Malaria! Common, right? Yet it is one of the oldest infectious diseases which has still not been eradicated from the surface of the earth. The Center for Disease Control and Prevention (CDC) was first set up to tackle malaria during the war days. There has been tremendous improvement but the parasites grow resistant to treatment drugs such as quinine and others. It has been said that in about 5 years, the drugs we use today will no longer be effective in treating malaria. What is the way forward? Journey with us to find out.
Malaria is an infectious disease which means it is caused by a microbial organism (they include bacteria, viruses, fungi, parasites, etc.) but the microbe responsible for malaria is caused by a parasite. Malaria is not caused by a mosquito as many of us have been made to believe. Instead, the mosquitoes are the carriers. They transport the parasites when they feed on humans.
There are about 100 species of mosquito parasites but only 5 cause malaria in humans. These 5 include: Plasmodium ovale, Plasmodium falicparum, Plasmodium vivax, Plasmodium knowlesi, Plasmodium malariae. The most common in Africa is Plasmodium falciparum. It is the one that is likely to cause severe infections and may lead to death if care is not taken. Fortunately, it can be prevented and controlled even in the presence of an infection.
As made mentioned, no malaria parasite can transport itself into a human host. They have derived means to do this through some species of mosquitoes. There are several types of mosquitoes but the one responsible for carrying the parasite is the female Anopheles mosquito. This is because, unlike other mosquitoes that feed on plants and other substances, they feed on human blood. Female anopheles mosquitoes need the blood from humans to grow their eggs because it contains nutrients. They only feed at night that is why any measure to prevent the mosquitoes from biting should be done in the evening. The parasites just take advantage of the situation and this is how it happens:
1. Infection is the state when a parasite enters the body and affect the tissues of the host. In malaria, it begins when an infected female Anopheles mosquito bite and injects the plasmodium parasites into the human blood during feeding. The parasite at this stage is called sporozoites.
2. The sporozoites (parasites) pass quickly from the bloodstream into the liver. (NB: Most substances and drugs which are injected into the body first go to the liver to be filtered and sent to the heart to be distributed).
3. Unfortunately for the liver, the parasites as its name suggest feeds on the cells of the liver to multiply and grow asexually. They do this for 7-10 days without causing any symptoms.
4. After this period, they are released from the liver back into the bloodstream again. This time not as sporozoites but as merozoites since they have grown and multiplied.
5. In the bloodstream, the merozoites attack the red blood cells (erythrocytes) and multiply again until the red blood cells burst. Then they invade more red blood cells. All this while, the parasite does not cause any symptoms. However, each time a red blood cell bursts, you become feverish. This is usually the first symptom caused by malaria.
It must be noted that these divisions are all asexual which means that they just replicate their structure.
6. Some of the merozoites develop into sexual forms of the parasite called gametocytes. These sex gametes of the parasites continue to circulate in the blood together with the asexual ones.
7. When another mosquito bites a human who has parasites (gametocytes) in the bloodstream, it ingests the blood which contains the parasites as well.
8. The male and female gametes of the parasite then fertilize inside the mosquito. The fertilized female gamete moves and settles at the midgut wall of the mosquito and forms oocysts on the exterior surface.
9. The oocyst contains several sporozoites. The oocyst burst and releases these sporozoites which travel to the salivary glands of the mosquito.
10. The cycle begins again when a mosquito bites a human and releases the sporozoites during its feeding.
Malaria can be mild or severe depending on some factors such as age, genetics and environmental conditions.
Mild or uncomplicated malaria
It is mild or uncomplicated because it affects no vital organs and usually, most people treat themselves at home without going to the hospital first. Symptoms can become severe if the host (infected human) has poor or no immunity against the parasites.
These symptoms last between 6 to 10 hours and recur every 48 hours, especially for P. falciparum. The other 4 species of the parasite may have different symptoms or longer cycles. Malaria symptoms will recur till it has been treated.
· Fever. (This is the most common symptom so many people refer to malaria as fever).
· Sweats, then return to normal temperature.
· Nausea and vomiting.
· Body aches.
· Malaise (Generally feeling sick).
In severe malaria, additional symptoms may be observed such as:
· Seizures or multiple convulsions may be observed.
· Deep breathing and respiratory distress
· Abnormal bleeding and signs of anaemia
· Clinical jaundice and evidence of vital organ dysfunction.
Humans have known since ancient times that mosquitoes are a nuisance. it is believed that Cleopatra of Egypt slept under bed nets to ward off these organisms. They believed that swamps and wet ground were breeding grounds for mosquitoes causing fevers. In the early 1600s, Spanish missionaries brought extract which is known as quinine. This extract was bitter so they added water, sugar, lime and gin and drank. This could treat malaria infections and prevent them. In the 1800s, the plasmodium parasite was discovered as the causative agent for malaria. Fast forward, there has been so many inventions and discoveries made so far but eradication is yet to be achieved.
1. There is confusion whether to focus on the mosquito that transmits them or the parasites that causes the diseases.
2. Mosquitoes are insects that are the most populated species in the world. It will be difficult to get rid of them.
3. The parasites have different stages which makes it difficult to focus on one particular stage and solve the problem. For instance, when the parasites (sporozoites) are first introduced into the blood via a mosquito, they stay in the blood for about 30 minutes and move into the liver. This makes it difficult to kill them at this stage when they are immature. After they get released into the blood the second time after visiting the liver, they become more difficult to remove since they attack the red blood cells directly.
There are ongoing vaccine trials to test for the efficacy of the malaria vaccine in humans.
Malaria treatment is usually through medications. Medications should be taken completely even if the person feels better along the way. Just like other diseases, malaria can be prevented if we
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