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What is a Microfilaria Parasite test? 

A microfilaria parasite test is done to diagnose the parasitic disease filariasis. Filarial worms in the early larval stage enter the bloodstream of an individual through an adult parasite which resides in host tissues. These filarial worms are the cause of diseases, such as elephantiasis, river blindness and Loa loa filariasis. There are three main types of filarial nematodes based on the part of the body they attack. 

Lymphatic filariasis affects the lymphatic system of the body, whereas subcutaneous filarial worms infest the subcutaneous layer of skin. The serous cavity filarial worms reside in the serous cavity of the abdomen.

  1. Why is a Microfilaria Parasite test performed?
  2. How do you prepare for a Microfilaria Parasite test?
  3. How is a Microfilaria Parasite test performed?
  4. What do Microfilaria Parasite test results indicate?

A microfilaria parasite test is done to detect the presence of microfilaria parasite in blood with the help of a blood smear. 

This test will be recommended to individuals who show apparent symptoms of microfilaria. These include

  • Fever
  • Pain in the genital area
  • Swelling of limbs

Since the test is performed by taking a blood smear, it is important to inform the doctor regarding any medications, such as supplements or antibiotics, which you are taking, as these could alter test results. If you have any existing medical condition, it should also be specified before the blood sample is taken.  

Since the blood smear test will be performed specifically for detecting microfilaria, it is important to take the blood sample during the night-time because microfilaria are active at night.

  • An elastic band is wrapped around the upper arm of the individual to stop blood flow. This will enlarge the veins present below the band to ensure easy insertion of the needle into the vein
  • The needle injection site is first cleaned using alcohol to sanitise the area
  • A needle is then inserted into the vein and a tube is attached to the needle to collect the blood sample
  • Once enough blood has been collected, the band is removed from the arm
  • Cotton is placed over the site as the needle is removed, pressure is applied to stop bleeding and a bandage is applied to prevent infections

Few individuals may feel a quick sting or pinch during blood withdrawal. A feeling of tightness may be felt when the band is wrapped around the upper arm. 

Some risks associated with this test are:

  • Difficulty in obtaining the sample
  • Excessive bleeding at the site of blood withdrawal
  • Unconsciousness
  • Hematoma (accumulation of blood under the skin)
  • Infection at the site where the needle is inserted

However, these risks can easily be reduced when proper precautionary measures are taken.

If the results are normal, it indicates that no microfilaria have been detected in the blood sample, and the possibility of filariasis can be out ruled; however, if microfilaria are detected in the bloodstream, it can indicate the presence of parasitic diseases, such as

  • Lymphangitis
  • Lymphadenitis
  • Elephantiasis
  • Tropical eosinophilia

Disclaimer: All results must be clinically correlated with the patient’s complaints to make a complete and accurate diagnosis. The above information is provided from a purely educational point of view and is in no way a substitute for medical advice by a qualified doctor. 

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  1. Kobayashi M et al. Detection of microfilarial antigen in circulating immune complex from sera of Wuchereria bancrofti-infected individuals. Am J Trop Med Hyg. 1997 Aug;57(2):200-4. PMID: 9288817
  2. Center for Disease Control and Prevention [internet], Atlanta (GA): US Department of Health and Human Services; Blood Specimens - Specimen Collection.
  3. Victorian Infectious Diseases Reference Laboratory. Filariasis (Microfilaria detection in blood). Melbourne, Victoria. [Internet]
  4. Bain BJ. Diagnosis from the blood smear. . N Engl J Med. 2005 Aug 4;353(5):498-507. PMID: 16079373
  5. University of Rochester Medical Center Rochester, NY. [Internet] Blood Smear
  6. Jaso J, Nguyen A, Nguyen AN. A synoptic reporting system for peripheral blood smear interpretation. Am J Clin Pathol. 2011 Mar;135(3):358-64. PMID: 21350088