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.

Number of Species of Malaria

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QUESTION

I recently read an ISOS world malaria day poster saying 5 species of plasmodium cause malaria. I think that is confusing as we always talked about 4, ovale, vivax, falciparum and malaria….are they referring to the way we now split ovale into 2 sub species? or is this a typo on their part?

ANSWER

That is a really interesting question, and a good observation on your part! I imagine the fifth species they are referring to is Plasmodium knowlesi, which is found in parts of south-east Asia, with the majority of cases being reported from Borneo. Originally known only from macaque monkeys, it appears to be occurring more frequently in humans. However, it is not known whether this is a new host switch, or whether it is simply a matter of better detection methods—the morphology of P. knowlesi closely resembles that of P. falciparum in its early trophozoite stages, and P. malariae in later trophozoite and other life stage forms. Moreover, some molecular-based tests for P. knowlesi cross-react with other forms of malaria, such as P. vivax, leading to greater diagnostic confusion.

There is also a hypothesis that changes in land use in tropical forests may be resulting in greater human exposure to the vectors which carry P. knowlesi, which accounts for its increased recent prevalence in humans. P. knowlesi is the only known malaria in humans (and indeed, in all primates) with a 24-hour reproductive cycle, which means that without treatment, high levels of parasitaemia can accumulate rapidly in the blood, and lead to severe clinical symptoms. This makes its apparent emergence of great public health concern in south-east Asia. Luckily, at this point, P. knowlesi is completely susceptible to chloroquine treatment and other medications, and so is easily controlled once diagnosed.

One of our contributors, Christina Faust, wrote a blog post last year on P. knowlesi entitled Of Macaques and Men. More information on recent research about P. knowlesi can be found in the article, Monkeys Provide Malaria Reservoir for Human Disease in South-East Asia.

Repeated Malaria Cases, New Guinea

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QUESTION

Hello, I live in Papua New Guinea. Myself, my wife and my 2 kids (both under 4 years old), get diagnosed with malaria approximately 3-4 times a year, usually vivax or falciparum. Our GP uses a prick of blood and examines under a microscope. Is it that easy/obvious to diagnose under this method and is it common to get this many attacks in a year? I also fear the affects of taking malaria tabs (eg Fansidar, Primaquin, Artemeter, Amodiaquine) this many times, especially for my young kids. Please help!

ANSWER

In high transmission areas, particularly in rural areas in sub-Saharan Africa, it certainly isn’t unusual for children to get as many a 5 or 6 malaria attacks in a year; adults tend to present with fewer clinical episodes, usually because they were heavily exposed as children and thus developed a significant level of immunity against malaria.

If you and your wife didn’t grow up in a malarial area, then you would not have that acquired immunity, and so you would be expected to get sick almost as often as your young children. Papua New Guinea certainly is a high transmission zone, and I think one thing which might help your family is to focus more on malaria prevention. Since malaria is transmitted by mosquitoes, the best way to avoid getting malaria is to avoid getting bitten by mosquitoes. You should all be sleeping under log-lasting insecticide-treated bednets, which kill and/or repel mosquitoes that try to bite you while you sleep (the mosquitoes that transmit malaria, of the genus Anopheles, are most active at dusk, at night, and at dawn—during the heat of the day they usually don’t feed, but may be found in cooler, heavily shaded areas).

You could also try spraying the walls of your house with a long-lasting insecticide like permethrin, which will also kill adult mosquitoes. Making sure your house is well-screened will also prevent mosquitoes from getting in and biting you at night and in the evenings, and if you are going out during these times, you and your family should wear long-sleeved clothing, and exposed skin should be covered with insect repellent. A DEET-based insect repellent is best, but you may not be comfortable using these regularly on young children, since it can have some potentially dangerous long-term effects, particularly on the liver.

In terms of your other questions, looking at your blood under the microscope is the normal way to diagnose malaria in many places, so it sounds like your GP is doing a good job. There is no indication of adverse effects from taking multiple, repeated doses of anti-malarials, but as I mention above, taking additional preventive measures may further help in reducing your family’s malaria incidence.

One thing you might want to talk to your doctor about is the fact that in some cases, Plasmodium vivax can cause relapses of infection weeks or even months after the initial infection. The reason is that P. vivax can form dormant life stages, which can hide out in the liver, and cannot be killed by the normal anti-malarial treatment. However, there is a medication, called primaquine, which can kill these liver forms, and prevent future relapse. People with a deficiency in a particular enzyme, called G6DP, may not be able to take this medication, as it may cause severe anaemia, so prior to taking the drug you might have to be tested for this deficiency. However, it is definitely something you should talk to your GP about.

Please take a moment to complete our Malaria Survey, as it will help us better understand the effects of malaria medications.

Coartem Treatment

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QUESTION

my husband has been taking coartem for 3 days now. He was fine yesterday and then last night the symptoms re-appeared like it was day one. Can I carry on with coartem and start another course? Or shall I switch to something else ? If so, what? We live in zambia by the way.

Thank you for your help.

ANSWER

If your husband still has strong symptoms after taking all doses of the Coartem, go back to see your doctor  or to the clinic for another blood test. If it is positive, then your doctor may recommend trying a different form of anti-malarial medication—artemisinin-based combination therapy (a group of medications that includes Coartem) is recommended as the first-line treatment against malaria, but a second line option could be atovaquone-proguanil (Malarone) or another medication. Please note that Fansidar (sulfadoxine and pyrimethamine) and chloroquine are not recommended for use in Africa as levels of resistance are high. 

It could be that the medication hasn’t had time to fully act, which is why it is important to wait until the full dose has been taken, and then to confirm that malaria is still present. Sometimes the side effects of anti-malarials can appear similar to malaria itself, such as nausea, chills, body aches, etc, so it is important not to start another course of treatment without further diagnosis.

We are actually very interested in learning about our readers’ experiences with anti-malarial medications, and so we would be very grateful if you might be able to take a few minutes to complete our malaria survey we are running on Malaria.com. We will post any findings that may be of interest to our readership on Malaria.com later this year—all submissions are completely anonymous. Many thanks for your time and help, and I hope your husband recovers fully soon.

World Malaria Day Date

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QUESTION

What is the background of 25 April to be celebrated as World Malaria Day? Why just 25 April?

ANSWER

World Malaria Day was instituted by the World Health Assembly at its 60th meeting in May 2007. As far as I know, the choice of April 25th was arbitrary – it was almost a full year after the instituting assembly meeting, perhaps intending to give the organizers plenty of time to make preparations for the first observance of the day. In any case, World Malaria Day is now a symbolic date and a rallying time point for malaria advocacy and control efforts.

Malaria in Kitwe Zambia

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QUESTION

Is it dangerous for my children two years old in Kitwe?

ANSWER

Kitwe has been part of the Roll Back Malaria campaign to control malaria in Zambia—the program has been very successful, reducing deaths by malaria by over 65% nationwide. However, there still is a risk of contracting malaria in most parts of the country, and so preventative measures should be taken when visiting or living in Kitwe, such as sleeping under a long-lasting insecticide treated bednet, wearing long-sleeved clothing in the evening and at night and screening doors and windows to prevent mosquitoes from entering.

Anopheles Mosquito

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QUESTION

What does Anopheles looks like?

ANSWER

Mosquitoes of the genus Anopheles are responsible for all transmission of malaria in mammals, including to humans. They are night-feeding mosquitoes, usually biting between dusk and dawn, though they may also be active during the day in heavily shaded environments.

Like all mosquitoes, Anopheles are usually found either as freshwater larvae, which prefer stagnant, still water, or flying adults, of which only the females feed on blood (the males exclusively feed on nectar).  Anopheles larvae lie parallel to the surface of the water where they live (in contrast to Aedes and Culex larvae which hang at an angle), whereas the adults rest with their bodies at a 45 degree angle upwards (again in contrast to Aedes and Culex adults, which rest parallel to their resting surface).

Anopheles Mosquito

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QUESTION

Why is it only the female anopheles mosquito alone can cause malaria but not the male anopheles mosquito or any other mosquitoes?

ANSWER

Malaria is actually caused by a single-celled parasite called Plasmodium—it is transmitted via the bite of a female mosquito, of the genus Anopheles, as she takes a blood meal from a human (or other mammal) host. Male mosquitoes do not feed on blood (they only feed on nectar), whereas females need the nutrients from blood in order to produce their eggs; as such, only female Anopheles transmit mosquito.

Why only Anopheles are able to transmit malaria to humans is interesting—birds and reptiles also can get Plasmodium (though different species than those that infect humans and other mammals), and these kinds of malaria can also be transmitted by other kinds of mosquitoes, such as Aedes and Culex. Other closely related blood parasites can even be transmitted by other flying insects, such as sand flies and black flies. However, it is true that only Anopheles can transmit human malaria.

How to Prevent Malaria

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QUESTION

How to prevent malaria?

ANSWER

There are a number of ways to prevent malaria. These can be placed into two categories: medication and vector protection.

For medication, there are drugs you can take to prevent the malaria parasite from developing after someone is bitten by an infected mosquito. These drugs are known as “chemoprophylaxis.”

There are several different kinds, such as doxycycline, mefloquine (marketed as Lariam), atovaquone-proguanil (marketed as Malarone) and chloroquine—the type you use depends on the type of malaria present in the area. For example, in much of Africa and India, malaria is resistant to chloroquine, so this cannot be used as a prophylactic. In parts of Thailand, resistance to mefloquine has emerged. However, if the appropriate type of prophylaxis is used, it is very effective against malaria.

The problem is that these drugs have not been tested for long-term use, can be expensive and may have side-effects. Therefore they are of limited use for people who live in areas where malaria is endemic, and are more appropriate for travelers who are in malarial areas for short amounts of time. However, anti-malarial medication may be used in a very specific way for people at particularly high-risk for malaria, such as pregnant women and young children. In these cases, the high-risk individuals receive a dose or series of doses of malaria medication in order to prevent malaria. This form of prevention is known as intermittent preventive therapy (IPT).

Vector prevention involves protecting oneself against getting bitten by mosquitoes. This can involve wearing long-sleeved clothing in the evenings and at night, when malaria mosquitoes are most active, or wearing insect repellent on exposed skin. Indoor residual spraying, whereby repellent and insecticides are sprayed inside the house, can also be used to bring down the number of mosquitoes.

Another very effective technique for preventing malaria is to sleep under a long-lasting insecticide-treated bednet. The mesh acts as a barrier against the mosquitoes, and the insecticide impregnated in the mesh further repels the mosquitoes and prevents them from biting through the mesh.

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.