Archive for the ‘Vaccinations’ Category

Mosquitoes – A story of bad news, good news, beer and Malaria

Thursday, March 25th, 2010 by

Two stories concerning mosquitoes caught my attention recently.  In the age-old “bad news, good news” tradition, it goes like this:

“The bad news is that if you drink beer, mosquitoes are more attracted to you and may bite you and give you malaria.  The good news is that scientists have developed a mosquito that could, in theory, vaccinate you against malaria with each bite.”

The first study, Beer Consumption Increases Human Attractiveness to Malaria Mosquitoes, was conducted in Burkina Faso by a team of researchers led by Thierry Lefèvre from Emory University and published by PLoS ONE, an interactive open-access journal.  It concluded that “beer consumption consistently increased volunteers’ attractiveness to mosquitoes.”  The researchers believe that the alcohol in the local beer causes the increased attractiveness; however, further studies are necessary to eliminate other possibilities.  I saw that the local beer is fairly low in alcohol content and wondered what the curve would look like as the strength varied.  Is it a linear relationship, or would it yield an upside-down “U” shape?  If the latter, one could stick to more toxic drinks (although this flies in the face of the researchers who also noted that alcohol consumption has other negative health effects and can lower one’s ability to defend against parasites and other threats to the immune system).  I was lucky enough to learn about the African drink, dawa, from my wife (it was a huge hit on our wedding night).  Dawa means “medicine” or “magical potion” in Swahili and is a much stronger drink than the local beer in Burkina Faso, so perhaps they already know about the shape of the curve.

The second study, Flying vaccinator; a transgenic mosquito delivers a Leishmania vaccine via blood feeding, was published in the April 2010 issue of Insect Molecular Biology and conducted by Associate Professor Shigeto Yoshida and his research team from Jichi Medical University. Unfortunately, there are ethical issues with using wild mosquitoes (are there domesticated ones?) to transmit a vaccine.  How would the pharmas get paid for it, for example?  Oh, yeah, that is not an ethical issue so much as an economical one.  In all seriousness, it does sound like this idea may be years away if it ever gets off the ground (no pun intended).  The mere fact that they did successfully use the mosquito’s saliva to deliver the payload, however, does hold promise for other therapies in the future.

Malaria is a very serious problem worldwide, affecting hundreds of millions of people each year and killing millions, mostly sub-Saharan children.  If you took the time to read this, please think about helping to stop this disease and perhaps contributing to a worthy organization.  It is money well spent. Also, if you are traveling to areas where malaria is a risk, learn about which preventive medicine is right for you and make sure that you take it.

Photo info: http://www.flickr.com/photos/trebol_a/ / CC BY-NC 2.0
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Emerging Antimalarial Drug Resistance – Cause for Alarm

Tuesday, February 9th, 2010 by

A report released yesterday by a United States Pharmacopeia program, in partnership with the World Health Organization, cited an increasing level of resistance to Artemisinin – the last affordable drug in the global arsenal against malaria.  The drug resistance is emerging in Uganda, Senegal, Madagascar, Cambodia, Thailand and Vietnam, and is thought to be due in large part to the sale of poor quality versions of Artemisinin in those countries.

The report indicated that between 16 and 40 percent of the drugs marketed as Artemisinin had impurities or did not contain enough active ingredient to be effective.  Drugs will typically lose effectiveness and allow parasites to develop resistance if not given at full strength or for the full recommended course. In the case of malaria, there is no useful replacement for Artemisinin currently available, and many could die or become gravely ill if the current trend continues.

“It is worrisome that almost all of the poor quality data that was obtained was a result of inadequate amounts of active ingredient or the presence of impurities in the product” said Patrick Lukulay, the director of the study.  Senegal had the most disturbing results, with over 40% of the Artemesisin based samples failing quality testing. Lukulay added “There are some countries where donated medicines are not subjected to quality controls, they are just accepted”.  This includes countries in Africa where Chinese products have been given and found later to be unacceptable.

Although results from other countries in the ten country study have not been released, preliminary evidence from the other countries surveyed – Cameroon, Ethiopia, Ghana, Kenya, Malawi, Nigeria and Tanzania suggest that failure rates in at least three of those countries were also high. 

Traditional antimalarial drugs such as malarone, doxycycline, chloroquin and mefloquin are still effective in many parts of the world where the malaria parasite is endemic.  In recent years, Artemesinin has been the last resort in areas where the parasite has developed resistance to these medications. However, for those travelling to sub Sahara Africa or southeast Asia, the risk of contacting Artemesinin resistant malaria is growing.  Although resistance is not yet widespread, it behooves the careful traveler to make sure that any Artemesinin based medication taken for treatment of a malaria infection is of good quality.

Photo info: http://www.flickr.com/photos/lonqueta/ / CC BY-NC-SA 2.0
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Vaccination Recommendations for Travelers

Friday, February 5th, 2010 by

In a recent Wall Street Journal post, Avoiding Illness on the Road, Dr. Phyllis Kozarsky, a travel health expert for the Centers for Disease Control (CDC), offered some good advice for travelers, particularly business travelers. 

In this piece Dr. Kozrsky correctly to advises those who are travelling overseas to get immunized, even if coincident with departure.  However, nascent travelers should be aware that protection is not immediate. In the case of the hepatitis A and B vaccines, for instance, full immunity cannot be guaranteed for everyone who receives the vaccine for at least one month.  Long lasting immunity requires a second vaccination anywhere from one month to one year after the first. 

According to the CDC, the only vaccine that is required by international health regulations is yellow fever for those travelling to sub-Saharan Africa and tropical South America. The CDC recommends that this vaccine be obtained at least ten days prior to arriving in an area where yellow fever is endemic.  In addition, the vaccine must be administered at an approved center that can provide the vaccinee an authentic “International Certificate of Vaccination”.  The yellow fever vaccine must be repeated at ten year intervals to remain effective.

Meningitis vaccinations are required in for those travelling to the “meningitis belt” across the middle of the African continent and parts of Saudi Arabia.  The vaccine provides protective antibodies after a week to ten days, with immunization lasting only three to five years.  There are vaccines for encephalitis, an infection of the brain, which must also be administered at least a week or two before travel in order to be protective. 

Those travelling abroad should consult with an infectious disease or travel medicine specialist at least one month prior to trip departure to insure adequate protection against infectious diseases.  Destination specific vaccination requirements can also be found on mPassport.com.

Photo info: http://www.flickr.com/photos/darwinwins/ / CC BY-NC-ND 2.0
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