Traditionally, diagnostic methods such as faecal egg counts (FEC) and faecal culture are used to assess infection status and guide treatment decisions. However, these approaches are not without limitations. FEC lacks sensitivity in detecting low-burden infections, may not reflect larval stages, and shows poor correlation between egg counts and actual worm burdens. Faecal cultures can help identify parasite species but are time-consuming and technically demanding.
A recent study by Falmata Kyari and colleagues from the Departments of Veterinary Parasitology and Veterinary Medicine at the University of Maiduguri, Nigeria, explored whether a novel blood-based index could provide a more accurate, non-invasive, and cost-effective diagnostic option. Their work focused on the Systemic Immune-Inflammatory Index (SII), a parameter calculated from routine haematological values: platelet count, neutrophil count, and total white blood cell count.
The SII is a composite biomarker reflecting the balance between pro-inflammatory and anti-inflammatory immune responses. It is calculated as:
SII = (Platelet count × Neutrophil count) ÷ Total white blood cell count
In human medicine, SII has been widely studied as a prognostic marker for systemic inflammation, sepsis, cardiovascular disease, and cancer progression. Elevated values typically indicate heightened inflammatory activity and a poorer clinical outlook.
In horses, however, the application of SII as a diagnostic tool is still in its infancy. Kyari’s study represents one of the first attempts to apply this marker in equine parasitology.
The research team conducted a cross-sectional study involving 164 apparently healthy horses. All animals underwent clinical examination to confirm baseline health and were excluded if they had received recent anthelmintic treatment.
Blood and faecal samples were collected. Based on faecal egg counts and faecal culture, the horses were classified as Infected (n = 66) and Non-infected (n = 98).
The SII was then calculated for each horse using routine haematology. Receiver Operating Characteristic (ROC) curve analysis was applied to assess the diagnostic accuracy of SII in predicting nematode infection status.
Key Findings:
- Prevalence: Overall nematode prevalence was 40.2%. Interestingly, cyathostomin infections were detected in only 14 horses (7 single infections and 7 mixed), a figure much lower than typically reported in temperate regions. This discrepancy may reflect climatic influences, differences in parasite ecology, or management and deworming practices in Nigerian equine populations.
- Infection severity: Horses with mixed nematode infections carried the heaviest burdens, averaging 1,805 ± 293 eggs per gram (epg). Cyathostomum spp. infections were particularly striking, with mean egg counts of 2,264 ± 133 epg.
- SII values: Surprisingly, SII values were lower in infected horses (0.06) compared to non-infected horses (0.19), a reversal of the pattern seen in human inflammatory conditions. This suggests that equine immune regulation during nematode infection may differ fundamentally from human responses.
- Correlation with egg counts: There was a significant negative correlation between SII and epg (r = -0.6023; P < 0.0001).
- Diagnostic performance: The SII demonstrated exceptional predictive accuracy, with an area under the ROC curve (AUC) of 0.990. An SII cut-off value of ≤0.108 offered 98.5% sensitivity and 100% specificity, validated by a high Youden index of 0.985.
This study suggests that SII, derived from simple blood parameters already included in routine haematology panels, could serve as a powerful adjunct tool for diagnosing nematode infections in horses.
However, certain caveats remain. The study was region-specific, and prevalence data differ markedly from findings in Europe and North America, where cyathostomins are often the dominant nematodes. Furthermore, the inverse SII response compared to human data highlights the need for further research into equine-specific immune mechanisms.
The work of Kyari and colleagues supports the potential of the Systemic Immune-Inflammatory Index as a novel diagnostic tool for nematode infections in horses. If validated across different populations and climates, SII could help veterinarians identify infected animals more reliably, enabling targeted anthelmintic treatment and better parasite management strategies.
For more details, see:
Kyari F, Pogu CJ, Mairiga IA, Adamu L.
The use of systemic immune inflammatory index as a predictor for nematodes infections in horses.
Parasite Epidemiol Control. (2025) 30:e00453.
No comments:
Post a Comment