How Long Does it Take for Malaria to Affect the Body?

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QUESTION

How long does malaria take to actually affect you?

ANSWER

When you are bitten by a mosquito that is infected with the parasites that cause malaria, some of the parasites enter your blood stream in the mosquito’s saliva. After that, it will take at least one week, and usually between two and four weeks, before you start to feel the symptoms of the disease. This is because the parasite first goes to the liver, where it infects liver cells and undergoes replication. These cells mature into a form called merozoites, which then re-enter the blood stream, and start to infect red blood cells. The stage in the liver is not symptomatic for the patient, and is known as the pre-patent stage; once the merozoites start infecting and killing red blood cells, the patient will begin to feel sick, and the infection is said to have become patent.

Malaria Effect on Host

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QUESTION

What is the effect of malaria on host?

ANSWER

In the human host, malaria can often make a person very sick, though the exact symptoms and severity of the disease depends on the type of malaria (five different kinds of malaria infect humans). Many people will have a high fever, chills, nausea and body aches. In a symptom very typical of malaria, a patient will experience cyclical fever, with periods of no fever in between, lasting between one and two days. In infections with Plasmodium falciparum, the most dangerous kind of malaria, patients may experience impaired consciousness, a sign of “cerebral malaria”, which can lead to loss of consciousness, coma and even death.

In terms of the mosquito host (more commonly called the vector), the insect does not experience “illness” in the same way as the human host, and the parasite does not seem to have a particularly negative effect on the mosquito. However, some research has shown that infection with malaria may cause a mosquito to seek out blood meals more frequently, which scientists argue is an adaptation of the malaria parasite to ensure that its life cycle is continued.

Structure and Size of Malaria

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QUESTION

What is the structure and size of malaria?

ANSWER

Malaria is caused by a single celled protist of the genus Plasmodium. It undergoes a complex life cycle, involving two separate asexual reproductive stages in the vertebrate host (including humans) and sexual reproduction as well as multiplication in the insect vector (all human malaria is transmitted by mosquitoes). As such, the parasite undergoes much structural and cellular change during its lifecycle, including to its size.

In terms of structure, most of the infectious stages of Plasmodium consist of a nucleus (which contains DNA, the cell’s genetic material), a mitochondrion (used for respiration and thus producing the energy for the cell), microtubules (for moving proteins and other molecules) and an apicoplast, which is a organ unique to this group of single-celled parasites which is thought to be implicated in the invasion of host cells. The surface of the organism is covered in different proteins, some of which are used for binding to target host cells.

Malaria Infectious?

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QUESTION

Is malaria infectious?

ANSWER

Yes, malaria is considered an infectious disease, though it is very rarely transmitted directly between people, and virtually all of the time must be transmitted via the bite of a mosquito (of the genus Anopheles).

Because part of the life cycle of malaria occurs in red blood cells in the human host, if sufficient amounts of blood are shared between people, for example during a blood transfusion, malaria can also pass between them this way, though screening measures reduce the likelihood of this occurring. Similarly, an earlier part of the life cycle occurs in the liver, so transplant of this organ can also result in transmission.

Finally, malaria is able to pass through the placenta, and so can be transmitted from a mother to her unborn child in this way, or also via blood during childbirth. When a baby contracts malaria from each mother, either via the placenta or during childbirth, it is known as “congenital” malaria.

Life Cycle of Malaria

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QUESTION

Why does the malaria parasite first enter the liver?

ANSWER

The malaria parasite enters the liver in order to transform from a sporozoite (which can infect liver cells) to a merozoite, which is capable of infecting red blood cells. Both stages also include a proliferation step, but in the blood, the merozoites are also able to differentiate into gametocytes, which are then taken back up by a mosquito during a blood meal, allowing the malaria parasite to continue its life cycle. If the red blood cell stage were first, followed by the liver, then it would be much harder for the gametocytes to be able to reach a new mosquito host, unless they were to enter the blood a third time.

The blood is also a difficult place for a parasite to survive, since it is the highway of the immune system, whereas the parasite is less easily destroyed when it is hiding out in the hepatocyte cells in the liver. It is also important to note that Plasmodium has a long evolutionary history, and may in some parts of its life cycle be constrained by physiological or life history characteristics of its evolutionary forebears, which may also contribute to our perception of the life cycle as being very complex!

Malaria Parasites Classification

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QUESTION

Where are malaria parasites classified?

ANSWER

The parasite that causes malaria comes from the genus Plasmodium, which is part of a Phylum of single-celled protist organisms called Apicomplexa. The Apicomplexans mostly posses an organ called an apicoplast, which is part of an apical structure designed to aid entry into a host cell. The Apicomplexa is split into two Classes, of which Plasmodium belongs to the Aconoidasida (lacking a structure called a conoid, which is like a set of microtubules), and then to the Order Haemosporidia, which contains parasites which invade red blood cells. Within this Order, Plasmodium belongs to the Family Plasmodiidae, which all share numerous characteristics, including asexual reproduction in a vertebrate host and sexual reproduction in a definitive host (a mosquito, in the case of the Plasmodium species that infect all mammals, including humans).

In the case of human malarias, the definitive host is often referred to as the vector. The family contains about twelve genera, of which one is Plasmodium, which itself is now often divided up into numerous sub-genera, and then again into hundreds of different species, of which five infect humans (P. falciparum, P. vivax, P. ovale, P. malariae and P. knowlesi).

Feeling Ill After Malaria Infection

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QUESTION

How soon after infection, will a person usually begin to feel ill?

ANSWER

There is a latent period, during which time the malaria parasites (which had entered the bloodstream via the bite of an infected Anopheles mosquito) migrate to the liver and undergo replication. The sporozoites (the life stage that enters the blood from the mosquito) differentiate in many merozoites, which are contained within a schizont in the liver cells. When the schizont ruptures, the merozoites are released and re-enter the blood, where they set about infecting red blood cells. Once in the red blood cells, the infected person will begin to experience symptoms—this is usually between 6-16 days after the initial infection, during which time the parasite is reproducing in the liver.

Pathophysiology of Malaria

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QUESTION

What is the pathophysiology of malaria?

ANSWER

Malaria causes disease through a number of pathways, which depend to a certain extent on the species. Malaria is caused by a single-celled parasite of the genus Plasmodium; there are five species which infect humans, beingPlasmodium falciparum, P. vivax, P. ovale, P. malariae and P. knowlesi.

All these species are introduced into the human blood stream through the bite of an infected mosquito; the life stage of malaria at this point is called a “sporozoite”, and they pass first to the liver, where they undergo an initial stage of replication (called “exo-erythrocytic replication”), before passing back into the blood and invading red blood cells (called “erythrocytes”, hence this is the “erythrocytic” part of the cycle). The malaria parasites that invade red blood cells are known as merozoites, and within the cell they replicate again, bursting out once they have completed a set number of divisions. It is this periodic rupturing of the red blood cells that causes most of the symptoms associated with malaria, as the host’s immune system responds to the waste products produced by the malaria parasites and the debris from the destroyed red blood cells. Different species of malaria rupture the red blood cells at different intervals, which leads to the diagnostic cycles of fever which characterise malaria; P. vivax, for example, tends to produce cycles of fever every two days, whereas P. malaria produces fever every three.

In addition, Plasmodium falciparum produces unique pathological effects, due to its manipulation of the host’s physiology. When it infects red blood cells, it makes them stick to the walls of tiny blood vessels deep within major organs, such as the kidneys, lungs, heart and brain. This is called “sequestration”, and results in reduced blood flow to these organs, causing the severe clinical symptoms associated with this infection, such as cerebral malaria.

More details on the exact biochemical mechanisms for sequestration and its effect on the pathology of the infection can be found on the Tulane University website.

What Causes Malaria

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QUESTION

What are the causes of malaria?

ANSWER

Malaria is caused  by infection with certain single-celled parasites of the genus Plasmodium. Specifically, there are five species which infect humans: P. falciparum (the most severe and dangerous form of malaria), P. vivax, P. ovale, P. malariae and P. knowlesi.

The symptoms of the disease occur when the parasite enters the blood stream (after a brief 1-3 week period of development in the liver) and begins to enter red blood cells, reproduce inside them, and then burst out, destroying the cell. The debris caused by this bursting, as well as various other aspects of the process, cause the body to mount an intense immune reaction which results in high fever, chills, aches and nausea. For P. falciparum infection, the infection is particularly severe because the parasite causes red blood cells it infects to stick inside the small blood vessels that lead to major organs, reducing blood flow and causing oxygen deprivation. When this occurs in the blood vessels in the brain, the result is impaired consciousness, unconsciousness, coma and even death – hallmarks of what is known as “cerebral malaria,” which is implicated in many of the deaths related to malaria each year.

What year was the cause of malaria discovered?

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QUESTION

When did they find out that a bug bite caused malaria, and what year was that?

ANSWER

In 1880, Charles Louis Alphonse Laveran observed that malaria was caused by a parasite in the blood; it wasn’t until 1897-1898 that Ronald Ross, a British Army medical doctor, discovered that the parasite could be transmitted between hosts (he used birds for his experiments) by mosquitoes.