Blood smear technique for veterinarians

Page last updated: Tuesday, 2 May 2017 - 4:26pm

Please note: This content may be out of date and is currently under review.

Troubleshooting blood smear errors

Reference: https://ahdc.vet.cornell.edu/Sects/ClinPath/sample/test/hema.cfm
Problem Solutions
Short smear
  • Use a larger droplet of blood.
  • Decrease the angle of the spreader slide.
  • Decrease the speed of the spreader slide.
Long smear/no feathered edge
  • Use a smaller drop of blood.
  • Increase the angle of the spreader slide.
  • Increase the speed of the spreader slide.
Thick smear
  • Use smaller drop of blood.
  • Decrease the angle of the spreader slide.
  • Increase the speed of the spreader slide.
Thin smear
  • Use a larger drop of blood.
  • Increase the angle of the spreader slide.
  • Decrease the speed of the spreader slide.
Smear has waves and ridges
  • Maintain even contact and a smooth motion.
  • Increase the speed of the spreader slide.
  • Relax the wrist, reduce downward pressure on the spreader slide.

Blood smears - common errors

Blood droplet error examples

The blood droplet on the left is too big and will result in a thicker smear. The blood droplet on the right is the preferred size.

Blood smear slides of perfect and undesirable examples.

Smear technique - left to right:

  • slide 1 - perfect smear
  • slide 2 - smear technique interrupted in middle
  • slide 3 - smear was skewed
  • slide 4 - blood droplet too thick
  • slide 5 - smear too short.

Infectious diseases in Australia diagnosed by blood smear

Disease Species Transmission Disease status
Anaplasmosis cattle tick-borne endemic-northern Australia
Babesiosis cattle tick-borne endemic-northern Australia
Mycoplasma ovis (eperythrozoonosis) sheep iatrogenic, blood-sucking insects (midges, mosquitoes, flies) endemic
Bovine anaemia due to Theileria orientalis group (BATOG) cattle tick-borne endemic in eastern Australia - first diagnosed in WA in 2013

cytology slide of bovine theileria

Bovine erythrocytes infected with protozoal parasites from the Theileria orientalis group. The parasite is known as a piroplasm when it is within an erythrocyte. Piroplasms appear in erythrocytes from day 10 post-infection. Naïve, young, pregnant or immunecompromised animals may develop severe anaemia and mortalities can be as high as 30% in a herd.

Haemaphysalis longicornis (common bush tick)
Haemaphysalis longicornis (common bush tick)

Ticks are vectors for many protozoal and mycoplasmal parasites. For Theileria spp., transmission in the tick is known to be transstadial or life stage-to-life stage. A larva or nymph stage tick transmits the parasite to the next animal it feeds on. Trans-ovarial transmission (transmission from infected females to their larvae) does not occur. Control of ticks and good sanitation when using needles and surgical equipment minimises the introduction of these infectious parasites into naïve populations.

Contact information

Livestock Biosecurity