What is malaria…?
An infectious disease caused by protozoan parasites from the Plasmodium family that can be transmitted by the bite of the Anopheles mosquito or by a contaminated needle or transfusion. Falciparum malaria is the most deadly type.
Malaria is caused by protozoa of the genusPlasmodium and is transmitted to humans by mosquitoes. The history of malaria shows that it was difficult to determine the disease’s mode of transmission. When some cultures reviewed the facts available to them, they concluded that malaria was caused by bad air without realizing that the same swamps that created foul-smelling air also were excellent breeding grounds for mosquitoes. In 1880, the parasite was identified in an infected patient’s blood.
There are several stages in the life cycle ofPlasmodium, including sporozoites, merozoites, and gametocytes. The bite of an infected mosquito transmits the sporozoite stage of the organism to humans. The parasite travels into the bloodstream and eventually makes its way to the liver, where it begins to multiply by producing merozoites. The merozoites leave the liver and enter red blood cells to reproduce. Soon, young parasites burst out in search of new red blood cells to infect.
Sometimes, the reproducing Plasmodia will create a form known as a gametocyte in the human bloodstream. If a mosquito takes a blood meal when gametocytes are present, the parasite begins to reproduce in the insect and create sporozoites that are infectious to people, completing the life cycle.
There are five species of Plasmodium that infect humans:
P. vivax: This species is most commonly found in Asia, Latin America, and parts of Africa. Infections can sometimes lead to life-threatening rupture of the spleen. This type of malaria can hide in the liver (this is called the “hepatic phase” of the life cycle). It may then return later to cause a relapse years after the first infection. Special medications are used to eradicate P. vivax from the liver.
P. ovale: This species is rarely found outside Africa or the western Pacific islands. Symptoms are similar to those of
P. vivax, Like P. vivax,P. ovale can hide in the liver for years before bursting out again and causing symptoms.
P. malariae: It is found worldwide but is less common than the other forms. This form of malaria is hard to diagnose because there are usually very few parasites in the blood. If untreated, the infection can last many years.
P. falciparum: This is the most life-threatening species of malaria. Although present throughout much of the tropical and subtropical world, it is particularly common in sub-Saharan Africa. P. falciparum is resistant to many of the older drugs used to treat or prevent malaria. Unlike P. vivax and P. ovale, this species does not hide in the liver.
P. knowlesi: Found predominantly in Malaysia, this species can also cause high levels of parasites in the blood, leading to organ failure or death.
Malaria can occur if a mosquito infected with thePlasmodium parasite bites you. An infected mother can also pass the disease to her baby at birth. This is known as congenital malaria. Malaria is transmitted by blood, so it can also be transmitted through:
An organ transplant
Use of shared needles or syringes
Malaria Incubation Period
The incubation period between infection with malaria by a mosquito bite and initial symptoms may range from one week to one year. Generally, the incubation period ranges from nine to 14 days for P. falciparum, 12-18 days for P. vivax, and 18-40 days.
Symptoms of Malaria?
The symptoms of malaria typically develop within 10 days to four weeks following the infection. In some people, symptoms may not develop for several months. Some malarial parasites can enter the body but will be dormant for long periods of time. Common symptoms of malaria include:
shaking chills that can range from moderate to severe
Is Malaria Contagious?
Fortunately, malaria is not contagious except in rare situations; it is not spread directly from person to person with the following exceptions. A few cases have occurred in other countries through blood transfusion, intravenous drug abuse with shared needles, or organ transplantation. An infected mother can spread malaria through the placenta to her unborn child. Except for these rare situations, transmission only occurs when a person is bitten by an infected mosquito. The infected person is not contagious to other individuals, and there is no need to isolate or quarantine the person to protect others from direct transmission. However, depending on the local public-health situation, an infected traveler returning home may be asked to stay indoors until well. Some areas may have mosquitoes that are able to transmit malaria, and transmission of malaria from a returning traveler by local mosquitoes has been reported. Public-health authorities may increase mosquito-control measures in the area, as well, to reduce this risk.
Diagnosis of malaria:
The mainstay of malaria diagnosis has been the microscopic examination of blood, utilizing blood films Although blood is the sample most frequently used to make a diagnosis, both saliva and urine have been investigated as alternative, less invasive specimens. More recently, modern techniques utilizing antigen tests or polymerase chain reactionhave been discovered, though these are not widely implemented in malaria endemic regions. Areas that cannot afford laboratory diagnostic tests often use only a history of subjective fever as the indication to treat for malaria.
Quantitative Buffy coat
The most economic, preferred, and reliable diagnosis of malaria is microscopic examination ofblood films because each of the four major parasite species has distinguishing characteristics. Two sorts of blood film are traditionally used. Thin films are similar to usual blood films and allow species identification because the parasite’s appearance is best preserved in this preparation. Thick films allow the microscopist to screen a larger volume of blood and are about eleven times more sensitive than the thin film, so picking up low levels of infection is easier on the thick film, but the appearance of the parasite is much more distorted and therefore distinguishing between the different species can be much more difficult. With the pros and cons of both thick and thin smears taken into consideration, it is imperative to utilize both smears while attempting to make a definitive diagnosis
From the thick film, an experienced microscopist can detect parasite levels (or parasitemia) as few as 5 parasites/µL blood. Diagnosis of species can be difficult because the early trophozoites (“ring form”) of all four species look similar and it is never possible to diagnose species on the basis of a single ring form; species identification is always based on several trophozoites.
Plasmodium malariae and P. knowlesi (which is the most common cause of malaria in South-east Asia) look very similar under the microscope. However, P. knowlesi parasitemia increases very fast and causes more severe disease than P. malariae, so it is important to identify and treat infections quickly. Therefore, modern methods such as PCR (see “Molecular methods” below) or monoclonal antibody panels that can distinguish between the two should be used in this part of the world.
For areas where microscopy is not available, or where laboratory staff are not experienced at malaria diagnosis, there are commercial antigen detection tests that require only a drop of blood. Immunochromatographic tests (also called: Malaria Rapid Diagnostic Tests, Antigen-Capture Assay or “Dipsticks”) have been developed, distributed and fieldtested. These tests use finger-stick or venous blood, the completed test takes a total of 15–20 minutes, and the results are read visually as the presence or absence of colored stripes on the dipstick, so they are suitable for use in the field. The threshold of detection by these rapid diagnostic tests is in the range of 100 parasites/µl of blood (commercial kits can range from about 0.002% to 0.1% parasitemia) compared to 5 by thick film microscopy. One disadvantage is that dipstick tests are qualitative but not quantitative – they can determine if parasites are present in the blood, but not how many.
The first rapid diagnostic tests were using Plasmodium glutamate dehydrogenase as antigen PGluDH was soon replaced by Plasmodium lactate dehydrogenase (pLDH). Depending on which monoclonal antibodies are used, this type of assay can distinguish between different species of human malaria parasites, because of antigenic differences between their pLDH isoenzymes. Antibody tests can also be directed against other malarial antigens such as the P. falciparum specific HPR2.
Modern rapid diagnostic tests for malaria often include a combination of two antigens such as a P. falciparum. specific antigen e.g. histidine-rich protein II (HRP II) and either a P. vivax specific antigen e.g. P. vivax LDH or an antigen sensitive to all plasmodium species which affect humans e.g. pLDH. It should be noted that such tests do not have asensitivity of 100% and where possible, microscopic examination of blood films should also be performed.
Molecular methods are available in some clinical laboratories and rapid real-time assays (for example, QT-NASBA based on the polymerase chain reaction) are being developed with the hope of being able to deploy them in endemic areas.
PCR (and other molecular methods) is more accurate than microscopy. However, it is expensive, and requires a specialized laboratory. Moreover, levels of parasitemia are not necessarily correlative with the progression of disease, particularly when the parasite is able to adhere to blood vessel walls. Therefore, more sensitive, low-tech diagnosis tools need to be developed in order to detect low levels of parasitemia in the field.
Another approach is to detect the iron crystal byproduct of hemoglobin that is found in malaria parasites feasting on red blood cells, but not found in normal blood cells. It can be faster, simpler and precise than any other method. Researchers at Rice University have published a preclinical study of their new tech that can detect even a single malaria-infected cell among a million normal cells, They claim it can be operated by nonmedical personal, produce zero false-positive readings, and it doesn’t need a needle or any damage done.
Areas that cannot afford laboratory diagnostic tests often use only a history of subjective fever as the indication to treat for malaria. Using Giemsa-stained blood smears from children in Malawi, one study showed that when clinical predictors (rectal temperature, nailbed pallor, and splenomegaly) were used as treatment indications, rather than using only a history of subjective fevers, a correct diagnosis increased from 2% to 41% of cases, and unnecessary treatment for malaria was significantly decreased.
Fever and septic shock are commonly misdiagnosed as severe malaria in Africa, leading to a failure to treat other life-threatening illnesses. In malaria-endemic areas,parasitemia does not ensure a diagnosis of severe malaria, because parasitemia can be incidental to other concurrent disease. Recent investigations suggest that malarialretinopathy is better (collective sensitivity of 95% and specificity of 90%) than any other clinical or laboratory feature in distinguishing malarial from non-malarial coma.
Quantitative Buffy Coat:
Quantitative buffy coat (QBC) is a laboratory test to detect infection with malaria or other blood parasites. The blood is taken in a QBC capillary tube which is coated with acridine orange (a fluorescent dye) and centrifuged; the fluorescing parasites can then be observed under ultraviolet light at the interface between red blood cells and buffy coat. This test is more sensitive than the conventional thick smear, however it is unreliable for the differential diagnosis of species of parasite.
Life-Threatening Complications of Malaria
Malaria can cause a number of life-threatening complications. The following may occur:
swelling of the blood vessels of the brain, or cerebral malaria
an accumulation of fluid in the lungs that causes breathing problems, or pulmonary edema
organ failure of the kidneys, liver, or spleen
anemia due to the destruction of red blood cells
low blood sugar
Malaria, especially Falciparum malaria, is a medical emergency that requires a hospital stay. Chloroquine is often used as an anti-malarial medication. However, chloroquine-resistant infections are common in some parts of the world.
Possible treatments for chloroquine-resistant infections include:
The combination of quinidine or quinine plus doxycycline, tetracycline, or clindamycin
Atovaquone plus proguanil (Malarone)
Mefloquine or artesunate:
The combination of pyrimethamine and sulfadoxine (Fansidar)
The choice of medication depends in part on where you were when you were infected.
Medical care, including fluids through a vein (IV) and other medications and breathing (respiratory) support may be needed..
With some simple yet effective precautionary measures, one can prevent malaria. Here are some of them which you can try –
Mosquitos breed in stagnant water – whether it is anallah near your house, a pond in the neighbourhood or a water puddle near your house from a long time. Get them closed, cleaned up as soon as possible. Even plants in pots, bird baths, fountains etc should not hold stagnant water. The water in the swimming pools needs to be circulated and chlorinated.
If you store water in the house due to its shortage, close the container.
Use mosquito screens, nets, fibre glass meshes or magnetic insect repellent screens for your windows if you live in a mosquito-infested area. If possible, avoid the time immediately after dusk to venture out especially so for children. If you need to, wear clothes that cover your body to a large extent. Cover the exposed parts with a mosquito repellent.
Indoor residual spraying with an insecticide is also recommended.
Insecticide treated bed nets should be used in areas where mosquitos and malaria are rampant.
If travelling to a malaria-endemic area, chemoprophylaxis is given to travellers. Consult your doctor and discuss your travel.