CBC Interpretation - JOJO (Dog)

Key Abnormal Values Extracted

Highest Suspected Differential Diagnosis

#1 - Ehrlichia canis (Canine Monocytic Ehrlichiosis / CME)

• Severe thrombocytopenia (PLT 38) - occurs in >90% of acutely infected dogs; it is the most consistent CBC finding in E. canis infection
• Lymphocytosis - reactive/granular lymphocytosis is a hallmark, especially in the subclinical and chronic phases
• Monocytosis - the organism infects monocytes/macrophages; monocytosis is expected
• Eosinopenia - a feature of the inflammatory/stress response concurrent with ehrlichiosis
• WBC mildly elevated - consistent with the immune-reactive phase

#2 - Immune-Mediated Thrombocytopenia (IMT / ITP)

• PLT of 38 × 10³/µL represents severe thrombocytopenia (normal in dogs: 175-500)
• IMT is the most common acquired cause of severe thrombocytopenia in dogs
• Can be primary (idiopathic) or secondary (triggered by infection, vaccine, neoplasia)
• Lymphocytosis here may represent reactive immune activation
• Critically: IMT and Ehrlichia can co-exist, as E. canis is a known trigger for secondary IMT

#3 - Tick-Borne Rickettsial Co-infection (Anaplasma platys / Rocky Mountain Spotted Fever)

• Anaplasma platys causes cyclic thrombocytopenia in dogs
• Rickettsia rickettsii (RMSF) causes thrombocytopenia + lymphocytosis
• The combined leukogram (lymphocytosis + monocytosis + eosinopenia) with severe thrombocytopenia overlaps significantly with rickettsial disease

#4 - Lymphoproliferative Neoplasia (Lymphoma)

• Absolute lymphocytosis (5.5 × 10³/µL) with high WBC raises concern
• Thrombocytopenia in lymphoma can be secondary to bone marrow infiltration or concurrent IMT
• Monocytosis can reflect tumor-associated inflammation
• Less likely given the absence of leukemia-range WBC, but blood smear review for atypical lymphocytes and lymph node assessment are warranted

#5 - Sepsis / Bacterial Endocarditis

• Monocytosis is occasionally the sole leukogram change in dogs with sepsis or bacterial endocarditis (as noted in Merck Veterinary Manual)
• Consumptive thrombocytopenia via DIC is possible

Summary of Priority

CBC Interpretation - GUFFY (Dog)

Values at a Glance

Key Pattern Interpretation

1. Severe thrombocytopenia (PLT 46) - only ~10% of normal
2. Elevated MCHC (37.1) + MCH (24.8) - hyperchromia pattern
3. Anisocytosis flag (AT) with low RDW-CV - unusual combination (machine detecting abnormal RBC size variation despite low CV)

Highest Probable Differential Diagnoses

#1 - Babesia canis / Canine Babesiosis ⭐ TOP DIAGNOSIS

• Severe thrombocytopenia - immune-mediated platelet destruction is a hallmark; occurs in virtually all Babesia-infected dogs
• Elevated MCHC + MCH (hyperchromia pattern) - intravascular hemolysis releases free hemoglobin, causing falsely elevated MCHC on automated analyzers; also, in-saline agglutination of RBCs is common in Babesia (the machine "reads" clumped cells with higher hemoglobin density)
• Anisocytosis (AT flag) - regenerative response with mixed cell sizes (large reticulocytes + small fragmenting cells); Babesia causes RBC fragmentation (microangiopathic changes)
• Normal to slightly elevated WBC with neutrophilia (GR 71.7%) - mild neutrophilia consistent with inflammatory/hemolytic process without the lymphocytosis seen in Ehrlichia
• Eosinopenia - stress/inflammatory response
• Coombs positivity occurs in majority of Babesia cases - immune-mediated component also affects RBCs

#2 - Immune-Mediated Hemolytic Anemia (IMHA) with Secondary Thrombocytopenia (Evans Syndrome)

• High MCHC is a classic feature of intravascular hemolysis - free hemoglobin inflates MCHC artifactually
• Anisocytosis with spherocytes can raise MCHC (spherocytes are hyperchromic due to reduced surface area-to-volume ratio)
• Thrombocytopenia can be concurrent (Evans Syndrome = IMHA + IMT together)
• HGB and HCT are still normal here, suggesting early/compensated hemolysis or pre-anemic stage
• WBC with mild neutrophilia (GR 71.7%) fits the inflammatory leukogram of IMHA

#3 - Ehrlichia canis (Canine Monocytic Ehrlichiosis)

• Thrombocytopenia is the most consistent CME finding (>90% of cases)
• However, this CBC lacks the lymphocytosis and monocytosis that were present in JOJO's result
• The normal lymphocytes and monocytes make Ehrlichia less likely here compared to JOJO
• Still possible in the acute phase before full leukogram changes develop

#4 - Disseminated Intravascular Coagulation (DIC) Secondary to an Underlying Disease

• Consumptive thrombocytopenia
• Microangiopathic hemolysis can cause anisocytosis and schistocytes (which the AT flag may be detecting)
• Usually accompanied by additional coagulation abnormalities (prolonged PT/APTT)

#5 - Hemolytic Uremic Syndrome / Leptospirosis

• Thrombocytopenia + hemolysis + renal involvement
• Leptospira can cause both thrombocytopenia and hemolytic anemia

Comparison: GUFFY vs. JOJO

Summary

• Severe isolated thrombocytopenia (immune-mediated platelet destruction)
• Elevated MCHC/MCH suggesting intravascular hemolysis (even before overt anemia develops)
• Anisocytosis flag (RBC fragmentation/regenerative changes)
• Normal lymphocytes and monocytes (argues against Ehrlichia)
• Eosinopenia (inflammatory/stress response)

1. Blood smear - look for intraerythrocytic piroplasms (pear-shaped pairs in RBCs), spherocytes, schistocytes
2. Babesia PCR - most sensitive
3. Saline slide agglutination test (in-saline agglutination = strong indicator)
4. Coombs test - often positive in Babesia
5. Urinalysis - hemoglobinuria?
6. SNAP 4Dx - screens for Ehrlichia/Anaplasma co-infection simultaneously
7. Serum biochemistry - assess renal and hepatic function

Image 1 - Morula in a Monocyte (Blood Smear, Wright-Giemsa Stain)

Image 2 - E. canis Membrane-Bound Inclusion (Buffy Coat, High Power)

Image 3 - Comparison: Blood Smear (a) vs Buffy Coat (b)

What You're Looking For - Key Microscopic Features

Practical Points

• Morulae are rare - found in only 4% of peripheral blood smears in acute phase; don't rule out Ehrlichia if not seen
• Buffy coat smears (concentrated WBC layer) dramatically increase detection chances - always prefer these
• Best window for detection: Acute phase (1-4 weeks post-tick bite); morulae disappear in chronic phase
• PCR is far more sensitive than microscopy and is the gold standard for confirmation
• SNAP 4Dx serology is the practical first-line test in clinic - detects antibodies to E. canis