Death from Malaria: Humans and Other Primates

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QUESTION

If not treated in some form, do most who acquire malaria die? What about primates, such as orangutans that live in the wild and would not be treated as such. Do they die or do they become chronically ill within period of remission?

ANSWER

That’s a really good question, and the answer is: it depends! In humans, the most deadly form of malaria is Plasmodium falciparum—when infected for the first time, if not given prompt treatment, many people will die from this infection. However, after repeated infections, people develop acquired immunity to the P. falciparum parasite which means they are increasingly able to survive subsequent infections without treatment. This reason of acquired immunity is why young children, who do not yet have immunity, and visitors to malarial areas tend to have the most severe infections and most require treatment in order to survive.

The other three major forms of human malaria, P. vivax, P. malariae and P. ovale, are generally less deadly, though they can also result in death in some circumstances if the person does not have immunity and is not treated. Although much less common than P. falciparum, P. knowlesi is the fifth type of malaria to infect humans (it is more commonly an infection of macaque monkeys in south-east Asia), and because it replicates in a 24-hour cycle (the other types of human malaria have either a 48 or 72 hour cycle), high parasite loads can establish very quickly, leading to severe disease. As such, P. knowlesi is also quite dangerous and a high proportion of untreated cases result in death.

It is great that you ask about malaria in other primate species—as with humans, some forms of malaria are tolerated reasonably well while others are more deadly. It varies depending on the type of malaria as well as the species of primate. So, for example, P. knowlesi in long-tailed macaques is rarely observed to cause severe disease. In fact, infected macaques sometimes don’t even appear to have any symptoms. In contrast, if rhesus macaques are experimentally infected with P. knowlesi (the transmission range of this type of malaria does not overlap with the natural range of rhesus macaques), almost 100% of them will die without treatment.

You ask specifically about orangutans: one problem is that it is unclear which, and how many, species of malaria infect these apes. Past research has uncovered two species which are thought to be unique to orangutans (namely P. silvaticum and P. pitheci) while molecular studies have also shown non-specific species, namely human P. vivax and macaque P. cynomolgi and P. inui. As such, while originally orangutan malaria was thought to be not very dangerous to these apes, more recently there have been reports of orangutans showing very human-like symptoms suggestive of more advanced disease. However, rarely do studies link symptoms and observations of parasites in the blood, so it is unclear which parasites are causing these symptoms, if indeed it is malaria at all (in some sanctuary/rehabilitation center settings, orangutans exhibiting malaria symptoms have responded positively to treatment with anti-malarials, though this is not definitive evidence that their symptoms were caused by malaria).

So, in short, more research should be done on wild primates, particularly using molecular tools, to ascertain accurately what species of malaria they are infected with, and whether they are associated with symptoms and/or severe disease.

Do Male Mosquitoes Bite?

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QUESTION

Why do male mosquitoes not bites humans?

ANSWER

Male mosquitoes do not possess the right kind of feeding apparatus to feed on humans—they only feed on nectar. This is because they do not need to produce eggs, which require lots of energy and protein to make, and so the female mosquitoes need a more comprehensive food source than just nectar when they are egg-laying, such as blood. This is why they feed on humans and other animals when egg-laying.

Socio economic conditions surrounding malaria

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QUESTION

What are the socio economic conditions surrounding malaria?

ANSWER

Malaria transmission requires the presence of Anopheles mosquitoes; as such, conditions which favor the growth and persistence of these mosquitoes will also be hotspots for malaria transmission, provided the climate is also sufficiently warm for the development of the parasite within the mosquito.

Rural areas without sophisticated water and sanitation systems often utilize streams or ponds for everyday water needs; if these produce stagnant patches of water, they can be an ideal location for the development of mosquito larvae.

Similarly, if rural farmers dig canals or ditches to irrigate their fields, these can become breeding areas. Urban areas tend to have less standing water, apart from cisterns, so in many cases transmission is less prevalent in urbanized locations.

As a further socio-economic factor, preventing mosquitoes from entering the house and biting people is  key way to prevent infection. Rich people in malarial areas may be more able to have fully screened houses, possibly even with air-conditioning, which will prevent mosquitoes from establishing in the house. They may also be more likely to have access to a long-lasting insecticide treated bednet, which further reduces mosquito bites, and also access to accurate diagnostic screening and treatment, if they do happen to get infected.

All of these factors contribute to making malaria burden highest in some of the world’s poorest areas, with the highest levels of mortality in sub-Saharan Africa.

Malaria: Mode of Transmission

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QUESTION

What is the mode of transmission of Malaria?

ANSWER

Malaria is transmitted normally via the bite of an infected mosquito. These mosquitoes, always female and of the genus Anopheles, carry malaria parasites in their salivary glands. The parasites, at this part of their life cycle known as sporozoites, are introduced into the host’s blood when the mosquito takes a blood meal. From there, the sporozoites travel to the liver, reproduce (this process may take several weeks), then finally re-enter the blood stream. At this point, the patient will begin to experience symptoms. Eventually, the malaria parasites change again, into gametocytes, which are picked up by another mosquito, again when it bites the infected person. In this way, the life cycle of the malaria parasite continues.

Because malaria reproduces in the blood and in the liver, in some cases malaria can be transferred via organ transplant or blood transfusion. In addition, malaria parasites can cross the placenta, and so can be transmitted from a mother to her unborn child, either in the womb or during childbirth. This is known as congenital malaria.

Malaria in Vietnam, Thailand, Bali

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QUESTION:

I am 5 months pregnant and I was thinking about going on holiday to Vietnam, Thailand, or Bali. What is the risk of malaria in this countries?

 

RESPONSE:

Malaria transmission occurs in all of the nations you mention, though certain areas within these nations are lower risk.

You can find out more about specific regions and local antimalarial resistance patterns at the CDC website.

You should certainly consult your prenatal doctor to discuss the variety of potential risks, in addition to malaria, associated with international travel in the developing world as you enter the third trimester of pregnancy. Malaria infection in pregnant women can be more severe than in nonpregnant women and can increase the risk for adverse pregnancy outcomes. For these reasons, and because no chemoprophylactic regimen is completely effective, women who are pregnant are usually advised to avoid travel to areas with malaria transmission if possible. If travel to a malarious area cannot be deferred, chemoprophylaxis is essential. Chloroquine containing medications are have not been found to have harmful effects on the fetus. For pregnant women travelling to areas where chloroquine resistance is present, mefloquine is usually recommended.

 

 

Malaria from Vietnam War

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QUESTION:

If my husband contracted malaria from serving in the Vietnam War but has never been treated for it, what are the symptoms that he might have experienced in the past that could have been caused by malaria but not diagnosed correctly?

Also is it possible that malaria infection could cause any type of birth defects to his children?

 

ANSWER:

Most people with primary malaria infection experience fevers, chills, sweats, muscle and joint aches, often accompanied by headache, nausea and diarrhea. While these symptoms resemble those of other illnesses that cause fever, these are often more severe in malaria and tend to recur in one, two, or three day cycles.

Certain forms of malaria can relapse  years after infection, and the symptoms of these relapses are similar to the initial (primary) infection.  Anemia, enlarged spleen, and low platelets are also common abnormalities in malaria. If your husband experiences any episodes of these symptoms, blood tests taken during fever might help determine if the malaria parasite is present. Other blood tests can determine if he’s been infected in the past.

While maternal malaria during pregnancy can increase the risk of poor pregnancy outcomes, malaria is not known to increase the risk of birth defects from father to child.

 

Malaria Fever and Recovery

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QUESTION

My 21 year old daughter spent 4 months on a study abroad program in Dakar. A week before returning home she started having night fevers and would complain of retrosternal pain and rib and neck and shoulder pain. The next day she would be fine.

The episodes came every other day and eventually it occurred to her that it might be malaria. It was evening so she went to a pharmacy for a rapid diagnostic test which they didn’t have but they felt she had malaria based on her symptoms and gave her a 3 day course of artesunate-mefloquine.

She returned to the United States and a day after taking her last dose, she was seen by a physician and tests were done which showed that she had contracted Plasmodium falciparum malaria. Other than the smears, all her lab tests and CXR were normal and there were no abnormal findings on physical exam, in fact she was the picture of health.

We were told that she was cured and that no follow up was necessary and that she could continue with her planned trip to Thailand the next day. About 6 hours before boarding the plane to Bangkok she developed fever of 100.9 but had absolutely no other symptoms or pain. About an hour later she had a bout of diarrhea. She had one more low grade fever on the flight (99.8). I spoke to another physician who seems more familiar with malaria and was told that she is not actually cured and may continue to have episodic fevers and symptoms for a while or it’s possible she was just suffering from an ordinary garden variety gastrointestinal bug.

I have many questions. I understand that her malaria is the most virulent type. How is it that all her lab work and physical exam is normal 1 day after completing treatment? Can we expect it to remain normal? What causes the episodic fevers if she is supposedly cured? She is on doxycycline again prophylactically (which she was on in Senegal) while in Thailand. Should she be on something else since she did contract malaria on doxycycline? (She took it religiously). Thanks for any advice. She will be seeing a physician in Bangkok ASAP, but since I won’t be there to ask questions, I am hoping you can give me some answers. Your site is the best information I have found on malaria.

ANSWER

Many thanks for the comprehensive information you have provided regarding your daughter’s condition. Even though your daughter did have the most virulent form of malaria, she was very smart to seek treatment relatively promptly, and lucky to receive appropriate medication (artemisinin-based combination therapies, such as artesunate-mefloquine, are recommended by the World Health Organization as first-line treatment against malaria). It is likely due to this prompt and effective action that her lab tests and blood parameters were all normal so soon after treatment; had she waited longer for treatment, the consequences could have been much more severe. No resistance to this medication has been detected in Africa as of yet, so she should be fully cured and thus her health should remain stable; a blood smear, where her blood is examined under a microscope, can determine this; this is a very standard procedure so could easily be carried out in Thailand if she wants.

Fever is a side effect of the body’s immune system responding to a disease threat, so it is not uncommon for some symptoms to carry on after treatment. In addition, mild side effects of anti-malarial medication can often mimic the symptoms of malaria itself, including fever and nausea.

Given also the (entirely reasonable) possibility of an additional, unrelated stomach bug, I suspect that your daughter has successfully beaten off this malaria attack, and while she should remain vigilant if similar symptoms arise again, her health in the future should not be adversely affected at all by this episode.

Also, as mentioned briefly above, medical professionals in Thailand should be well equipped to diagnose and treat malaria if she suspects she has been reinfected. It is worth noting that malaria in south-east Asia has shown signs of resistance to mefloquine (as well as other drugs, such as chloroquine and sulfadoxine-pyrimethamine), so if she does require treatment while there, she should make sure the medication they provide does not contain any of the afore-mentioned compounds.

Regarding doxycycline, it’s great that your daughter took it religiously—that is certainly the first step towards protection. Randomized placebo controlled trials have shown it is between 92-96% effective in preventing P. falciparum malaria, which is very good, but obviously not 100% perfect – even when taken perfectly, some infections do occur. In addition, there is some data which suggests that dairy products, taken together with doxycycline, may limit  the uptake of the drug. This is rarely communicated to patients, who are instead contrarily told sometimes that taking the pills together with dairy products can reduce side effects! As such, please let your daughter know that she should avoid dairy products for 2-3 hours around the time she takes her doxycycline.

Malaria Statistics 2008-2012

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QUESTION

Where i go if i want statistic of malaria from 2008-2011

ANSWER

Without more information, I am assuming you would like statistics on malaria cases and deaths for 2008-2012. The best data on malaria comes from the World Health Organization, which retrospectively publishes its best estimated for malaria in its annual World Malaria Reports. Each report publishes the figures from the previous year, and the 2012 report has not yet been published, so at this point the WHO can only provide data for 2008-2010. It is also worth mentioning that as more information is collected, past estimates can sometimes be revised, but here I will present the figures from each annual report itself, rather than longer retrospective estimates.

In 2008, the number of cases was estimated at 243 million, with 863,000 deaths. In 2009, the report did not explicitly summarize the number of cases, but reported that deaths were down to approximately 781,000. In 2010, the number of cases and deaths both dropped yet further, to an estimated 216 million cases and 655,000 deaths. Despite these gains, the aim is to work towards a world with no malaria deaths at all by the year 2015, so much control work remains to be done.

Rash and Malaria

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QUESTION

Is random rash-like swelling on parts of your body coupled with back pains and joint aches and cold sweats all malaria symptom? If so, what is the parasite type and the cure?

ANSWER

Rashes are not usually associated with malaria infection; the symptoms you describe are however consistent with several other infections, some of which can be quite serious, such as dengue fever. You should go to your doctor or a hospital to have a blood test which can assist in diagnosing you.

For future reference, if you did have malaria, you would still probably need to have a blood test to determine which species of malaria you had, and therefore what kind of treatment would be appropriate.

Untreated Malaria

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QUESTION

If I am infected with malaria and I get a wrong diagnosis and be treated for flu, can the other symptoms disappear but continue to experience severe headache especially on the right side temple and jawbone area combined with general weakness and numbness in the legs?

ANSWER

Certainly the symptoms of malaria can often be confused with other infections, including flu. Given that treatment for flu will often include anti-fever medications such as aspirin or paracetamol, these drugs may also ameliorate some of the symptoms associated with malaria, without actually curing them.

However, numbness in the legs is not usually characteristic of malaria infection, though headache and weakness could be—again, these are general symptoms of many other infections as well.

If you suspect you have been misdiagnosed and have malaria, you should ask your doctor for a blood test; these can also be carried out at any local hospital or clinic. There, by looking at your blood under a microscope or using it in a rapid diagnostic test, they will be able to determine accurately whether you have malaria.