Detection of La Crosse virus RNA in clinical specimens obtained from children with La Crosse infection.

BACKGROUND

La Crosse virus (LACV), a member of family Peribunyaviridae, genus Orthobunyavirus, is the leading cause of neuroinvasive arboviral infection in children in the United States. Diagnosis relies on detecting specific antibodies (IgG or IgM), a 4-fold titer rise or seroconversion, in patients with compatible presentations. NAAT used for LACV detection has largely been limited to mosquito, animal models or postmortem brain tissue. There is a lack of data on the performance of NAATs in clinical specimens from living patients.

METHODS

Children who had positive arbovirus serology tests and a diagnosis of LACV encephalitis were identified. Remnant specimens including plasma, serum, CSF, throat swab (THT) or nasopharyngeal sample (NP) submitted to the laboratory for other diagnostic testing were retrieved and tested with LACV-PCR. Medical records were reviewed for demographics, presenting symptoms and test results.

RESULTS

From June 2015 to October 2021, 61 patients had remnant specimens available for LACV-PCR and were included in this study. A total of 179 clinical specimens from these patients were tested, including 64 sera, 31 plasma, 33 CSF, 23 THT and 28 NP. Ten (5.3 %) samples collected from 8 (13.1 %) unique patients were positive for LACV RNA. The positive rates were 3.2 %, 0, 6.5 %, 3.5 % and 21.7 % for sera, plasma, CSF, NP and THT respectively.

CONCLUSION

There is limited utility of NAATs for diagnosis of LACV infection. NAATs may be useful in cases with delayed seroconversion or in immunocompromised individuals.