Question

The Microscope:

You are a medical doctor specializing in blood diseases, especially malaria. Malaria is caused by a parasite that infects red blood cells. The easiest way to diagnose the presence of the malaria parasite is to create a blood smear and view it under the microscope.

Explain in detail some of the procedures you would have to follow to create a slide that is visible under a microscope that will help you to identify the parasite. E.g. what type of microscope would you use? How will you determine what the total magnification of the specimen under the microscope (explain using an example)?Which parts of the microscope will you use to focus the blood cells? How will you ensure that the blood smear is optimally lit (i.e. what part of the microscope will help with the illumination?). Once you are done, how will you clean the lenses? And how will you store the microscope (e.g. position of objective lenses). (to avoid losing unnecessary points, make sure you address every part of this question. Also this is a discussion question, make sure you write full sentences with proper grammar).

Answer 1

Malaria is caused by Plasmodium falciparum, Plasmodium vivax and other species of Plasmodium. Direct microscopic visualization of the parasite on the thick and/or thin blood smears is done in almost all laboratory settings to diagnose malaria.

Smear preparation:

• Hold the third finger of the left hand and wipe its tip with spirit swab; allow to dry
• Prick the finger with disposable needle/lancet; allow the blood to ooze out
• Take a clean glass slide. Take 3 drops of blood 1 cm from the edge of the slide, take another drop of blood one cm from the first drop of blood
• Take another clean slide with smooth edges and use it as a spreader and make thin smears. Allow it to dry
• Make a circular thick smear of 3 drops of blood taken at 1 cm from the edge. Allow it to dry

Thick smear: Thick smear is dried for 30 minutes and not fixed with methanol. Thus, red blood cells will be hemolyzed, and leukocytes and any malaria parasites present will be the detectable elements. Hemolysis and slow drying, can cause the distortion of the Plasmodium morphology, making differentiation of species difficult. Therefore, thick smears are used for detection of infection, and estimation of parasite concentration.

Thin smear: After air drying thin smear is fixed in methanol.

Staining: Giemsa staining can be done to screen the trophozoites and ring stages of Plasmodium spp. in the smear.

Bright field light microscope can be used to view the slides under 100X magnification using immersion oil. To determine the total magnification of specimen under microscope, we consider eye piece (10X magnification) and objective lens (100X magnification lens). Therefore, the total magnification of specimen will be 1000X. Coarse and fine adjustment knobs are used to focus the blood cells. Adjustable diaphragm is used to adjust the illumination. Lenses should be cleaned using xylene in a tissue paper to clean the lenses.