Mosquito Management Strategy
Draft -- For Public Comment
FROM: Beyond Pesticides/National Coalition Against the Misuse of Pesticides
DATE: March 2002
SUBJECT: National Mosquito Management Strategy
Mosquito-borne diseases are quickly spreading throughout the United States. Citizens are afraid of these potentially fatal illnesses, and public officials are often pressured into ordering broadcast pesticide spraying because it is a quick and obvious response. To assist policymakers in solving this dilemma, we have worked with public health officials, mosquito control officers, and environmental health groups to develop a strategy that protects the public from both mosquito-borne diseases and the pesticides used to kill adult mosquitoes.
We recommend a national mosquito management strategy that emphasizes community education, prevention, and monitoring methods. While we do not recommend spraying pesticides, if a community decides to do this, it is important that they spray responsibly. First, the public must be notified in advance so they can prevent exposure to dangerous chemicals. Second, pesticide operators should be properly protected and trained on when, where, and how to spray.
This report also explains why it is necessary to develop mosquito management policies that reduce the reliance on toxic chemicals. Each week we receive inquiries from concerned citizens about pesticide spraying near their homes, schools, organic farms, and other sensitive areas. Often these calls are from people who have become ill from pesticide exposure.
Currently, many counties have inadequate prevention and public education policies. This results in a heavy reliance on spraying pesticides to kill adult mosquitoes. We often receive reports claiming that counties spray irresponsibly, for nuisance mosquitoes, or when they find dead crows. In response to these concerns, this report discusses the dangers and low efficacy of using pesticides to kill adult mosquitoes, and the facts about West Nile virus, St. Louis encephalitis, and dengue fever.
[include info about costs of spraying vs. less toxic methods of control]
Pesticides/National Coalition Against the Misuse of Pesticides (NCAMP)
is a national environmental organization that advocates public protection
from pesticides and promotes safer pest management practices.
The ideal mosquito management strategy emphasizes prevention and monitoring. Successful control of mosquito populations requires that community leaders teach residents and business owners how to reduce breeding habitats and mosquito bites through strong public education campaigns. Using the prevention and monitoring techniques outlined in this report, many communities will find that they can significantly reduce or even eliminate their reliance on pesticides while calming the public's fears over uncontrolled mosquito populations.
Tracking larval and adult mosquito populations, species types, breeding locations and virus outbreaks is an essential part of any mosquito management program. Knowing when and where the virus is likely to strike allows for precise, targeted control techniques.
Spraying should be done responsibly. The decision to use pesticides should only be made after carefully evaluating all of the contributing factors to human epidemics and weighing them against the likelihood of pesticide-related illnesses. The public must be notified in advance so they can prevent exposure to potentially dangerous pesticides. Most importantly, pesticide operators should be properly protected and trained on when, where, and how to spray.
The latter half of this report provides information about the dangers and inefficacy of spraying pesticides. Aside from the adverse health effects posed to humans, adulticiding may actually increase the number of mosquitoes by destroying their natural predators. Additionally, mosquitoes that survive the spraying may become resistant, longer-lived, more aggressive, and have an increased prevalence of the virus within their bodies.
Further studies are urgently needed to accurately determine the health effects and the efficacy of spraying pesticides, and to help determine whether adulticiding should continue to be used in the battle to control mosquitoes. Work must also be done to reduce the effects of global warming, which is the root cause of this growing epidemic of mosquito-borne diseases.
Mosquito-borne diseases are becoming more prevalent nationwide. With outbreaks of West Nile virus in the east, St. Louis encephalitis in the south, and Dengue fever in the west part of Hawaii, there is an urgent need to develop a national mosquito management strategy. This becomes especially critical as scientists expect global warming will increase insect-borne diseases.
Many communities around the country are using ineffective and pesticide-intensive mosquito management strategies. This report was prepared to provide policymakers and community leaders with information on effective strategies that reduce reliance on toxic chemicals, thus controlling mosquito populations with a more human-friendly approach.
Most experts agree that an efficient mosquito management strategy emphasizes prevention and monitoring methods. However, if these methods are not used properly, in time, or are ineffective, communities must decide whether or not to use pesticides. They must determine if they should risk exposing vulnerable populations to potentially fatal diseases caused by mosquitoes or to chronic or deadly illnesses caused by pesticides.
Should pesticides be used, and if so, when, how often and what products? This report provides information on how to make these difficult choices. Unfortunately, until scientists can provide better evidence on the effectiveness of spraying, there is no way to know for certain if it is worth the risks of spraying. At the same time, the proven health threats associated with pesticide exposure can no longer be ignored.
I. The Ideal Mosquito Management Strategy
The ideal mosquito management strategy emphasizes prevention and monitoring methods. Adulticides should be used only as a last resort. A successfully implemented strategy requires the cooperative efforts of individuals, state and local governments, and businesses.
Step 1a: Mosquito Prevention: What People Can Do at Home
§ Clean up standing
water on your property.
Avoid the Bite
Warning: Avoid products that contain DEET (N,N-diethyl-meta-toluamide), especially when choosing a product for children or when using it in combination with other chemicals or medications. Several cases of DEET poisonings have been reported by EPA, including three fatalities. Doctors recommend using products that contain no more than 30 percent DEET for adults. The EPA recommends that DEET should not be used on children or infants.[cite] A recent study by Duke University researchers found that combined exposure to DEET and permethrin, which is a mosquito spray, can lead to motor deficits and learning and memory dysfunction. We strongly recommend that only DEET-free products be used.
§ For home barbeques
or other outdoor gatherings, set up large fans.
Step 1b: Mosquito Prevention: What the Community Can Do
Step 2: Mosquito and Virus Monitoring
Monitoring is an essential part of an effective mosquito management program, and should be done regularly throughout the season. Tracking larval and adult population numbers, species types, and breeding locations provides invaluable information used for determining when, where, and what control measures might be needed. Knowing when and where the virus is likely to strike allows for precise, targeted control techniques. Identification of potential disease carriers and a gauge on the program's effectiveness are also afforded through population counts.
Monitoring can be labor intensive and costly. However, an accurate index of this information over time assists the program manager in predicting and anticipating control needs. Local weather reports should also be consulted regularly to help prepare the community for possible outbreaks of mosquitoes, which usually occur after heavy rains.
"Birds serve as important natural hosts for the virus in the disease cycle," states a report from three professors from Texas A&M. "Public health officials often survey migrating bird populations to determine the incidence of virus and the potential for transmission to man and animal by feeding mosquitoes."
Step 3: Larviciding: What's Safe to Use
Because not all breeding sites can be eliminated, it may be necessary to use larvicides, which kill mosquito larvae. It is recommended that products containing B.t.i. (Bacillus thuringiensis var. israelensis) be used in such places as storm drains and sewer treatment plants. B.t.i. is proven to be effective and is virtually non-toxic to humans and wildlife. Some say it is even safe to pour it directly into horse troughs. When sprayed into larval pools, B.t.i. is ingested by feeding mosquito larvae and kills them. The use of Methoprene (Altosid) should be avoided. It is an endocrine disruptor and has been linked to wildlife deformities. However, as with any pesticide, larvicides should not be used widely because mosquitoes may become immune to them.
A critical component of any successful application is monitoring to ensure that the insect population is at its most susceptible stage for B.t.i. application. B.t.i. is only effective against insects in their larval feeding stages and must be ingested.
Step 4: Adulticiding: Use Only as a Last Resort
How Do We Decide When
It is Necessary to Spray?
Experts agree that by the time a human illness is detected, it is already a month too late to start spraying pesticides. It takes approximately two to ten days for symptoms to show up and at least two to three weeks for blood tests to confirm a positive link to the virus. The efficacy of spraying will be much greater if earlier detection of infected mosquito pools and other factors mentioned above are used as spray indicators, rather than humans.
It is not efficacious to spray around the location of dead birds. Only mosquitoes can transmit the disease; birds cannot. And, as discussed in Appendix 1, some of the mosquitoes known to carry WN virus usually only travel within a few mile radius of their pool. Since most birds can travel much farther than this, spraying around dead birds does not get rid of the source problem. Some experts use sentinel species, such as chickens or ducks, to first detect infected mosquito populations. However, as mosquito species and vectors can vary in different areas, it is critical to have a good understanding of the ecology of each prior to beginning any spraying program.
Public Officials Must Warn the Public
City or town officials have a duty to warn the public about the dangers of pesticides and provide information on ways to minimize exposure. In an EPA document entitled Questions and Answers: Pesticides and Mosquito Control, they stated in bold that " no pesticide is 100 percent safe and care must be used in the exercise of any pesticide." Public officials should embrace and utilize the following guidelines:
§ Notify the
public at least 72 hours in advance. Utilize the media and/or send notices
to every household, school, hospital, and business in the community to
tell them when the spraying will occur so they will have ample time to
protect themselves. Alert the public that pesticides are not safe. [Dr.
Gaffney gave me extensive feedback on improving the efficiency of the
notification system-I'll include in final draft]
How Communities Can Spray Responsibly
Responsible spraying should adhere to the guidelines provided above and below.
§ Identify and
locate the infected mosquito pool(s). As discussed in Appendix 1, an adult
Culex mosquito can only fly within a few mile radius.
§ Leave the area*
*Infants, children, pregnant women, the elderly, and individuals with compromised immune systems are the most vulnerable populations and should take extra care to avoid pesticide exposure.
II. Spraying Pesticides is Dangerous
The two types of pesticides used in spraying adult mosquitoes include synthetic pyrethroids and organophosphates. Scientific studies show that both types are dangerous, especially to vulnerable populations. Ironically, the same population that is most susceptible to severe encephalitis is also at risk of getting sick from pesticides: the elderly and people with compromised immune systems. A study conducted by the National Research Council found that pregnant women, infants, and children also have a greater risk of getting sick from pesticides.
According to the New York State Department of Health, more people got sick from pesticide spraying than from exposure to the virus in 2000. Pesticide spraying may also leave the public with a false sense of security, and they may not take personal precautions. Worse, communities may feel it is no longer necessary to follow the prevention guidelines that will eliminate breeding sites.
Synthetic pyrethroids, which include resmethrin (Scourge) and sumithrin (Anvil), are adulticides patterned after pyrethrum, an extract from the chrysanthemum flower. While similar to pyrethrum, synthetic pyrethroids have been chemically engineered to have greater toxicity and longer breakdown times. Additionally, almost all synthetic pyrethroid mosquito products are combined with synergists, which increase potency and compromise the human body's ability to detoxify the pesticide. Symptoms of exposure include: dermatitis and asthma-like reactions, nasal stuffiness, headache, nausea, incoordination, tremors, convulsions, facial flushing and swelling, and burning and itching sensations. Synthetic pyrethroids are endocrine disruptors and have been linked to breast cancer. Deaths due to exposure have resulted from to respiratory failure. People with asthma and pollen allergies should be especially cautious. Breakdown times range from a few hours in direct sunlight, to several months in damp, dark environments.
Organophosphates, which include malathion (Fyfanon), naled (Dibrom) and chlorpyrifos (Mosquitomist), are a highly toxic class of pesticides that affect the central nervous, cardiovascular and respiratory systems. Symptoms of exposure include: numbness, tingling sensations, headache, dizziness, tremors, nausea, abdominal cramps, sweating, incoordination, blurred vision, difficulty breathing, slow heartbeat, unconsciousness, incontinence, convulsions and fatality. Some organophosphates have been linked to birth defects and cancer. [get sources from john] Breakdown times range from a few days in direct sunlight, to several months in damp, dark environments.
Mixing Chemicals is Dangerous
Another concern is that the Environmental Protection Agency (EPA) does not adequately review the synergistic effects of active and inert ingredients within the same product or those of different products before registering a product.
Two chemicals commonly used to control adult mosquitoes may be a dangerous combination. A recent scientific study showed cell destruction in laboratory animals when a pyrethroid called Permethrin was combined with insect repellents containing DEET. Dr. Mohammed Abou-Donia, a Duke University pharmacologist and co-author of this study, recommends that DEET should not be used with other chemicals or by people who are taking medication.
Dr. Abou-Donia is concerned that these chemicals are not only used in areas where there are healthy people, but where there are infants, children, and pregnant women. These and other vulnerable populations have a higher risk of becoming ill due to pesticide and DEET exposure. Additionally, several cases of DEET poisonings have been reported by EPA, including three fatalities. A recent study by Duke University researchers found that combined exposure to DEET and permethrin, which is a mosquito spray, could lead to motor deficits and learning and memory dysfunction.
Although the Environmental Protection Agency tests individual chemicals, they do not test the synergistic effects of using combined chemicals. More research needs to be done to determine the negative health effects of combined chemicals.
Pesticide Spraying is Harmful to the Environment
Pesticide spraying is harmful to ecosystems and wildlife. Moreover, wildlife and ecosystems depend on mosquitoes for their survival. As we discuss below, pesticide spraying often kills mosquito predators.
III. Pesticide Spraying is Inefficient, Not Proven Effective, and Expensive
Pesticide Spraying is Inefficient
The CDC states that spraying pesticides intended to kill adult mosquitoes, known as adulticiding, is usually the least efficient mosquito control technique. Preventative measures such as removing breeding areas are much more efficient in eliminating mosquito threats.
Dr. David Pimentel, a professor of entomology at Cornell University, estimates that pesticides sprayed from trucks hits less than 10 percent of the targeted spray area. "And you have to put out a lot of material to get that one-tenth of a percent onto the mosquito," Dr. Pimentel added. In a study Pimentel wrote for the Journal of Agricultural and Environmental Ethics, he estimated that less than .0001 percent of ultra low volume (ULV) pesticide sprays reach target insects. The rest of the pesticides is sprayed on unintended areas. Additionally, it is difficult for trucks to reach over and in between tall buildings or other structures.
Pesticide Spraying is Not Proven Highly Effective
The CDC also states that adulticiding should only be used as a last resort, when all prevention methods have failed. According to the CDC's website, "The underlying philosophy of mosquito control is based on the fact that the greatest control impact on mosquito populations will occur when they are concentrated, immobile and accessible. This emphasis focuses on habitat management and controlling the immature stages before the mosquitoes emerge as adults. This policy reduces the need for widespread pesticide application in urban areas."
While many report that lower mosquito counts occur immediately after spraying pesticides, it is not certain what percentage of the population is reduced. Most studies of the efficacy of adulticides are conducted with caged mosquito monitoring traps, which of course is not a realistic representation of mosquitoes in their natural environment.
Dr. Ray E. Parsons,
a medical entomologist and the assistant director for the Mosquito Control
Division in Houston, Texas, says it is difficult to determine the effectiveness
of pesticide spraying because there are currently no accurate means of
measuring Culex mosquito populations. (As we discuss in Appendix 1, Culex
is the most common type of mosquito that carries West Nile virus.) Therefore,
scientists cannot accurately determine what percentage of the population
has decreased after spraying.
An article in the Journal of the American Mosquito Control Association showed that long-range effects of pesticide spraying can actually increase the number of mosquitoes by destroying their natural predators. Additionally, mosquitoes that survive the spraying may become resistant, longer-lived, more aggressive, and have an increased prevalence of the virus within their bodies.
Costs: It May be Cheaper??? to Focus on Prevention Methods
[Does anyone have
examples of any cost/benefit analyses?]
Costs for mosquito management programs vary with size and geography. Education, larviciding, and monitoring can be costly, yet many??? communities still have considerable savings. Reduced risks to the public and our environment make the investment well worth it.
Legal Concerns of Improperly Trained Pesticide Applicators
New York and Maine
now face hefty pesticide-related lawsuits. Five spray operators who worked
for a New York City contractor in 2000 filed a complaint with the Occupational
Safety and Health Administration. They said they became sick because of
improper training and prolonged exposure to the chemicals. Another lawsuit,
worth $125 million, came from commercial fisherman who claimed there was
a dramatic decrease in their lobster harvest because of pesticides used
against mosquitoes believed to carry the WN virus.
In order to conduct adequate risk/benefit analyses of spraying adult mosquitoes when there is a disease outbreak, we need to implement two key monitoring systems. First, scientists should develop better ways of measuring mosquito populations in a given area. We should not spray pesticides on such a widespread basis until we have more accurate measurements of its efficacy. It is simply not worth the risks. Existing studies demonstrate that by spraying pesticides, we are compounding the low risks of acquiring this disease with another public health threat.
Secondly, pesticide poison monitoring systems must be created so that we can accurately determine the number of illnesses caused by spraying adulticides. In order to make this happen, public health officials must educate doctors and nurses, and community leaders must educate the public about symptoms of pesticide poisoning. Additionally, nonprofits or public agencies will need to develop an accurate and reliable infrastructure for measuring the amount of mosquitoes.
The CDC recommends
the following research priorities for St. Louis encephalitis: developing
a standardized national surveillance program; characterize overwintering
mechanisms and other aspects of enzootic maintenance cycle; evaluate vector
control strategies; determine biological basis for increased risk with
age; and develop more effective systems for disease prevention. The CDC
also recommends the following priorities for Dengue fever: develop improved
laboratory-based international surveillance; develop rapid, sensitive
and specific diagnostic tests; develop more effective community-based
prevention programs; and develop tetravalent dengue vaccine.
Culex Mosquito Life Cycle
In the United States, WNV is primarily associated with the Culex mosquitoes. Within this genus, three species, namely C. pipiens, C. restuans, and C. salinarius make up the majority of those mosquitoes found to be infected with WNV. Only female mosquitoes take blood meals.
Adult females may live 2-4 weeks or more, depending on climate, species, predation, and a host of other factors. Like other insects, mosquitoes are cold-blooded. They are most active at 80º F, become lethargic at 60º F, and cannot function below 50º degrees F.
All mosquitoes go
through a complicated life cycle called "complete metamorphosis."
Complete metamorphosis involves four distinct stages - egg, larva, pupa,
and adult. The length of time that each stage lasts depends on a number
of variables with temperature having the greatest impact.
After mating, the female requires a blood meal in order to produce over 250 eggs. It takes her three to four days to digest the blood and produce the eggs. Females transmit diseases when they live long enough to spread infection from the first blood meal victim to the second blood meal victim. Only a very small percentage of females live this long. Culex mosquitoes are generally weak fliers and do not move far from their larval habitat, although they have been known to fly up to two miles.
What is West Nile virus?
West Nile (WN) virus is a mosquito-borne disease that was first detected in the United States in 1999. WN virus can cause a potentially fatal illness known as encephalitis or inflammation of the brain. Birds act as hosts for the virus, and mosquitoes spread it through their bites. Current evidence shows that only mosquitoes can spread the disease; humans or other animals cannot. The information in this section is primarily based on information from the Centers for Disease Control and Prevention (CDC) website.
What is the likelihood that someone will become ill?
Most people's immune systems are able to fight the virus. Only a small percentage of the population will get the virus. Some may develop flulike symptoms. People older than 50 years and those with weakened immune systems have the highest risk of severe encephalitis. "Less than one percent of those infected with West Nile virus will develop severe illness," according to the CDC. Birds, horses, and other animals are also at risk.
What are the symptoms?
Most people who become infected will have mild symptoms that include fever, head and body aches, skin rash, and swollen lymph glands. However, if you have high fever, experience confusion, muscle weakness, and severe headaches, call your health care provider immediately. It may take 3 to 15 days for any of these symptoms to show.
Where is WN found?
WN virus is spreading throughout the United States. As of July 2001, the virus has been found in Connecticut, the District of Columbia, Florida, Georgia, Maryland, Massachusetts, New Hampshire, New Jersey, New York, Ohio, Pennsylvania, Rhode Island, and Virginia. The disease is also found throughout the world, including Africa, West Asia, Eastern Europe, and the Middle East. In areas where mosquitoes carry the virus, less than one percent of the mosquitoes are infected.
When is it most common?
Late summer and early fall is when mosquitoes infected with WN virus are common in most areas of the United States. In southern Florida and other warmer regions of the world, this disease can occur year-round. In the northeast, residents are advised to take precautions until there are two hard frosts.
The Facts about St.
The Facts about Dengue
on Protection from Mosquitoes and Pesticides
Connecticut Case Study
(Discuss the state's policy to not use pesticides for mosquito management)
New York Case Study