Necrotizing mycotic vasculitis with cerebral infarction caused by Aspergillus niger in a horse with acute typhlocolitis

An 18-year-old Morgan mare was presented to the Veterinary Medical Teaching Hospital, University of Illinois, with a 10-day history of watery diarrhea , depression, and dysphagia. On admission, the animal was severely dehydrat ed, depressed, and unable to swallow and had no clinical signs of diarrhea. The respiratory and heart rate and body temperature were within normal lim its. Following fluid therapy, the mare developed severe watery diarrhea and continued to be depressed, incoordinated, and dysphagic. The animal died o n the fourth day after admission and was sent to the Laboratories of Veteri nary Diagnostic Medicine for necropsy. Gross postmortem findings were consi stent with an acute cerebral infarction in the right cerebral hemisphere, a n acute necrotizing typhlocolitis, multifocal petechial and ecchymotic hemo rrhages, enlarged and congested pars intermedia of the pituitary gland, and marked bilateral adrenocortical hyperplasia with multifocal areas of necro sis and hemorrhage. Histologic evaluation of the affected brain demonstrate d an area of coagulative necrosis of the gray matter, with hemorrhage, vasc ulitis, and thrombosis. There were many fungal hyphae 3.5-6.0 mu m, pale ba sophilic, septate, and occasionally branching at 45 degrees present in the arterial walls and throughout the necrotic tissue. Immunohistochemical anal ysis revealed Aspergillus niger as the etiologic agent responsible for the mycotic vasculitis and infarction in the brain. Bacteria culture and immuno histochemical staining of the colon and cecum failed to demonstrate specifi c pathogens.