Equine common variable immunodeficiency: lessons from 100 clinical cases.
Authors: Julia M, Felippe B
Journal: Equine veterinary education
Summary
# Editorial Summary: Equine Common Variable Immunodeficiency Recurrent infections and fever should prompt investigation for underlying immunodeficiency, particularly common variable immunodeficiency (CVID)—a late-onset B cell disorder characterised by inadequate antibody production that, whilst rare, carries significant clinical and management implications for equine practitioners. Analysis of 100 clinical cases revealed that affected horses most frequently present with recurrent respiratory infections, meningitis, ataxia, cholangiohepatitis, infectious colitis, and severe parasitism, alongside immune-mediated or lymphoproliferative conditions that complicate diagnosis and treatment. Diagnostic confirmation requires persistent hypogammaglobulinemia documented on at least two occasions—specifically serum IgG below 10.00 g/L and often IgM below 0.50 g/L—typically accompanied by peripheral B cell counts below 6% of circulating lymphocytes, though normal B cell distributions do not exclude the condition. The aetiology remains unknown despite examination of diverse breeds and geographic distribution, with no identified genetic mutations or clear inheritance patterns, suggesting either environmental triggers or heterogeneous disease mechanisms. Given that clinical management is intensive and costly with uncertain outcomes, practitioners must weigh diagnostic findings carefully against prognosis when counselling clients, particularly regarding the difficult decisions surrounding long-term management or euthanasia.
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Practical Takeaways
- •Recurrent fevers and infections should prompt immunodeficiency screening; diagnosis requires two separate IgG measurements below 10.00 g/L
- •Clinical management of CVID is intensive and expensive—early diagnosis is critical for discussing realistic prognosis and euthanasia decisions with owners
- •B cell counts alone are not diagnostic; immunological findings must be interpreted alongside clinical signs and serological data for definitive diagnosis
Key Findings
- •CVID diagnosis requires persistent serum IgG <10.00 g/L on at least 2 measurements, often with serum IgM <0.50 g/L
- •Most horses with CVID show peripheral blood B cell distribution below 6% of total lymphocytes, though some fall within normal reference intervals
- •Common clinical presentations include recurrent upper/lower respiratory infections, meningitis, ataxia, and cholangiohepatitis
- •No genetic mutation has been identified and disease distribution across multiple breeds and geographic locations does not support an obvious inherited mechanism