Comparison of Sarcocystis neurona isolates derived from horse neural tissue

Sarcocystis neurona is a protozoan parasite that can cause neurological def icits in infected horses. The route of transmission is by fecal-oral transf er of sporocysts from opossums. However. the species identity and the lifec ycle are not completely known. In this study, Sarcocystis merozoites from e ight isolates obtained from Michigan horses were compared to S. neurona fro m a California horst (UCD1), Sarcocystis from a grackle (Cornell), and five Sarcocystis isolates from feral opossums from Michigan. Comparisons were made using several techniques. SDS-PAGE analysis with silv er staining showed that Sarcocystis spp. from the eight horses appeared the same, but different from the grackle isolate. One Michigan horst isolate ( MIH6) had two bands at 72 and 25 kDa that were more prominent than the UCD1 isolate and other Michigan horse isolates. Western blot analysis showed th at merozoites of eight of eight equine-derived isolates, and the UCD1 S. ne urona isolate had similar bands when developed with serum or CSF of an infe cted horse. Major bands were seen at 60, 44, 30, and 16 kDa. In the grackle (Cornell) isolate, bands were seen at 60, 44, 29, and 16 kDa. DNA from mer ozoites of each of the eight equine-derived isolates and the grackle-derive d isolate produced a 334 bp PCR product (Tanhauser et al., 1999). Restricti on fragment length polymorphism (RFLP) analysis of these horse isolates sho wed banding patterns characteristic for S. neurona. The grackle (Cornell) i solate had an RFLP handing pattern characteristic of other S. falcatula spe cies. Finally, electron microscopy examining multiple merozoites of each of these eight horse isolates showed similar morphology, which differed from the grackle (Cornell) isolate. We conclude that the eight Michigan horse is olates are S. neurona species and the grackle isolate is an S. falcatula sp ecies. (C) 2001 Elsevier Science B.V. All rights reserved.