Barely one year after Dr Thomas Kollars, a research scientist from America used colours that are attractive to mosquitoes to develop an artificial poisonous flower that attracts and kills the insect; another study headed by an African scientist is promising to provide a synthetic product with odor similar to humans, to lure the same insect to a death.
A study headed by Dr Fredros O. Okumu, Biomedical and Environmental Scientist at the Ifakara Health Institute (IHI) in Tanzania, and also a lecturer at the University of Nairobi as well as the London School of Hygiene and Tropical Medicine in the United Kingdom, has already evaluated two synthetic products, which attracted three to five times more mosquitoes than humans when the two baits were used in experimental huts with the absence of humans.
However, when put in the same room with human beings, mosquitoes seemed to have almost similar preference to both. According to the researchers, disease transmitting mosquitoes locate humans and other blood hosts by identifying their characteristic odour profiles. Using their olfactory organs, the insects detect compounds present in human breath, sweat and skins, and use these as cues to locate and obtain blood from the humans.
“These odour compounds can be synthesized in vitro, then formulated to mimic humans. While some synthetic mosquito lures already exist, evidence supporting their utility is limited to laboratory settings, where long-range stimuli cannot be investigated,” states the early findings in the preamble, as published in the PlosOne Health Journal.
A documentation of the early field trials indicates that a blended odor made up of components known to attract mosquitoes was utilized. The components include carbon dioxide, ammonia and carboxylic acids, which was optimized at distances comparable with attractive ranges of humans to mosquitoes.
According to the report, binary choice assays were conducted inside a large-cage semi-field enclosure using attractant-baited traps placed 20 meters apart. This enabled optimization of concentrations at which the individual candidate attractants needed to be added so as to obtain a blend maximally attractive to laboratory-reared Anopheles gambiae, the most common vector for malaria transmission in Africa.
Further field experiments were conducted inside experimental huts, where the blend was compared with 10 different adult male volunteers (20-34 years old) in order to find out if the concoction with the synthetic odor would as well attract wild mosquitoes.
“As a result, the blend attracted three to five times more mosquitoes than humans when the two baits were in different experimental huts (10100 meters apart), but was equally or less attractive than humans when compared side by side within same huts,” says the report titled 'Development and Field Evaluation of a Synthetic Mosquito Lure That Is More Attractive than Humans.'
It was then concluded that the highly attractive substitute for human baits might enable development of technologies for trapping mosquitoes in numbers sufficient to prevent rather than merely monitor transmission of mosquito-borne diseases.
If successful, the study would provide results using a similar concept like the one used by Dr Kollars, a professor at Georgia Southern University at Statesboro in the United States of America, who has designed a flower-shaped plastic trap in blue, green, red and black, which often attract mosquitoes.
Laboratory tests of the Dr Kollars' project by Walter Reed Army Institute of Research indicated that the flower, dubbed 'ProVector Flower Bt' successfully attracted and killed between 50 to 100 per cent of all mosquitoes that landed on it within days.
Though studies show that some mosquitoes have started feeding on alternative animals apart from human beings, scientists are still not sure of the processes the insects use to evaluate potential blood meal. At the same time, little is known as to why some people are highly attractive to mosquitoes than others.
Researchers have found out that female mosquitoes use carbon dioxide exhaled by human beings as their primary cue to identify their location. Once on the skin, they use several short range attractants to identify an acceptable blood meal host.
Folic acid has been identified as one of the lead cues. However, fragrances like sprays, perfumes, scented soaps can guise these chemical cues. Scientists have also discovered that mosquitoes more often than not are attracted to dark colours than bright ones.
Generally, human blood is very important especially to female mosquitoes because without it, they cannot develop fertile eggs. This further explains exactly why male mosquitoes do not bite. The female mosquitoes require a blood meal for any batch of eggs they lay.
However, both male and female mosquitoes feed on nectar, fruit juices and liquids from plants for their nutritional needs. From this, scientists say that the plant sugar is converted into energy required for them to fly around, while blood is reserved particularly for egg production.