Control of Aedes aegypti from the Perspective of a Mosquito Control District Christopher Lesser and Mark Latham Manatee 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 Larviciding Aerial Applications of Larvicides

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)

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

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

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) – 3 oz/ac – Altosid 5% applied at 4 oz/ac

Cost: $34.57/acre (Chemical Costs) 89.3% Seasonal Population Reduction

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