Serological investigation of transplacental infection with Neospora hughesi and Sarcocystis neurona in broodmares.
Authors: Pusterla Nicola, Mackie Sarah, Packham Andrea, Conrad Patricia A
Journal: Veterinary journal (London, England : 1997)
Summary
# Editorial Summary: Transplacental Transmission of Neospora hughesi and Sarcocystis neurona Neospora hughesi and Sarcocystis neurona are protozoan parasites associated with neurological disease in horses, yet their routes of transmission remain incompletely understood. Using serological testing via indirect fluorescence antibody assay (IFAT), researchers tracked eight foals born to three persistently infected mares carrying N. hughesi and 174 foals from S. neurona-seropositive mares across two farms over several years. All eight foals from N. hughesi-positive dams showed maternal antibodies pre-colostrum, with notably high titres (640–20,480), whereas only one of 174 foals from S. neurona-exposed mares tested seropositive (titre 80). These findings suggest that transplacental transmission of N. hughesi occurs reliably from latently infected mares to their offspring, presenting a significant pathway for foal infection that differs substantially from S. neurona, which appears rarely transmitted in utero. For equine practitioners, this distinction is clinically important: broodmares with confirmed N. hughesi seropositivity warrant closer monitoring of their offspring for neurological signs, whilst the low transplacental transmission rate for S. neurona suggests other epidemiological routes (possibly vector-borne or environmental) merit greater investigative focus in endemic regions.
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Practical Takeaways
- •Broodmares with N. hughesi seropositivity should be considered at risk for transmitting infection to foals in utero; foals born to infected mares warrant serological monitoring
- •S. neurona seroprevalence in mares does not reliably predict foal infection, suggesting other transmission routes (environmental exposure) are more significant
- •Serological testing of foals before colostrum ingestion is essential to differentiate transplacental infection from passive maternal antibodies
Key Findings
- •8 foals born to 3 mares with persistent N. hughesi infection were seropositive pre-colostrum with titers ranging 640-20,480, indicating transplacental transmission occurred
- •Only 1 of 174 foals born to S. neurona seropositive mares tested positive (titer 80 pre-colostrum), suggesting transplacental transmission is rare for this pathogen
- •N. hughesi demonstrates consistent vertical transmission from latently infected dams, while S. neurona does not commonly transmit via this route