Detecting Heartworms in Dogs With a Microfilarial Concentration Test

Heartworm in dogs is a parasite that, if allowed to go unchecked, can ultimately lead to congestive heart failure. While a microscopic examination of a blood sample can confirm the presence of offspring (microfilaria), it isn't sensitive enough to totally rule out heartworms if the microfilaria aren't visible. For that, a microfilarial concentration test is necessary.

Microfilarial Concenteation Tests

There are two types of microfilarial concentration tests for identifying the existence of heartworms. Both require taking a blood sample for examination and treating it with a chemical to break down the blood cells.

  • The filter test - the treated blood sample is forced through a filter, trapping the microfilaria. The filter is then subjected to microscopic analysis to determine the presence of microfilaria.
  • The modified Knott's test - the treated blood sample is spun in a mechanical device called a centrifuge. The top part of the separated blood is poured away and the contents in the bottom of the tube are microscopically examined for the presence of microfilaria.

Medication as Treatment For Heartworm in Dogs

Once the microfilaria are identified, appropriate dog heartworm treatment begins. Heartworm medication is prescribed and once the full course of treatment is complete, a follow-up microfilarial concentration test will usually be conducted to ensure the heartworm infestation has been eliminated.