5/16 5/23 5/31 6/6 6/13 6/20 6/27 7/5 7/11 7/18 7/25 8/1 8/8 8/15 8/22 8/29 9/6 9/12 9/19 9/26 10/3 10/100
20
40
60
80
100
120
140
160
180
24.1
32.8 31.1
53.5 51.6
27.2
48.240.7
30.5
53.8
70.2
60.555.7
52.1
62.3 59.8
64.6
64.160.6
51.9
60.0
29.9
23.3
34.9
66.9
161.5167.2
107.1110.1
78.2
104.3
88.7
62.2 63.6
99.4
91.2
57.0
69.7
130.8
94.7
52.1
25.2 26.123.1
31.4
18.1
9.6
2011: Efficacy of Aerial Larviciding upon Ae. aegypti/albopictus Populations(Values Indicate Average # of Eggs & Larvae at 15 Sampling Sites within each
group)
Control
Polynomial (Control)
Treatment
Date of Collection
Aerial Larvicide - Methoprene on 8/16, 8/31 and 9/14; Midnight - 2am128-acres
Num
ber of Eggs and L
arvae
5/2 5/9 5/16 5/23 5/31 6/6 6/13 6/20 6/27 7/5 7/11 7/18 7/25 8/1 8/8 8/15 8/22 8/29 9/6 9/12 9/19 9/26 10/3 10/100
20
40
60
80
100
120
140
160
180
24.1
32.8 31.1
53.5 51.6
27.2
48.240.7
30.5
53.8
70.2
60.555.7
52.1
62.3 59.8
64.6
64.160.6
51.9
60.0
29.9
23.3
34.9
66.9
161.5167.2
107.1 110.1
78.2
104.3
88.7
62.2 63.6
99.4
91.2
57.0
69.7
130.8
94.7
52.1
25.2 26.1 23.131.4
18.1
9.6
2011: Efficacy of Aerial Larviciding upon Ae. aegypti/albopictus Populations(Values Indicate Average # of Eggs & Larvae at 15 Sampling Sites within each
group)
Control
Polynomial (Control)
Treatment
Date of Collection
Aerial Larvicide - Methoprene on 8/16, 8/31 and 9/14; Midnight - 2am128-acres
Num
ber of Eggs and L
arvae
Effective, but …..SLOW and EXPENSIVE!
Adulticides• Ground/Truck ULV – Has been found to be somewhat
effective at the population level in some situations and most MCD’s have access to this spray equipment, but…..– Slow (only treat a few hundred acres per evening)– Relies upon ambient winds (at the ground-level) to carry
spray cloud (little in nocturnal periods)– Often need multiple spray events in a short window to be
effective (2x per week) – Higher public exposure to the spray operations; more
complaints (as compared to aerial applications)
4/16 4/23 4/30 5/7 5/14 5/21 5/30 6/4 6/11 6/18 6/25 7/2 7/9 7/16 7/23 7/30 8/6 8/13 8/20 8/27 9/3 9/10 9/17 9/24 10/10
20
40
60
80
100
120
140
160
180
200
6.1
33.129.0
0.0
97.0
68.8
59.456.1
102.6
181.1
150.2
62.554.9 57.3
38.0
27.3
39.6
28.1
19.4
2013: Efficacy of Weekly Daytime-Ground ULV Adulticide - Fyfanon 97% upon Ae. aegypti/albopictus Populations
(Values Indicate Average # of Eggs & Larvae at 15 Sampling Sites within each group)
Treatment
Control 1
Control 2
Date of Collection
Start of Weekly ULV Applications
76% Reduction during treat-ment period per Henderson-Tilton (control variation cor-rected)
4/16 4/23 4/30 5/7 5/14 5/21 5/30 6/4 6/11 6/18 6/25 7/2 7/9 7/16 7/23 7/30 8/6 8/13 8/20 8/27 9/3 9/10 9/17 9/24 10/10
20
40
60
80
100
120
140
160
13.5
48.5
24.9 27.1
51.2
76.7
41.3
64.1
84.2
145.5
50.1
28.7
81.5
45.0 47.7
102.0
28.0
38.9
28.7
38.7
23.9
2013: Efficacy of Weekly Night-Ground ULV Adulticide - Fyfanon 97% upon Ae. aegypti/albopictus Populations
(Values Indicate Average # of Eggs & Larvae at 15 Sampling Sites within each group)
Treatment
Control
Control 2
Date of Collection
Start of Weekly ULV Applications 68% Reduction during treatment
period per Henderson-Tilton (control variation corrected)
Aerial Adulticiding for Ae. aegypti ….Will it Work?
• Studies from SE Asia and western Pacific nations have typically shown quite good aegypti control via aerial ULV applications (but application rates are much higher than allowed here in the US).
• Studies in Caribbean countries have typically found poor and unacceptable results….. Why?
* Endophilic mosquitoes, large droplets, caged mosquitoes, wrong “spray-
on” time.
Methodologies – Aerial Adulticide Applications - Aedes aegypti
• Study site in commercial fishing village
• Spray Platform: Hughes 500D
• Treatment area aerially-adulticided 1x per 2 week interval starting in mid June; and ending on July 30, 2013; total of 4 applications. Each application covered approx. 800 acres
• Adulticide: Fyfanon (97% malathion) delivered at 3 oz/ac through high-pressure spray system at 700psi via 9 PJ20 nozzles; VMD = approx 30 microns
• Measured mosquito population dynamics via 10-Landing Rate Count stations at 2-day intervals
• “Spray-On” was consistent at 30-45minutes prior to sunset
2012 - Aerial Daytime Adulticiding in Cortez Village
97%Reduction
94%Reduction
78%Reduction
Average Mortality = 89.7%
Night-Aerial Adulticiding for Ae. aegypti/albopictus???
Will it work on a day-active mosquito?
And why switch from a “day-spray” activity previously shown to be successful?
13-Jun
16-Jun
19-Jun
22-Jun
25-Jun
28-Jun
1-Jul
4-Jul
7-Jul
10-Jul
13-Jul
16-Jul
19-Jul
22-Jul
25-Jul
28-Jul
31-Jul
3-Aug
6-Aug
9-Aug
12-Aug
15-Aug
18-Aug
21-Aug
24-Aug
27-Aug
30-Aug
2-Sep5-Sep
0.0
2.0
4.0
6.0
8.0
10.0
12.0
14.0
16.0
2013: Efficacy of Night-Aerial ULV Applications on Aedes aegypti popula-tions - Night Applications
Lan
din
g R
ate
Cou
nts
Aerial applications; 6/20, 7/3, 7/15, and 7/30 Spray-On: 30-45 min after astronomical sunset
Population Reduction: 6/20 - 98.6% 7/3 - 86.5% 7/15 - 94.0% 7/30 - 85.9% Avg: 91.2%
Discussion
• The practices of nocturnal aerial adulticiding appears to have a significant population level impact upon exophilic mosquitoes when appropriate droplet sizes and spray techniques are used.
• Not a great deal of observed difference between “evening” (pre-sunset) and night (post-sunset) aerial spray events.
• Would this be enough to truncate a Dengue epidemic or local transmission?
Back to the Real World: If we had a Local case of Dengue or Chik ….. What Would
We Do? What Technique Would be Most Efficacious?
• 2014 – Evaluated Efficacy of: – Surveillance-based Aerial Adulticide, vs……– Surveillance-based Aerial Adulticides + Aerial
Larvicide Applications (think …. “IPM” for domestic mosquitoes)
– Malathion @ 3 oz/ac– Altosid 5% applied at 4 oz/ac
17-May 24-May 31-May 7-Jun 14-Jun 21-Jun 28-Jun 5-Jul 12-Jul 19-Jul 26-Jul 2-Aug 9-Aug 16-Aug 23-Aug 30-Aug 6-Sep0.0
1.0
2.0
3.0
4.0
5.0
6.0
7.0
8.0
9.0
10.0
8.6
1.3 1.2
1.92.1
2.62.8 2.7 2.7
3.1
2.62.8
3.1
4.2
2.6
3.13.4
3.6
3.8
5.5
1.4
0.7
1.8
3.3
0.4
1.7
0.9
0.2
1.2
0.3 0.20.5
0.3 0.3 0.3
Larvicide + Adulticide
Control
Date
Popu
latio
n Si
ze -
Avg
Lan
ding
Rat
e Co
unt
A&L
A L L A L
Effects of Aerial Larviciding and Adulticiding on Ae. aegypti/albopictus Populations (IPM - approach)
17-May 24-May 31-May 7-Jun 14-Jun 21-Jun 28-Jun 5-Jul 12-Jul 19-Jul 26-Jul 2-Aug 9-Aug 16-Aug 23-Aug 30-Aug 6-Sep0.0
1.0
2.0
3.0
4.0
5.0
6.0
7.0
8.0
9.0
10.0
8.6
1.3 1.2
1.92.1
2.62.8 2.7 2.7
3.1
2.62.8
3.1
4.2
2.6
3.13.4
3.6
3.8
5.5
1.4
0.7
1.8
3.3
0.4
1.7
0.9
0.2
1.2
0.3 0.20.5
0.3 0.3 0.3
Larvicide + Adulticide
Control
Date
Popu
latio
n Si
ze -
Land
ing
Rate
Cou
nt
A& L A L L A L
89.3% Overall Popula-tion Reduction
Effects of Aerial Larviciding and Adulticiding on Ae. aegypti/albopictus Populations (IPM - approach)
17-May 24-May 31-May 7-Jun 14-Jun 21-Jun 28-Jun 5-Jul 12-Jul 19-Jul 26-Jul 2-Aug 9-Aug 16-Aug 23-Aug 30-Aug 6-Sep0
2
4
6
8
10
12
1.5
2.5
5.4
2.0
5.3
2.7
9.6
10.8
3.8
8.8
10.3
2.0
6.6
5.5
2.1
3.0
Effects of Aerial Adulticing on Ae. aegypti/albopictus Populations
Adulticide Only
Control
Date
Popu
latio
n Si
ze -
Land
ing
Rate
Cou
nt L & A
Summary• Sanitation is far too expensive
• (Optimized) Truck adulticiding may be effective in small geographic areas but limited to large scale mosquito control approaches; Crepuscular vs. nocturnal efficacy? (related to wind conditions?). May have poor acceptability in many residential areas
• Aerial larviciding is very effective but costly and doesn’t target active vectors
• Aerial adulticiding is very effective but gains are short-lived
• IPM – approaches (ie active surveillance + aerial larvicides + aerial adulticide) yield excellent long-term control