Malaria Mosquito

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QUESTION

Which mosquito causes malaria?

ANSWER

Malaria mosquito vector map CDC

Map of the main global mosquito vectors of malaria (image courtesy of CDC)

It is important to note that mosquitoes do not CAUSE malaria—the disease itself is caused by microscopic, single-celled animals called Plasmodium. These Plasmodium parasites live and reproduce inside the mosquito, and when the mosquito bites a person, the parasites are transferred into that person’s blood via the mosquito’s saliva. If another mosquito bites a person with malaria, they will pick up the parasites from the person’s blood, and the cycle continues.

Malaria parasites are simply transmitted by mosquitoes, and specifically of the genus Anopheles, of which a variety of different species are capable of transmitting it to humans. In Africa, the species most responsible for transmission is An. gambiae, which actually consists of a group of very similar and closely related species; the group as a whole is known as the An. gambiae species complex. An. funestus is also a wide-spread and important vector species in Africa. Below is a map, courtesy of the CDC, which shows the distribution of some of the main malaria vector mosquitoes worldwide.

Where does malaria come from?

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QUESTION

Where does malaria normally come from?

ANSWER

Malaria is caused by single-celled parasites of the genus Plasmodium; the parasites enter the human body via the bite of an infected mosquito. However, the mosquito has to pick up the infection in the first place from another infected human; so in a sense, you could say that malaria both comes from mosquitoes, as well as from other people, although only indirectly!

More generally, your question could be read as asking where does malaria come from geographically—malaria is actually distributed over most of the world, and at some point or another has been found on all continents except Antarctica. In modern times, it tends to be restricted to the tropics and sub-tropical regions of the world, since temperature is a key factor pertaining to its survival. However, seasonal transmission (especially in the summer, hotter months) still persists even in some temperate regions. Moreover, with global climate change, it is feared that the distribution of malaria will continue to spread, and even more people will be affected.

What does malaria cause?

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QUESTION:

What does malaria cause?

ANSWER:

Malaria is a disease. It is caused by tiny single-celled parasites called Plasmodium, which are transmitted through the bite of infected Anopheles mosquitoes. There are many symptoms that occur as a result of infection with malaria, namely fever, chills, headaches and nausea, among others. Malaria can be a very serious disease, especially if not treated promptly, and so when spending time in malaria-infection areas (such as many areas of low to moderate elevation in the tropics and sub-tropics) precautions should be taken to avoid mosquito bites and thus infection. If a person finds themselves suffering from some of the above symptoms after being in a malaria transmission region, it is crucially important they get diagnosed straight away; if they do indeed have malaria, then they can be given treatment to facilitate a quick and safe recovery.

Origin of Malaria

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QUESTION:

What is the origin of malaria?

ANSWER:

Malaria is caused by a single-celled parasite called Plasmodium; different species cause the different forms of malaria we see in different parts of the world. Malaria has been in existence for millions of years; it likely evolved from similar infections in other apes. Ancient people recognised the symptoms of malaria as early as 2700 BCE, when it was first described in a Chinese medical text. The ancient Romans, Greeks and Egyptians also knew about it, but it wasn’t until the 19th century when the causative agents were first seen in a patient’s blood by a French surgeon called Charles Louis Alphonse Laveran. A few years later, a British Army doctor called Ronald Ross first discovered that the parasites were transmitted via mosquitoes. He won the Nobel Prize for his work in 1902.

What pathogenic organisms cause malaria?

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QUESTION:

What pathogenic organism causes the disease?

ANSWER:

Malaria is caused by single-celled organisms, called protozoans, of the genus Plasmodium. Different forms of malaria are caused by different species of Plasmodium. The most severe and deadly form is caused by P. falciparum, which is responsible for 90% of the global deaths from malaria, the majority of these in Africa, and mostly in young children. Other species of Plasmodium which commonly infect humans include P. vivax, P. ovale and P. malariae. Recently, a fifth form, P. knowlesi, has been found infecting rural communities in south-east Asia.

The disease is caused when the parasite enters the patient’s red blood cells, reproduces rapidly and then bursts out of the cell, destroying it in the process. The resultant immune response, combined with the chemicals and debris produced by theparasites, induces the fever, nausea, aches and other symptoms of a malaria infection.

How do mosquitoes cause malaria?

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QUESTION:

How can the mosquito cause malaria?

ANSWER:

Actually, mosquitoes don’t cause malaria themselves, they just transmit it from one person to another! The disease is actually caused by a tiny parasite, of the genus Plasmodium, several species of which infect humans. Part of the parasite’s life cycle takes place in the human host, and the other part in the mosquito; it needs to go through both to survive. Mosquitoes become infected when they feed on the blood of a human host that is infected; the parasites are then transmitted to a new, uninfected human hosts in the mosquitoes saliva, when they again take a blood meal.

Having Malaria after being tested negative

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QUESTION:

In April 2010 I was in India, had symptoms of malaria, had blood work done, platelets low but rapid antigen and smear were negative. One year later, May 2011, had low platelet count, chills, no fever or fever spikes. Could this be malaria again even though I was tested negative.

ANSWER:

This response is courtesy of Dr Jaya Swarup Mohanty, a physician in India:

Malaria doesn’t affect the platelet count or the white blood cell count. The Plasmodium species causing malaria are either lodged in the hepatocytes (liver cells) or the RBCs (red blood cells) where they undergo asexual multiplication.
Any change in platelet count would rather indicate dengue (another mosquito borne disease with fever, chills, prostration, bone pain, low platelet count) or some blood disorders (where there would only be decrease or increase in platelet count). In this case there is only low platelet count and chills with no fever or fever spikes which may indicate some disorder in blood or immune system or as a reaction to some medication. It would be advisable to consult a physician as soon as possible for further work up.

Causes of malaria, treatment with drugs and emerging resistance

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QUESTION:

What is malaria and what causes it besides bacteria? What is the name of the causal agent for malaria, which drug is used to cure it and how do the pathogens become resistant to the drugs?

ANSWER:

There are many questions in there! Malaria is actually caused by a single-celled animal, called a protozoan; it’s not a bacterial disease. There are different species of these protozoans, which form a genus called Plasmodium; the different species cause different types of malaria, for example Plasmodium falciparum, the most deadly and severe form, and Plasmodium vivax, which is widespread throughout the world but is a less acute infection. These different forms of malaria are each treated with different medications, depending on what is most effective and available; P. vivax, for example, can be treated with chloroquine, whereas in many places, P. falciparum has become resistant to this drug. In areas where resistance to chloroquine has emerged, other drugs are used; in Africa, artemisinin-based combination therapies (ACTs) are commonly used against chloroquine-resistant P. falciparum. Other drugs used to treat malaria include quinine compounds such as quinine sulphate, mefloquine, sulfadoxine-pyrimethamine and medications combining proguanil with atovaquone (marketed as Malarone).

The emergence of resistance to these drugs is a worrying phenomenon with respect to malaria; it is such a widespread and deadly disease, that the consequences of failed treatment are very high. Resistance can be caused by many factors, at the level of the drug, the human host, the mosquito host and also the malaria parasite itself. For example, poor drug compliance during treatment can lead to a failure to clear an infection completely, allowing the remaining parasites, which were less susceptible to the drug, to survive and reproduce. With successive generations, natural selection will lead to the evolution of strains of malaria parasites which are firmly resistant to that drug. The same process occurs when mass drug administration programmes, for example in areas of high malaria endemicity, give people sub-therapeutic doses of medication (in other words, doses of the drug that are too low to kill the parasite). Another problem is when people are not checked for their infection status after having been treated for malaria; if treatment fails for some reason, they will still have parasites in their blood, and should be treated again to ensure that all the malaria has been killed. If this doesn’t happen, the parasites can carry on reproducing, as in the processes described above. For these reasons, it is crucially important for people to be given accurate doses of medication, to ensure that they complete the full course of treatment, and that once treatment has been completed, they are accurately tested as negative for the malaria parasite. Finally, there are factors related to the affinity of the malaria parasite to its vector mosquito hosts which can lead to the emergence of drug resistant strains. For example, it has been shown that strains of malaria which are resistant to chloroquine are better able to survive and reproduce inside their mosquito hosts, leading to a greater population size of resistant parasites compared to drug-susceptible ones. It is for these reasons that malaria treatment and control programmes are now being very careful with the ways in which they administer drugs and monitor infections, in order to limit any further reisstance developing; similarly, pharmaceutical and biochemical researchers are constantly on the look-out for new compounds or methods of killing malaria parasites, which can be developed into new forms of treatment.

How do you get malaria?

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QUESTION:

How do you get malaria?

ANSWER:

Malaria is caused by parasites called Plasmodium, of which different species cause different types of malaria. A person gets malaria when they are bitten by certain female mosquitoes (of the species Anopheles) that carry Plasmodium parasites in their saliva. The mosquitoes themselves pick up the parasite by feeding on the blood of people already infected with malaria.

Once a person has been bitten by an infected mosquito, the parasites are released into their bloodstream. Inside the body, they reproduce and multiply—different types of malaria have different lengths of reproductive cycle and different locations in the body where the life stages reside. It is the process of reproduction and movement through the body that causes the fever, chills and other symptoms that are associated with a malaria infection.

Is malaria caused by a dietary absence?

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QUESTION:

Is malaria caused by the absence of one of the following in diet: bacteria, virus, fungi, protozoa?

ANSWER:

If I understand your question correctly, you are asking if malaria is caused by the absence of a particular organism from a person’s diet—in fact, malaria is caused by a protozoan, but infection is not linked to a person’s diet. Instead, people are infected with the protozoans (small, single-celled organisms—in the case of malaria, they belong to the genus Plasmodium) when a mosquito feeds on the person’s blood. The malaria parasites are present in the mosquito’s saliva gland, and enter the human bloodstream as the mosquito is drinking. When a mosquito feeds on a person already infected with malaria, it picks up malaria parasites in the blood it takes in. This is how malaria is transmitted, in the vast majority of cases.