Can the PCR blood test identify hypnozoites?

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QUESTION

I have never been diagnosed with malaria but returned from Turkey in 2007 (P. Vivax endemic area; Diarbykar & Mardin areas). My symptoms were consistent with malaria and I have now had 5 relapses since then, averaging one occurrence per year. I now have impaired kidney functioning and I am uncertain if this could be because of undiagnosed malaria? Would the PCR blood test at anytime be an option to conclusively rule out malaria or would blood need to be drawn during an actual relapsing event?

ANSWER

You have certainly done your research! It’s great to hear from someone who is so well informed about the risk areas they traveled too and the diagnostic options. You’re right in thinking that PCR is only appropriate during an active relapse; while the malaria parasites are dormant in the liver (called hypnozoites, in that form), they are extremely hard to detect. One option could be to investigate the possibility of taking a test to look for antibodies to the P. vivax parasite. These tests are often referred to as ELISAs (enzyme-linked immunosorbent assays) and they can sometimes be useful for testing for malaria in between relapses because the antibodies your body produces against the malaria parasite during the relapse phase can stick around in the blood for weeks, or even months or years. Therefore these tests are not very useful for people in endemic areas (who may always have these antibodies, regardless of their current infection status) but for travelers who have been exposed a limited number of times, this test may be able to say whether you have at some stage been infected with P. vivax; together with your clinical history, this will provide strong evidence to your doctor that you might need to discuss the possibility of taking primaquine, the drug which can kill the dormant hypnozoites and prevent further relapse.

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.