New Mosquito Repellents Are Better than DEET
A computer algorithm and DNA info has helped scientists find new mosquito repellants that are cheaper and much safer than DEET.
Researchers said Wednesday they had discovered four natural mosquito repellents to succeed DEET, a compound whose origins go back to World War II.
DEET -- the abbreviation for N,N-diethyl-meta-toluamide -- was introduced by the US Army in 1946 after troops deployed in the Pacific theatre fell sick from malaria and other mosquito-borne diseases. It remains the primary insect repellent in use today, but has many limitations. It has to be applied frequently and is expensive, which rules it out for combatting disease in regions where malaria is endemic.
It also dissolves types of plastic, synthetic fabrics and painted surfaces. More worryingly, there is some evidence that flies and mosquitoes are developing resistance to it, and that the chemical disrupts an important enzyme in the mammalian nervous system called acetylcholinesterase.
In experiments that combined entomology and data-crunching computing, scientists at the University of California at Riverside uncovered four alternatives that may send DEET into retirement after 67 years.
"The candidates contain chemicals that do not dissolve plastic, are affordable and smell mildly like grapes, with three considered safe in human foods," says their study published Wednesday in the journal Nature. "Our findings pave the way to discover new generations of repellents that will help fight deadly insect-borne diseases worldwide."
The scientists' first step was to understand how mosquitoes sense DEET and become repelled by it. For this, they turned to a cousin of the mosquito called the fruit fly, or Drosophila melanogaster, one of the most closely-studied lab creatures of all. The answer, they found, lies in a receptor called Ir40a, found in nerve-system cells in a pit-like structure in the fruit fly's antenna.
The next step was to look for an odor molecule that would fit and activate the receptor, rather like a key turns a lock. It also had to be a natural substance, found in fruits, plants or animals.
The data pool proved to be a mini-ocean, comprising nearly half a million potential compounds. This was whittled down to nearly 200. Of these, 10 compounds seemed the most promising and were put to the test on fruit flies. Of the 10, eight turned out to be good repellents on fruit flies. Four of them were then tested on mosquitoes, all of which worked.
The good news is that out of the four, three have already been approved as food flavors or fragrances by the US Food and Drug Administration (FDA). Called methyl N,N-dimethyl anthranilate, ethyl anthranilate and butyl anthranilate, they can be applied to bed nets, clothes and curtains to ward off insects, say the scientists.
The secret behind the breakthrough was to locate the Ir40a receptor and develop an algorithm to screen potential chemicals, said Anandasankar Ray, an associate professor of entomology. Ir40a, according to the probe, is highly conserved, a scientific term meaning that it shows little signs of evolutionary change. That, too, is good news. One of the problems for drug designers is when they face a moving target -- a mutational shift in DNA that means the treatment becomes less effective.
The receptor is also common across many flies and other insects that are a pest for humans and plants.
"Our findings could lead to a new generation of cheap, affordable repellents that could protect humans, animals and, in the future, our crops," said Ray.
So far, finding an inexpensive and safe chemical for combatting disease in regions where malaria is endemic has proved a challenge.
Rarely has anyone looked at a potentially fatal infectious disease and exclaimed, "Now, that is a thing of beauty." One sculptor, however, has taken bacteria and viruses from their invisible world and placed them in ours.
Artist Luke Jerram has created a collection of glass artwork in the shape microorganisms -- bacteria and viruses no less that have the potential to infect or even kill human beings. By bringing these microscopic marauders to the light, Jerram demystifies these otherwise unknowable microorganisms. And using glass as a medium reinforces not only the fragility of the work, but also our own in the face of these diseases.
In this slide show, take a closer look at some of the highlights from Jerram's glass microbiology collection.
Turning HIV into a work of art is a seemingly impossible task. The virus is responsible for the deaths of an estimated 34 million people worldwide since the epidemic was first reported in 1981, according to UNAIDS, the joint United Nations Programme on HIV/AIDS.
The HIV virus sculpture was the first Jerram built for his collection.
If there's one disease that has plagued humankind throughout its history, it's malaria. In 2010, the World Health Organization estimated that more than 200 million people were infected with the disease, mostly in poverty-stricken regions of sub-Saharan Africa, but also parts of South America and Southeast Asia.
Malaria is transmitted through mosquito bites. Mosquito nets, insect repellant and pesticides are all effective means of prevention, but only for those with the available resources and access to afford them.
Looking at this spindly sculpture might make you the slightest bit queasy, and for good reason. E. coli is represented by this glass artwork. Although most E. coli strains are in fact harmless to humans, the strains we're most acquainted with are the ones that cause food poisoning.
This alien-looking sculpture is actually T4 Bacteriophage, a virus that targets E. coli bacteria.
Bacteriophages are small viruses that attach to the cell membrane of bacteria. The virus injects its DNA into the bacteria, which then produces replicas of the virus, filling the bacterium until it bursts.
If this model is giving you that nostalgic feeling of plagues past, you might not be surprised to find out that this work represents Severe acute respiratory syndrome, or SARS.
SARS made global headlines in 2003 when people in 37 countries and nearly reached pandemic levels. Although coverage of the illness was widely criticized for overstating the threat, nearly 9,000 were infected with the disease, with had a nearly 10 percent fatality rate.
Swine flu, shown here, was another contagious disease that drew global attention that Jerram selected for his exhibition, but this time it was personal. According to his website, Jerram came down with swine flu and constructed the sculpture "with a fever whilst swallowing my Tamiflu tablets every few hours."
Swine flu, or H1N1 strain of the influenza virus, made global headlines in 2009 as the next potential major flu epidemic. Though common among pigs, swine flu is rarely transmitted among humans. When it does infect a human, however, the symptoms associated with the virus, typical of other flu strains, are particularly acute.
Given just how common the Human Papilloma Virus (HPV) is among humans, you'd think this virus, pictured here, wouldn't be so controversial. In fact, it isn't, but the use of a vaccine to prevent the infection, which can lead to certain kinds of cancers in women.
Because the virus can be transmitted sexually, however, the idea of vaccinations, particularly compulsory ones for children -- the vaccine is in fact intended only for people 25 and younger -- generated a considerable pushback, despite the obvious benefits of the treatment.
Hand, foot and mouth disease might not get a lot of press, but these disease outbreaks are in fact fairly common, particularly among infants and children. Occasionally, they can be fatal. Symptoms are similar to the flu, with the exception of sores that can appear all over the body, but particularly the hands, feet and mouth of the carrier.
This final entry is an unrealized future mutation for a disease that doesn't exist yet. Look for it in a contaminated water main, food source or loving pet near you. (But seriously, don't.)