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Confidently identify parasites on blood smears
Blood film evaluation skills a little rusty when it comes to hemoparasites? Have no fear. Read on for tips to help you prepare a readable blood smear and identify what you see.


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Mycoplasma haemofelis

Facts

Mycoplasma haemofelis (formerly Haemobartonella felis) is an epicellular bacteria that may be transmitted by arthropod vectors (fleas), from queen to kitten, through direct cat bites, or through blood transfusions.

• Acute, recovery, and carrier states exist, and clinical disease is often seen in immunosuppressed cats.

Identification

Mycoplasma species are seen well with new methylene blue stain.

• These bacteria are typically seen along the periphery of erythrocytes within the feathered edge of the smear.

• They appear as extremely small cocci, rods, or rings with multiple bacteria per erythrocyte (Figures 6A & 6B). They are easily confused with Howell-Jolly bodies and stain precipitate (Figures 7 & 8).


6A & 6B. Mycoplasma haemofelis on a blood smear, which should not be confused with Howell-Jolly bodies (Figure 7) or stain precipitate (Figure 8). These very small epicellular inclusions are routinely seen on the edge, but inclusions can be seen on top of the red blood cell (Wright’s stain; 6A—40x, 6B—100x).

8. Stain precipitate can interfere with identification of any blood parasite. Mycoplasma haemofelis would be impossible to identify under these conditions (Wright’s stain).

7. Howell-Jolly bodies on a blood smear, which can be confused with M. haemofelis (Wright’s stain; 40x).

Clinical signs

• Cyclic fevers, weight loss, and fatigue

• Acute extravascular immune-mediated hemolytic anemia, or acute hemolytic anemia (feline infectious anemia)

Treatment

• Supportive treatment should be given as appropriate.

• There is no guaranteed treatment, but to target the infection, cats may be given doxycycline (10 mg/kg orally once a day for 21 days) chased with water or enrofloxacin (5 mg/kg orally once a day for 14 days).

To become proficient at identifying all hemoparasites, you should look at both normal and abnormal smears often. You will gain experience in determining the difference among stain precipitate, normal inclusions, and invaders. Good luck in your search.

Melissa Andrasik, BS, RVT, is an adjunct instructor for Maple Woods Veterinary Technology Program in Kansas City, Mo.


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