Heartworm detection: direct smear. What is the first step after collecting a sample?

Heartworm detection: direct smear. What is the first step after collecting a sample?

• A. Examine the slide under the 10x objective.
• B. Stain the slide with a dye and wait.
• C. Air-dry the smear before examining.
• D. Immediately after collecting sample, place a single drop of blood on a microscope slide and add cover slip.

Answer: (D)

In a direct blood smear for heartworm detection, you want to observe living microfilariae in fresh blood. The first step after collection is to place a single drop of blood on a clean slide and cover it with a coverslip to create a quick wet mount. This preserves motility and clear morphology for rapid microscopic viewing. Staining isn’t used here because it would kill or obscure the organisms, and letting the smear air-dry would cause drying artifacts and make motile microfilariae harder to detect. Placing the blood on the slide and applying the cover slip right away gives the best chance to see any organisms present.

In a direct blood smear for heartworm detection, you want to observe living microfilariae in fresh blood. The first step after collection is to place a single drop of blood on a clean slide and cover it with a coverslip to create a quick wet mount. This preserves motility and clear morphology for rapid microscopic viewing. Staining isn’t used here because it would kill or obscure the organisms, and letting the smear air-dry would cause drying artifacts and make motile microfilariae harder to detect. Placing the blood on the slide and applying the cover slip right away gives the best chance to see any organisms present.