Description And Life Cycle Of Malaria Biology Essay

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Malaria is caused by a parasite known as plasmodium, which is an organism that lives and feeds off another organism. There are many different types of plasmodium, but only five cause malaria in humans:

Plasmodium falciparum is mostly found in Africa. It is responsible for the majority of malaria deaths worldwide.

Plasmodium vivax is found mainly in Asian and Latin America. This parasite produces less severe symptoms, but can stay in the liver for up to three years, which can result in relapses of the condition.

Plasmodium ovale is usually found in Africa. This parasite can stay in your blood for several years without producing any symptoms.

Plasmodium malariae is relatively rare. It is only found in West Africa.

Plasmodium knowlesi is extremely rare. It is found in parts of Southeast Asia.

Figure Female anopheles mosquitoThe plasmodium parasite is spread by female anopheles [3] mosquitoes. If a mosquito bites a person infected with malaria, it can then carry the parasite and spread it to other people after it has developed in the mosquito. Firstly, the parasite enters your blood through a bite which travels straight to your liver. Then, it develops there and re-enters the bloodstream and invades the red blood cells. Once it invaded the red blood cells, the parasites grow and multiply. Eventually, the infected red blood cells burst and release even more parasites into blood. The infected cells usually burst every 48-72 hours. Each time this happens, the patient will experience an attack of chills, fever and sweating. http://hopespreads.org/wp-content/uploads/2010/01/Malaria2.jpg

http://www.impactlab.com/wp-content/uploads/2009/02/malaria.jpg

Figure Spread of malaria disease in our bodyThe effects of malaria [4] significantly affect a person's quality of life both physically and mentally. Apart from taking lives, the malaria parasite can also cause serious damage to the organs, such as the liver, kidneys, gal bladder, spleen and brain function. It is not uncommon to see both children and adults suffer significant organ dysfunction after surviving serious attacks of malaria. In addition, severe malaria can affect the rest of the central nervous system. It's characterized by changes in the level of consciousness, convulsions and paralysis.

Epidemiology [5] 

Approximately half of the world's population is at risk of malaria. Most malaria cases and deaths occur in sub-Saharan Africa. However, Asia, Europe and America are also affected and deaths may occur due to the malaria infections.

Young children in transmission areas who have not yet developed protective immunity against the most severe forms of the disease.

Non-immune pregnant women are at risk as malaria causes high rates of miscarriage (up to 60% in P. falciparum infection) and the death rates of 10-50%.

Semi-immune pregnant women in areas of high transmission. Malaria can result in miscarriage and low birth weight, especially during the first and second pregnancies. An estimated 200 000 infants die annually as a result of malaria infection during pregnancy.

People with HIV/AIDS are at increased risk of malaria disease when infected.

International travelers from non-endemic areas are at high risk of malaria and its consequences because they lack immunity.

Immigrants from endemic areas and their children living in non-endemic areas and returning to their home countries to visit friends and relatives are similarly at risk because of waning or absent immunity.

C:\Documents and Settings\Student\Desktop\MalariaFig3(1).gif

Figure Malaria infection in age group during 2005 in Indiana

The graph demonstrates that the age groups would affect the risk of malaria. The children, the age of 20 to 29, and 70 to 79 may pose a serious threat to them. Especially, malaria infection in pregnant women is much severe than any other age or sex groups, because malaria may increase the risk of problems with the pregnancy, including prematurity, abortion, and stillbirth. Statistics indicate that in sub-Saharan Africa, between 75,000 - 200, 000 infants die from malaria per year, worldwide.

Distribution of MalariaC:\Documents and Settings\Student\Desktop\estimateddeaths.jpg

Figure 5 (Malaria free countries in periods of control, preelimination, elimation, and prevention of reintroduction. Taken from WHO World Maria Report)

Figure 4 (Estimated deaths from malaria, 2006. Taken from WHO World Malaria Report 2008)C:\Documents and Settings\Student\Desktop\controlpreeliminationeliminationprevreintroduction.jpg

Life Cycle of Malaria

Figure 6 Life cycle of Malariahttp://www.uni-tuebingen.de/modeling/images/malaria_LifeCycle.gif

Signs and Symptoms [6] 

Figure 7 Symptoms of Malaria for parts of our bodyThe common symptoms of malariahttp://upload.wikimedia.org/wikipedia/commons/thumb/b/b0/Symptoms_of_Malaria.svg/565px-Symptoms_of_Malaria.svg.png

Flu-like illness with fever,

Chills

Muscle aches

Headache

Some patients may develop

Nausea

Vomiting

Cough

Diarrhead

The signs and symptoms of a more severe case of malaria include

Serious organ failure

Metabolism abnormalities

Acute anemia

Extreme respiratory distress

Blood coagulation abnormalities

Low blood pressure

Kidney failure

Hypoglycemia

The early symptoms of malaria may be irritable and drowsy, with poor appetite and trouble sleeping. These symptoms are usually followed by chills, then a fever with rapid breathing. The fever may either gradually increase over 1 to 2 days or may rise very suddenly to 40.6 celsius or above. Then, as fever ends and body temperature quickly returns to normal, the patient has an intensive sweating. [7] 

The same pattern of symptoms - chills, fever, sweating - may repeat 2 or 3 day, depending on which particular species of malaria parasite is causing the infection. It can be difficult to diagnose if the initial symptoms are not specific. Symptoms can appear in 7 days. Occasionally, the time between exposure and signs of illness may be as long as 8 to 10 months.

The following list is the specific days which the symptoms may occur with specific malaria parasites: [8] 

9 to 14 days for Plasmodium falciparum

12 to 18 days for P. vivax and P. ovale

18 to 50 days for P. malariae

11 to 12 days for P. knowlesi

Diagnosis [9] 

Diagnosis of malaria involves identification of malaria parasite or its antigens/products in the blood of the patient. The different forms of the four malaria species, the endemicity of different species, the population movements, the inter-relation between the levels of transmission, immunity, parasitemia, and the symptoms can all have a bearing on the identification and interpretation of malaria parasitemia on a diagnostic test.

The diagnosis of malaria is confirmed by blood tests and can be divided into microscopic and non-microscopic tests.

Microscopic tests [10] 

The direct microscopic visualization of the parasite on the thick or thin blood smears has been accepted method for the diagnosis of malaria in most settings.

The microscopic test involve staining and direct visulisation of the parasite under the microscope.

Peripheral smear study

Quantitative Buffy Coat (QBC) test

Peripheral smear study for malarial parasites - The MP test [11] Blood Smear from an 'apapane

The classic and most used test is the blood smear on a microscope slide that is stained to show the parasites inside red blood cells. Although this test is easily done, correct results are dependent on the technical skill of the lab technician who prepares and examines the slides with a microscope.

Figure 8 Blood smear from an 'apapane infected with Plasmodium relictum. The parasites (red arrows) develop within the circulating red blood cells and stain purple. Red blood cell nuclei (black arrows) in parasitized cells are frequently pushed to one end of the cell.This test involves collection of a blood smear, its staining with Romanowsky stains and examination of the Red Blood Cells for malarial parasites. Thick smears are 20-40 times more sensitive than thin smears for screening of malaria parasites. The diagnostic accuracy relies on the quality of the blood smear and experience of laboratory personnel.

Sometimes no parasites can be found in peripheral blood smears from patients with malaria, even in severe infections. This may be explained by partial antimalarial treatment or by sequestration of parasitized cells in deep vascular beds. In these cases, parasites, or malarial pigment may be found in the bone marrow aspirates. Presence of malarial pigment in circulating neutrophils and monocytes may also suggest the possibility of malaria.

Non-Microscopic Tests [12] 

Several attempts have been made to take the malaria diagnosis out of the realm of the microscope. There have been advanced diagnostic tests including fluorescence microscopy of parasite nuclei with acridine orange, "rapid dipstick immunoassay, and Polymerase Chain Reaction assays. These tests involve identification of the parasitic antigen or the antibodies or the parasitic metabolic products

Rapid diagnostic tests (RDT) [13] 

Rapid diagnostic tests are not yet widely available and are more expensive than the traditional Giemsa blood smear. Some investigators suggest such immunologic based tests be confirmed with a Giemsa blood smear.

RDTs detect species-specific circulating parasite antigens targeting either the histidine-rich protein or a parasite-specific lactate dehydrogenase. http://www.ncbi.nlm.nih.gov/bookshelf/picrender.fcgi?book=mal3&part=pg119&blobname=119f1.jpg

Figure 9

Management

Prevention of malaria in many countries has been heavily dependent on anti-malarial drugs and residual insecticides. It is important to note that none of the anti malarial drugs are 100% effective in preventing malaria.

Five common antimalarial drugs & common side effects

Chloroquine [14] 

Figure 10 ChloroquineChloroquine was once a very popular anti malarial drug. However, it has become resistant in some areas, therefore it is not as effective in providing full protection against strains of malaria. Minor side effects such as stomach upset and blurred vision occur frequently. These can be controlled by taking tablets with food, or taking half the dose on two occasions each week. They are safe in pregnant women and children in correct doses. http://www.royalgroupweb.com/images/product_images/CHLOROQUINE_TABLETS.jpg

Figure 11 MalaroneMalarone [15] http://www.isradoctor.co.il/blog/uploads/malarone_small.jpg

Malarone is a relatively new anti malarial medication. A combination of atovaquone and proguanil are in a single tablet of malarone. It is particularly useful where malaria is resistant to chloroquine and mefloquine. It appears to be very safe and effective, but is expensive.

For prevention of malaria, Malarone is taken once a day, starting 1 day before entering malarial risk area and continuing for one week after leaving the malarious area. It should be taken with food or milk. The side effects of malarone are uncommon. However, nausea, vomiting, abdominal pain, and diarrhea occur when higher doses of the drug are used for treatment.

Doxycycline [16] 

Doxycycline is an alternative tablet for short-term travelers. It is approved for a period of up to 8 weeks only, but is probably safe for longer use. Side effects of doxycycline include thrush, stomach & bowel upsets and sunlight sensitivity. Using sunscreen and taking the drug in the evening may avoid some of the side effects of doxycycline. https://www.rxprohub.com/images/P/doxycycline.jpg

Figure 12 Doxycyline

Mefloquine [17] 

Figure 13 MefloquineMinor side effects such as nausea, vomiting, heartburn and loose stools occur in about 20% of users, but this is no more frequent than with other antimalarials. Taking ½ tab twice a week with food will help reduce the side effects.http://static.flickr.com/72/194940997_c0d52999d2_m.jpg

Unfortunately, mefloquine frequently produces annoying side effects such as insomnia, vivid dreams, dizziness, mental clouding, anxiety and coordination problems. These are sufficient to interfere with daily activities in up to 10 % of users. For these reasons, any person requiring a clear mind and good co-ordination should not use mefloquine

Proguanil [18] 

Proguanil is one of the safest antimalarial drugs. The side effect of proguanil is mouth ulcers which is an annoying complication in up to 37% of travelers. It is taken two tablets daily, starting one day before entering malarial area and continuing for four weeks after leaving the area. http://www.interhealth.org.uk/swatches/swatch.62.sw_image.jpg

Figure 14 ProguanilAnother management of preventing malaria is by using mosquito-control programs aimed at killing mosquitoes that carry the disease. If you travel to an area of the world with a high risk for malaria, you can install window screens, use insect repellents, and place mosquito netting over beds. Insecticide-impregnated bed netting has successfully reduced the number of malarial deaths among African children.

Prognosis

Malaria caused by four different intracellular plasmodium parasites, is a worldwide infection that affects 300 million and kills 1 million people each year. According to the World Health Organisation (WHO) 90% of deaths from Malaria occur in sub-saharan Africa where Malaria is the leading cause of death in children younger than five years old. [19] 

Prognosis will vary depending on geographical location but in general:

Most patients with uncomplicated malaria exhibit marked improvement within 48 hours after the initiation of treatment and are fever free after 96 hours.

The WHO in its latest estimate of malaria mortality, has concluded around 881,000 people died from the disease in 2006. Around 91% of those who died were children in Africa. [20] 

The following are statistics from various sources about deaths related to Malaria:

C:\Documents and Settings\Student\Local Settings\Temporary Internet Files\Content.IE5\RLWX2KO2\art027f2[1].jpg

Figure 15 Mortality rate of the world population - 1969 to 2001

Some statistics of mortality rate in Africa:

About 1,136,000 deaths from malaria in Africa 2002 (The World Health Report, WHO, 2004)

About 1,000 deaths from malaria in The Americas 2002 (The World Health Report, WHO, 2004)

About 65,000 deaths from malaria in South East Asia 2002 (The World Health Report, WHO, 2004)

About 2,000 deaths from malaria in Europe 2002 (The World Health Report, WHO, 2004)

About 57,000 deaths from malaria in Eastern Mediterranean 2002 (The World Health Report, WHO, 2004)

About 11,000 deaths from malaria in Western Pacific 2002 (The Health Report, WHO, 2004) [21] 

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