Seroprevalences of Toxoplasma gondii and Neospora sp. infections in Swedish horses.

This research perspective investigates the prevalence of two parasitic infections in Swedish horses, Toxoplasma gondii and Neospora sp., indicating that 0.5% and 1% of tested horses carried T. gondii and Neospora sp. antibodies, respectively. The study emphasized the need for a critical evaluation of serological analyses, particularly for methods that haven’t been validated for the animal species under investigation.

Methodology and Findings

• The researchers collected serum samples from 414 Swedish horses and tested for the presence of Toxoplasma gondii and Neospora sp. antibodies.
• The T. gondii direct agglutination test (DAT) was employed. From 414 sera, 5 (or 1%) had a titre (a measurement of the concentration of antibodies) greater than 1:40.
• Of these 5 sera, only 2 were positive when tested through immunoblotting against T. gondii antigens, leading to a T. gondii seroprevalence (the level of a pathogen in a population as measured by antibody presence) of 0.5%.

Neospora Testing

• The Neospora iscom-ELISA test, despite not being validated for equine sera, was used initially, selecting all sera with an optical density exceeding 0.200 absorbance units for further scrutiny using immunoblot analysis.
• Out of the 39 sera tested by immunoblotting for Neospora, 4 reacted with at least two of the immunodominant Neospora antigens that were recognized by the positive control sera, indicating positive results.
• These 4 positives in testing resulted in a Neospora infection seroprevalence of 1% in the tested Swedish horse population, marking the first evidence of Neospora infection in Swedish equines.

Research Implications

• The study draws attention to the necessity of scrutinizing and critically evaluating results of serological analyses. It underlines that some evaluation methods may not be valid or reliable for certain animal species, hence validation for those specific animal species is necessary for accurate results.
• In this study, the Neospora iscom ELISA test had not been validated for equine sera, resulting in initial screening only and necessitating follow-up testing using immunoblot analysis.
• The results led to the first-ever confirmation of a Neospora infection in Swedish horses. It added to the epidemiological data on the prevalence of parasitic infections in horses, an issue of considerable veterinary importance for control and potential prevention strategies.