Malaria Detection

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QUESTION

what’s the newest form of malaria detection?

ANSWER

While the traditional form of malaria detection has been through microscopy of a blood film slide, two new technologies have recently emerged. The first is the use of reagent strips, which are impregnated with molecules that bind to various other proteins present in the blood during a malaria infection. These reagent strips are usually manufactured as part of a rapid diagnostic test (RDT) kit, whereby a patient only has to provide a single drop of blood, and the result can be read within minutes, a bit like a pregnancy test. The other new method which has emerged is based on PCR (polymerase chain reaction) technology. This method looks for malaria DNA directly in the patient’s blood, using specific sequences of DNA that are unique to the malaria parasite. This method is expensive and takes several hours at minimum, but is very sensitive, and even very low levels of malaria can be detected.

Simple Rapid Diagnostic Tests (RDTs) for Malaria Work Well

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When a person living in a malarial area gets a fever, health workers need to know the cause to make absolutely sure they give the right treatment. For many years in sub-Saharan Africa primary health workers have often assumed a fever is caused by malaria, and given antimalarial drugs. This approach means sometimes people receive the wrong treatment for their illness. It also wastes resources and, over time, can promote resistance to available drugs.

A new Cochrane Systematic Review examines the accuracy of Rapid Diagnostic Tests (RDTs), which are designed to detect malaria based on the presence of parasite antigens, using a quick and easy to use format. The World Health Organization (WHO), now strongly recommends health staff confirm a malaria diagnosis prior to treatment with artemisinin combination therapies (ACT’s), but in many settings, this demands a major shift in practice and is not as easy as it may seem to adopt.

Up until recently, confirming a diagnosis of malaria infection was done by detecting parasites in a blood sample using a microscope. This requires highly trained staff, reagents and equipment, all of which are in short supply in many areas where malaria is common. RDTs use carefully manufactured molecules (antibodies) that when in contact with an infected patient’s blood can bind with the malaria parasites and trigger a colour change on a test strip that can be easily seen with the naked eye. While these tests are technically difficult to manufacture, once built they are relatively simple to perform, require no specialised equipment and provide accurate results in many geographical settings.

“After reviewing available data in 74 different studies, we can say that the these antigen-detecting tests will identify at least 19 out of 20 cases, a success rate that would be very useful in clinical practice,” says Katharine Abba, who carried out this review at the Liverpool School of Tropical Medicine, UK.

“The use of Rapid Diagnostic Tests is another step towards reaching the goal of universal accuracy in the diagnosis of malaria and key to ensuring that the correct treatment is given to patients. Resources can be saved with the rational use of anti-malarial drugs and it will also reduce the pressure on drug resistance.”

There are various different RDTs designed to detect the malaria parasite. “All the tests performed reasonably well, but we do need more research to address issues such as how easy these tests are to use and what barriers there may be to adopting them,” says Abba.

Malaria is caused by the parasitic protozoan Plasmodium. It causes high fevers, headaches and aches and pains elsewhere in the body. If not treated early, malaria quickly evolves from an uncomplicated state into a severe disease where the brain is involved and the risk of death or brain damage is high. Malaria kills over 700,000 people a year worldwide, mostly children in Africa. In addition there are cases in Asia, Latin America, the Middle East and parts of Europe.

Source: Wiley

Do I have malaria?

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QUESTION:

Hi, I went to Ivory Coast August/2003 back March/2004, took some pills to help prevent Malaria on my trip but ran out and did not get more. While I was there I got many mosquito bites.

Around October/03 became very sick, got tested for malaria at the hospital in Quebec but negative. Now May/2011 still have all the same symptoms, flu like symptoms, feeling cold most of the time, chills headaches, tired.

Is there any way I got it? I’ve gone to doctors and doctors and no one can seem to find what is causing this? I am tired of taking tylenols all the time for the body ache. My wife is from there and she’s so sure that I got it from seeing how I am since she’s been around it all her life. Can you help me?

ANSWER:

There are definitely types of malaria that can cause relapses of symptoms many months or even years after an initial infection. These types are not common in the Ivory Coast but if you had many mosquito bites then it is certainly possible that you were exposed. What kind of test did you have for malaria when you returned to Canada?

Often, the test is by looking at a microscope slide of your blood under the microscope—the problem with this test is that it is not very sensitive for low levels of malaria, for example, after the worst of infection, and especially with the types of malaria that cause relapse (these types, P. ovale and P. malariae being the ones you might expect from Ivory Coast, tend to cause less severe illness than the more common type of malaria in Africa, called P. falciparum, doesn’t relapse in the same way, but results in much higher levels of the malaria parasite in the blood, which makes it easier to diagnose on blood slides). Also, since malaria is relatively rare in northern countries like Canada, laboratory technicians are not as experienced at diagnosing the parasite as they are in countries where malaria is endemic.

Having said that, there are of course lots of other illnesses which also cause symptoms similar to that of malaria – fevers, chills, etc. What I would recommend is that you re-visit the doctor, and ask for a more sophisticated test for malaria. Mention that you have had a relapse of symptoms—this should prompt them to use more sensitive tests, such as PCR or a rapid diagnostic test, and to look specifically for P. ovale or P. malariae. Not only will this answer your question about whether you have malaria, but it will allow the doctors to give you the appropriate treatment for your current symptoms (probably chloroquine) as well as treatment to prevent any further relapses (primequine).

Hope this helps!