This technology includes a novel, isolated reassortant mammalian Orthoreovirus (MRV) isolated from pigs with neurological symptoms, for use in the development of vaccines and diagnostic tests. This isolate has S1 gene from MRV1 closed to bovine isolated, M2 gene from MRV2 and other 8 genes from MRV3 based on full-genome sequence analysis. MRV3 has been reported and isolated from the US pigs with diarrhea symptom. Compared to the reported swine MRV3 isolates that cause diarrhea in pigs, the novel reassortant MRV causes neurological disease in pigs.