Thogotoviruses/Bourbon Virus Clinical Presentation

Thogoto virus infection presents as a febrile illness with CNS involvement. Other Thotogovirus infections may also cause meningitis and encephalitis.

In 1966, 2 cases of Thogoto virus infection were reported in Nigeria. One of them presented in an adult as a febrile syndrome and optic neuromyelitis. The second case manifested in a 14-year-old boy as meningitis and resulted in death within a week as a result of complications from underlying sickle cell disease. ^[1]

Five cases of Dhori virus infection were described in laboratory workers infected accidentally while preparing cultural agents. In 3 cases, the infection manifested as acute fever (of up to 4 days’ duration) and severe toxic symptoms. The other 2 patients had central nervous system involvement manifesting as encephalitis with subcortical symptoms, pyramidal signs, and encephalopolyradiculoneuritis with paresthesia. ^[7]

In 2014, the newest member of the genus, Bourbon virus, was isolated when it infected a 50-year-old man with a known history of recent prior tick exposure in Bourbon County, Kansas, United States. He presented with obtundation, fever, leukopenia, and thrombocytopenia. He eventually developed multiorgan failure and cardiopulmonary arrest despite treatment with doxycycline for presumptive tick-borne infection. In a specimen that was sent to the Centers for Disease Control and Prevention (CDC) to evaluate for Heartland virus, the presence of a novel virus was noted in traditional viral isolation cell culture, as well as plaque reduction neutralization tests. Subsequent next-generation sequencing and phylogenetic analysis revealed a virus with significant resemblance to Thogoto virus. ^{[1, 8]}

A subsequent case of fatal Bourbon virus infection, reported in Missouri in 2017, included hemophagocytic lymphohistiocytosis (HLH) as a manifestation. The CDC confirmed Bourbon virus as the etiology. ^[6]

Physical examination may reveal several manifestations, such as fever, papular rash, lymphadenopathy, altered mental status, meningismus, and pyramidal signs. ^[1]

Thogotoviral infection may manifest as nonspecific symptoms such as the following:

• Nausea
• Vomiting
• Weakness
• Diarrhea
• Fever
• Papular rash
• Lymphadenopathy

Most viruses from the genus Thogotovirus affect the central nervous system, causing altered mental status, meningismus, headaches, and pyramidal signs. Infection may also manifest as sensitivity abnormalities and polyradiculoneuropathy. ^{[1, 7]}

Laboratory evaluation in most cases shows normal blood counts; however, Bourbon virus has been reported to cause leukopenia, lymphopenia, and thrombocytopenia, in addition to mild hyponatremia, hypokalemia, and increased levels of liver enzymes. ^[1]

Dhori virus infection in mice showed fulminant systemic illness, leukopenia, and increased levels of liver enzymes. ^[4]