BioQuakes

AP Biology class blog for discussing current research in Biology

Tag: #mosquitoes

Why is it That I Tend to Get More Mosquito Bites Than All Of My Friends?

Have you ever wondered why some people get more mosquito bites than others? To your surprise it is not because they have “sweet blood,” there is actually an odor that our body produces, some more than others, that attracts mosquitoes. Jason Arunn Murugesuu, a reporter for the New Scientist, recently published an article regarding research conducted by Maria Elena De Obaldia at Rockefeller University in New York. In this study, they posed the question of whether body odor affects mosquitos’ attractiveness to an individual.

Aedes aegypti CDC-Gathany

In this experiment, there were two boxes that contained nylon fabric swatches that were worn by two different individuals, and in each box lay the fabrics. The third box held  female Aedes aegypti mosquitoes. The researchers tested which box most attracted the Aedes aegypti. After numerous trials, it was found that their results stayed persistent.

It was determined that nylon fabrics that most attract mosquitoes were worn by individuals that happened to have a higher concentration of carboxylic acids present in their body odor. The bacteria on our skin produce carboxylic acids, which are a result of sebum, a substance composed of lipids that lie on the skin’s surface as a protective barrier.

Carboxylic-acid

Sadly, one cannot necessarily prevent the amount of carboxylic acids our body produces to limit the number of mosquito bites. According to De Obaldia, our body’s odor comes down to our genetics, skin microbiome and diet. It is unlikely for body odor to be altered based on mild changes, such as a temporary change in diet. Skin bacteria live deep down in our pores, so it is unlikely that they can be removed, which is why they are a significant factor in our body odor.

Moreover, De Obaldia repeated the study but replaced the  Aedes aegypti mosquitoes with genetically modified mosquitoes that have a weakened ability to sense acids. After this experiment was conducted, the researchers found that some of the mosquitoes had a lessened preference for nylon fabrics that contained a higher concentration of carboxylic acids. 

This study concludes that mosquitoes do, in fact, have a preference as to who they are choosing to bite. Scientists now have a reasonable solution to decrease mosquitoes’ preference for humans and spread diseases, which is to genetically modify the mosquitoes. 

Now, after reading this, if you notice that you are getting more mosquito bites than all of your friends, it is possible that you have a higher amount of carboxylic acids present in your body odor. 

 

A New Mosquitoes Exterminator: CRISPR

Mosquitoes might be just pesky little insects that might start appearing again in a few months. They leave their saliva in your skin, and this causes an itchy bump. But in other parts of the world. Estimates report that mosquitoes have killed up to 52 billion people in history by spreading malaria, yellow fever, and dengue. It is currently killing 1 million people per year, even with advanced medicine and healthcare around the world. Doesn’t that horrifying statistic shock you? 

Aedes aegypti

A close shot of Aedes aegypti

To drastically lower this number, researchers took a smart approach and decided to eliminate the source of the problem. They decided to use CRISPR to genetically alter the male flies so that they become sterile.  Professor Craig Montell from UC Santa Barbara altered the gene of Aedes aegypti, the main type of mosquito that transmits dengue, yellow fever, Zika, etc. 

Previously, scientists just radiated and applied chemicals to sterilize male mosquitoes in hopes to alter their genes since “there are enough genes that affect fertility that one will likely be altered,” making them infertile. However, this would leave, many of the mosquitoes to be sick and die prematurely since other genes that don’t relate to fertility are also changed.

Using CRISPER/Cas9, researchers removed B2t, a gene that specifically affects male fertility in mosquitoes. Unlike in previous efforts, the sterile mosquitoes were completely healthy. 

This whole effort to sterilize insects is part of a greater method called the sterile insect technique (SIT). Scientists release way more sterile insects than there exist in the wild. The population will crash as females will not be mating with a lot of males that are capable of making offspring. A benefit of releasing males instead of females is that males feed on nectar, not blood,  so it will not cause major disturbance to communities.

To sexually reproduce, a sperm cell must meet an egg. Each gamete is a haploid that has a single set of chromosomes. The sperm and egg combine to produce a zygote making it a diploid with a complete set of chromosomes. If a male is sterile, then they are not able to produce or release their sperm, making it impossible for those insects to reproduce.

The effect of this technique is more effective after each cycle, so when you release the same amount of mosquitoes after 3 cycles, the population change will be way more drastic. A downside to this is that sterile male mosquitoes need to be reintroduced after they die off since they cannot pass on their mutated gene.

Although researchers have successfully identified a way to isolate the gene and remove it to make male mosquitoes fertile, they still needed to find the optimal ratio of lab mosquitoes to wild type to ensure that they do not wipe out the species in an area since that has dramatic effects on the whole ecosystem. The researchers conducted many trials and found that, in a week, a ratio of about “5 or 6 sterile males to one wild-type male” decreased female fertility by 50% while, a ratio of 15:1 suppressed female fertility to about 20%, where it leveled off. So depending on the situation, they now release the more precise amount. 

I think that this is one of the brilliant uses of CRISPR, and it only goes to show how far we can go if we master this technique. An ethics question that this research brings up is, do humans have the right to wipe out an entire species just because it is causing harm to humans?

Hello, CRISPR and Goodbye, Malaria

Everybody hates mosquitoes. Not only are they annoying pests that bite us during the summertime, but they are also transmitters of the parasite that spreads malaria–Plasmodium.  However, scientists believe that they have found a way to wipe out malaria for future generations. By using CRISPR in order to alter the fibrinogen-related protein 1 (FREP1), Plasmodium can be stopped from spreading amongst human beings.  The alteration stops the plasmodium from reaching the mosquitoes’ salvatory glands, effectively halting transmission into the human bloodstream.

However, although CRISPR is a lot less drastic than simply wiping out the mosquito population, it does come with minor setbacks.  The alteration made to the FREP1 gene causes the fertility of the mosquito as well as the egg-hatching rate to drop.  These effects cause the reproduction rates of the altered mosquitoes to be significantly lower than that of other mosquitoes.  If the modified mosquitoes are not able to reproduce, then the genetic modifications are unlikely to have any real effect on the transmission of malaria since they are not being passed on generationally.

The solution? Alter the female mosquitoes.  Only female mosquitoes transmit malaria, so scientists have realized that altering the genetic code of female mosquitoes might be the way to solve the problem with reproduction.  This way, the mosquitoes are able to maintain the genetic resistance to Plasmodium whilst avoiding the dramatic drop in reproduction.

Even though the alteration of mosquitoes’ genetics is definitely a scientific feat, there are no certainties when it comes to this attempt to stop malaria. Nobody is positive about whether or not CRISPR is the solution, but it is definitely a huge step in the right direction.

Harmless Mosquitoes…Yes Please

What are the most annoying things on Earth? Why, mosquitoes of course. They bite you and their bites are extremely irritating. Mosquitoes also carry life-threatening viruses, such as Malaria. However, scientists have come up with a way to get rid of mosquitoes carrying Malaria with the help of gene drives.

A gene drive is a self-generating “cut-and-paste system” that can sterilize mosquitoes. Well how do gene drives work? They operate using CRISPR/Cas9, precision molecular scissors that cut DNA. Scientists used CRISPR/Cas9 to disrupt the genes that are active in mosquito ovaries. If a female mosquito is missing one of these genes, they become sterile. Gene drives insert themselves into a target gene to assimilate every unaltered gene they pass. They break normal inheritance rules by being able to pass themselves into over 50% of an altered animal’s offspring.

NHGRI-97218

The first gene drive that was made stopped mosquitoes from transmitting Malaria. This new gene drive would eliminate Malaria-carrying mosquitoes in the future by making the females sterile, unable to reproduce. This gene drive is not 100% perfect yet, but scientists are hoping to perfect it soon to be able to release it. They hope that this gene drive will be able to control different insect populations, not only mosquitoes.

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