Prevalence of antibodies to Neospora sp. in horses from Alabama and characterisation of an isolate recovered from a naturally infected horse [corrected].

The research aimed to determine the prevalence of antibodies to Neospora, a parasitic eldentity, in horses based in Alabama and also sought to characterise an isolate found in a naturally infected horse. The findings indicated that the antibodies were present in 11.5% of the tested horses. It further speculated that the horse-derived isolate is likely another instance of N. hughesi, suggesting that this infection might be widespread in different geographical locations in the United States.

Study Methodology

• The researchers utilized an Indirect Fluorescent Antibody Test (IFAT) to detect for the presence of Neospora-specific IgG antibodies in serum collected from five hundred and thirty-six horses that were asymptomatic and were initially being tested for equine infectious anemia virus infection.
• A special case in the study involved a 13-year-old horse that exhibited Central Nervous System (CNS) disease. The horse’s postmortem examination was conducted with an aim to isolate and cultivate any protozoal organisms that may be present.

Results and Findings

• The results demonstrated that 11.5% of the serum samples (62 out of 536) contained IgG antibodies to Neospora, with Endpoint titres for the positive samples ranging from 1:50 to 1:1600.
• Tachyzoites, a phase in the lifecycle of certain protozoan parasites, were first observed in bovine turbinate cell cultures 32 days after they were inoculated with spinal cord homogenates from the CNS-diseased horse. These tachyzoites were reactive to serum known to be positive for N. caninum from different animals but did not react to murine anti-Toxoplasma gondii or equine anti-Sarcocystis neurona serum.
• Through comparison of ultrastructural features and immune-dominant proteins of tachyzoites, it was determined that these were identical to N. hughesi, a species recently described from a naturally infected horse.

Conclusion

• The researchers concluded that the isolate, designated as NA1, from the naturally infected horse is likely N. hughesi, but this required additional molecular characterisation for definite confirmation.
• The study provides further evidence that N. hughesi is indeed a valid species and that Neospora infections may be quite widespread across different regions in the United States.