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UC Riverside researchers have demonstrated how ammonia and amine odorants can be used to combat insect-borne diseases such as malaria and dengue virus. New research by scientists at the University of California, Riverside, has potential for insect control through volatile repellents that could be applied to surfaces such as window sills, cabin eaves, house entrances, backyards, outdoor produce storage areas, entrances to cattle sheds, etc. alongside crops. the first research work is entitled “Chemosensory Detection of Aversive Concentrations of Ammonia and Basic Volatile Amines in Insects” and appears in the journal iScience. the second research paper is titled “Pentylamine Inhibits Moisture Recognition in Insect Vectors of Human and Plant-borne Pathogens”.
Researchers initially focused on ammonia, a basic volatile compound found in insect environments. At low concentrations, such as in human sweat, ammonia is an attractant to mosquitoes and other insects, but at high concentrations, such as in household cleaners, ammonia is no longer attractive. Researchers studied what happens to the olfactory system, or smell, and the gustatory system, or taste, of fruit flies and mosquitoes in the presence of ammonia.
Ananda Sankar Ray, a professor of molecular, cell and systems biology who led the studies, described the science behind this phenomenon: “We found that the olfactory neurons appear to have a burst of activity and then go quiet for a while. During the resting period, the neurons cannot detect odorants, meaning insects cannot effectively detect human skin odor.”
When Ray’s team tested the taste systems of fruit flies and mosquitoes (Aedes aegypti), they found a similar response. “In terms of taste, we found that ammonia and ‘amine’ derivatives of ammonia that make up many synthetic odorants don’t produce the flash activity that we see in the olfactory system,” explained Ray.
According to Ray, the discovery could be used to create effective insect repellents in the future.
“While compounds like ammonia, which have a high pH and are basic, cannot be used on the skin due to their caustic properties, they can be used in other ways. Many stinging insects fly into houses from the outside. In most parts of the world, insects sting people and pets indoors and often at night.” He explained how the repellents can be applied to a variety of surfaces: “For example, if there are walls where insects will land and wait, a material with a high pH included, mosquitoes would be affected. When a high pH compound, such as An amine, for example, spread around entrances to houses and animal pens could similarly repel mosquitoes.”
In the second research, Ray’s lab examined behavioral modifications as a function of humidity in the Asian citrus flea, an insect that transmits citrus leaf disease, and in mosquitoes. The lab discovered that amine odorants inhibit the moisture response. Ray explained, “We identified neurons in the ACP that sense moisture and found that certain amines might inhibit their moisture perception. We then showed that this was conserved in fruit flies. This is probably the first time researchers have shown that moisture sensing can be inhibited by odorants.”
“This means that by blocking the insects’ ability to sense water with a volatile odorant, we can manipulate their moisture-sensing pathway and alter their behavior in predictable ways,” Ray said. “In the future, it may be possible to manipulate amines to prevent insect oviposition in certain areas.”
Diseases caused by insects are worldwide with approx 241 million cases of malaria worldwide in 2020, with several million more cases in 2021. Third world countries are particularly affected, with almost half the world’s population living in regions where malaria and dengue fever are risky. In addition, insects are often pears that destroy a third of agriculture.
