Case report: Diagnostic findings of bovine neurological cases at the Iowa State University Veterinary Diagnostic Laboratory between January 2017 and May 2021

Abstract

This study reviews the Iowa State University Veterinary Diagnostic Laboratory (ISU-VDL) computer records of bovine neurological cases submitted from January 2017 to May 2021. There were 236 cases diagnosed as follows: listeriosis (83), polioencephalomalacia (44), thrombomeningoencephalitis (23), miscellaneous bacteria (22), lead toxicosis (21), nitrate toxicosis (18), urea toxicosis (9), nervous coccidiosis (5), hypomagnesemia (5), sodium toxicosis (3), rabies (1), herpesvirus type 6 (1), and epsilon toxin from Clostridium perfringens type D (1). Most histories did not provide specific descriptions of the type of neurological signs, which could better target diagnostic investigation. However, each condition had specific peculiarities relevant from a post-mortem diagnostic perspective. For listeriosis, confirmation of Listeria monocytogenes using IHC was considered superior to bacterial culture, with 16/19 (84%) positive by IHC compared to 23/59 (38.9%) of cases positive by culture. In 44/83 (53.0%) of cases, histopathological examination mentioned that cerebellum and cerebrum were unremarkable, implying that without submission of the entire brain, particularly brain stem and obex, listeriosis cannot be ruled out. In 44 cases histologically diagnosed as polioencephalomalacia, when ultraviolet light (Wood’s lamp) was performed, it revealed multifocal areas of apple-green autofluorescence in 13/21 (61.9%) of brains, indicating that false negatives can occur with this technique. A substantial number of submissions were toxicoses that required specific sample types to confirm a diagnosis. For lead, whole blood, liver or kidney was necessary. For nitrate and urea toxicosis, appropriate samples were ocular fluid or the incriminating feed/water source. Confirmation of sodium toxicosis relied on sodium analysis of brain tissue.