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

Historical (and effective) Mosquito Control Paradigm in the US ……

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

Artificial Containers

More Challenging …..

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

Domestic Complaints received by Manatee County MCD June, July, August 2011

•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

Truck applications of Larvicides….

Aerial LarvicidingAerial Applications of Larvicides

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)

Efficacy of Aerial Adulticide Applications on Aedes aegypti Populations

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?

Aerial Adulticiding in Cortez Village

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)

Cost: $34.57/acre (Chemical Costs)

89.3% Seasonal Population Reduction

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

Cost: $12.19/acre (Chemical Costs)

65.5% Seasonal Population Reduction

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