(Kiosk 3) An Equine Decline: Lacrosse and Jamestown Canyon Meningoencephalopathy Following Horse Bite

Case Diagnosis: Jamestown Canyon and La Crosse Viral meningoencephalitis

Case Description or Program Description: A 21-year-old female presented following a horse bite with fever, urinary retention, headache, photophobia, phonophobia, and diplopia evolving to include neck stiffness, flaccid quadriparesis, and altered mental status. She required intubation and hospitalization.

Setting: Acute inpatient rehabilitation

Assessment/Results: MRI brain and spine showed diffuse leptomeningeal enhancement of the cerebrum, cerebellum, and entire spinal cord as well as long segmental myelitis of the spinal cord. Serology was Jamestown Canyon Virus (JCV) IgM equivocal and La Crosse Virus (LCV) IgM positive, confirmed with positive JCV and LCV plaque reduction neutralization tests (PRNT). The patient required tracheostomy and PEG tube placement, and had return of function in bilateral upper extremities with continued lack of motor function in bilateral lower extremities. She was discharged to inpatient acute rehabilitation and progressed to minimal assistance for ADLs and independent for wheelchair mobility due to persistent lower extremity weakness. After tracheostomy decannulation and PEG tube removal, she was discharged to subacute rehabilitation for ongoing care.

Discussion (relevance): LCV and JCV are mosquito-borne California serogroup orthobunyaviruses and are exceedingly rare infections. LCV has an annual incidence rate of 0.004 per 100,000 adults. There are 10-75 cases of JCV annually in the United States. Patients present with fever, malaise, neck stiffness and GI upset; hyponatremia and upper respiratory symptoms are seen in LCV and JCV infections, respectively. LCV is diagnosed with detection of elevated LCV IgM antibody in serum, while JCV diagnosis is made via positive JCV IgM in serum and/or CSF and confirmation by PRNT due to significant cross-reactivity among the California serogroup. No antiviral therapy or vaccine exists for LCV or JCV and management is supportive. There are no reported cases of meningoencephalitis with co-infection of LCV and JCV.

Conclusions: This case describes meningoencephalitis with co-infection of LCV and JCV, and highlights improvement despite persistent weakness through supportive care and intensive inpatient rehabilitation.