Adventure Doc

Mosquito Bite Prevention

700,000,000 people get a disease from a mosquito, each year. Of those diseases, 1 out of 17 people currently alive will die from the disease.

The species to know about are Aedes, Culex and Anopheles. These are the bad girls that carry diseases such as malaria, yellow fever, dengue fever and filariasis. I say “bad girls” because on the female mosquito bites mammals. The growth on new mosquitoes requires a blood meal. The males are content to only feed from flowers. Certain types of mosquitoes prefer animals, some prefer humans and some feed from both.

Attraction:

What attracts mosquitoes is not fully clear, yet. Mosquitoes do have developed senses of vision, thermal/heat sense and smell. They use all of their senses to find food. It is believed that the olfactory (smell) sense is the most important in finding victims.

During the daytime, dark colored clothing and movement help a female mosquito “lock on” to its target, at long range. As the mosquito nears her prey, the senses of smell and thermal sense take over. Carbon Dioxide and Lactic Acid are two of the most studied mosquito attractants. CO2 is mainly found in exhaled breaths and lactic acid can be found on the skin when muscles are being used, as in exercise. Lastly, skin temperature and skin moisture guide the mosquito to where they want to bite, on the body. It is widely assumed that certain species of mosquito prefer different body parts; hands, face, feet, etc. This could be due to the differences in local skin temperatures. Scented soaps, cologne, lotions and hair products can also attract mosquitoes.

As for personal preference, adults are preferred over children. Men are more commonly bitten than women and larger people get bit more than smaller people, possible due to their increased CO2 output. It also appears my wife is preferred over to me.

Chemical Repellents:

DEET (N,N Diethyl 3 Methylbenzamide) is the gold standard of insect repellent. It has been well studied for over 50 years and provides protection not only against mosquitoes but also flies, chiggers, ticks and fleas. The concentrations of DEET available range from 5% to 100% and the higher the concentration of DEET, the longer the time of protection. Concerns over long term exposure to high doses of DEET have led to the US Military to adopt a 35% slow release formula. The medical literature disagrees over a formula that accurately predicts number of hours of protection and DEET percentage. One study indicates a 4 hour protection with 50% DEET while another indicates 12.5% DEET protected for 6 hours. Products with 20-35% DEET generally provide adequate coverage for most instances. There are reports of skin irritation occurring more frequently with percentages greater than 35%. The Pediatricians advise nothing more than 10% DEET for children less than 12 years old. Use of DEET with sun-block lowers the efficacy of the sun-block. So, more frequent applications of sunscreen will be needed for adequate solar protection. The DEET spray is applied to the skin, first. Sunscreen is applied over the top of the DEET spray. I remember this because the DEET protects your blood and stays the closest. Sunscreen protects against the sun, which is further away. DEET is a well studied and commonly used chemical. High dose DEET has been shown to not be a neuro-toxin. There have been several cases of encephalopathy (brain swelling), mostly in children, with prolonged exposure and inappropriate use of DEET. DEET works by inhibiting signals from the mosquitoes’ antennae and making it hard for them to find you.

Avon Skin-So-Soft is known to be a mosquito repellant. Lab studies showed a 30-minute protection time against Aedes mosquitoes. Ideas as to why it is a repellent center around either fragrance of the cream or the chemicals it contains, benzophenone and diisopropyl adipate.

Permethrin is an insecticide that kills or stuns bugs. Permethrin is effective against mosquitoes, ticks, flies, chiggers and fleas. The chemical does not easily absorb into the skin. This is applied to clothing, bed nets or screens, as a spray.

Citronella is known as the “natural” mosquito repellent. Derived from a plant, Cymbopogon Nardus, the oil has a lemon-like scent. Studies have shown that burning citronella candles and/or incense decrease the number of insect bites, for those near to the candles or incense.

Timing is Everything

Most species of mosquitoes bite at dawn and dusk. Avoiding being outside will lessen your chances of bites. When you are sleeping at night, in open air environments, a bed net is definitely shown to decrease bites. Often, those staying in nicer hotel rooms, with climate control, do not need netting. Open windows mean a need for netting.

Learn more about mosquito carried diseases such as Malaria, Dengue Fever and Yellow Fever over at www.AdventureDoc.org

A few more cases of malaria have been confirmed in Kingston, Jamaica, bringing the total number of confirmed cases to 370. The outbreak started in fall of 2006 and involves Plasmodium Falciparum, the most severe type.

Malaria is not normally found on Jamaica and the CDC is advising chloroquine, as prophylaxis, for those staying overnight in Kingston. The other areas of Jamaica are not considered at risk.

The Jamaican government is working to control vectors (mosquitoes) by spraying and destroying possible breeding grounds.

This is believed to be a temporary problem, but the advice is still to take prophylaxis for people sleeping in Kingston, for now.

Here is a CDC link for more information:
CDC Malaria in Kingston, Jamaica

Hope this helps!

Long Term Malaria Prophylaxis

I seem to be hearing this question a lot, lately. I will try to give a brief summary of what I know…

Atovaquone/Proguanil (Malarone)

Basically, there is not a lot of good literature on long term use of atovaquone/proguanil (Malarone). This seems to be an area that needs some more research. Most of the data that is being discussed, currently, centers around a short study of UN Peacekeepers who took the drug combo for approx 6 months with no severe reactions noted. It is a small study with only a few hundred patients, if memory serves. Nothing solid. The two drugs in the compound are both, individually, well studied and safe for long term use. Proguanil is not suitable for solo-protection as drug resistance is common. Oh, I got a good bit of info about malarone and it’s efficacy being increased when taken with a fatty meal versus an empty stomach. This appears to be true, as the fat in the meal helps it absorb. The EU has set a limit of use that ranges from 5 weeks to 3 months, depending on the country. The USA does not have any restriction on its use, with respect to time.

Chloroquine

Well studied and commonly used, often for long term use. The main thing to know is “Will this protect me?” This is only a drug to be used in geographic areas with known sensitivity to chloroquine. There is a link between long term chloroquine use and retinopathy (eye problems). Literature disagrees on how many YEARS that is, but a commonly accepted value is 5 years of 300 miligrams per week or 3 years if taking 100 miligrams per day. Most all people I see and talk with get advised to have a regular eye exam (every 6 months) after 2-3 years of any dose of chloroquine.

Mefloquine (lariam)

There is a lot of study on the long term use of this medication and it seems to be safe for long term use. If you can tolerate the mefloquine for the first 3-4 weeks, you should be fine for several years of use.

Doxycycline

Again, if you can tolerate the side effects of the medication (sun sensitivity, risk of vaginal yeast infections, GI/diarrhea and dietary restrictions), this medication seems safe for long term use, greater than 6 months. Most of the studies do not show any data of use longer than six months.

This information is from a collection of resources including:

Travel and Tropical Medicine Manual
Author: Jong and McMullen

TravMed
TravMed.com

Pretty good journal link about long term malaria protection (technical)
Malaria Prophylaxis for Long-Term Travelers
This is a PDF from Communicable Disease and Public Health

Many, many issues of The Journal of Travel Medicine and too many years of higher education.
If there are any other opinions or sources out there that have some good data, please send them to me…I am always trying to learn more!

Glaxo experimental malaria vaccine works in babies
Wed 17 Oct 2007, 16:00 GMT
Reuters Africa

By Ben Hirschler

LONDON, Oct 17 (Reuters) – African babies — the group most at risk of dying from malaria — may be protected against the mosquito-borne disease by an experimental vaccine, researchers said on Wednesday.

The finding clears the way for final-stage testing of GlaxoSmithKine Plc’s shot and increases the chance that the world will have a usable vaccine within five years.

Malaria kills one person every 30 seconds, most of them young African children. Doctors believe a vaccine, given as part of routine infant immunisation, is the best hope in fighting the disease.

A clinical trial in Mozambique of 214 infants aged 10 to 18 weeks found the vaccine was safe and reduced new infections by 65 percent over a three-month period after treatment. Clinical illness was cut by 35 percent over six months.

Although such efficacy rates are not as good as for some childhood vaccinations, experts believe the huge burden of malaria means the new shot can still save millions of lives.

“This is a very major breakthrough,” lead investigator Dr Pedro Alonso of the University of Barcelona told reporters in a conference call.

“These tantalising and unprecedented results further strengthen the vision that a vaccine may contribute to the reduction of the intolerable burden of disease and death caused by malaria.”

ONE MILLION DEATHS A YEAR

Malaria, caused by a parasite carried by mosquitoes, kills more than 1 million people every year and makes 300 million seriously ill.

The latest findings, published online in the Lancet, are broadly in line with a 45 percent reduction in new infections reported in 2004 when Glaxo’s vaccine, known as Mosquirix or RTS,S/AS02, was given to children aged 1- to 4-years old.

Mosquirix will now go into a large-scale Phase III trial in the second half of 2008, involving 16,000 infants and young children in seven African countries.

If all goes well, the vaccine — which is the most advanced of a number in development — will be submitted for regulatory approval in 2011, suggesting it could be commercially available in 2012.

Glaxo has promised to sell Mosquirix at low prices in developing countries. The exact price will be negotiated with purchasers, who are likely to be multilateral groups who would cover the cost on behalf of countries where malaria is endemic.

Glaxo has spent $300 million developing Mosquirix and expects to spend another $50 million to $100 million in future.

But the trials programme is also being financed by the nonprofit PATH Malaria Vaccine Initiative, helped by a $107 million grant from the Bill & Melinda Gates Foundation.

Mosquirix — which is given in three doses — targets just one stage in the malaria parasite’s life cycle and its success has surprised some scientists, given the complexity of the disease.

The fact that it works suggests an improved vaccine, targeting multiple elements in the life cycle, might be even more effective.

http://africa.reuters.com/wire/news/usnL17759798.html
Link to Story

http://www.cdc.gov/malaria/risk_map/

CDC Malaria Risk Map

The CDC just released a new Malaria Risk Map that is interactive and pretty cool. The link is to the homepage and the just select to open the map, in a new window. Kinda like google earth with bugs!