Causes of Malaria

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QUESTION:

What causes malaria?

ANSWER:

Malaria is a disease caused by a parasitic single-celled animal known as Plasmodium. There are different species of Plasmodium, which cause different kinds of malaria. The main types which infect humans are P. falciparum, P. vivax, P. ovale and P. malariae. The parasite is transmitted by certain species of mosquito; the parasite lives in the human blood stream and so goes in to the mosquito when the insect feeds. When the same individual mosquito then feeds on another person, it transmits parasites into a new host.

The symptoms of malaria are caused by the actions that the parasite undertakes while in the human host. For example, part of its reproductive cycle involves invading and then multiplying inside red blood cells. Once several cycles of reproduction have occurred, the new parasites burst out of the red blood cell, destroying it. The cycles are times so that all the new parasites burst out of the red blood cells at the same time; this coordinated destruction of the red blood cells, either every 24, 48 or 72 hours, depending on the malaria species, causes the one day, two day or three day cycles of fevers and chills that characterise malaria infection episodes.

What is malaria?

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QUESTION:

What is malaria?

ANSWER:

To answer your question, I have copied below the answer to an earlier post, published on the 1st of May, 2011, which also asked “What is malaria?”:

Malaria is a disease caused by parasites of the genus Plasmodium. Transmitted by mosquitoes, there are several different kinds of malaria distributed throughout the tropical and sub-tropical regions of the world, causing somewhere between 300-500 million cases of disease each year, and as many as 1 million deaths. In fact, malaria is one of the biggest killers of children under the age of five in sub-Saharan Africa, one of the regions of the world where the burden from malaria is the highest. Malaria is usually an acute disease, manifesting itself with severe fever, chills, headache and often nausea as well. Some types of malaria can have relapsing episodes over a time period of many years.

Having said this, malaria is easily preventable, through avoiding mosquito bites by wearing appropriate clothing and sleeping under insecticide-treated bednets, or through taking preventative medication (called prophylaxis). Malaria is also treatable once symptoms appear, through ingesting safe, effective and relatively cheap drugs. With such control measures at hand, you may ask why malaria is still such a huge problem in our world; the answer is that delivering control strategies and treatment to populations most at risk is difficult, and often countries with high malaria burdens don’t have efficient and effective health systems in place to coordinate control efforts.

International non-governmental organisations such as the World Health Organisation, as well as a multitude of non-profit organisations such as the Malaria Consortium and Malaria No More, work tirelessly to bring malaria control and treatment to the places that need it most, with the aim to eradicate malaria as a disease of public health importance.

 

What is malaria?

by

QUESTION:

What is malaria?

ANSWER:

Malaria is a disease caused by parasites of the genus Plasmodium. Transmitted by mosquitoes, there are several different kinds of malaria distributed throughout the tropical and sub-tropical regions of the world, causing somewhere between 300-500 million cases of disease each year, and as many as 1 million deaths. In fact, malaria is one of the biggest killers of children under the age of five in sub-Saharan Africa, one of the regions of the world where the burden from malaria is the highest. Malaria is usually an acute disease, manifesting itself with severe fever, chills, headache and often nausea as well. Some types of malaria can have relapsing episodes over a time period of many years.

Having said this, malaria is easily preventable, through avoiding mosquito bites by wearing appropriate clothing and sleeping under insecticide-treated bednets, or through taking preventative medication (called prophylaxis). Malaria is also treatable once symptoms appear, through ingesting safe, effective and relatively cheap drugs. With such control measures at hand, you may ask why malaria is still such a huge problem in our world; the answer is that delivering control strategies and treatment to populations most at risk is difficult, and often countries with high malaria burdens don’t have efficient and effective health systems in place to coordinate control efforts.

International non-governmental organisations such as the World Health Organisation, as well as a multitude of non-profit organisations such as the Malaria Consortium and Malaria No More, work tirelessly to bring malaria control and treatment to the places that need it most, with the aim to eradicate malaria as a disease of public health importance.

 

How does malaria spread?

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QUESTION:

How does malaria spread?

ANSWER:

Malaria is a vector-borne disease; this means that it has to be spread through a “vector” species, which in this case are female mosquitoes of the genus Anopheles. The female mosquito needs to feed on blood in order to produce eggs; most species lay eggs every 2-3 days, which means each female mosquito needs to take very regular blood meals.

Around 20 species of Anopheles mosquito have been implicated in the transmission of malaria; some species are better than others at acting as a vector. The most important group in Africa is the Anopheles gambiae complex; these mosquitoes are also relatively long-lived, which is important for transmission since it means that whole portions of the malaria parasite’s life cycle can be completed inside the vector mosquito.

When the female mosquito takes a blood meal, she inserts her slender mouth part (called a ‘proboscis’) into a tiny cut she makes uses specialized slicing parts of her mouth. She probes until she finds a small surface blood vessel, from which she feeds. The proboscis contains two narrow tubes – one delivers her own saliva into the wound (containing chemicals to stop the blood coagulating as well as a slight pain-killer, to stop you feeling the bite) while the other sucks up blood.

The mosquito’s saliva also contains the malaria parasite; this is how the parasite is delivered into the human body. Similarly, the parasite passes back into the mosquito through the blood she ingests, once the human portion of the life cycle has been completed. As mosquitoes pass between human to human, and indeed also between other animals, they spread the malaria parasite through the delivery of saliva and the uptake of blood.

What is malaria? What Causes Malaria?

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QUESTIONS:

What is malaria?
What causes malaria?

ANSWER:

I have copied below the text from an earlier question, also asking about the causes of malaria and explaining what it is:

Malaria is a disease caused by a parasitic single-celled animal known as Plasmodium. There are different species of Plasmodium, which cause different kinds of malaria. The main types which infect humans are P. falciparum, P. vivax, P. ovale and P. malariae. The parasite is transmitted by certain species of mosquito; the parasite lives in the human blood stream and so goes in to the mosquito when the insect feeds. When the same individual mosquito then feeds on another person, it transmits parasites into a new host.

The symptoms of malaria are caused by the actions that the parasite undertakes while in the human host. For example, part of its reproductive cycle involves invading and then multiplying inside red blood cells. Once several cycles of reproduction have occurred, the new parasites burst out of the red blood cell, destroying it. The cycles are times so that all the new parasites burst out of the red blood cells at the same time; this coordinated destruction of the red blood cells, either every 24, 48 or 72 hours, depending on the malaria species, causes the one day, two day or three day cycles of fevers and chills that characterize malaria infection episodes.


What is Malaria?

by

QUESTION:

What is malaria?

ANSWER:

Malaria is a disease caused by parasites of the genus Plasmodium. Transmitted by mosquitoes, there are several different kinds of malaria distributed throughout the tropical and sub-tropical regions of the world, causing somewhere between 300-500 million cases of disease each year, and as many as 1 million deaths. In fact, malaria is one of the biggest killers of children under the age of five in sub-Saharan Africa, one of the regions of the world where the burden from malaria is the highest. Malaria is usually an acute disease, manifesting itself with severe fever, chills, headache and often nausea as well. Some types of malaria can have relapsing episodes over a time period of many years.

Having said this, malaria is easily preventable, through avoiding mosquito bites by wearing appropriate clothing and sleeping under insecticide-treated bednets, or through taking preventative medication (called prophylaxis). Malaria is also treatable once symptoms appear, through ingesting safe, effective and relatively cheap drugs. With such control measures at hand, you may ask why malaria is still such a huge problem in our world; the answer is that delivering control strategies and treatment to populations most at risk is difficult, and often countries with high malaria burdens don’t have efficient and effective health systems in place to coordinate control efforts.

International non-governmental organisations such as the World Health Organisation, as well as a multitude of non-profit organisations such as the Malaria Consortium and Malaria No More, work tirelessly to bring malaria control and treatment to the places that need it most, with the aim to eradicate malaria as a disease of public health importance.

How long has malaria existed?

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QUESTION:

How long has malaria been going on?

ANSWER:

The answer to your question depends on the kind of malaria as well as how exactly you define ‘malaria’. The parasites which cause all forms of malaria, in humans as well as other mammals and birds, belong to a group called Plasmodium; scientists believe, based on genetic information, that this genus evolved around 130 million years ago, which is before the dinosaurs went extinct! These ancient ‘malaria’ parasites probably infected lizards; some types of malaria still infect reptiles today.

Plasmodium parasites have since evolved to infect primates, including humans; some scientists argue that this ‘jump’ has probably occurred several times in evolutionary history, whereas other suggest it has only happened once; the debate on this will likely continue for some time!

In terms of when human malaria first evolved, the four main types of malaria that infects humans are P. vivax, P. malariae, P. ovale and P. falciparum; the first three likely either co-evolved with humans or at least first became associated with infecting humans very soon after anatomically modern humans evolved. This dates these types of malaria back to the Middle Stone Age, which started around 300,000 years ago in Africa.

P. falciparum, on the other hand, probably crossed over much more recently, and the most up-to-date genetic evidence suggests that it evolved from a type of malaria which is found in gorillas. Estimates for when this transfer occurred are shaky at best, but it might have only been in the region of 10,000 years ago.

For more reading on the debate regarding the origin and evolutionary histories of Plasmodium as a whole and human forms of malaria more specifically, the following scientific articles may be a good place to start:

Joy, DA; Feng X, Mu J, Furuya T, Chotivanich K, Krettli AU, Ho M, Wang A, White NJ, Suh E, Beerli P & Su XZ, (2003). ‘Early origin and recent expansion of Plasmodium falciparum’, Science 300 (5617): 318–21

Liu, W; Y Li, GH Learn, RS Rudicell, JD Robertson, BF Keele, JN Ndjango, CM Sanz, DB Morgan, S Locatelli, MK Gonder, PJ Kranzusch, PD Walsh, E Delaporte, E Mpoudi-Ngole, AV Georgiev, MN Muller, GM Shaw, M Peeters, PM Sharp, JC Rayner & BH Hahn (2010), ‘Origin of the human malaria parasite Plasmodium falciparum in gorillas’, Nature 467.

Yotoko KSC & Elisei C (2006), ‘Malaria parasites (Apicomplexa, Haematozoea) and their relationships with their hosts: is there an evolutionary cost for the specialization?’, Journal of Zoological Systematics and Evolutionary Research 44 (4): 265–73