WHY DO MOSQUITO SURVEILLANCE? Rosmarie Kelly Public Health Entomologist GDPH
Nuisance mosquito control programs (MOSQUITO CONTROL) Vector mosquito control programs (PUBLIC HEALTH) Used to control various species of mosquitoes which cause distress to humans and animals due to biting. Used to control one or more species of mosquitoes which transmit diseases to humans or animals. Both programs can co-exist and be mutually beneficial. Large numbers of mosquitoes can have serious economic implications. Types of Control Programs
In the absence of diseases, mosquitoes can become so abundant that they cause disruptions in community services and cause severe stress in the affected local human, pet and livestock populations.
Without surveillance, mosquito control becomes a matter of luck. With surveillance, mosquito control becomes more targeted, more effective, and more economical.
Integrated Pest Management (IPM) IPM reduces dependence on pesticides by integrating non-chemical methods to help control or prevent pest populations.
Identify the pest
Use surveillance of some type to evaluate pest level
Target control - don’t make applications based on a calendar
Integrated Mosquito Management Source Reduction Larval Surveillance - Larval Control Adult Surveillance - Adult Control Community Education / Communication Mapping / Record Keeping Arboviral Surveillance (where appropriate) Best Management Practices
S.P.L.A.T. S urveillance P ublic Awareness L arviciding A dulticiding T iming
Some Common Mosquito Species Larval Habitat Biting Time Flight Range Aedes albopictus artificial containers & tree holes Day 100 - 300 yards Culex quinquefasciatus ground pools, catch basins, artificial containers Crepuscular, Night 1/4 - 1/2 mile Aedes vexans Flooded grassy and wooded areas Day, Crepuscular, Night 5 - 8 miles Coquillettidia perturbans Cattail marshes Crepuscular, Night 1 - 5 miles
"Landing Rate" - the number of mosquitoes that land on the observer over a designated period of time. It is suggested that they be taken over either a 1 or 5 min period. If the landing rates exceed 50 in 30 sec, the interval can be shortened to protect observers that are expected to conduct numerous counts. Landing rates may involve identification, but they are normally employed in areas where a single, known species is the sole cause of annoyance.
Emergency mosquito control is needed due to flooding
For Aedes albopictus , remind the caller to dump out or throw out containers that can hold water (this will also help with Culex quinquefasciatus , our WNV vector). Containers need to be dumped at least once a week. Larvicides can be applied to water that can not be dumped out or eliminated. Both mosquito dunks (Bti) and mosquito torpedoes (methoprene) can be bought at stores like Home Depot, Lowes, and some of the big chain pet stores in the ornamental pool area.
Always remind people to wear mosquito repellent when outside. Recommended repellents are those that contain DEET, picaridin, IR3535, or PMD (oil of lemon eucalyptus).
If the mosquitoes are biting after dark, or during the day in shady areas, they can be any of a number of species. Floodwater species may be abundant after heavy rains. Face biters tend to be any number of Psorophora spp, although other mosquitoes will bite above the waistline. Landing counts done after dark will help determine if the mosquitoes constitute a serious problem needed adulticiding. THIS WILL NOT TELL YOU WHERE TO APPLY LARVICIDES.
Remember, landing counts will give you info on whether human biting mosquitoes are present. Landing counts, along with field ID of Aedes albopictus , will let you know if adulticiding is needed. Landing counts will NOT give you info about where to larvicide unless you are also ID’ing the mosquitoes.
The SIMPLE SCOOP is the "dipping to get water" method that is the least effective method used. It consists of simply scooping a dipperful of water. This is probably the most commonly used method, particularly by new inspectors, and it is often the method referred to in much of the literature as "the standard dipping procedure." While it can be successfully used to collect Culex larvae, it is still not the method of choice . WHAT NOT TO DO
The first and usually the best method to start with is the SHALLOW SKIM. The shallow skim consists of submerging the leading edge of the dipper, tipped about 45 degrees, about an inch below the surface of the water and quickly, but gently, moving the dipper along a straight line in open water or in water with small floating debris. End the stroke just before the dipper is filled to prevent overflowing. The shallow skim is particularly effective for Anopheles larvae that tend to remain at the surface longer than Aedes and Culex. Anopheles are usually associated with floating vegetation and debris.
The second method to try in open water, with or without floating objects, is the COMPLETE SUBMERSION. Many mosquito larvae, particularly those of the genera Aedes and Psorophora, are very active and usually dive below the surface quickly if disturbed. In this case, a quick plunge of the dipper below the surface of the water is required, bringing the dipper back up through the diving larvae. Bring the dipper up carefully to avoid losing the larvae in the overflow current.
When you need to sample at the edges of emergent vegetation, try the PARTIAL SUBMERSION technique. To do this, push the dipper, tilted at about 45 degrees, straight down adjacent to the vegetation. This causes the water around the vegetation to flow into the dipper, carrying the larvae with the flow. There is no need to move the dipper horizontally. Pull the dipper up before it is full.
In very shallow water, try the FLOW-IN method. Larvae can be collected by pushing the dipper into the substrate of the pool and letting the shallow surface water, debris and larvae flow into the dipper. Do not move the dipper horizontally.
To sample for larvae that may be under floating or emergent vegetation, use the SCRAPING technique. This method is used in habitats that contain clumps of vegetation such as tussocks of sedges, floating mats of cattails or water lettuce or other plants that are too large to get in the dipper, or clumps of submerged vegetation such as hydrilla or bladderwort. Dip from the water in towards the vegetation and end by using the dipper to scrape up against the base or underside of the vegetation to dislodge larvae. This method is usually more effective if the bottom of the dipper is screened and it is often used to sample for Coquillettidia and Mansonia mosquitoes .
The dipper can also be used as BACKGROUND. This is especially useful in woodland pools and other shallow water or when larvae are disturbed and dive to the bottom. Submerge the dipper completely to the bottom litter and slowly move it around. The darker mosquito larvae and pupae will stand out against the background of a white or aluminum dipper. Once larvae appear in the dipper, just lift it upward.
One or more of these methods, properly used, can determine the mosquito species composition of most aquatic habitats, excluding those whose openings are smaller than the dipper, such as tires, rock pools, treeholes and tree root systems like those found in cedar and red maple swamps. In those cases, a smaller container, such as a vial, measuring spoon or tea strainer can be used in the same seven ways as the dipper described above. Then there is the tubular dipper, the chef's poultry baster, for those really hard to get to places like plant axils, treeholes and tree root holes.
ID OF LARVAE IS IMPORTANT NOT ALL LARVAE NEED TO BE CONTROLLED The larvae of this mosquito are found in permanent vegetated waters. The adults are not known to bite humans.
An action point is a trigger for initiating a control measure. It is a point at which pest populations or environmental conditions indicate that pest control action must be taken USING THE DATA – when should control occur
Here, an action point would occur whenever mosquito populations rose above the baseline. This is useful when controlling vector species where you have well-defined risk and population data. Mosquito surveillance 0 5 10 15 20 25 30 35 40 45 50 55 27 28 29 30 31 32 33 34 35 36 37 week # mosquitoes Average # Mosquitoes current data take action Human cases
For nuisance species, a threshold can be set based on numbers of complaints and/or mosquito population size. EIL – economic injury level; angry population ET – economic threshold; acceptable level of complaints number of complaints
Mosquitoes are identified and graphs are used to monitor changes in mosquito populations
When predetermined action thresholds are exceeded, an action (press release, education, monitoring, larviciding, adulticiding, etc) occurs
Arboviral “testing” sites are established throughout the area
The public, the community, and the municipalities are encouraged to take active roles in decreasing mosquito populations through community cleanup, personal protection measures, and mosquito control - the role of the health department is supportive