Comparison of Coccidioides immitis serological antibody titres between forms of clinical coccidioidomycosis in horses.
Authors: Higgins Jill C, Pusterla Nicola, Pappagianis Demosthenes
Journal: Veterinary journal (London, England : 1997)
Summary
# Serological Antibody Titres as Prognostic Indicators in Equine Coccidioidomycosis Coccidioides immitis infection in horses manifests across a spectrum of clinical forms—from reproductive loss to life-threatening disseminated disease—yet the relationship between serological antibody responses and disease severity remains poorly characterised. Higgins and colleagues analysed 39 confirmed cases from a 23-year database at UC Davis, stratifying horses into six disease categories and quantifying IgG titre distributions to identify prognostic patterns. Significantly higher geometric mean antibody titres were associated with the most severe presentations: disseminated disease (titre 104) and pneumonia with thoracic effusion (titre 226) showed mortality rates of 90%, whilst localised forms including abortion (titre 4), osteomyelitis alone (titre 13) and cutaneous involvement (titre 5) demonstrated survival rates exceeding 80%. Statistical differences were confirmed between abortion cases and all pulmonary manifestations (P=0.001 to 0.003), suggesting that titre measurement could serve as a practical prognostic tool alongside clinical and radiographic findings. For practitioners managing suspected coccidioidomycosis in endemic regions, serology titre quantification may help guide treatment intensity and owner counselling regarding survival expectations, particularly when distinguishing between localised disease amenable to medical or surgical management and overwhelming systemic infection.
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Practical Takeaways
- •In horses with suspected coccidioidomycosis, serological titre levels can help predict disease severity and prognosis—high titres (>100) generally indicate disseminated or severe pulmonary disease with poor survival outlook
- •Horses presenting with abortion or localized bone/skin lesions typically have low titres and better survival rates, warranting more aggressive treatment attempts
- •Use serological titre results alongside clinical signs to inform owners about realistic treatment outcomes and management decisions
Key Findings
- •Significant statistical differences in IgG antibody titre distribution were found between abortion cases (geometric mean titre=4) and pulmonary/disseminated disease categories (P=0.001–0.003)
- •Higher serological titres were associated with poorer prognosis; disseminated disease (GMT=104) and pneumonia with effusion (GMT=226) were overwhelmingly fatal (19/21 deaths)
- •Lower titre categories showed better survival rates: abortion, bone involvement, and cutaneous disease had 10/12 survivors with less severe clinical manifestations
- •Serological antibody titre measurement may serve as a prognostic indicator to distinguish disease form and severity in equine coccidioidomycosis