Overview of Arboviruses

Q. What is an arbovirus?

A. Arboviruses (Arthropod-borne viruses) cause diseases such as West Nile virus infection, eastern equine encephalitis, St. Louis encephalitis, Powassan encephalitis, etc. They are viruses that are transmitted by blood feeding arthropods like mosquitoes and ticks. Arboviruses are maintained in nature in a cycle of transmission between an animal host (the reservoir) and the mosquito or tick.

Transmission of Arboviruses

Q. How do people get infected with West Nile (WNV) or eastern equine encephalitis (EEE) virus?
A. The main route of human infection with West Nile and EEE virus is through the bite of an infected mosquito. Neither virus can be passed between people by coughing, sneezing, shaking hands, sharing food, etc

Additional routes of human infection were identified for WNV during the 2002 West Nile epidemic. It is important to note that these other methods of transmission represent a very small proportion of cases. Investigations have identified WNV transmission through transplanted organs and through blood transfusions. There is one reported case of transplacental (mother-to-child) WNV transmission, and one reported case of transmission of WNV through breast-milk. Transmission in the laboratory has also been reported.

Q. How are arboviruses spread to humans or horses by mosquitoes?

A. Getting infected with an arbovirus is a bit like winning the lottery. The chances of it happening are very slim, but the consequences can be life-changing. The process of infection works like this:

1) A female mosquito (of a species that bites both birds and mammals) first must bite a bird infected with an arbovirus (male mosquitoes don’t bite).

2) The blood of the infected bird contains arbovirus particles, so the mosquito biting the bird draws in the disease-causing virus with her blood meal.

3) The mosquito digests her meal for several days, and then lays her eggs. While her meal is being digested and she is laying eggs, the virus particles move from the insect’s gut to her salivary glands.

4) After the mosquito lays her eggs (if she is lucky enough to live that long), she seeks another blood meal. This time she bites a horse or a human.

5) She lands, inserts her mouthparts, and injects saliva. Along with her saliva, she injects some of the virus particles. If enough virus particles are in the saliva, the person or horse will be infected. This is the same process by other animals are infected also.

Please note: Humans and equines are “dead-end” hosts for WNV and EEE. Mosquitoes that bite humans or equines infected with WNV or EEE don’t pick up enough virus particles to pass the disease along to the next human (or animal) they bite.

Q. Do all mosquitoes spread WNV and EEE?

A. No. There are approximately 42 different species of mosquitoes in Maine. Some of them have habitats that overlap, and others have separate habitats based on their specific breeding requirements. Some mosquitoes feed on birds, some on mammals, and a few on both birds and mammals.

The mosquitoes of most concern are those that feed on both birds and mammals; these are called “bridge” vectors. This type of mosquito may become infected with an arbovirus by feeding on an infected bird, and then later feed on a human, thus providing the “bridge” that allows arboviruses to spread to humans.

Q. If I live in an area where birds or mosquitoes with WNV or EEE have been reported and a mosquito bites me, am I likely to get sick?
A. No. Even in areas where these viruses are circulating, very few mosquitoes are infected. Even if the mosquito is infected, less than 1% of people who get bitten and become infected will get severely ill. The chances you will become severely ill from any one mosquito bite are extremely small.

Q. Can you get WNV or EEE directly from other insects or ticks?
A. Infected mosquitoes are the primary source for WNV and EEE. Although ticks infected with West Nile virus have been found in Asia and Africa, their role in the transmission and maintenance of the virus is uncertain. However, there is no information to suggest that ticks played any role in cases of either disease identified in the United States.

Q. Can you get WNV or EEE from another person?
A. No. WNV and EEE are NOT transmitted from person-to-person. For example, you cannot get either virus from touching or kissing a person who has WNV or EEE, or from a health care worker who has treated someone with either disease.

Q. Are all wetlands breeding grounds for arboviruses?

A. No. The few potential WNV vector species primarily breed in two types of areas: stagnant water and high elevation salt marsh pools. The stagnant water areas can be found in artificial containers such as bird baths, tires, buckets, kiddy pools, stormwater and catch basins, drainage ditches, etc. where water may not be regularly exchanged and becomes stagnant. Many of these structures can be emptied regularly to eliminate mosquito breeding conditions. High elevation salt marsh pools are located above the normal high tide line in marine areas. These areas are typically only flooded during significant storms or other extremely high tide events, often only once per month. Some of them contain fish that will act as natural predators, keeping the mosquitoes from surviving and breeding. However, the pools without fish provide good mosquito breeding habitat.

The mosquito primarily responsible for maintaining EEE in nature rarely feeds on humans, but is important because it infects birds, which can then infect mosquitoes that feed on birds AND mammals, like humans and horses. This mosquito, called a maintenance vector, primarily breeds in acidic freshwater wetlands like red maple and cedar swamps or bogs, which represent only a few of the many types of freshwater wetland habitats found in Maine.

All wetlands need to be respected and preserved, as they:

Play important roles in keeping streams and rivers flowing, and recharging groundwater.
May serve as vital sources of irrigation water for agriculture.
Are extremely important for wildlife; some of our threatened or endangered species must have access to wetlands, or face extinction.
Constitute our most productive natural resources with great diversities of plants, insects, amphibians, fish, birds, and mammals.

Testing for and Treating Arboviruses in Humans

Q. I think I have symptoms of WNV or EEE. What should I do?
A. Contact your health care provider if you have concerns about your health. If you or your family members develop symptoms such as high fever, confusion, muscle weakness, and severe headaches, you should see your doctor immediately.

Q. How do health care providers test for WNV, EEE, or other arboviruses?
A. Arboviral infection can be suspected in a person based on clinical symptoms and patient history. Laboratory testing of blood or cerebrospinal fluid (CSF) samples is required for a confirmed diagnosis. These tests may not be positive when symptoms first occur, but will usually be positive in infected people within 8 days of the beginning of symptoms.

Persons that test positive for an arboviral infection by these tests will have a second confirmation test completed at the national Centers for Disease Control.

Q. How is WNV or EEE treated?
A. There is no specific treatment for WNV or EEE. In more severe cases, intensive supportive therapy is indicated, often involving hospitalization, intravenous fluids, airway management, respiratory support (ventilator), prevention of secondary infections (pneumonia, urinary tract, etc.), and good nursing care.

Q. If an arbovirus test is a “false positive” what does that mean?

A. A “false positive” occurs when an initial tests indicates that a person does have WNV or EEE, but a later, more specific tests indicates that the person does not actually have the infection. While it is important for the Maine CDC to get an accurate picture of where people are being infected in order to focus prevention and control efforts, the result does not have a great impact on the individual person. There is no specific treatment that the person would receive due to WNV or EEE. The person may want to work with their physician to see if another cause of the illness needs to be identified.

Arboviruses and Animals

General

Q. How many types of animals have been found to be infected with West Nile or EEE virus?
A. The vast majority of WNV and EEE infections have been identified in birds. WNV has been shown to infect horses, llamas, alpacas, bats, chipmunks, skunks, squirrels, and domestic rabbits. A relatively small number of WNV infected dogs (<40) and only 1 WNV infected cat have been reported nationally during 2003. Experimentally infected dogs showed no symptoms after infection with WNV. Some infected cats exhibited mild, nonspecific symptoms during the first week after infection--for the most part only showing a slight fever and slight lethargy. It is unlikely that most pet owners would notice any unusual symptoms or behavior in cats or dogs that become infected with WNV.

EEE can also infect horses, llamas, and alpacas, and although cloven-hoofed livestock may be susceptible, their level of risk is unknown. Some states have discovered whitetail deer infected with EEE, but no one has studied just how serious those infections are. Emus and Ring-necked pheasants are very susceptible to EEE infection, and infected pheasants can serve as a source of virus for mosquitoes to spread the disease further.

Q. Can I use insect repellent on my pets and livestock?
A. DEET-based repellents, which are recommended for humans, are not approved for veterinary use (largely because animals tend to ingest them by licking.) Talk with your veterinarian for advice about the appropriate product for use on your pets or livestock.

Horses

Q. What are the signs of WNV or EEE in horses?
A. Clinical signs of WNV in horses include stumbling, depression, incoordination, and weakness of limbs (partial paralysis or inability to stand), and muscle twitching. However, some infected horses may not show any signs. Although about two-thirds of infected horses that become ill will survive and have a full recovery, West Nile virus can and has caused deaths in horses.

Clinical signs of EEE in horses are similar to those of WNV, but EEE is serious in equines (horses and their relatives) and usually fatal.

Q. How do the horses become infected with WNV or EEE?
A. The same way humans become infected—by the bite of infectious mosquitoes. The virus is located in the mosquito's salivary glands. When mosquitoes bite or "feed" on the horse, the virus is injected into its blood system. The virus then multiplies and may cause illness. The mosquitoes become infected when they feed on infected birds or other animals.

Q. Can I get infected with WNV or EEE by caring for an infected horse?
A. These diseases are transmitted by infectious mosquitoes. There is no documented evidence of person-to-person or animal-to-person transmission of WNV or EEE. Normal veterinary infection control precautions should be followed when caring for a horse suspected to have these or any viral infection.

Q. Can a horse infected with WNV or EEE infect horses in neighboring stalls?
A. No. There is no documented evidence that WNV or EEE is transmitted between horses.

Q. Can I vaccinate my horse against WNV and EEE?
A. There are WNV and EEE vaccines available for equines. Please note that the vaccines offer NO cross-protection; i.e., the WNV vaccine does not protect against EEE, and vice versa.

To be protected, horses must be fully vaccinated or boostered at least two weeks before exposed to mosquitoes. Please consult your veterinarian for more information.

Q. What is the treatment for a horse that has WNV or EEE? Should it be destroyed?
A. There is no reason to destroy a horse just because it has WNV or EEE. Treatment would be supportive and consistent with standard veterinary practices for animals infected with a viral agent.

Arboviruses and Wild Game/Meat

Q. Is there a risk of getting infected with WNV or EEE if I eat turkey or another animal that has been infected with the virus?
A. There is no evidence that people can become infected with WNV or EEE from eating infected meat. The small, theoretical risk of infection can be eliminated by proper handling and thorough cooking of meat before it is consumed.

Several well-known and potentially serious food-borne illnesses can occur when turkey and other meats are improperly handled or undercooked. For more information on food safety, please see: http://www.cdc.gov/foodsafety/.

A small number of squirrels have tested positive for the West Nile virus. There is no evidence that people could become infected with the West Nile virus by being near an infected squirrel or in the yard with a dead one. However, the presence of an infected squirrel does mean that there could be infected mosquitoes nearby, and people should use protective clothing and repellent, and avoid maintaining mosquito-breeding sites on their property.

Q. What is known about the risk of WNV or EEE from dried, uncooked meat (jerky)?
A. There are no published studies that directly address this question. Most studies indicate that while mammals can become infected with West Nile or EEE virus, they do not develop high concentrations of virus in their blood or tissues. Although it is unlikely that dried meat from mammals would have much virus present, and probable that gastrointestinal digestion would further limit the possibility of infectiousness, there is insufficient evidence to determine whether dried meat presents a risk of WNV or EEE to humans or other animals.

Q. Are duck and other wild game hunters at risk for WNV or EEE infection?
A. Because of their outdoor exposure, game hunters may be at risk if they are bitten by mosquitoes in areas with arboviral activity. The extent to which WNV or EEE may be present in wild game is unknown.

Q. What should wild game hunters do to protect themselves against WNV and EEE?
A. Hunters should follow the usual precautions when handling wild animals. If they anticipate being exposed to mosquitoes, they should apply insect repellent to clothing and skin, according to label instructions, to prevent mosquito bites. Hunters should wear gloves when handling and cleaning animals to prevent blood exposure to bare hands and meat should be cooked thoroughly.

Arboviral Surveillance in Maine

Q. What is Maine doing about WNV and EEE?

A. The Maine Center for Disease Control has developed an Arboviral Surveillance system to track the occurrence of WNV and EEE in Maine, generally beginning in mid-June and lasting through to mid-October. Surveillance efforts include adult mosquito trapping and testing, collecting dead bird data, testing dead birds, llamas, alpacas, and horses, and testing people who are ill with symptoms similar to those of an arbovirus infection.

By doing this, prevention and education efforts can be focused on higher risk areas, including showing the public how to protect themselves and their families from diseases. In addition, other state agencies, health professionals and non-governmental groups have worked together since 2000 to increase awareness and promote preventive measures. Further information on arboviruses, their prevention, and Maine’s arboviral surveillance data can be found at http://www.maine.gov/dhhs/boh/ddc/west_nile_virus.htm.

Q. What should I do if I find a dead bird?
A. The usual bird surveillance season in Maine is from June through October. If you find a dead bird in these months, call the Maine CDC Dead Bird Reporting Line at 1-888-697-5846, and you will be provided with further instruction. Testing of dead birds in 2006 will limited to corvids (ravens, crows, and blue jays), unless there are unusual circumstances. Captive pheasants and emus are notable exceptions, and owners of these species or veterinarians providing care for these species are also encouraged to call the Bird Reporting Hotline if they detect severe illness or death in their birds. Even though not all dead birds will be collected or tested, all reports will be recorded; this information can be very useful in detecting clusters of dead birds that occur over time, and can indicate if and when the testing protocol should be modified.

If you must touch a dead bird, or local authorities tell you to simply dispose of it: Avoid bare-handed contact with any dead animals, and use gloves or an inverted plastic bag to place the bird carcass in a garbage bag and dispose of it with your routine trash. There is NO evidence that a person can get WNV or EEE from handling live or dead infected birds. However, persons should avoid bare-handed contact with ANY dead animals, and use gloves or double plastic bags if handling them is necessary.

Q. Should I report any other ill or dead animals?
A. Equines, llamas, and alpacas make up an important component of the Maine CDC Arboviral Surveillance program. Owners and veterinarians are urged to report cases of illness in these species so that the Maine CDC can determine if arboviral testing is appropriate. Any equine, llama, or alpaca that dies with neurological abnormalities, or is euthanized due to illness with neurological abnormalities, should be reported to either the Maine CDC Disease Reporting Hotline at 1-800-821-5821 or the Bird Reporting Hotline at 1-888-697-5846.

Only dead animals of these species can be tested for arboviral infection, as they must first be tested for rabies. If a veterinarian, while treating an animal of these species, obtains serology results positive for an arbovirus, the Maine CDC urges them to report those results to the phone number stated above, even if the animal survives. It is also important that a WNV/EEE vaccination history be submitted with any specimens and included in any reports. Reports of potential arboviral cases in these species can be made year-round.

Overview of West Nile Virus

Q: What is West Nile virus?
A. West Nile virus (WNV) is commonly found in Africa, West Asia, and the Middle East. It is closely related to St. Louis encephalitis virus, another arbovirus found in the United States. WNV can infect humans, birds, mosquitoes, horses and some other mammals.

Q. How long has West Nile virus been in the U.S.?
A. It is not known exactly how long it has been in the U.S., but it was first detected in North America during the summer of 1999, when infection with the virus caused an outbreak of illnesses in New York City. Within the next four years, the virus spread to almost all areas of North America. The continued expansion of West Nile virus in the United States indicates that it is permanently established.

Q. Is the disease seasonal in its occurrence?
A. In temperate zones, West Nile encephalitis cases occur primarily in the late summer or early fall. In the southern climates where temperatures are milder, West Nile virus can be transmitted year round.

Q. What parts of Maine are affected by West Nile Virus? Is it spreading further?

A. WNV was first identified in Maine in 2001. During 2003, West Nile Virus was documented (through testing of dead birds and mosquitoes) in twelve of Maine’s 16 counties. In 2005, 22 birds tested positive for WNV in Maine, one in Cumberland County, and the rest in York County.

Experts believe that WNV is well established in the ecologic systems of most areas in the United States and that it continues to spread and that it will remain with us for many years to come. The Maine Center for Disease Control recommends that citizens and municipalities assume that the risk of acquiring WNV infection exists in all Maine communities.

Cases of West Nile Human Disease

Q. How many cases of West Nile disease in humans have occurred in the U.S., and in Maine specifically?
A. The national Centers for Disease Control and Prevention (CDC) maintains West Nile virus infection data for the United States at http://www.cdc.gov/ncidod/dvbid/westnile/surv&control.htm. In 2005, there were 12,819 human WNV cases in the United States. Maine, New Hampshire and Vermont were among the eight states that had no human cases. Massachusetts had six cases and New York had 14. The really high numbers of human cases (more than 100) occurred in central and western states.

To date, there have been NO human cases of West Nile virus infection ever identified in Maine.

Q. What proportion of people with severe illness due to West Nile virus die?
A. Among those with severe illness due to West Nile virus, case-fatality rates range from 3% to 15% and are highest among the elderly, who appear to be more likely to get severe illness from infection with West Nile virus than do younger individuals. Less than 1% of people who become infected with West Nile virus will develop severe illness -- most people who get infected do not develop any disease at all.

Who's at Risk for West Nile Virus Infection

Q. Who is at risk for getting West Nile encephalitis?
A. Anyone who is exposed to mosquitoes is potentially at risk of mosquito-borne disease. All residents of areas where virus activity has been identified are at risk of getting West Nile encephalitis; persons over 50 years of age have the highest risk of severe disease. It is unknown if immunocompromised persons are at increased risk for WNV disease.

Q. Is a woman's pregnancy at risk if she gets infected with West Nile virus?
A. There is one documented case of transplacental (mother-to-child) transmission of WNV in a human. Although the newborn in this case was infected with WNV at birth and had severe medical problems, it is unknown whether the WNV infection itself caused these problems or whether they were coincidental. More research will be needed to improve our understanding of the relationship - if any - between WNV infection and adverse birth outcomes.

Nevertheless, pregnant women should take precautions to reduce their risk for WNV and other arboviral infections by avoiding mosquitoes, using protective clothing, and using repellents containing DEET (See the Personal Measures to Prevent WNV and EEE Infection section). When WNV transmission is occurring in an area, pregnant women who become ill should see their health care provider, and those whose illness is consistent with acute WNV infection, should undergo appropriate diagnostic testing.

Q. Are infants at higher risk than other groups for illness with West Nile virus?
A. No. West Nile virus illnesses in children younger than 1 year old are infrequent. During 1999-2001, no cases in children younger than one year of age were reported in the United States. In 2002, 2,500 total West Nile Virus disease cases were reported in the United States, and only six occurred in children less than one year of age.

Symptoms of West Nile Virus Infection

Q. What are the symptoms of West Nile virus (WNV) infection?
A. Infection with WNV can be asymptomatic (no symptoms), or can lead to West Nile fever or severe West Nile disease. It is estimated that about 20% of people who become infected with WNV will develop West Nile fever. Symptoms include fever, headache, tiredness, and body aches, occasionally with a skin rash (on the trunk of the body) and swollen lymph glands. While the illness can be as short as a few days, even healthy people have reported being sick for several weeks.

The symptoms of severe disease (also called neuroinvasive disease, such as West Nile encephalitis or meningitis or West Nile poliomyelitis) include headache, high fever, neck stiffness, stupor, disorientation, coma, tremors, convulsions, muscle weakness, and paralysis. It is estimated that approximately 1 in 150 persons infected with the West Nile virus will develop a more severe form of disease. Serious illness can occur in people of any age; however people over age 50 and some immunocompromised persons (for example, transplant patients) are at the highest risk for getting severely ill when infected with WNV.

Most people (about 4 out of 5) who are infected with West Nile virus will not develop any type of illness (an asymptomatic infection); however you cannot know ahead of time if you'll get sick or not when infected.

Q. What is the incubation period in humans (i.e., time from infection to onset of disease symptoms) for West Nile disease, and how long do symptoms last?
A. The incubation period of West Nile disease is usually 2 to 15 days. Symptoms of West Nile fever will generally last a few days, although even some healthy people report having the illness last for several weeks. The symptoms of severe disease (encephalitis or meningitis) may last several weeks, although neurological effects may be permanent.

Q. What is meant by West Nile encephalitis, West Nile meningitis, West Nile poliomyelitis, “neuroinvasive disease” and West Nile fever?
A. The most severe type of disease due to a person being infected with West Nile virus is sometimes called “neuroinvasive disease,” because it affects a person's nervous system. Specific types of neuroinvasive disease include: West Nile encephalitis, West Nile meningitis, West Nile meningoencephalitis and West Nile poliomyelitis. Encephalitis refers to an inflammation of the brain, meningitis is an inflammation of the membrane around the brain and the spinal cord, meningoencephalitis refers to inflammation of the brain and the membrane surrounding it, and poliomyelitis refers to an inflammation of the spinal cord.

West Nile Fever is another type of illness that can occur in people who become infected with the virus. It is characterized by fever, headache, tiredness, aches and sometimes rash. Although the illness can be as short as a few days, even healthy people have been sick for several weeks.

Q. If I have West Nile Fever, can it turn into West Nile encephalitis?
A. When someone is infected with West Nile virus (WNV) they will typically have one of three outcomes: No symptoms (most likely), West Nile fever (WNF in about 20% of people) or severe West Nile disease, such as meningitis or encephalitis (less than 1% of those who get infected). If you develop a high fever with severe headache, consult your health care provider.

West Nile fever is characterized by symptoms such as fever, body aches, headache and sometimes swollen lymph glands and rash. West Nile fever generally lasts only a few days, though in some cases symptoms have been reported to last longer, even up to several weeks. West Nile fever does not appear to cause any permanent health effects. There is no specific treatment for WNV infection. People with West Nile fever recover on their own, though symptoms can be relieved through various treatments (such as medication for headache and body aches, etc.).

Some people may develop a brief, WNF-like illness (early symptoms) before they develop more severe disease, though the percentage of patients in whom this occurs is not known.

Occasionally, an infected person may develop more severe disease such as “West Nile encephalitis,” “West Nile meningitis” or “West Nile meningoencephalitis.” Encephalitis refers to an inflammation of the brain, meningitis is an inflammation of the membrane around the brain and the spinal cord, and meningoencephalitis refers to inflammation of the brain and the membrane surrounding it. Although there is no treatment for WNV infection itself, the person with severe disease often needs to be hospitalized. Care may involve nursing, IV fluids, respiratory support, and prevention of secondary infections.

Overview of Eastern Equine Encephalitis

Q. What is eastern equine encephalitis?

A. Eastern equine encephalitis (EEE) is a member of the family Togaviridae, genus Alphavirus, and is closely related to western and Venezuelan equine encephalitis viruses. It occurs primarily in the eastern half of the US. Because of the high case fatality rate, EEE is regarded as one of the more serious mosquito-borne diseases in the United States.

The primary EEE transmission cycle is between birds and mosquitoes. Several species of mosquitoes can become infected with EEE virus. The most important mosquito in maintaining the enzootic (animal-based, in this case bird-mosquito-bird) transmission cycle is Culiseta melanura.

Q. What are the symptoms of EEE, and how serious is it?

A. Symptoms range from mild flu-like illness to encephalitis (inflammation of the brain), coma and death.

The EEE case fatality rate (the % of persons who develop the disease who will die) is 35%, making it one of the most serious mosquito-borne diseases in the US. It is estimated that 35% of people who survive EEE will have mild to severe nervous system effects.

Q. What parts of Maine are affected by eastern equine encephalitis?

A. EEE was first identified in Maine in 2005. During 2005, twelve birds tested positive for EEE, two from Cumberland County, and ten from York County. Also from York County, two horses and one mosquito pool (the bird-feeding Culiseta melanura) tested positive for EEE.

Due to our 2005 surveillance data, and the EEE activity in the parts of New Hampshire that border Maine, southwestern Maine appears to be at the greatest risk of EEE activity. However, the Maine Center for Disease Control recommends that citizens and municipalities assume that the risk of EEE exists in all Maine communities, and to practice the prevention methods described in the Personal Measures to Prevent WNV and EEE Infection section.

Q. How many and where have human disease cases occurred?

A. From 1964 to 2004, there have been 220 confirmed cases of human EEE in the United States, averaging 5 cases per year (with a range from 0-15 cases). The states with the traditionally largest number of cases are Florida, Georgia, Massachusetts, and New Jersey.

In 2005, there were 20 human cases of EEE in the United States. New Hampshire had the most with seven cases (six more than the previous year), two of which died. Florida had five, Massachusetts four, Alabama two, and South Carolina and Georgia one each.

There have been NO human EEE cases identified in Maine to date.

The EEE transmission cycle between birds and bird-feeding mosquitoes is most common in coastal areas and freshwater swamps. Human cases occur relatively infrequently, largely because the primary transmission cycle takes place in swampy areas where human populations tend to be limited.

Q. Who is at risk for developing EEE?

A. Residents of and visitors to areas with an established presence of the virus, people who engage in outdoor work and recreational activities, and persons over age 50 and younger than age 15 seem to be at greatest risk for developing severe disease.

Personal Measures to Prevent West Nile and EEE Infection

Q. What can I do to reduce my risk of becoming infected with West Nile and EEE virus?

A. Here are preventive measures that you and your family can take:

Protect yourself from mosquito bites:

· Apply insect repellent to exposed skin. Generally, the more active ingredient a repellent contains the longer it can protect you from mosquito bites. A higher percentage of active ingredient in a repellent does not mean that your protection is better—just that it will last longer. Choose a repellent that provides protection for the amount of time that you will be outdoors.

o Repellents may irritate the eyes and mouth, so avoid applying repellent to the hands of children.

o Whenever you use an insecticide or insect repellent, be sure to read and follow the manufacturer's DIRECTIONS FOR USE, as printed on the product.

· Spray clothing with repellents containing permethrin or another EPA-registered repellent since mosquitoes may bite through thin clothing. Do not apply repellents containing permethrin directly to exposed skin. Do not apply repellent to skin under your clothing.

· When weather permits, wear long-sleeved shirts and long pants whenever you are outdoors.

· Place mosquito netting over infant carriers when you are outdoors with infants.

· Consider staying indoors at dawn, dusk, and in the early evening, which are peak mosquito biting times.

· Install or repair window and door screens so that mosquitoes cannot get indoors.

Water gardens, poorly adjusted gutters, discarded tires, pool covers, and rain barrels are examples of sites that can support high numbers of mosquito larvae. Help reduce the number of mosquitoes in areas outdoors where you work or play, by draining sources of standing water. In this way, you reduce the number of places mosquitoes can lay their eggs and breed, and ultimately can reduce the number of adult mosquitoes.

At least twice a week, empty water from flower pots, pet food and water dishes, birdbaths, swimming pool covers, buckets, barrels, and cans, or placing them under cover, so they don’t fill up with water.
Check for clogged rain gutters and clean them out.
Remove discarded tires, and other items that could collect water.
Be sure to check for containers or trash in places that may be hard to see, such as under bushes or under your home.

Q. What Are Mosquito Traps, “Bug Zappers”, and Ultrasonic Devices? Are They Effective?
A. Until recently, traps worked to collect some specimens and determine which species were present, but didn’t control mosquitoes. Now some traps touted as potential mosquito control devices. Some of the mosquito traps now available use carbon dioxide as their principal attractant, and others add octenol or other attractants. Some of these newer traps capture many times the number of mosquitoes as their predecessors, and may help reduce mosquito annoyance. Results, however, can vary, and no reports have appeared in the scientific literature that measure mosquito numbers or bite counts to compare traps with other control measures. So it is really not known how effective they are at reducing the risk of getting bitten, especially by the critical species that spread arboviruses. Mosquito traps on the market can be very expensive. You can buy many years’ worth of repellent for the cost of one trap.

Electric bug “zappers” are commonly sold, and some promotional literature claims they kill mosquitoes. While these devices may “zap” the occasional mosquito, they don’t reduce mosquito problems. However, the zappers do kill a large number of harmless insects and many beneficial insects. The ultraviolet light attracts beetles, flies, moths, caddisflies and many other insects, but few pests. These products are ineffective mosquito control devices.

Ultrasonic mosquito repellents also have NO effect in reducing mosquito problems, and their claims of effectiveness are misleading or false.

Q. What can be done to prevent outbreaks of West Nile and EEE infections?
A. Prevention and control of these and other arboviral diseases is most effectively accomplished through integrated vector management programs. These programs should include surveillance for West Nile and EEE virus activity in mosquito vectors, birds, horses, other animals, and humans, and implementation of appropriate mosquito control measures to reduce mosquito populations when necessary. Additionally, when virus activity is detected in an area, residents should be alerted and advised to increase measures to reduce contact with mosquitoes.

Q. Are there human vaccines against West Nile or Eastern Equine encephalitis?
A. There are currently NO human vaccines available for either West Nile or EEE virus.

Q. Are there equine vaccines against West Nile or Eastern Equine encephalitis?

A. There are vaccines available to protect horses from both WNV and EEE. Consult your veterinarian for more information.

Q. Should people take the West Nile and EEE virus vaccines that are licensed for use in horses?
A. No. These vaccines have not been studied in humans and could be harmful. Veterinary vaccines and other veterinary drugs should never be used in humans.

Insect Repellent Use and Safety

Q. Why should I use insect repellent?
A. Insect repellents can help reduce exposure to mosquito bites that may carry viruses such as West Nile or EEE virus that can cause serious illness and even death. Using insect repellent allows you to continue to play and work outdoors with a reduced risk of mosquito bites.

Q. When should I use mosquito repellent?
A. Apply repellent when you are going to be outdoors. Even if you don’t notice mosquitoes there is a good chance that they are around. Many of the mosquitoes that carry West Nile and EEE virus bite between dusk and dawn. If you are outdoors around these times of the day, it is especially important to apply repellent.

Q. How often should repellent be reapplied?
A. In general, you should re-apply repellent if you are being bitten by mosquitoes. Always follow the directions on the product you are using. Sweating, perspiration or getting wet may mean that you need to re-apply repellent more frequently.

Q. How does mosquito repellent work?
A. Female mosquitoes bite people and animals because they need the protein found in blood to help develop their eggs. Mosquitoes are attracted to people by skin odors and carbon dioxide from breath. The active ingredients in repellents make the person unattractive for feeding. Repellents do not kill mosquitoes. Repellents are effective only at short distances from the treated surface, so you may still see mosquitoes flying nearby.

Q. Which mosquito repellents work best?
A. The Maine CDC recommends using products that have been shown to work in scientific trials, and that contain active ingredients which have been registered with the EPA (http://www.epa.gov/pesticides/health/mosquitoes/insectrp.htm#choosing) for use as insect repellents on skin or clothing. When EPA registers a repellent, they evaluate the product for efficacy and potential effects on human beings and the environment. EPA registration means that EPA does not expect a product, when used according to the instructions on the label, to cause unreasonable adverse effects to human health or the environment.

Of the active ingredients registered with the EPA, two have demonstrated a higher degree of efficacy in the peer-reviewed, scientific literature (For more detailed information, see http://www.cdc.gov/ncidod/dvbid/westnile/publications.htm). Products containing these active ingredients typically provide longer-lasting protection than others:

• DEET (N,N-diethyl-m-toluamide)
• Picaridin (KBR 3023)

Oil of lemon eucalyptus [active ingredient: p-menthane 3,8-diol (PMD)], a plant- based repellent, is also registered with EPA. In two recent scientific publications, when oil of lemon eucalyptus was tested against mosquitoes found in the US it provided protection similar to repellents with low concentrations of DEET.

Q. How does the percentage of active ingredient in a product relate to the amount of protection it gives?
A. Typically, the more active ingredient a product contains the longer it provides protection from mosquito bites. The concentration of different active ingredients cannot be directly compared (that is, 10% concentration of one product doesn’t mean it works exactly the same as 10% concentration of another product.)

DEET is an effective active ingredient found in many repellent products and in a variety of formulations. Based on a 2002 study (Fradin and Day, 2002; See http://www.cdc.gov/ncidod/dvbid/westnile/publications.htm):

• A product containing 23.8% DEET provided an average of 5 hours of protection from mosquito bites.
• A product containing 20% DEET provided almost 4 hours of protection
• A product with 6.65% DEET provided almost 2 hours of protection
• Products with 4.75% DEET were both able to provide roughly 1 and a half hour of protection.

These examples represent results from only one study and are only included to provide a general idea of how such products may work. Actual protection will vary widely based on conditions such as temperature, perspiration, and water exposure. Choose a repellent that provides protection for the amount of time that you will be outdoors. A product with a higher percentage of active ingredient is a good choice if you will be outdoors for several hours while a product with a lower concentration can be used if time outdoors will be limited. If you are outdoors for a longer time than expected and start to be bitten by mosquitoes, simply re-apply repellent (following label instructions).

Q. Why does the Maine CDC recommend certain types of insect repellent?
A. The Maine CDC recommends products containing active ingredients which have been registered with the EPA for use as insect repellents on skin or clothing.

All of the EPA-registered active ingredients have demonstrated repellency; however, some provide longer lasting protection than others. Additional research reviewed by the Maine CDC suggests that repellents containing DEET (N,N-diethyl-m-toluamide) or picaridin (KBR 3023) typically provide longer-lasting protection than the other products and oil of lemon eucalyptus (p-menthane-3,8-diol) provides longer lasting protection than other plant-based repellents. Permethrin is another long-lasting repellent that is intended for application to clothing and gear, but not directly to skin. In general, the more active ingredient (higher concentration) a repellent contains, the longer time it protects against mosquito bites.

People who are concerned about using repellents may wish to consult their health care provider for advice. The Maine Board of Pesticides Control is a local source for insect repellent information, and can be reached at 1-207-287-2731, or http://www.maine.gov/agriculture/pesticides/public/repellents.htm. The National Pesticide Information Center (NPIC) can also provide information through a toll-free number, 1-800-858-7378 or http://npic.orst.edu/.

Q. How can you know which active ingredient a product contains?
A. Check the product label if you have questions-–repellents must specify their active ingredients. In some cases you will note the chemical name in addition to/instead of the “common” name:

• DEET is N,N-diethyl-m-toluamide, Dimethyl-m-toluamide + related isomers, or N,N-Dimethyl-m- toluamide m-meta DEET + related isomers
• Picaridin (trade name KBR 3023), sometimes known as “Bayrepel,” is 2-(2-hydroxyethyl)-1-piperidinecarboxylic acid 1-methylpropyl ester

• The active ingredient in oil of lemon eucalyptus is p-menthane 3,8-diol (PMD)

Q. What is permethrin?
A. Certain products which contain permethrin are recommended for use on clothing, shoes, bed nets, and camping gear, and are registered with EPA for this use. Permethrin is highly effective as an insecticide and as a repellent. Permethrin-treated clothing repels and kills ticks, mosquitoes, and other arthropods and retains this effect after repeated laundering. The permethrin insecticide should be reapplied following the label instructions. Some commercial garments are available pretreated with permethrin.

Q. Where can I find these repellents?
A. Most of these repellents are sold at multiple retail, discount and drug stores. A wider selection may be available at “outdoor” stores or in hunting and camping sections.

Q. Where can I find more information about picaridin?
A. A technical fact sheet covering picaridin is available from the EPA at http://www.epa.gov/opprd001/factsheets/picaridin.pdf, or contact the Maine Board of Pesticides Control at 1-207-287-2731.

Using Repellents Properly

Q. What are some general considerations to remember when using insect repellents?
A. Always follow the requirements appearing on the product label.

• Use enough repellent to cover exposed skin or clothing. Don't apply repellent to skin that is under clothing. Heavy application is not necessary to achieve protection.

• Do not apply repellent to cuts, wounds, or irritated skin.

• After returning indoors, wash treated skin with soap and water. (This may vary depending on the product. Check the label.)

• Do not spray aerosol or pump products in enclosed areas.

• Do not spray aerosol or pump products directly to your face. Spray your hands and then rub them carefully over the face, avoiding eyes and mouth.

Q. What are some reactions to be aware of when using insect repellents?
A. Use of repellents products may cause skin reactions in rare cases. Most product labels also note that eye irritation can occur if product gets in the eye. If you suspect a reaction to a product, discontinue use, wash the treated skin, and call the poison center at 1-800-222-1222. If product gets in the eyes flush with water and consult a health care provider or the poison center. If you go to a doctor, take the product label with you.

Q. Can insect repellents be used on children?
A. Repellent products must state any age restriction. If there is none, EPA has not required a restriction on the use of the product.

Since it is the most widely available repellent, many people ask about the use of products containing DEET on children. No definitive studies exist in the scientific literature about what concentration of DEET is safe for children. No serious illness has been linked to the use of DEET in children when used according to manufacturer’s recommendations. The American Academy of Pediatrics (AAP) Committee on Environmental Health has updated their recommendation for use of DEET products on children in 2003, available at http://www.aap.org/family/wnv-jun03.htm, citing: "Insect repellents containing DEET (N,N-diethyl-m-toluamide, also known as N,N-diethyl-3-methylbenzamide) with a concentration of 10% appear to be as safe as products with a concentration of 30% when used according to the directions on the product labels." AAP recommends that repellents with DEET should not be used on infants less than 2 months old.

AAP has not yet issued specific recommendations or opinions concerning the use of picaridin or oil of lemon eucalyptus for children.

According to the label, oil of lemon eucalyptus products should NOT be used on CHILDREN UNDER 3 YEARS of age.

Parents should choose the type and concentration of repellent to be used by taking into account the amount of time that a child will be outdoors, exposure to mosquitoes, and the risk of mosquito-transmitted disease in the area.

If you are concerned about using repellent products on children you may wish to consult a health care provider for advice, the Maine Board of Pesticides Control at 1-207-287-2731, or contact the National Pesticide Information Center (NPIC) through their toll-free number, 1-800-858-7378 or at http://npic.orst.edu/.

Q. What guidelines are available for using a repellent on children?
A. Always follow the recommendations appearing on the product label when using repellent:

• When using repellent on a child, apply it to your own hands and then rub them on your child. Avoid children's eyes and mouth and use it sparingly around their ears.

• Do not apply repellent to children's hands. (Children may tend to put their hands in their mouths.)

• Do not allow young children to apply insect repellent to themselves; have an adult do it for them.