Testing for Dormant Malaria

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QUESTION

When malaria is dormant in the body can it be detected in a blood test?

ANSWER

Not directly, no. A normal malaria blood test consists of a thick or thin smear, which is often stained and then looked at under a microscope; with these tests, you would not be able to see any sign of the malaria which is lying dormant in the liver. However, there is another type of blood test, known as serology, which looks for the body’s antibodies against malaria. These are proteins produced by the immune system when the patient becomes infected with malaria. These antibodies are specific to the type of malaria the person was infected with, and can persist for many months and even years. As such, if a patient was infected with one of the types of malaria which can become dormant (i.e. P. vivax and P. ovale), a serology test might be able to tell whether the patient had ever been infected with one of these two types, and then suggest that they might continue to have a dormant infection.

About Malaria Proteins

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QUESTION

Please tell about about malarial causitive proteins.

ANSWER

I’m not sure what your question is, as malaria is not caused by a protein, but rather by a single-celled parasite called Plasmodium, which contains many different types of proteins. Some of these are indeed used for entering host cells and thus causing disease. Many of these proteins, and particularly ones on the surface of the malaria parasite, induce the host’s immune system, and so are called antigens. One of the most well known malaria antigens is called the Duffy antigen, and it is found on two types of malaria (Plasmodium knowlesi and Plasmodium vivax). It is used by the parasite to invade host red blood cells, and it is interesting because many populations of people in Africa have genetic changes in the parts of the red blood cell which the Duffy antigen binds to. This means these people, called Duffy negative, are much less susceptible to these types of malaria than people who are so-called Duffy positive and have normal red blood cells.

Malaria Test – Can Malaria Return?

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QUESTION

I am working in Tanzania. I felt sick about 10 days ago and I went for a test for malaria and the test was positive. The doctor gave me some pills and said I must come back in one week for a test again. I went back and it was negative but now I don’t feel too good. Is it possible for the malaria to come back after 10 days?

ANSWER

It is unlikely that the malaria has come back, and if your malaria test is negative, then you probably don’t have malaria any more, and you can be confident the treatment worked. It sometimes takes a few days or even a couple of weeks to fully recover from the infection, since it takes quite a toll on the body’s immune system. Also, the medication you take to treat malaria can also have side effects, such as nausea and headaches, which actually seem similar to the symptoms of malaria itself.

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.

Can Child Be Affected by Mother’s Malaria

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QUESTION
If the baby’s mother has malaria, can it affect the child?

ANSWER

If the mother is pregnant when she gets malaria, particularly if it is her first pregnancy and particularly if she has never had malaria before, the effects on both the mother and child can be very serious. For the mother, this is because her immune system changes when she gets pregnant. This leaves her more vulnerable to the effects of malaria, including anaemia.

The most dangerous type of malaria, P. falciparum, also seems very able to infect cells in the placenta, leading to a higher intensity infection, and also reducing oxygen delivery to the baby. This, combined with the mother’s illness and anaemia, can lead to low birth weight, anaemia and other complications in the child once it is born. Malaria can also pass through the placenta, or be transferred to the baby through blood during childbirth, resulting in “congenital malaria”; that is, malaria which has been passed from mother to infant. Since newborns have inexperienced immune systems, malaria in the first days or weeks of life, and especially if the child is already low birth weight, can be very dangerous.

As such, a lot of effort has gone to finding ways to prevent malaria in pregnancy and to treat women who do get malaria while pregnant to prevent negative effects both to her and her unborn child. These efforts mainly involve the distribution of long-lasting insecticide treated bednets, and in some places also include the administration of intermittent preventive therapy, where women are given periodic doses of anti-malarials during pregnancy to protect against the disease.

Persistent Antibodies to Malaria?

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QUESTION

I had malaria as child, more than 30 years ago. It was successfully treated with no relapse. I have since travelled to malaria- endemic countries, but the last time was over 3 years ago. No symptoms. I recently donated blood and routine screening has detected malaria antibodies. How long do the antibodies persist?

ANSWER

Based on your experience, I would say at least three years! While I doubt your antibodies would persist since your infection as a child, it is more likely that in your more recent trips to malarial areas you have been re-exposed to the parasite, but for whatever reason, the infection didn’t progress into a full-blown episode of malaria. This could well be due to some residual immunity from childhood, or you just received a light enough infection that your general immune system was able to fight off. Either way, this would have produced new antibodies against malaria, which were picked up by the blood screen.

The length of time antibodies persist is important information in the control of malaria, since serological tests (which detect antibodies) can be used for screening of populations in low-transmission environments, but their efficacy is reduced in locations where people have been treated for malaria but their antibodies persist. Also, understanding how antibodies are created and maintained in the body is necessary for gaining an appreciation of how preventive measures, such as bednets, might potentially leave populations more vulnerable to malaria later on, through lack of acquired immunity.