Mosquitoes Most Deadly Enemy Of The Human Race
June 18, 2018 at 3:08 p.m.
By Max [email protected]
If either occurs, and both are likely, mosquitoes will no doubt be the vectors.
Mosquitoes are our most persistent and deadly enemy. They have killed great leaders, decimated armies and decided the fates of nations. Alexander the Great, for example, was likely killed by malaria in 323 B.C.
Mosquitoes are responsible for a host of devastating, difficult-to-treat diseases, including dengue, elephantiasis and malaria, diseases that affect more than 10 percent of the world’s population.
Mosquitoes are unique in terms of their numbers, varieties, lifecycles, geographic distribution, appetites and habits. They are also attracted to some people more than others. Fortunately, mosquitoes can be repelled by a number of chemicals and their repellant properties can be predicted from the chemical structure. One bite is all it takes to be infected with West Nile virus or other mosquito-borne diseases.
Diseases
Mosquito-borne diseases include malaria; Japanese, California, Eastern Equine, Western Equine, St. Louis and Venezuelan encephalitis; dengue and dengue hemorrhagic fever; Rift valley fever; yellow fever; elephantiasis; and Chikungunya fever. The pathogens that cause these diseases are transmitted by injection of saliva into susceptible hosts by female mosquitoes needing protein from a blood meal to develop their eggs.
Mosquitoes are responsible for diseases in more than 700 million people each year. Malaria alone kills 3 million people each year, including one child every 30 seconds. In the United States, arboviruses (arthropod-borne viruses) transmitted by mosquitoes continue to cause sporadic outbreaks of eastern equine encephalitis, western equine encephalitis, St. Louis equine encephalitis, and La Crosse encephalitis.
Eastern equine encephalitis is the most lethal of the mosquito–borne encephalitides. The infection first became evident in the suburbs of Boston in 1938, but the virus had been isolated from horses five years earlier. In 1999, West Nile virus was discovered for the first time in the New York City area, where 62 people were infected. The virus has been detected in 27 states, and is expected to spread unabated across the United States.
Repellents
In many circumstances, applying repellents to the skin is an advisable way to protect against insect bites. The best known and most widely used chemical insect repellent is DEET. It was developed in 1953 and remains the gold standard based on its excellent human use safety record. The mechanism of action, however, has remained a mystery. Just recently, several researchers have discovered that DEET blocks odorant receptors in the nervous system of insects, masking odors that would ordinarily attract mosquitoes. Thus, mosquitoes smell and deliberately avoid DEET.
DEET, however, may be washed off by perspiration or rain, and its efficacy decreases dramatically with rising outdoor temperatures. DEET is also a plasticizer, capable of dissolving watch crystals, frames of glasses, and some synthetic fabrics.
Attractions
Body temperature, carbon dioxide in the breath and certain skin chemicals, such as lactic acid, all help mosquitoes orient and find their next blood meal. This means that exercise that boosts the levels of all three signals makes us more appealing than just sitting around. Evidence also suggests that mosquitoes are more attracted to black or red clothing. White is the best choice. It is less certain whether perfume or other body products attract mosquitoes, but it may be wise to avoid products with floral scents.
New research also indicates that pregnant women are twice as attractive to mosquitoes as those who are not pregnant. Pregnant women in an advanced stage exhale 21 percent greater volume and mosquitoes are attracted to the moisture and carbon dioxide in exhaled breath. Moreover, the abdomens of pregnant women are 0.7 C hotter than the abdomens of women who are not pregnant, which suggests that pregnant women release more volatile substances from their skin, allowing mosquitoes to detect them more easily.
There is recent research indicating that children with malaria are even more attractive to mosquitoes because they emit specific odors from their skin and thus invite further bites and risks of infection.
Identifying these human-derived compounds could provide an opportunity to use them for chemical lures to trap mosquitoes. Until then, the best bet for preventing bites includes wearing long sleeves and pants, using repellents, and staying away from shady areas and vegetation.
Mysteries
The key to combating the scourge brought on by mosquitoes is to better understand them. After more than a century of research there are a number of mysteries.
No one has explained why mosquitoes use blood in their reproductive process. Nor do we know how mosquitoes distinguish between hosts. Moreover, we do not understand the basics, such as how a mosquito develops the sucking force necessary to pull blood through a feeding tube with a diameter so small that resulting friction should make it impossible.
In addition, it is still a mystery as to why certain species of mosquitoes support the development of one type of pathogen and not another.
Max Sherman is a medical writer and pharmacist retired from the medical device industry. He can be reached by email at maxsherman339@ gmail.com.
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If either occurs, and both are likely, mosquitoes will no doubt be the vectors.
Mosquitoes are our most persistent and deadly enemy. They have killed great leaders, decimated armies and decided the fates of nations. Alexander the Great, for example, was likely killed by malaria in 323 B.C.
Mosquitoes are responsible for a host of devastating, difficult-to-treat diseases, including dengue, elephantiasis and malaria, diseases that affect more than 10 percent of the world’s population.
Mosquitoes are unique in terms of their numbers, varieties, lifecycles, geographic distribution, appetites and habits. They are also attracted to some people more than others. Fortunately, mosquitoes can be repelled by a number of chemicals and their repellant properties can be predicted from the chemical structure. One bite is all it takes to be infected with West Nile virus or other mosquito-borne diseases.
Diseases
Mosquito-borne diseases include malaria; Japanese, California, Eastern Equine, Western Equine, St. Louis and Venezuelan encephalitis; dengue and dengue hemorrhagic fever; Rift valley fever; yellow fever; elephantiasis; and Chikungunya fever. The pathogens that cause these diseases are transmitted by injection of saliva into susceptible hosts by female mosquitoes needing protein from a blood meal to develop their eggs.
Mosquitoes are responsible for diseases in more than 700 million people each year. Malaria alone kills 3 million people each year, including one child every 30 seconds. In the United States, arboviruses (arthropod-borne viruses) transmitted by mosquitoes continue to cause sporadic outbreaks of eastern equine encephalitis, western equine encephalitis, St. Louis equine encephalitis, and La Crosse encephalitis.
Eastern equine encephalitis is the most lethal of the mosquito–borne encephalitides. The infection first became evident in the suburbs of Boston in 1938, but the virus had been isolated from horses five years earlier. In 1999, West Nile virus was discovered for the first time in the New York City area, where 62 people were infected. The virus has been detected in 27 states, and is expected to spread unabated across the United States.
Repellents
In many circumstances, applying repellents to the skin is an advisable way to protect against insect bites. The best known and most widely used chemical insect repellent is DEET. It was developed in 1953 and remains the gold standard based on its excellent human use safety record. The mechanism of action, however, has remained a mystery. Just recently, several researchers have discovered that DEET blocks odorant receptors in the nervous system of insects, masking odors that would ordinarily attract mosquitoes. Thus, mosquitoes smell and deliberately avoid DEET.
DEET, however, may be washed off by perspiration or rain, and its efficacy decreases dramatically with rising outdoor temperatures. DEET is also a plasticizer, capable of dissolving watch crystals, frames of glasses, and some synthetic fabrics.
Attractions
Body temperature, carbon dioxide in the breath and certain skin chemicals, such as lactic acid, all help mosquitoes orient and find their next blood meal. This means that exercise that boosts the levels of all three signals makes us more appealing than just sitting around. Evidence also suggests that mosquitoes are more attracted to black or red clothing. White is the best choice. It is less certain whether perfume or other body products attract mosquitoes, but it may be wise to avoid products with floral scents.
New research also indicates that pregnant women are twice as attractive to mosquitoes as those who are not pregnant. Pregnant women in an advanced stage exhale 21 percent greater volume and mosquitoes are attracted to the moisture and carbon dioxide in exhaled breath. Moreover, the abdomens of pregnant women are 0.7 C hotter than the abdomens of women who are not pregnant, which suggests that pregnant women release more volatile substances from their skin, allowing mosquitoes to detect them more easily.
There is recent research indicating that children with malaria are even more attractive to mosquitoes because they emit specific odors from their skin and thus invite further bites and risks of infection.
Identifying these human-derived compounds could provide an opportunity to use them for chemical lures to trap mosquitoes. Until then, the best bet for preventing bites includes wearing long sleeves and pants, using repellents, and staying away from shady areas and vegetation.
Mysteries
The key to combating the scourge brought on by mosquitoes is to better understand them. After more than a century of research there are a number of mysteries.
No one has explained why mosquitoes use blood in their reproductive process. Nor do we know how mosquitoes distinguish between hosts. Moreover, we do not understand the basics, such as how a mosquito develops the sucking force necessary to pull blood through a feeding tube with a diameter so small that resulting friction should make it impossible.
In addition, it is still a mystery as to why certain species of mosquitoes support the development of one type of pathogen and not another.
Max Sherman is a medical writer and pharmacist retired from the medical device industry. He can be reached by email at maxsherman339@ gmail.com.
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