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.

Diagnostic Blood Test: Malaria in Nepal and India

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QUESTION

My daughter has returned from a 6 week trip to Nepal and then India. About 20 minutes into the flight home she developed pains and aches in her hips and legs, fever, generally feeling dreadful but no nausea or diarrhea. When she arrived after the 10 hour flight her temperature was 100.5. We were concerned about malaria, but when she saw her primary care doctor the next morning she felt much better and her temperature was normal.

Blood taken at that visit showed no sign of malaria, but the doctor said that she could develop a recurrence in 3-4 weeks time when blood test should be repeated to confirm malaria if present.

I don’t doubt her doctor, but do these symptoms suggest malaria? How common is it for an initial episode of malaria to show up as negative on blood tests? She started taking tablets 3 days before entering a high risk area and took them for 3 weeks, but stopped during a brief diarrheal illness and did not restarted her anti malaria tablets.

ANSWER 1 – From Malaria.com Editor:

I think your GP might be mistaken about this – the only way to diagnose malaria is through a blood test which is positive for the disease! I have never heard of any cases where the initial blood test is negative, followed by a positive recurrence several weeks later. There are cases were the initial level of infection is quite low, in which case sometimes the parasites can be missed when looking at the blood film; however, when symptoms are present, this is rare. Moreover, there is no biological reason for a recurrence in several weeks; usually, reoccurrence occurs when treatment is given and for whatever reason is unsuccessful, allowing the malaria parasites to come back (and this assumes they are positively observed in the first place!).

Another diagnostic option, if you want to double check, is to see if you can find a rapid diagnostic test for malaria, which uses a drop of the patient’s blood to look for proteins produced by the malaria parasite. Similarly, there are tests which look for antibodies against malaria; this kind of test, known as serology, is not good for diagnosing active infections since antibodies can persist after the infection has been cleared, but may give you an indication of whether your daughter was exposed to malaria at all during her time in Nepal. Both of these are even more sensitive than blood smears, and although not as common as blood smears, are available in many places, particularly through hospitals which have tropical medicine departments or experts. All in all, if your GP is insisting on a second malaria test in a few weeks, by all means there is no harm in doing that, but in the meantime I would seek a second opinion since I think it is more likely your daughter has another infection (possibly a gastrointestinal bug, or a viral infection) which may risk going undiagnosed if your GP fixates on malaria as the answer.

Regarding the symptoms, unfortunately the symptoms of malaria are very general and it is almost impossible to accurately diagnose the disease on the basis of symptoms alone, hence why a blood test is so important. The blood test, with positive observation of the malaria parasites, is also crucial to determine which species of malaria the patient has, which may have implications for the appropriate treatment.

Answer 2: From Malaria.com Medical Advisor (MD)

The diagnosis of malaria should always be considered for patients with a fever who have traveled to malaria endemic areas. Your concerns that this may be malaria are well founded. Malaria symptoms in the first few days of infection are similar to the early stages of many other febrile illnesses, including viral and bacterial infections. In malaria, the fever also typically waxes and wanes in the manner you described. Confirming the diagnosis requires detecting parasites or their products in a blood sample. The most common test involves inspecting blood under a microscope for the presence of malaria parasites. Sometimes early in the disease there aren’t enough parasites for detection by this method. For this reason, several blood smears taken at 12-24 hour intervals are sometimes required to rule out a diagnosis of malaria in a symptomatic patient.

Additionally, your daughter was vulnerable to infection because she stopped taking antimalaria medicines while traveling in a region of malaria risk. To offer protection, these medicines must be taken for the duration of the stay, and depending on the medicine, up to 4 weeks after the last possible malaria exposure.

Unfortunately most medical doctors in regions where malaria is very rare, like the the United States and Europe, have little experience diagnosing and managing malaria. I would advise you to seek attention at a travel clinic or infectious disease specialist without delay, where it is likely further blood tests will be undertaken immediately to establish laboratory confirmation, and the prompt initiation of treatment for malaria if present.

Test for Malaria?

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QUESTION

Is there a way to verify that someone has had malaria? I had symptoms that were treated with only 10 days of proper 14 days prescription and had a relapse a year later. Have felt weak and keep my drinking to a very light level as a result. Is there test that can be taken to verify having/had plasmodium vivax?

ANSWER

The best way to test for relapsing malaria (i.e. Plasmodium vivax or Plasmodium ovale) is via a blood test while you are experiencing a recurrence of symptoms. Symptoms are associated with the parasite re-entering the blood, and so at this point, they can be visualized on a blood film, or their proteins detecting using a rapid diagnostic test. Other than that, you could also investigate having a serological test done (some forms of these tests are called ELISAs, standing for enzyme-linked immunosorbent assay).

These test for antibodies to specific proteins associated with malaria, and so can be designed to test for a particular strain, such as P. vivax. As antibodies can persist in the blood for weeks or even months after the initial infection has cleared, this could be a way for you to determine whether you had P. vivax without waiting for another relapse. This paper describes the development of a P. vivax-specific serological assay, though I am not sure whether such a test is commercially available as of yet.

If you are diagnosed with Plasmodium vivax, you should ask your doctor about the possibility of taking primaquine to kill the dormant liver stages and prevent future relapse. Primaquine is not recommended for people with G6DP deficiency, so you should be tested for this before taking the medication.

Late Malaria Confirmation

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QUESTION

I was given a field diagnosis of malaria 1 1/2years ago and was treated. Can I still get a blood test to confirm if I truly had malaria?

ANSWER

That’s a very interesting question, and the answer is: it depends. Since you were treated, you will no longer have the parasites in your blood stream, and so you cannot use a traditional blood film, looked at under a microscrope, which is the standard diagnostic method in many places.

However, there are other blood tests which look for the presence of antibodies against specific malaria proteins. These antibodies can remain in the blood for a long time after the malaria infection – probably months, but perhaps even years, though the exact length of time may vary from person to person, as well as between antibodies. If you wanted, you could inquire in your hospital whether it would be possible to get a serology test for malaria (serology tests look for antibodies) – if they tell you the brand they use then you could also contact the manufacturer to ask if they have done tests on the length of time the antibodies stay in the blood.