Bovine immune-mediated hemolytic anemia: 13 cases (November 2008-August 2009).

BACKGROUND

Immune-mediated hemolytic anemia (IMHA) occurs in cattle; however, there are few reported cases.

OBJECTIVE

The aim of this study was to investigate the prevalence of IMHA in cattle with anemia, describe the associated clinical and laboratory findings, including osmotic fragility, and identify potential causative infectious agents or drugs.

METHODS

This study included 42 anemic cattle (HCT < 27.5%) comprising 31 females and 11 bulls with a mean age of 3.5 years referred to the University of Tehran Veterinary Teaching Hospital during a 10-month period. CBCs, saline osmotic fragility tests, direct Coombs' tests, and biochemical profiles were performed, and blood smears were evaluated for spherocytosis, parasites, and microscopic agglutination. Five clinically healthy cattle were used as controls for testing osmotic fragility of RBCs.

RESULTS

The Coombs' test was positive in 13/42 (30%) cattle; 5 had no evidence of concurrent disease or history of drug administration, and 8 had underlying or concurrent diseases, positivity for BLV, or exposure to drugs. The HCT (mean ± SE) of Coombs'-positive cattle (16 ± 1.7%) was significantly lower than that of Coombs'-negative animals (21 ± 0.8%). Hematologic and biochemical findings in cattle with IMHA included anisocytosis (2), polychromasia (2), basophilic stippling (2), spherocytosis (2), hyperfibrinogenemia (5), left-shifted neutrophilia (3), and hyperbilirubinemia (8). RBCs from Coombs'-positive anemic cattle were more fragile than those from Coombs'-negative anemic cattle. Four osmotically different populations of RBCs were detected in cattle with IMHA, whereas RBC populations were homogeneous in the Coombs'-negative anemic cattle and in normal cattle.

CONCLUSION

IMHA was identified in a significant proportion of anemic cattle. Idiopathic IMHA and IMHA secondary to infectious diseases and administration of certain drugs occur in cattle.