Evaluation of antigen and antibody assays for surveillance of Lassa virus in peri-domestic rodents in southeastern Sierra Leone: a cross-sectional study

Résumé fourni par la source

BACKGROUND: Lassa fever, caused by Lassa mammarenavirus (LASV), is a rodent-borne disease endemic to west Africa. Zoonotic surveillance of LASV provides epidemiological insights into its potential presence. We aimed to assess LASV antigen and antibody prevalence in peri-domestic rodents in southeastern Sierra Leone. METHODS: In this cross-sectional study, small mammal trapping was conducted in Kenema District, Sierra Leone, from Nov 8, 2018 to July 10, 2019. LASV antigen was detected with a nucleoprotein antigen rapid diagnostic test at necropsy, then compared with gold-standard quantitative RT-PCR in a subset of specimens to assess specificity and sensitivity. LASV IgG antibodies against nucleoprotein and glycoprotein were tested using a semi-quantitative ELISA in Mastomys and Rattus species. FINDINGS: Of the 373 specimens tested, 74 (20%) were positive for LASV antigen. Compared with qRT-PCR, antigen testing showed a specificity of 61·9% (95% CI 52·5-70·6) and sensitivity of 100·0% (95% CI 2·5-100·0%). 40 (11%) specimens tested positive for LASV nucleoprotein-specific IgG, whereas an additional 12 (3%) were only positive for LASV glycoprotein-specific IgG, respectively. Simultaneous antigen and IgG antibody presence was observed in some Mastomys sp specimens (odds ratio 0·43 [95% CI 0·24-0·73], p=0·0011). However, the relative strength of antigen response did not explain the variability in the IgG response to either glycoprotein (ρ 0·04 [95% CI -0·34 to 0·41], p=0·85) or nucleoprotein (ρ -0·23 [95% CI -0·52 to 0·11], p=0·17). INTERPRETATION: Although further evaluation is needed, the tools used in this study can aid in generating valuable public health data for LASV surveillance and in prioritising specimens for further downstream analyses. FUNDING: National Institute of Allergy and Infectious Diseases of the National Institutes of Health.

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