Examination of Malaria Parasite

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QUESTION

How can you examine malaria parasites?

ANSWER

Malaria parasites are usually examined under a microscope using a peripheral blood smear method (also called a blood film). Thick blood smears, which use a large unsmeared drop of blood, are sensitive since a large number of red blood cells can be examined, though the parasites, if present, are difficult to distinguish morphologically.

For species-level identification of malaria parasites, a thin blood film is more commonly used, whereby a small volume of blood is smeared thinly across the slide and then stained, usually with Romanowsky stain, in order to see the detailed structures which differentiate the different species of malaria. It is crucial to make the blood films soon after the blood sample has been taken, and to store the blood in an appropriate anti-coagulate.

Characters to look out for include the presence of Maurer’s dots on the surface of red blood cells infected with Plasmodium falciparum. You may also see multi-infected red blood cells with this species, and it is rare to see mature trophozoites or schizonts with this parasite since when this stage is reached the red blood cells are usually sequestered deep within major organs and so are not readily present in the peripheral blood.

These parasites have crescent-shaped gametocytes. Plasmodium vivax, on the other hand, enlarges red blood cells that it infects and seems to show a preference for immature red blood cells. The presence of Schüffner’s dots is also characteristic – these looks like specks or granules on the cell surface of the infected red blood cell. P. ovale is very similar to P. vivax, in that it also enlarges the red blood cells and can have Schüffner’s dots, but fewer merozoites tend to be present per cell and infected red blood cells tend to look elongated. P. malariae does not alter the size or shape of the red blood cell it infects and tends to form rosette-like patterns of 8-10 merozoites. Later on in maturation, its trophozoites may form characteristic band-like patterns across the cell.

I am getting malaria every 6 months

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QUESTION:

I am getting malaria every six months, after taken chloroquine medicine tablets. Is this  normal,when my resistance is low, or is it coming aging, is there any medicine to clear the malaria?

ANSWER:

While taking chloroquine can be used to treat malaria, it will not prevent re-infection, unfortunately. One thing to check though is whether you are living in an area where the local types of malaria might be resistant to chloroquine; if so, it will be worth seeing if you can be treated with artemisinin-based combination therapies (ACTs), such as Coartem or Lonart, instead.

Again, these will not prevent re-infection, however, so you need to also take other preventative actions, such as sleeping under a long-lasting insecticide treated bednet and wearing long-sleeved clothing in the evenings and at night to prevent mosquito bites.

It sounds from your question like you live in an area where malaria is common; however, if you are actually only travelling to malarial areas regularly, you could also ask your doctor about the possibility of taking preventative medicine against malaria for the time that you are travelling (these are called “prophylactics”).

You should also check which species of malaria parasite you are infected with – this can be determined when you are diagnosed with the infection, either through looking at your blood under a microscope or by using a rapid diagnostic test (RDT). If you Plasmodium ovale or Plasmodium vivax, there is a possibility that even though the initial acute phase of the infection is responding to treatment with chloroquine, the parasite is remaining dormant in your liver, and causing the recurrences every 6 months. In this case, you should ask your doctor about the possibility of taking a drug called primaquine, which kills these liver stages and prevents further relapse of the disease.

Diagnostic test for malaria?

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QUESTION:

What are the possible diagnoses tests?

ANSWER:

A blood test is usually required to diagnose malaria, although the blood can be used in a number of different ways. The most common, traditional form of diagnosis is a blood smear, observed under a microscope by a qualified technician. These can be “thick” or “thin”; the “thick” smear examines a whole drop of blood for the presence of the malaria parasites infecting the patient’s red blood cells. Because a relatively large volume of blood is examined in this way, the thick smear is useful for detecting low levels of parasites in the blood, and therefore is good for an initial “positive or negative” diagnosis. The thin smear allows for a closer look at the infected blood cells, and thus can be used to identify the species of malaria, which can be important for giving the patient appropriate treatment. The danger with blood smears is that very low intensity infections can sometimes be missed, given the a low number of parasites in the blood.

More recently, a number of antibody tests have been developed to test for malaria. These so-called “rapid diagnostic tests” (or RDTs) do not require the expertise of a blood smear and only need a tiny droplet of blood, and so can even be performed at home as part of a self-testing kit. Different tests have been developed to test between the various different species of malaria. While quick and easy, there are some concerns over the sensitivity and specificity of the various tests; trials in the field have gone some way to quantifying the effectiveness of these tests in different contexts. One potential advantage of RDTs is that in some cases they seem capable of positively diagnosing low intensity infections, that would be missed by traditional blood smear. A disadvantage for wide-spread use of these tests, especially in low resource settings, is that they are very expensive.

Finally, the advent of DNA-based techniques for identifying malaria parasites means that PCR (polymerase chain reaction) can be used on a patient’s blood for an almost fool-proof diagnosis, not only of species but also, to a certain extent, of intensity. However, this procedure takes time, is expensive and requires a fully equipped laboratory with trained personnel; as such, it is not usually used for every day diagnosis of malaria infections, and especially not in developing countries where the vast majority of malaria cases occur.