A 1.5-year-old, F/S, mixed breed dog named Moxie was adopted from a rescue organization two weeks prior to presentation. One day ago, Moxie began to have hemorrhagic diarrhea and vomited once. CBC shows hematocrit of 35.7%, eosinophilia 3.17K, thrombocytopenia 130K. One blood smear with CBC data from the clinic hematology analyzer was submitted.
Notes: CBC data with results from the day prior listed on the right side. Values “flagged” with an asterisk should be confirmed by blood smear and/or dot plot review.
Questions: Why might some of the results be flagged? Why should they be reviewed microscopically?
Possible platelet clumps, which artifactually decrease the automated platelet count.
Unusual leukocyte distribution or detection (eg. eosinophilia, basophilia, atypical cells).
Cells that the analyzer cannot accurately differentiate (eg. bands, atypical cells).
Feathered edge of the smear. This area is reviewed for platelet clumps, large cells, leukocytes pushed out to the end of the smear, etc. There is large structure at the arrow.
Is this debris? A gauze fiber? Fibrin? A worm? If this is “real,” what is it?!
2. Mild normocytic, normochromic, non-regenerative anemia
3. Probable mild inflammatory leukogram with antigenic stimulation
4. Mild-to-moderate eosinophilia and mild basophilia
5. Mild thrombocytopenia
ClinPath Notes: Blood smear evaluation is of particular importance in veterinary species for a variety of reasons. In this case, the CBC data was confirmed and refined by a manual leukocyte differential and interpretation of the hematologic changes, but there was also a surprise finding of circulating microfilaria. Microfilaria are seen in patients with heartworm disease caused by Dirofilaria immitis, but microfilaria from Acanthocheilonema reconditum, which is non-pathogenic, can look very similar and should be differentiated by confirmatory testing.
Common hematologic abnormalities in dogs with heartworm are seen in this patient and include mild non-regenerative anemia, neutrophilia, thrombocytopenia, and eosinophilia with or without basophilia. These findings overlap with other parasitic infections and in a rescue dog with hemorrhagic diarrhea, these can also be due to gastrointestinal parasites, so it is important to exclude all potential underlying etiologies.
For more information regarding heartworm disease, please see the American Heartworm Society’s website.