Mosquito control can save lives

J. Lyell Clarke III, Ph.D.
President, Clarke Mosquito Control
Roselle, Illinois

Mosquitoes have always been a nuisance at public recreational areas, including parks, golf courses, gardens, tennis courts, outdoor festivals and playgrounds, and at outdoor work sites, such as construction sites, park districts and road work sites. Increasingly, however, is the very serious health threat mosquitoes can bring to an entire community. Numerous mosquito-borne diseases have plagued the United States and other countries around the world. From 1974 to 1977, a severe encephalitis outbreak struck 2,500, as reported by the Centers for Disease Control (CDC), and spread well beyond its starting point in St. Louis, reaching 35 states.

Most recently, the public health threat of West Nile Virus has been the latest disease to make its way into the Western Hemisphere from overseas. West Nile Virus was first seen in the United States in New York City in the summer of 1999. And, Dengue is once again a threat to the United States from bordering countries in the South, while pockets of Malaria also are reappearing in the United States.

While there are many theories as to what first brought these alarming diseases to the United States many years ago, much emphasis continues to be placed on controlling the disease-carrying mosquitoes to prevent further disease spread. Mosquito control programs began to take form in the early 1900s when the state of New Jersey, after years of being plagued by mosquitoes, began the first organized mosquito control program. Those early programs formed the basis of what are now highly technical, Integrated Mosquito Control or Pest Management Programs, implemented around the world to help control the threat of public disease outbreak from the bite of an infected mosquito.

Earlier this year, Dr. Norman Gratz, the former director of vector biology and control for the World Health Organization, spoke before hundreds of health and government officials at a seminar on the West Nile Virus. He noted that the disease, "...is here to stay in the United States and likely to spread." Gratz also urged health officials across the United States "not to relax" in their fight against the virus that has claimed nine lives the past two summers in New York and New Jersey.

To prevent the spread of mosquito-borne disease and lessen mosquito nuisance, county or municipality offices have been contracting with outside companies to provide Integrated Mosquito Control programs or have undergone intensive training to provide their own mosquito control services. Mosquito control products used for larviciding (to eradicate mosquito larvae before they hatch into adult mosquitoes) and for adulticiding (used to combat in-flight adult mosquitoes) are reviewed and approved by the Environmental Protection Agency (EPA), which assesses the safety of using the products in a community to combat a public health problem. In addition, the products are often studied or reviewed by the CDC.

An Integrated Mosquito Control Program is most often a detailed, four-step process:

Step 1: Surveying and Mapping
The first step in an integrated control plan is to survey and map the mosquito population in the area and forecast the arrival of mosquito broods. Clarke Mosquito Control uses a Targeted Mosquito Management System (TMMS), which is a computerized database that keeps records of any mosquito breeding grounds inspected by the company during the last five years. This listing gives a complete outline of surveyed breeding site locations, including whether the site is man-made or natural, what types of mosquitoes breed there, and even when the site is most active during the mosquito season.

Using this and other information, such as the types of control agents available and the situations under which they are most effective, a seasonal plan of mosquito control is set for municipalities, counties and townships, which helps determine the ideal inspection and treatment times.

Step 2: Surveillance and Monitoring
In addition to tracking mosquito-breeding areas, it is important to use the Mosquito Brood Prediction Method to forecast the arrival of mosquito broods and the expected peak annoyance periods. By looking at precipitation, daily average temperatures and other environmental data, a mosquito control company is able to predict when mosquito broods are likely to hatch, and what the most problematic areas will be. This routine surveillance determines the distribution and density of mosquito populations, and their proximity to human living areas.

Light traps help mosquito control companies keep abreast of emerging mosquito populations, and alert a company when annoyance threshold levels are reached. Additionally, calls from the public help identify areas of heavy infestation.

Step 3: Larviciding
With a number of changes and advances in the mosquito control industry, the focus has shifted from controlling adult mosquitoes to controlling breeding sites. Once breeding sites have been identified, they are treated to prevent larval development. Prescription larvicides like Vectolex(r) (Bacillus sphaericus), Altosid(r) (methoprene) or Abate(r) (temephos) are introduced into ponds, open street catch basins and subdivisions where mosquito eggs are hatching, and specifically attack mosquito larvae.

Step 4: Adulticiding
While adult mosquitoes are no longer the primary targets of mosquito control, it is necessary and warranted to use adult control measures if the adult mosquitoes invade human populations in large numbers. Adulticiding has undergone a number of changes over the years, and is now a well-calculated, technology-driven control measure relying upon extensive field and laboratory research, careful evaluation of surveillance and monitoring data and the use of sophisticated equipment and application techniques. When employing adulticiding techniques, Clarke uses mosquito control products such as Anvil(r) (sumithrin), Biomist(r) (permethrin) among others that do not bioaccumulate, meaning they only affect adult mosquitoes and break down easily without lingering in the environment.

This four-step process ensures that proper mapping and surveillance is completed to best plan mosquito control efforts before larvicidal treatments and, if necessary, adulticidal applications take place in public areas.

Integrated Mosquito Control programs are not only an effective tool in reducing the nuisance of mosquitoes in outdoor work and recreational sites, but also a necessary part of public programming to help protect the health and safety of workers and entire communities from the spread of mosquito-borne illnesses, which contributes overall to a healthier quality of life.

J. Lyell Clarke can be reached at (630) 671-3114 or by e-mail at clarke@clarkemosquito.com.