Mosquitoes Essay

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There are few animals in the world that have as medically significant biology as mosquitoes. Carrying diseases that annually kill thousands, if not millions, of people worldwide, mosquitoes and the way they interact with pathogens are topics of concern for many researchers. As invertebrates, mosquitoes possess various immune responses designed to rid themselves of pathogens. Study of these immune responses has led to a deeper understanding of the ways in which the immune cells of mosquitoes, hemocytes, function and serve the purpose of killing the invasive pathogen. In conjunction with the circulatory system of the mosquito, these immune cells react in various ways upon infection with a pathogen such as a bacterium or virus. The Hillyer Lab…show more content…
This vector behavior leads to mosquitoes’ transmission of harmful diseases including malaria (N. Becker et al., 2010), a severe disease that kills millions around the globe annually. For species of the Plasmodium genus that cause malaria in humans, certain species of anopheline mosquitoes act as hosts, with Anopheles gambiae being studied in most detail by the Hillyer Lab. The process by which pathogens interact with their mosquito hosts varies, but the path of Plasmodium species is rather complex. As stated by N. Becker, Plasmodium species replicate sexually in mosquitoes but asexually in vertebrate hosts (2010). After entering the mosquito midgut by ingestion in a blood meal from an infected vertebrate, the parasite develops into an ookinete, travels to the midgut epithelium, and then forms many sporozoites. These sporozoites are the form of the parasite that travel throughout the hemocoel and eventually enter the salivary glands where they can be transmitted to another host through a blood meal (N. Becker et al., 2010). This pathway is just one example of how a certain parasite interacts with mosquitoes, and each pathogen can interact with and be dealt with differently by the mosquito…show more content…
With the aim of initially keeping the pathogen outside of the internal compartments of the mosquito, the cuticle is the first line of defense in preventing infection (Hillyer, 2016). As stated by Hillyer, breaching of this barrier can be done through wounds or enzymatic digestion. Once internalized, the pathogens are then subjected to a few main forms of degradation: cell-mediated phagocytosis, melanization, and lysis (Hillyer, 2010). There are other forms of degradation and pathogen elimination including RNA interference, but these methods are not as well understood (Hillyer, 2016). The cells of the immune system in mosquitoes that regulate these processes are called hemocytes, and they can either circulate in the hemolymph of the mosquito (circulating hemocytes) or be attached at a specific location (sessile hemocytes). The first method of elimination is phagocytosis, a very prominent response of the immune system of mosquitoes that is executed by a hemocyte’s (granulocyte) internalizing of the pathogenic particle into a phagosome followed by degradation via hydrolytic enzymes (Hillyer, 2010 and Hillyer, 2016). Melanization is a process in which a series of phenoloxidase based reactions occur that convert tyrosine to melanin precursors, forming a darkened capsule surrounding the pathogen that results in its
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