According to the Centers for Disease Control (CDC), malaria is a disease caused by several parasites from the genus Plasmodium that is spread to humans by certain species of mosquitoes. While the disease was eradicated in the United States in the 1950’s, malaria is a deadly illness across the world and can easily be reintroduced into an area if one infected person enters. When infected, people experience fever, chills, and a flu-like illness. If the disease is not quickly treated then further complications can occur and the patient may die. In 2013 alone there were an estimated 198 million cases of malaria worldwide which caused 500,000 deaths. While there are currently many different methods for the prevention of malaria, including pesticides and mosquito netting, it is clear that these methods have not been effective enough in protecting people. Unfortunately, malaria is most active in extremely poor parts of the world which do not have the infrastructure to make use of all the preventative measures we enjoy in America. Realizing this shortcoming, scientists have begun researching novel methods of prevention designed to fight malaria by targeting its vector: the mosquito.
According to the Centers for Disease Control (CDC), malaria is a disease caused by several parasites from the genus Plasmodium that is spread to humans by certain species of mosquitoes. While the disease was eradicated in the United States in the 1950’s, malaria is a deadly illness across the world and can easily be reintroduced into an area if one infected person enters.
Malaria is transmitted between humans by female mosquitoes of the Anopheles genus. This genus is spread worldwide on every continent except Antarctica, and malaria is spread by whichever Anopheles species inhabits that area. These female mosquitoes need to consume blood to produce eggs, and therefore whenever they reach that reproductive stage of their life cycle they actively search out humans or cattle to feed on. The malaria parasite is ingested into the mosquito when it feeds on infected creatures, be it human or otherwise. Once the mosquito has consumed the parasite, it takes approximately 10 to 21 days to become infectious to humans. After this time, if a mosquito bites another creature then that creature will become infected. The successful spread of malaria involves the parasites infecting both the female Anopheles and human beings. In humans the parasite first resides in the liver before traveling to the red blood cells where it grows multiple generations before bursting and destroying the cells. This process allows the release of the daughter parasites allowing them to invade other red blood cells. If any of these infected red blood cells are consumed by a female Anopheles mosquito, the parasite stays in the mosquito’s saliva and can easily be spread to another host.
There are several government sponsored interventions for malaria in developing countries where the disease is still widespread. While heavy insecticide use has been largely abandoned due to negative effects on the ecosystem, limited application in one’s home or on existing mosquito netting is highly recommended. Travelers to these countries can take certain medications and wear proper apparel to decrease the likelihood of infection. Unfortunately places like Africa have a favorable climate for Malaria which, along with the lack of infrastructure or reliable healthcare, makes the disease all that more dangerous. In these countries there is often preventative treatment for pregnant women and infants to help limit cases of malaria in these high risk groups. However, despite all of these efforts, the colossal number of humans suffering from this disease remains each year and it seems that other solutions need to be considered.
Scientist hope that with time, a species can be selected for, bred, and then used to replace current species that transmit the disease.
Modern scientists have begun to take an interest in the Anopheles mosquito that transports the strain itself. One promising method is simply selecting for a species of Anopheles mosquito where the parasite cannot survive as efficiently. The parasite cannot use every species of Anopheles equally, and certain species will not allow it to form properly to become infectious. Scientist hope that with time, a species can be selected for, bred, and then used to replace current species that transmit the disease. Unfortunately, there currently exists no easy and cost efficient mechanism to replace one species with another. Hypothetically however, the simplest solution would be to make the selected for species a better fit for the environment than the current wild type and therefore natural selection would allow the new species to slowly over time replace the old.
Other scientists focus on altering the gender of the mosquitoes because only the females spread the parasite. One group of scientists have studied a slightly different species of mosquito responsible for Dengue Fever and have engineered a female-specific flightless phenotype.
Other scientists focus on altering the gender of the mosquitoes because only the females spread the parasite. One group of scientists have studied a slightly different species of mosquito responsible for Dengue Fever and have engineered a female-specific flightless phenotype. This solution, while not specifically for a malaria carrying mosquito, could also hypothetically be produced for an Anopheles species. The advantages of this solution are manifold. Because these females cannot fly, they are effectively sterile because they cannot perform the mating dance necessary for reproduction. Moreover, because this lethality acts late in the organism’s development, any stage of the insect can be released. Instead of being forced to release adult members of the species which are fragile and cannot be stored long, eggs can be released which allow for long term storage, lower cost, and easier release. While this is not a direct answer to the problem of malaria, this solution certainly has promise and could be similarly applied to Anopheles species.
Another group of scientists is looking for a way to distort X-linked gene expression using dosage compensation. Dosage compensation is essentially the equalization of gene expression between different genders in a species. It is this regulation of gene expression that allows each gender to produce functional adults despite possessing different numbers of genes. Recent studies into dosage compensation in mosquitoes have suggested that with further study it would be possible to alter X-linked gene expression and selectively target females of the species. Scientists believe that with further study it may be possible to convert females of the species to male or to alter them in some other sex specific way. That said, research into dosage compensation in the Anopheles mosquito has been very superficial and far more research will be required before any possible treatment will be produced.
While each of these methods have promise, they are all very new ideas and therefore there is not enough substantiated research that has been done to test their feasibilities. Scientists have made strides toward a more permanent genetic solution to malaria, yet more research and development before any of these possible solutions can even be tested on a large scale. There is hope, however, in knowing that there are currently optimistic solutions being produced that may revolutionize how malaria is treated globally and perhaps even eventually eradicate the disease.
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Jiang, X., Biedler, J., Qi, Y., Hall, A., & Tu, Z. (2015). Complete Dosage Compensation in Anopheles stephensi and the Evolution of Sex-Biased Genes in Mosquitoes. Genome Biol Evol Genome Biology and Evolution, 1914-1924. Retrieved August 16, 2015.
Hall, A., Basu, S., Jiang, X., Qi, Y., Timoshevskiy, V., Biedler, J., . . . Tu, Z. (2015). A male-determining factor in the mosquito Aedes aegypti. Science, 1268-1270. Retrieved August 17, 2015, from http://www.sciencemag.org.proxy.bc.edu/content/348/6240/1268.full
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