With the huge spread of the COVID-19 virus, the communities forgot about the other infections that could happen seasonally or due to any kind of interaction with potent organisms. Dengue virus is one of those fatal viruses and is caused by mosquito bites. In this article, we will examine mosquito behavior, how infections occur through mosquito bites, and what is this dengue virus. Then, we will give a few recommendations on how to prevent from mosquitoes and most interestingly we will briefly explain how Singapore and a few other countries fight off mosquitoes by making use of genetic engineering technology.
Mosquitoes are insects that undergo a life cycle including metamorphosis that takes place in watery areas. They undergo different stages of development, the first being an egg that is laid by an adult female mosquito after feeding on blood, which then becomes larva in 2 to 3 days. Larva takes nutrients from the water source and breathes by its spiracles to develop further and becomes pupa in 4-5 days just to become an adult mosquito a few days later. So, in general, mosquitoes take about a week to completely develop, but this could differ according to the species and environmental conditions such as temperature. Considering that a single female mosquito can lay about 100 eggs, mosquitoes quickly increase in number and surround a large area. These are insects that love warm and humid climates and can even live up to 3 weeks in such environments, and that’s why we mostly deal with these little annoying insects during the summer period. During these warm intervals, even a little herd of mosquitoes coming to a neighborhood would breed and multiply their numbers by thousands. Furthermore, several plants such as nectars where they can feed on could also attract more and more mosquitoes than expected. And more interestingly, mosquitoes can also be attracted to dirty and untidy living spaces. These insects are known to most work around nighttime; however, this is not applicable for all species, especially not for the Aedes aegypti species that transmit the dengue virus, and can also be impacted by other environmental conditions such as rainy weather.
We know that the main feeding source of mosquitoes, specifically female ones, is blood. But how can these little insects detect where they should feed on? How can they detect a human being and find the most appropriate part of the body to drink blood from? The first detection technique they use is the carbon dioxide (CO2) we breathe out. Mosquitoes have developed sensory systems using their sensitive antennae to detect the carbon dioxide a human breathes out from up to 50 meters away. Using this information, they can easily conclude that there are feeding sources around and move closer. Another detection mechanism is by making use of lactic acid which is one of the components of human sweat. Considering that we sweat at peak levels during warm temperatures, we instantly become the target sources of food for mosquitoes and directly attract many. A few research findings concluded that several floral perfumes also attract mosquitoes. These are a few mechanisms that mosquitoes use to detect their victims. But how and why do they stick to a specific part of our body and come back even after we repel them? Mosquitoes have developed heat-detecting systems. This system functions to detect where blood is the closest to your skin surface. By feeling the heat, they find the easiest part of your body to feed on and stick on there.
The main point of the previous paragraphs about mosquito behavior was that we are constantly fighting against mosquitoes and in order to minimize the mosquito bites we have to take some measures and precautions. Considering that mosquitoes can breed anywhere, avoiding them by using window screens or repellents will not do the job completely. Although these are also ways that you can avoid mosquitoes for a while, comprehensive pest control measures are crucial in this case to target mosquitoes in every stage of their lives.
Before moving on to Singapore’s gene-editing methods to deal with mosquitoes, here are some basic precautions you can take to minimize the breeding of mosquitoes. The first way we will recommend is to make sure there are no unnecessary water collections around your household. Mosquitoes need water to survive and breed and they can make use of the smallest amount of water even in flower pots or rain gutters. Hence, make sure that water is absorbed completely in such items. You can use repellents, traps, or sprays to avoid mosquitoes as well. If you are dealing with an extensive amount of mosquitoes that become unbearable at some point, you can also call for professional help. The professionals will perform some investigations and apply necessary measures such as water-based fogging to eradicate flying adults, larviciding at mosquito breeding sites to eliminate larvae and pupae, or placing comprehensive mosquito traps. However, in most cases, these preventions above are not permanent solutions and may lose their effectiveness after a while. That’s why Singapore developed a system using gene engineering methods and tried to clear nearly the whole mosquito population off.
The so-called Wolbachia Project was pioneered by scientists at Monash University and is based on the mating of different species and spaying the mosquitoes and currently is being used across Asia and Latin America as well. In this method, the dengue virus carrier Aedes mosquitoes are mated with the Wolbachia mosquitoes which cannot carry diseases. Wolbachia mosquitoes carry a special bacteria that hinders the fertility of Aedes mosquitoes. These mosquitoes are bred in laboratories in rows of pallets. Then the male ones are separated and sent to the environment to find themselves female companions from the Aedes species and mate with, but not produce. This breeding of different species prevent the eggs of mosquitoes from hatching and thus put an end to the life cycle of mosquitoes. Using this method, some areas in Singapore have seen up to a 90% decline in the mosquito population, released by the official head of the Wolbachia Project, Ng Lee Ching. However, this project has a weak point. Although many people are informed about the release of these mosquitoes, when they encounter any mosquito they will not have the chance to examine it and see whether if it is Aedes or Wolbachia. Thus, several Wolbachia mosquitoes can also end up dead or trapped and this would disturb the mechanism.
So, we’ve been talking about how mosquitoes find their victims, how and where they can breed, how to avoid them both in short terms and permanently and how Singapore deals with the high populations of mosquitoes around the country. We’ve also been talking about the dengue virus spread by the Aedes mosquito but now let’s see what this virus actually is, from a medical perspective. The dengue virus has been on peak for the past few decades and has expanded to more than 100 countries today. It is a viral disease transmitted by the Aedes mosquitoes to the humans. When a person is bit by an infectious Aedes mosquito, the dengue virus multiplies in the patient’s body and it takes about 4-7 days for the patient to develop symptoms. Although some patients can be asymptomatic, some could show symptoms such as fever, headache, pain behind the eyes, nauseous, vomiting, and many more. There are no specific anti-viral drugs for the treatment of dengue as well as a preventative vaccine. Although there is a vaccine developed against the dengue virus, it can only be injected into patients who have at least one contracted the virus. Thus, preventative measures are critical.
Although the methods that are developed to decrease the number of possible infectious mosquitoes do help with a decline, we know that mosquitoes will not extinct and thus will continue to infect people by feeding on their blood. Hence, along with the other viral diseases the world population deals with, the dengue virus is also one that needs further studies to develop drugs or vaccines.
 Yeo, Written by Junie. “Mosquitoes in Singapore – When Are MOSQUITOES MOST ACTIVE?” DeBugged SG – The Pest Control Blog, 23 Mar. 2021, http://www.rentokil.com.sg/blog/mosquitoes-active-can/.
 “Mosquitoes & Mosquito Borne Diseases.” National Environment Agency, http://www.nea.gov.sg/docs/default-source/resource/section-a—mosquitoes-amp-mosquito-borne-diseases-pdf-1-41-mb-.pdf.
 Su, Edgar, and Joseph Campbell. “Singapore Battles Record Dengue Outbreak with More Mosquitoes.” Reuters, Thomson Reuters, 28 Aug. 2020, http://www.reuters.com/article/us-singapore-environment-dengue-idUSKBN25O03A.
 Chandrashekhar, Vaishnavi. “The Mosquitoes That Are Fighting Dengue and Zika.” BBC Future, BBC, 2018, http://www.bbc.com/future/article/20180104-the-mosquitoes-that-are-fighting-dengue-and-zika.
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 image only: https://thenativeantigencompany.com/dengue-in-2019/