ArtsAutosBooksBusinessEducationEntertainmentFamilyFashionFoodGamesGenderHealthHolidaysHomeHubPagesPersonal FinancePetsPoliticsReligionSportsTechnologyTravel

DILEMMA

Updated on April 9, 2016

Dilemma

Referenced from Jade Jordan

Genetic resistance and antimalarial drug action against P. vivax and P. falciparum.

Malaria is a tropical disease that, without immediate treatment, can be fatal. More than 40% of the world living in malaria-risk areas with around 90% of all malaria cases reported in Sub-Saharan Africa followed by Southeast Asia and South America. There are five species of Plasmodia known to cause malaria in humans and of these, Plasmodium vivax and Plasmodium falciparum are the most common and the ones that will be discussed here.

P. vivax mostly affects populations outside of Africa especially in South America and Southeast Asia, where it is the most prevalent species of Plasmodia. Whilst this malarial parasite is the most widespread in the world, infection with the species rarely results in death. On the other hand, P. falciparum is the deadliest and most pathogenic of the five human malarial parasites, as it multiplies more rapidly in the blood than the other species. Also the parasite can cause small clots in blood vessels for example, cerebral malaria is when this occurs in the brain. P. falciparum is the most common parasite affecting sub-Saharan Africa and this is where it is mainly found.

As malaria is prevalent only in particular parts of the world, population genetics plays an important role in malarial resistance: these areas often have unique gene pools, consisting of sometimes unexpectedly high numbers of some genes. This is due to natural selection for some traits such as sickle cell and duffy negative blood cells due to their role in resistance to malaria. Still, there is a great need for the development of new drugs in the fight against malaria, as resistance has developed to many commonly used therapies. In order to this, we need to understand the structures and life cycles of the parasites in question as will be discussed in this essay.

Plasmodium Life Cycle

P. vivax and P. falciparum have more or less the same complex life cycle involving a human and mosquito vector. The parasites carry out the asexual stage of the life cycle in the human host and reproduces sexually in the mosquito.

The first stage in its life cycle is the exo-erythrocytic cycle. When a malaria-infected female Anopheles mosquito feeds on a human host’s blood, the parasite enters the host in its sporozoite form, via the saliva of the mosquito. Once in the bloodstream, the sporozoites travel to the liver where they infect hepatocytes. The sporozoites do this through the specific binding of their surface proteins and the basolateral domain of hepatocytes and it is this binding that initiates the invasion into the liver cells.

Once the sporozoites have invfected the liver, the parasite usually becomes a schizont. However, P. vivax can also become hyponozoites. When in the hypnozoite state, the infection lies dormant for a few months or even years before it re-enters the cycle to form schizonts and causes relapse in the patient. Schizonts contain thousands of merozoites and one it is mature, the vessel ruptures, releasing the merozoites and entering the erythrocytic cycle.

In this stage of the life cycle, these merozoites infect erythrocytes (red blood cells) in the bloodstream and form trophozoites. It is at this point where malaria can be first detected and diagnosed in a patient. Ring stage trophozites are those that use energy acquired from the red blood cell, to become schizonts and release more merozoites to spread the infection. Other trophozoites mature and differentiate into male and female micro- and macrogametocytes respectively. The gametocytes of P. vivax and P. falciparum vary slightly in structure as can be

seen in Figure 1. It is these gametocytes that re-enter the mosquito to commence the sexual stage of the parasite’s life cycle: the sporogonic cycle. During a blood meal, the mosquito ingests the gametocytes and they fuse to form zygotes in the mosquito’s stomach. The zygotes elongate and develop into motile ookinetes. These penetrate the wall of the mosquito’s midgut where they mature into oocysts ,which grow and rupture to release sporozoites. In the mosquito, sporozoites travel to the salivary glands where they remain until the mosquito feeds on another human host so the whole cycle can repeat.

Comments

    0 of 8192 characters used
    Post Comment

    No comments yet.

    working

    This website uses cookies

    As a user in the EEA, your approval is needed on a few things. To provide a better website experience, hubpages.com uses cookies (and other similar technologies) and may collect, process, and share personal data. Please choose which areas of our service you consent to our doing so.

    For more information on managing or withdrawing consents and how we handle data, visit our Privacy Policy at: https://hubpages.com/privacy-policy#gdpr

    Show Details
    Necessary
    HubPages Device IDThis is used to identify particular browsers or devices when the access the service, and is used for security reasons.
    LoginThis is necessary to sign in to the HubPages Service.
    Google RecaptchaThis is used to prevent bots and spam. (Privacy Policy)
    AkismetThis is used to detect comment spam. (Privacy Policy)
    HubPages Google AnalyticsThis is used to provide data on traffic to our website, all personally identifyable data is anonymized. (Privacy Policy)
    HubPages Traffic PixelThis is used to collect data on traffic to articles and other pages on our site. Unless you are signed in to a HubPages account, all personally identifiable information is anonymized.
    Amazon Web ServicesThis is a cloud services platform that we used to host our service. (Privacy Policy)
    CloudflareThis is a cloud CDN service that we use to efficiently deliver files required for our service to operate such as javascript, cascading style sheets, images, and videos. (Privacy Policy)
    Google Hosted LibrariesJavascript software libraries such as jQuery are loaded at endpoints on the googleapis.com or gstatic.com domains, for performance and efficiency reasons. (Privacy Policy)
    Features
    Google Custom SearchThis is feature allows you to search the site. (Privacy Policy)
    Google MapsSome articles have Google Maps embedded in them. (Privacy Policy)
    Google ChartsThis is used to display charts and graphs on articles and the author center. (Privacy Policy)
    Google AdSense Host APIThis service allows you to sign up for or associate a Google AdSense account with HubPages, so that you can earn money from ads on your articles. No data is shared unless you engage with this feature. (Privacy Policy)
    Google YouTubeSome articles have YouTube videos embedded in them. (Privacy Policy)
    VimeoSome articles have Vimeo videos embedded in them. (Privacy Policy)
    PaypalThis is used for a registered author who enrolls in the HubPages Earnings program and requests to be paid via PayPal. No data is shared with Paypal unless you engage with this feature. (Privacy Policy)
    Facebook LoginYou can use this to streamline signing up for, or signing in to your Hubpages account. No data is shared with Facebook unless you engage with this feature. (Privacy Policy)
    MavenThis supports the Maven widget and search functionality. (Privacy Policy)
    Marketing
    Google AdSenseThis is an ad network. (Privacy Policy)
    Google DoubleClickGoogle provides ad serving technology and runs an ad network. (Privacy Policy)
    Index ExchangeThis is an ad network. (Privacy Policy)
    SovrnThis is an ad network. (Privacy Policy)
    Facebook AdsThis is an ad network. (Privacy Policy)
    Amazon Unified Ad MarketplaceThis is an ad network. (Privacy Policy)
    AppNexusThis is an ad network. (Privacy Policy)
    OpenxThis is an ad network. (Privacy Policy)
    Rubicon ProjectThis is an ad network. (Privacy Policy)
    TripleLiftThis is an ad network. (Privacy Policy)
    Say MediaWe partner with Say Media to deliver ad campaigns on our sites. (Privacy Policy)
    Remarketing PixelsWe may use remarketing pixels from advertising networks such as Google AdWords, Bing Ads, and Facebook in order to advertise the HubPages Service to people that have visited our sites.
    Conversion Tracking PixelsWe may use conversion tracking pixels from advertising networks such as Google AdWords, Bing Ads, and Facebook in order to identify when an advertisement has successfully resulted in the desired action, such as signing up for the HubPages Service or publishing an article on the HubPages Service.
    Statistics
    Author Google AnalyticsThis is used to provide traffic data and reports to the authors of articles on the HubPages Service. (Privacy Policy)
    ComscoreComScore is a media measurement and analytics company providing marketing data and analytics to enterprises, media and advertising agencies, and publishers. Non-consent will result in ComScore only processing obfuscated personal data. (Privacy Policy)
    Amazon Tracking PixelSome articles display amazon products as part of the Amazon Affiliate program, this pixel provides traffic statistics for those products (Privacy Policy)