Malaria Is A Parasitic Protozoan Biology Essay


Malaria is classified under the eukaryotic kingdom Protista. Furthermore it is placed under the phylum Apicomplexa comprising of single celled protist organisms. It belongs under the class Aconoidasida-which do not have microtubule like conoids. As it is a parasite which attacks red blood cells it falls under the order Haemosporidia, within this order it belongs to the family Plasmodiidae. It reproduces asexually in a definitive vertebrate host. There are twelve genera in this family. Malaria belongs to the Plasmodium genus under which many different species exist. There are five species which are known to attack humans namely: P. falciparum, P. vivax, P. ovale, P. malariae and P. knowlesi. It is the Anopheles mosquito which contains and spreads the Plasmodium into the bloodstream.

Sporozoites are the form through which the Plasmodium parasite enters the person's bloodstream. These sporozoites are injected through the saliva of the Anopheles mosquito. According to (Anon., n.d.), sporozoites are 10 -15 µm in length and about 1 µm in diameter. They have a thin outer membrane, a double inner membrane and below which lays the subpelicular microtubules. 14 chromosomes and 5,300 genes have been completely sourced through Plasmodium falciparum (the most common Plasmodium causing malaria in humans). 'Knobs' or protrusions occur on the outer membrane of infected erythrocyte this can be seen in Error: Reference source not found. These knobs are caused by the parasite and many parasite proteins are associated with them (Wiser, n.d.).

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The life cycle of the Plasmodium parasite takes place within two specific hosts-the female Anopheles mosquito and humans. When these mosquitos are pregnant they become hungry for human blood. Human blood serves as protein which is essential for the laying of her eggs (How Stuff Works,inc, n.d.). Saliva is injected through the proboscis to stop blood from clotting. The saliva carries the malaria parasite in the form of sporozoites. Sporozoites now enter the bloodstream and move towards the liver. Inside the liver the Kupffer cell allows the parasite to enter the liver tissue (Kakkilaya's, n.d.). By infecting liver cells it kills several in the process. They soon mature into Schizonts and inside those, through the process of asexual reproduction, thousands of merozoites are produced. When the Schizonts rupture, these merozoites escape. They are adapted to attack red blood cells or Erythrocytes however they are able to infect new liver cells in order to produce more parasites. These parasites are able to hide from the immune system in these red blood cells as well as reproduce further inside them. Some of these turn into ring-formed trophozoites that split again to form schizonts (Easmon, n.d.). When schizonts become mature they burst releasing more merozoites into the bloodstream. Some become male or female gametocytes which are sexual forms of the parasite. This is the furthest the parasite can progress inside a human host. Gametocytes are taken in by a new female Anopheles mosquito when it bites an infected person. When the warm human blood cools inside the mosquito's stomach, the sexual process is initiated (Kakkilaya's, n.d.).Both male and female gametocytes form gametes. The female gamete matures into an egg, while the male forms sperm. They fuse to form a diploid Zygote which develops into a motile and elongated ookinete. They soon burrow into the mid-wall of the gut forming oocysts. Each oocyst produces thousands of sporozoites and after 8-15 days in raptures releasing them into the body of the mosquito. They move to the salivary gland for the cycle to begin again. Error: Reference source not found is a detailed diagram showing the life cycle of the Plasmodium parasite.

There are two hosts involved in the life cycle of the parasite. The female Anopheles mosquito is referred to as being the vector as it carries the parasite from host to host without itself being affected by the parasite inside it. Sexual reproduction takes place in the vector while asexual multiplication occurs in a vertebrate host. The different species of Plasmodium infect many vertebrate hosts including reptiles, birds. Mammals especially primates (including humans) are susceptible (Standley, n.d.). Humans are known to be the primary host or definitive hosts and mosquitos are the secondary hosts.

According to (Kakkilaya's, n.d.) Malaria is the world's most widespread infection. The statistics of the World Malaria Report 2011 confirm malaria is prevalent in 106 countries of the tropical and semitropical world, with 35 countries in central Africa bearing the highest burden of cases and deaths. As the Anopheles mosquito is the vector for malaria, malaria's distribution is limited to areas which the habitable to the mosquito. Malaria occurs mainly in tropical and sub-tropical biomes however the Anopheles mosquito is able to survive in cooler conditions (South African Encyclopedia (SAE), n.d.). Insecticides have prohibited the expansion of the Plasmodium parasite in cooler areas. P.Vivax is prevalent in cooler areas Closer to the equator malaria infection is all year round and is more intense. Malaria will not spread in regions of very high altitude, during colder seasons and in deserts (Centre for Disease Control and Prevention (CDC), n.d.). Female Anopheles mosquitos exist in the United States and Western Europe however public health measures and economic development have destroyed malaria.

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Since Plasmodium is a parasite its habitat occurs in the body of its hosts. During its life cycle the parasite occurs in many different places and in different forms. The skin of the host contains the parasite during transmission. Liver cells facilitate the transformation from sporozoites to merozoites. The blood stream contains thousands of new parasites which infect erythrocytes. Sexual reproduction takes place in the gut of the mosquito after it has bitten an infected host. Oocysts occur in the mid-gut of the mosquito, which will release sporozoites when it ruptures. The Anopheles mosquito can survive in a range of habitats as mentioned above.

In the past it was thought that malaria was transmitted through the air, hence the name mal-bad and aria-air. Nowadays it is well known the primary form of the transmission of malaria or the Plasmodium parasite is through the female Anopheles mosquito. Of more than 480 species of Anopheles, only about 50 species transmit malaria, with every continent having its own species of these mosquitoes (Kakkilaya, n.d.). When a mosquito bites an infected host the gametocytes are transmitted to the mosquito, wherein sexual reproduction can take place. The mosquito will transmit sporozoites to a host when biting them through its proboscis. The parasite is injected through the salivary gland of the mosquito. According to (Kakkilaya, n.d.) malaria can be transmitted through different forms. Congenital malaria occurs when a mother passes infected red blood cells to her child. Malaria can also be transmitted through a blood transfusion by transfusing the blood of an infected donor and it is one of the most common transfusion infections today. Several case of transmission through needle stick injuries has been reported.

Generally the incubation period of Malaria is 10 days to 4 weeks after being bitten (Arthur Schoenstadt, n.d.). Some people only show symptoms several years later. The type of Plasmodium parasite also plays a role in the incubation period. P Falciparum tends to have the shortest incubation period while P.Malariae. When the parasite is inside the liver it can remain inactive, during this time no symptoms may be visible. This inactivity can last for several months before the parasite starts attacking the erythrocytes. Antimalarial drugs can cause an increase in incubation period, sometimes leading to a misdiagnosis (Standley, n.d.).

Initial symptoms of malaria are flu-like symptoms which include fever, headaches and general pain. Chills, diarrhea, nausea accompany the initial malaria symptoms. As the parasite infects red blood cells the victim may experience anemia and jaundice. Severe malaria occurs when organs begin failing. If malaria is not treated hastily symptoms of severe malaria such as: behavior abnormalities, comas, seizures, neurological abnormities, cardiovascular collapse and shock, decrease in blood platelets, pulmonary edema and even death can result. In children ataxia, speech difficulties, blindness and deafness are observed. Malaria during pregnancy may lead to a low birth weight baby and premature delivery. P.Falciparum symptoms can include the enlargement of the liver and an increased respiratory rate. A cyclical fever is evident in almost all malaria patients. The parasite does not have a negative effect on the mosquito host and doesn't appear to harm it in any way. Recent studies have shown that the parasite may cause the mosquito to seek out blood and a new human host quickly enough to ensure its lifecycle continue (Standley, n.d.).

A quick and accurate diagnosis is critical in preventing fatalities through malaria. This is sometimes difficult as symptoms may be too general and if the parasite is hidden the immune system can't act against it; therefore there is a cyclic pattern of symptoms. Diagnosis also depends on the species of the parasite, different stages in the life cycle and the form the parasite is in during the certain phases (Kakkilaya, n.d.). Microscopic blood tests on thick or thin blood smears are generally what are used to diagnose malaria.

The treatment of malaria depends on the infecting species of the Plasmodium parasite, the clinical situation of the patient and the drug susceptibility of the infecting parasite according to (Charles Patrick Davis, n.d.) however (Kakkilaya, n.d.) argues associated conditions and diseases must also be taken into account such as: pregnancy, epilepsy, renal failure and cardiac disease must also be taken into account. There are two main methods of treatment which are suppressive and radical treatments. In suppressive treatment involves alleviating the symptoms of malaria during the erythrocytic stage. Blood schizonticidal drugs are given to patients and it involves the administration of Chloroquine. In areas of high risk malaria it should be presumed that any fever is viewed as malaria however if malaria is confirmed full treatment must take place. Radical treatment is necessary for all confirmed malaria cases. Primaquine is administered to these patients (Kakkilaya, n.d.). In rural Africa and in Kenya traditional herbal medicine and healing practices are used to treat malaria. These remedies are drunk with teas or are eaten alone. Some are purchased from markets but mostly they collected through the wild. These remedies are currently being pharmaceutically investigated (Davis&Jessa, n.d.). In England Opium laced beer was used as a treatment while many South American cultures have used the cinchona bark to varying degrees of success. The Chinese used the herb Artemisia annua (sweet wormwood) as seen in Error: Reference source not found (Kakkilaya, n.d.). Another alternative treatment is through pyrimethamine/sulfadoxine (Fansidar) or mefloquine. These drugs can be used in areas where there is a resistance to chloroquine. In certain parts of Asia however there has been a resistance to mefloquine. It is sometimes used together with the herb Artemisia annua as mentioned above (United Nations Children's Fund (UNICEF), n.d.).

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There are many methods to preventing malaria however there is still no vaccination although there is a lot research going into the subject. Vector control has been used as a preventative measure. This involves the killing of mosquitos in certain areas and has been relatively successful in the United States and southern Europe. Another way this is possible is by draining swamps and aquatic habitats of mosquito larvae. Research has also gone into find out ways to sterilize or genetically modify mosquitos to become resistant to the parasite. Many drugs which can be taken for the treatment of malaria can be taken preventatively however at a lower dose. Locals can rarely maintain the use of these drugs as they are expensive and the have negative side-effects. One should start taking preventative drugs one to two weeks before entering an area with malaria and for four weeks after leaving. Indoor residual spraying is used as an insecticide to kill mosquitos in the interior of homes in malarial areas. Mosquitos that rest on walls inside the house will pick up this insecticide and die. There are fears that mosquitos are becoming resistant to this spray through evolution. Mosquito nets are useful in stopping mosquitos from biting people and preventing malaria. They are twice as effective when coated in insecticide. Anopheles mosquitos feed at night so it is essential one is protect while sleeping and that the entire bed is covered in the net. These net are expensive to locals. An alternative method is the use of spores of the fungus Beauveria bassiana, sprayed on walls and bed nets, to kill mosquitoes (News Medical, n.d.). There have been attempts at making a malaria vaccine by using dosage of radiated sporozoites in order to build up immunity against however there are many medical dangers to this. Some people with repeated infection with multiple strains of malaria can develop a tolerance against it. Travelers should be well informed about malaria when visiting a malarial area. One should try avoiding outbreaks of malaria and be aware of peak exposure times and places. Opium protection is advised. This spray is an effective repellent. Residents and travelers should protect themselves by exposing a minimum amount of skin as possible by wearing long pants, boots and hats (William C. Shiel Jr., n.d.). Awareness and education are key weapons in the fight against malaria. People should be well aware of risks and how to prevent mosquito's bites. Considering the expense of medical treatment and the lack of funds the majority of people have in these areas it is essential that prevention should be the number one priority instead of treatment.

Malaria perpetuates a cycle that is difficult to escape for many countries in malaria stricken areas. Millions of people are killed through malaria each year leading to a gap in the work force and economy. This naturally generates a lower income for the governments of these countries. Malaria prevention and treatment is viewed as a high priority for these countries however by allocating too much money to this cause the country as a whole will suffer and a lack of development will take place. This lack of development plunges the country into further poverty perpetuating the cycle. Therefore I believe it is critical more foreign investment be put into this cause in order for these countries to develop themselves enough to help their residents overcome this problem. The lack of development leads to a situation where education is not funded sufficiently. This is a major problem as education and awareness are keys to preventing malaria. Foreign investment also decreases as malaria threatens company's success. This again leads to a lack of funding for the government. Factors such as deteriorating health systems, growing drug and insecticide resistance, failure of water management but also socioeconomic, land-use factors, and climate are hypothesized to influence the emergence of malaria (Krefis, 2010). Climate change is increasing the risk of malaria and spreads the Anopheles mosquito to new areas. For Example rising temperatures on Mount Kenya have put an extra 4 million people at risk of infection. This allows the disease to move into higher altitudes and infect people with little or no immunity (tolerance) to the disease (, n.d.). Climate change is attributed to the spread of malaria into Afghanistan, Indonesia and East Africa (Science Daily, n.d.).