Toxoplasma gondii seroprevalence and association with equine protozoal myeloencephalitis: A case-control study of Californian horses.
Authors: James K E, Smith W A, Packham A E, Conrad P A, Pusterla N
Journal: Veterinary journal (London, England : 1997)
Summary
# Editorial Summary: Toxoplasma gondii and Equine Protozoal Myeloencephalitis Toxoplasmosis has largely been overlooked as a potential neurological disease in horses, despite variable seroprevalence rates reported across different geographic regions. This Californian case-control study examined 720 horses presenting with neurological signs consistent with equine protozoal myeloencephalitis (EPM) alongside matched controls, using indirect fluorescent antibody testing (IFAT) to detect *Toxoplasma gondii* antibodies across multiple titre thresholds. Horses displaying clinical EPM signs demonstrated 3.55-fold higher odds of testing seropositive at the critical titre of 320 (P<0.01), with the association strengthening substantially during autumn months, when affected horses showed 6.4 times greater odds of high *T. gondii* titres compared to neurologically normal animals. These findings suggest that concurrent or primary toxoplasmosis may contribute to EPM-like clinical presentations and warrant investigation of cerebrospinal fluid (CSF) serology and organism isolation in suspected EPM cases. For practitioners managing neurological horses, particularly in autumn, considering *T. gondii* as a differential diagnosis and employing targeted serological testing—including paired serum and CSF samples—could improve diagnostic accuracy and refine treatment protocols accordingly.
Read the full abstract on PubMed
Practical Takeaways
- •Consider T. gondii serology and CSF testing in horses presenting with neurologic signs consistent with EPM, particularly during autumn months
- •Use standardized titre cut-offs (≥320) for T. gondii serologic interpretation in EPM suspects to improve diagnostic accuracy and clinical decision-making
- •Recognize that T. gondii infection may be more prevalent in California horses with neurologic disease than previously appreciated, warranting investigation in differential diagnosis
Key Findings
- •Horses with clinical signs compatible with EPM had 3.55 times the odds of T. gondii seropositivity at titre 320 compared to healthy controls (P<0.01)
- •In autumn season specifically, EPM suspect horses had 6.4 times the odds of T. gondii seropositivity at the same titre cut-off
- •Seroprevalence of T. gondii varied significantly across different titre thresholds, demonstrating importance of standardized cut-off selection
- •High T. gondii titres may be reflective of toxoplasmosis as an associated or contributing factor in EPM cases