A Fatal Case of Powassan Virus Encephalitis. Issue 11 (5th October 2020)

• Record Type: Journal Article
• Authors: Yu, Qiqi; Matkovic, Eduard; Reagan-Steiner, Sarah; Denison, Amy M; Osborn, Rebecca; Salamat, Shahriar M
• Is Part Of: Journal of neuropathology and experimental neurology. Volume 79:Issue 11(2020)
• Page Start: 1239
• Page End: 1243
• Publication Date: 2020-10-05
• Subjects: Encephalitis -- Flavivirus -- Powassan virus -- Transmission electron microscopy -- Wisconsin; Neurology -- Diseases -- Periodicals; Neurology -- Diseases -- Physiopathology -- Periodicals; 616.8047
• DOI: 10.1093/jnen/nlaa094
• Languages: English
• ISSNs: 0022-3069

Abstract

Abstract: Powassan virus (POWV) is a flavivirus of the tick-borne encephalitis serogroup that causes a rare and potentially life-threatening neuroinvasive disease. Viral transmission occurs during zoonotic spillover from mammals by the bite of an infected tick in endemic regions of North America. The number of reported POWV cases has recently increased in the United States. We report a fatal case of POWV meningoencephalomyelitis in Northern Wisconsin following a documented tick bite. Histologic examination of the brain demonstrated widespread intraparenchymal and perivascular lymphohistocytic infiltration, microglial nodule formation, and marked neuronal degeneration, most severely involving the substantia nigra, anterior horn of spinal cord and cerebellum. Although no viral inclusions were seen in routine light microscopy, electron microscopy identified multiple neurons containing cytoplasmic clusters of virus particles ∼50 nm in diameter. POWV infection was confirmed using immunohistochemical analysis and reverse transcription-polymerase chain reaction. This report demonstrates in detail regional central nervous system involvement and ultrastructural characteristics of Powassan viral particles by transmission electron microscopy, while highlighting the utility of evaluating fixed autopsy tissues in cases of unexplained meningoencephalomyelitis.