West Nile Questions
Louisiana State University Ag Center
Dr. Grodner

What chemical or product can a homeowner use to control mosquito populations in a roadside ditch that fronts on their property? (especially in those ditches receiving sanitary wastewater from home septic systems)

The only product available to the homeowner is “Mosquito Dunks” which contain the insect growth regulator Methoprene, a larvicide.

What is the most effective over-the-counter bug spray to use around the outside of a home to control mosquito populations?

I really do not believe there is one; most of the bug sprays one can buy may help with wasps, etc but mosquitoes are much more elusive and the adults are difficult to control in such a small area. The control of larvae is much more effective.

Are electronic bug killers effective in controlling mosquito populations around a residence?

Not really. They attract most insects and kill very few.

Can the sterile male technology be used to control mosquito populations?

No. This technology only works well in species where the female only mates once. However, the female mosquito is very promiscuous and will mate multiple times.

Do mosquito populations develop resistance to pesticides in the manner that some agricultural pests develop pesticide resistance?

Yes. Mosquito populations react the same as other insect populations; some are just more efficient than others.

What insecticides are used in attempts by public agencies to control mosquito populations? How do they differ from DDT?

DDT belonged to a class of chemicals known as chlorinated hydrocarbons (organochlorines). The 3 major chemicals used now as adulticides are resmethrin, a pyrethroid; malathion & dibrom, which are organophosphates. None of the chemicals are as persistent as DDT was.

If the BT gene is in plants, have those plants been genetically altered?

Technically yes. The gene directing the production of the Bt toxin is a bacterial gene that has been inserted into the DNA of the plant

Are there any new pesticides being used to prevent the spread of the West Nile virus?

No. There are no new ones available.

Insect repellents are advertised “with DEET.” What is DEET and what advantages does it offer over other repellent chemicals?

DEET is the common name for N, N-diethyl-m-toluamide. The advantage of DEET is that it works when used following directions.

What is the best mosquito repellent product to use for protection against mosquitoes that carry the West Nile virus?

Repellents that contain DEET are the most effective. DEET disrupts the ability of biting insects to detect the source of carbon dioxide—the gas naturally given off by our skin and in our breath. Carbon dioxide attracts mosquitoes and other insects to us. Insects are not killed, they just cannot find you for a period of hours.

Would DDT be more effective than currently used chemicals when used by mosquito control agencies?

Perhaps, but it is impossible to make that comparison without side-by-side tests

How does the consumption of an excessive amount of water kill a child as was reported in the news this summer?

Normally our body maintains a steady-state, that is factors such as pH and electrolyte balance remain within a certain range. However, with the consumption of too much water that range is disrupted and the body cannot function properly

How much milk would a person have to drink to reach the theoretical toxic level of vitamin D?

It would be almost impossible to drink that much milk over a short period of time.

Is the public being properly protected from pesticide exposure by standards based on the usual testing done today?

Yes. If the pesticides are handled and applied properly, according to label directions, the public is safe.

What are the implications for public safety in recent research that shows:
1. humans are more sensitive than rats to some toxins
2. most commonly used rat species are significantly more resistant to some toxins than some other rat species.

When the United States Environmental Protection Agency makes a decision about the safety of the chemicals as far as humans are concerned, the agency takes into account the various differences between the test species and humans.

Recent research shows that some toxins do not follow the common statement that the dose makes the poison. These toxins are exhibiting a U-shaped curve for the dose-response relationship, that is a very small or a very large dose elicits a significant response but an intermediate does not. What are your thoughts on this observation?

I am not familiar with this work; therefore, any explanation I would give would be speculation, which is not a good idea.

West Nile Questions
Calcasieu Parish Mosquito Control
Mr. Terracina

Are mosquitoes the only carriers of the West Nile virus?

Mosquitoes are considered the primary vector of WNV. However, the virus has been found in ticks, but their role in transmission is not known. With ongoing study of the virus, this question hopefully will be answered.

Are mosquitoes killed by the West Nile virus?

No. The virus does not kill mosquitoes.

What is the probability that we will experience another outbreak of West Nile infections among the human population next summer?

The West Nile virus probably will appear again in 2003, but to what magnitude is uncertain. This virus is now well established in nature and will be a possibility to appear in any given year. However, trying to make this type of prediction is really impossible.

Can the West Nile virus be transmitted through cooked bird (i.e., chicken, ducks, geese, or quail)?

By thoroughly cooking meat the virus is killed.

How is the West Nile virus transferred from the mosquito to a person or other animal?

When the mosquito acquires the virus from an infected host, the virus grows in the gut of the mosquito. In about 10-12 days, the virus has replicated itself enough that the mosquito will then be able to transmit the virus when it feeds again. It will actually inject virus into the person or animal through a fluid used to keep blood from coagulating.

Will the type of weather we have in the winter of 2002-03 impact the number of West Nile cases in the area next spring and summer?

Hopefully, winter conditions will lesson the number of mosquitoes capable of surviving. This would in turn possibly reduce the early appearance of the virus, but probably have little long-term impact on the overall occurrence of WNV. The number of cases in 2003 will most probably hinge on the widespread occurrence of the virus in the bird population and the number of mosquitoes present during the peak of virus circulation. So weather conditions during the mosquito season itself will be of greater importance.

What climate factors favor the transmission of West Nile virus to humans and other animals?

With WNV climatic conditions may not be as important as with some other forms of encephalitis. That is because there seems to be a larger number of mosquitoes capable of transmitting the virus. If it were only 1 or 2 species, then climatic conditions favoring those species would likely dictate disease activity.

What are the plans of Mosquito Control for control of West Nile outbreaks next year?

Mosquito control will continue to closely monitor for the presence of not only WNV but also St. Louis and Eastern Equine Encephalitis. This monitoring will begin in late winter, to hopefully catch any signs of virus early. This will include watching for clusters of dead birds, particularly blue jays and crows. Control efforts will also be directed at known breeding areas to keep vector populations low.

With mosquitoes such a problem in Calcasieu Parish, why do we make such extensive use of open ditches?

Not all open ditches breed mosquitoes. In fact, the vast majority of open ditches with fresh water do not serve as production sites for mosquitoes. The problem ditches are those utilized as septic overflow outfalls, which do not properly drain and are heavily vegetated. However, even if the ditches were covered, it would not prevent them from serving as a breeding ground for mosquitoes. This is evident by some of our more prolific production areas being in underground drainage pipes. Although we are not endorsing open ditches, it is actually easier for mosquito control to find and treat open ditches compared to those that are covered.

Relying on restricting the impact of mosquito-transmitted diseases, can we make a case for gradually eliminating the discharge of sanitary wastewater into roadside ditches in Calcasieu Parish?

Roadside septic ditches are one of the primary sources of production for one of our more prolific disease carrying mosquitoes. So reducing the amount of septic overflow and the number of septic ditches would assist greatly in the reduction of mosquitoes of vector importance.

Can the West Nile virus be spread to humans by something other than mosquitoes?

West Nile disease can be spread through blood transfusion, organ transplant, possibly breast milk, intrauterine (mother to unborn child), and most recently from handling infected animals (lab workers were infected when their skin was cut while handling infected animals). As research continues, other means of transmission may be uncovered.

Are there cases of humans being infected with the West Nile virus through insects other than mosquitoes?

There is no literature to support this theory. However, ticks have been isolated with the virus, but their role is yet unknown.

Can the West Nile virus be transmitted from person to person by direct contact?

There is no evidence of direct person-to-person transmission through casual contact.

Why are mosquitoes attracted to people?

There are a variety of things that attract mosquitoes to people. Some can be controlled, while others are solely dependent upon your body metabolism. Carbon dioxide, the air you exhale, is one of the primary factors in mosquitoes searching you out. Not only is this chemical expelled through breathing but carbon dioxide is also emitted from other areas of your body during rest and play. Many other chemicals that help to attract mosquitoes are emitted through normal body metabolism and physical exercise. Since everyone’s metabolism is different, everyone will have a different attractiveness.

Many of these things mentioned above cannot be controlled. However, some external factors that can be controlled also come into play. The color of your clothes could be a factor along with the type and amount of cologne or perfume you may be wearing. Wear light colored clothing and limit or eliminate fragrant colognes and perfumes.

What are the air temperatures associated with mosquito populations carrying the West Nile virus?

Air temperature probably is not a major factor in the transmission of WNV. This is evident in the fact that some transmission has occurred in the winter months.

What is the best mosquito repellent product?

Any product with DEET seems to work the best. Be sure to always read the label and use the product responsibly.

Do mosquitoes develop a resistance to the repellent sprays so that the material is no longer effective?

There is no evidence that mosquitoes develop resistance to repellents.

The use of fabric softener sheets to repel mosquitoes has been a topic of conversation around town. Is there any truth to these claims?

There is no scientific documentation to support the claim. However, it would not be the first time a product intended for another use has proven effective for something else.

When a sentinel chicken tests positive for West Nile virus, is the bird destroyed or is it kept for later testing?

Once a second test verifies that the chicken is positive, the animal is removed from the testing cage. Since mosquitoes cannot acquire the virus from the chicken, there is no need to destroy infected animals. They are placed in a flock as a yard bird.

Has the West Nile virus infected commercial poultry flocks?

It is probably a given that WNV has infected these flocks. But because the virus does not kill the chickens, this infection has had little impact on the flock.

When intensive application of insecticides to control larvae and adults mosquitoes, are measures taken to prevent the development of mosquito populations that are resistant to the agents used?

Most mosquito control agencies monitor closely for any signs of insecticide resistance. This is done through controlled testing in the lab and field. Operationally, agencies utilize strategies to prevent resistance from becoming a problem. One step is to alternate products, so as to not continually use the same agent all the time. Another is to not use the same products for treating both larvae and adults, therefore eliminating the continual exposure of a population to the same product at all stages of development. If a certain population of mosquitoes does begin to show signs of tolerance to some insecticides, a lot of pressure needs to be placed on the larval stages with known effective products to try and reverse the situation.

Does the West Nile virus kill chickens in commercial poultry facilities?

No.

Can the same mosquito infect more than one person with the West Nile virus?

Yes. Once a mosquito is infected with the virus, the insect is capable of transmitting the virus every time a blood meal is taken.

If a person must be in contact with mosquitoes because of work or recreation activities, what is the best way to protect against the West Nile virus?

Use an effective repellent and wear appropriate clothing, preferably light in color.

Has transgenic research been applied to control of mosquito populations through the development of transgenic mosquitoes?

There has been little success with experiments of this type on mosquitoes. The shear numbers of mosquitoes and their habits make this task extremely difficult. However, there is ongoing research in the hopes that something can be found to assist in control measures.

A black residue appears to be left behind on vegetation and structures following aerial spraying for mosquitoes. Can you comment on what may be the cause and is the residue dangerous?

Mosquito control products have never been implicated with leaving any type of black residue following applications. And since there has been little to no change in products or application technologies since incorporation of the program, I doubt that the residue in question is the result of these applications. The residue possibly could be the result of large populations of aphids or whiteflies, which will result in a black mold residue on leaf surfaces. But without seeing and investigating the situation, the cause is difficult to determine.

There has been talk of dead grass and bushes in roadside ditches following spraying for mosquitoes. Is this likely and what is the cause?

Products used for treating larvae in roadside ditches will not affect any plant life. They are water-based products and are not phytotoxic. Adult application rates and techniques render these products safe for use without threatening plant life. The dead grass and bushes are probably the result of a herbicide application and not the result of applying mosquito control products.

Please give an update on “alternative approaches” for mosquito control such as

A. dewatering dredge spoils areas used to deposit sediments from the Calcasieu Ship Channel,
B. use of natural enemies of mosquitoes such as bats, fish or microbes
C. release of sterile males

A. Mosquito control has worked with Corp of Engineer officials in an attempt to have them dewater the dredged spoil banks. Unfortunately, we have had little success in this endeavor. We do have an ongoing agreement for reimbursement of expenses for controlling mosquitoes on these sites up to $50,000 per year.

B. The use of natural enemies is ongoing and used where practical. Most of the larvicides used are naturally occurring microbes, which are now being massed marketed. As for bats, they do feed on mosquitoes, but their value as a control agent is questionable. They are advantageous feeders and do not concentrate on just mosquitoes. Studies have shown that the majority of their diet actually consists of other larger insects. As with most advantageous feeders, bats are going to feed on what is available and what will cost them the least amount of energy to collect. Larger insects are easier to catch and will satisfy their needs more quickly. Fish have been used in the past and are always considered an option.

C. Sterile male release has proven ineffective in mosquito control.

Sentinel chickens were positive for West Nile infection in the Mossville area in May.   What public alert was given?

Was any local alert issued to nearby residents in Mossville?

How will the public be notified next spring in the event of a reappearance of the virus?

A public alert was issued via all media outlets (TV, radio, newspaper). Mosquito control employees also went door to door throughout the Mossville area informing residents and handing out informational pamphlets. The same approach will be utilized again this year upon evidence of WNV in the parish. We are also looking at other means of quick notification by involving the Office of Emergency Preparedness.

The West Nile virus appears to impact crows in the north and blue jays in the south. Does the virus kill other bird species, for example the humming bird?

There is evidence that WNV has impacted many species of birds besides crows and blue jays. The extent of impact on hummingbirds is unknown.

What can the public do to prepare for another outbreak of West Nile virus-related disease when the weather turn warm again next spring?

The best advice is to mosquito proof your property and work with neighbors to do the same. Mosquitoes produced around the home are the most difficult to control, so the assistance of everyone is needed. Also, use good practical sense when venturing out when mosquitoes are a problem. Bring along repellents and wear appropriate clothing.

Will mosquitoes carrying the West Nile virus stay in one area? About how long will mosquitoes carrying the West Nile virus stay in one area?

Mosquito movements vary by species. Some move long distances, up to 30 miles per day, while others move very little, less than a block, from where they are produced. Since there is a variety of species capable of transmitting the virus, this question is really impossible to answer. The fact that mosquitoes are mobile and once infected carry the virus until they die, means that mosquitoes will more than likely move the virus around.

Do marsh mosquitoes carry the West Nile virus during the winter months?

Any mosquito, which is active in the winter months and picks-up the virus, has the potential to transmit the virus. Some marsh mosquitoes can be active during this time, so the answer to this is yes they could under the right circumstances.

West Nile Questions
Louisiana Department of Health and Hospitals
Dr. Ratard

West Nile Questions
Louisiana Department of Health and Hospitals
Dr. Ratard

Why is the virus named West Nile?

The virus is named for the West Nile Province of Uganda where it was discovered.

For how long has the West Nile virus been a problem in the United States?

The virus was first identified in New York in 1999.

What is the difference between meningitis and encephalitis?

Meningitis is a disease of the lining of the brain and spinal cord. Encepohalitis is an infection of the inside of the brain.

Please describe the progression of encephalitis in humans caused by infection with the West Nile virus.

For a detailed description go to www.cdc.gov, then click Health Topics A-Z, and click on W and then West Nile.

Why is infection by the West Nile virus deadly?

Infections by the West Nile virus can be deadly because the virus kills brain cells. If a relatively small number of brain cells are involved, the person can compensate when the disease subsides. If a larger number of cells are killed, permanent brain impairment can result. If a larger number of cells in a critical part of the brain are involved, the patient will not survive.

What is the status of West Nile diseases among birds, horses and people in the region of Africa from which the virus was imported into the United States?

For a description of the disease in Africa, go to www.cdc.gov, then click Health Topics A-Z, and click on W and then West Nile

Is the West Nile virus present in southern Europe, the Balkans, or West Asian countries?

Yes, the virus is present in those regions.

In the event of another outbreak of West Nile virus-related diseases, what should be done with dead birds found around homes and playgrounds?

Dead birds are not a risk to other birds, mosquitoes, or people. Simply report their presence to your parish health unit and discard the bird

What precautionary steps should be taken to protect children from infection by the West Nile virus?

The steps to protect children are the same as those for protecting adults: long pants and long-sleeve shirts and mosquito repellents. If possible stay indoors during peak mosquito periods of the day.

What are the most common symptoms of a person suffering from infection by the West Nile virus?

The complete descriptions of symptoms can be found at www.cdc.gov, then click Health Topics A-Z, and click on W and then West Nile. The following was copied from the CDC Web page.

Most people who are infected with the West Nile virus will not have any type of illness. About 20% of those infected will develop West Nile fever: mild symptoms, including fever, headache, and body aches, occasionally with a skin rash on the trunk of the body and swollen lymph glands.

The more severe outcomes are called West Nile encephalitis or meningitis and are seen in about 1 of every 150 people infected with the virus. The symptoms include headache, high fever, neck stiffness, stupor, disorientation, coma, tremors, convulsions, muscle weakness, and paralysis.

What should as person do if they suspect that they are infected with the West Nile virus?

If the symptoms are apparent, go to your doctor.

What is the probability that the West Nile virus will spread throughout the United States?

The virus has spread already.

Are domestic pets threatened by the West Nile virus? What can a pet owner expect in the way of symptoms if their pet comes down with West Nile disease?

Most pets are infected but they do not have any signs of illness.

Will the West Nile epidemic become as deadly as the great plagues of the past like plague, small pox, or yellow fever?

No. Only a small number of people become infected with the virus, and a small portion of the infected people exhibit a fatal disease.

Do the antigenic properties of the West Nile virus change each year?

Not enough to present a problem to the immune system.

Do lactating mothers pass the West Nile virus to their offspring?

Yes in rare occasions.

Should a mother that intends to or is breastfeeding a child be tested for the West Nile virus?

No. The risk is extremely small.

Can the West Nile be transferred through body fluids or through sexual contact?

Between birds Yes. Between people, No.

Can the West Nile virus be transferred directly from one person to another?

Not in normal circumstances. The virus can be transferred by blood transfusions.

What is the treatment for someone who has developed symptoms associated with West Nile infection?

Treatment to reduce the brain swelling can be done. Nothing will kill the virus.

What is the treatment for horses that develop encephalitis?

The treatment for horses is the same as that employed on humans.

Does the urine or feces from infected horses or other animals contain infective virus particles?

Horses no. Birds yes.

Do people with mild cases of the West Nile virus have similar symptoms year after year for the rest of their life?

Not at all.

After being bitten by a mosquito carrier about how much time is required for the appearance of the first symptoms?

The incubation period is 5 to 15 days.

Is there any evidence that the West Nile virus is transmitted from mother to fetus during pregnancy? Does a child become contaminated during childbirth if the mother carries the West Nile virus?

Very rarely.

Is race a factor in developing symptoms from West Nile infection?

Probably not.

Does body size appear to have a role in the course of infections by the West Nile virus?

No.

Where do you see the West Nile epidemic years from now?

The West Nile virus will remain in the US for years to come. Some years will be good in terms of the number of cases and fatalities, and some years will be really bad in terms of cases and fatalities.

What is the current thinking concerning the suggestion that West Nile was imported into the country by terrorist from the Middle East?

Probably not. The West Nile virus is not choice for biological warfare or terrorism because the virus causes symptoms in such a small fraction of the human population and only a small fraction of those with symptoms die because of the infection. Bringing the virus into the country through New York would have been a bad idea if a person were interested in killing people. The climate and other factors make the choice of New York a poor idea for a terrorist.

In what areas of the Louisiana do you expect to see West Nile infections in the spring of 2003?

Throughout the state.

Do we know if West Nile infections occur in animals other than horses and birds?

Yes. They get the virus, but they are not usually sick.

Will the human health problems caused by the West Nile infections respond to any over-the-counter medications?

No.

Can family practice physicians diagnose West Nile infections?

Yes. They know which lab tests to request to make a definitive diagnosis.

How many people died from West Nile infections in Louisiana and the United States over the spring and summer of 2003?

The data are available with maps and tabular information on the Web site maintained by the Center for Disease Control. Go to www.cdc.gov, then click Health Topics A-Z, and click on W and then West Nile.

Is it true that the elderly among the human population are more susceptible to severe West Nile encephalitis resulting in death?

Yes. The general physical condition and immune system of the elderly are not usually as robust as in younger people. Consequently, the elderly are more susceptible to infection by the West Nile virus and other pathogens.

Is it true that younger people have a greater resistance to infection caused by the West Nile virus?

Yes. The general physical condition and immune system of the young are usually more robust. Consequently, the young are more able to handle infections by the West Nile virus and other pathogens. If the immune system is compromised, infections can be severe.

Is a vaccine currently available for vaccination against West Nile infection?

Vaccination is available only for horses.

Are human infants more susceptible to West Nile infections?

No.

Can other animals, wild or domestic, become infected by the West Nile virus by eating birds that have died from West Nile infection, for example a cat eating a dead blue jay?

Yes. They may get infected, but they usually do not have any signs of the disease.

About how long does the virus remain viable in dead birds?

A few hours.

How many infected mosquitoes are needed to transmit the West Nile virus to humans?

One would be enough.

Since I was diagnosed with West Nile encephalitis last fall, what are the chances that I will come down with the disease again?

None. You are protected for the rest of your life.

If a person infected with the West Nile virus experiences symptoms of less severity than encephalitis will that person be immune to future infections by this virus?

Yes.

The office of my family physician had little information on West Nile infection when called during the summer. Can we expect that physicians will have more information about West Nile infection available next year?

Physicians have received and will receive information on West Nile infections. If uncertainty persists, suggest that they go to the CDC Web site at www.cdc.gov, then click Health Topics A-Z, and click on West Nile

Are the properties of the West Nile virus such that a vaccine usable by humans can be developed without the difficulties experienced in trying to develop an anti-AIDS vaccine?

Yes. Developing a protective vaccine effective against the West Nile should be much easier than the development of an anti-AIDS vaccine.

Is the West Nile virus more or less deadly to people than other mosquito-transmitted viruses that cause encephalitis in humans?

About the same as the others.

Is there a possibility that the West Nile virus can be transmitted through municipal water supplies?

No.

Do veterinarians test for the West Nile virus?

For horses, yes.

I was told that a child hospitalized in Lake Charles died from the West Nile virus this past summer. Is this true?

No.

Could an alligator become infected with the West Nile virus?

There was some discussions about this happening. No one is sure.

From a prevention point of view, what can a person do to enhance their immune system?

Healthy lifestyle.

Will natural bird populations, for example the blue jays, develop an immunity to the West Nile virus?

If an infected bird lives, that bird will have immunity to the virus. As the birds that are not capable of mounting an effective response to the virus are killed, the remainder of the population that can withstand the infection (assuming that some can mount a successful immune response) will gradually become a greater fraction of the total bird population.

How safe is the human blood supply in regards to the West Nile virus?

Very safe, but nothing is 100%