Assessing rodents as carriers of pathogenic leptospires in the U.S. Virgin Islands: the risk to animal and public health

Authors: HAMOND, C - Oak Ridge Institute For Science And Education (ORISE); BROWNE, A - US Department Of Health And Human Services (HHS); Hornsby, Richard; LECOUNT, K - US Department Of Agriculture (USDA); ANDERSON, T - US Department Of Agriculture (USDA); STUBER, T - US Department Of Agriculture (USDA); DE WILDE, L - US Department Of Health And Human Services (HHS); CRANFORD, H - US Department Of Health And Human Services (HHS); BROWNE, S - US Department Of Health And Human Services (HHS); BLANCHARD, G - US Department Of Agriculture (USDA); HORNER, D - National Park Service; TAYLOR, M - US Department Of Health And Human Services (HHS); EVANS, M - Us Fish And Wildlife Service; ROTH, J - US Department Of Health And Human Services (HHS); BISGARD, K - Centers For Disease Control And Prevention (CDC) - United States; SALZER, J - Centers For Disease Control And Prevention (CDC) - United States; SCHAFER, I - Centers For Disease Control And Prevention (CDC) - United States; ELLIS, B - US Department Of Health And Human Services (HHS); Alt, David; SCHLATER, L - US Department Of Health And Human Services (HHS); Nally, Jarlath; ELLIS, E - US Department Of Health And Human Services (HHS)

Submitted to: Scientific Reports
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/30/2021
Publication Date: 1/21/2022
Citation: Hamond, C., Browne, A.S., Hornsby, R.L., Lecount, K., Anderson, T., Stuber, T., De Wilde, L.H., Cranford, H.M., Browne, S.K., Blanchard, G., Horner, D., Taylor, M.L., Evans, M., Roth, J., Bisgard, K., Salzer, J., Schafer, I., Ellis, B., Alt, D.P., Schlater, L., Nally, J.E., Ellis, E.M. 2022. Assessing rodents as carriers of pathogenic leptospires in the U.S. Virgin Islands: the risk to animal and public health. Scientific Reports. 12. Article 1132. https://doi.org/10.1038/s41598-022-04846-3.
DOI: https://doi.org/10.1038/s41598-022-04846-3

Interpretive Summary: The U.S. Virgin Islands were directly struck by Category 5 Hurricanes Irma and Maria in September 2017, generating record-breaking rainfalls and extensive flooding. Following these natural disasters, the Virgin Islands Department of Health reported the first-ever cases of leptospirosis and a follow-up seroprevalence study among residents showed evidence of exposure to Leptospira. Since the transmission of leptospirosis is maintained by persistently infected rodents, we collected serum and kidney samples from USVI rodents to determine their role in the carriage of pathogenic Leptospira. Results confirm that almost half of all rodents sampled were actively excreting Leptospira into the environment. Three different species of pathogenic Leptospira were identified including L. borgpetersenii, L. kirschneri and L. interrogans. These results provide novel findings that will be applied to limit future zoonotic transmission of leptospirosis in USVI.

Technical Abstract: Leptospirosis is a global zoonotic disease. Rodents are a major reservoir host of disease transmission; leptospires colonize the proximal renal tubules and are excreted via urine to contaminate water and soil where they may survive for extended periods of time. Leptospirosis can be severe for both humans and domestic animals. The aim of this study was to determine if rodents in the U.S. Virgin Islands are reservoir hosts of leptospires and what species of Leptospira may be involved. Rodents were trapped in each of the three main US Virgin Islands: Saint Croix (STX), Saint Thomas (STT) and Saint John (STJ). Kidney samples were collected aseptically at necropsy and examined for the presence of leptospires by dark-field microscopy (DFM), culture, fluorescent antibody testing (FAT), and real time PCR (rtPCR). A total 140 rodents were captured comprising Mus musculus (112) and Rattus rattus (28): 73 in STX, 28 in STT and 39 in STJ. Forty-nine (35 percent) samples were positive by DFM. By FAT, 63/140 (45 percent) were positive. Sixty (42.8 percent) samples were culture positive and 61/140 (43.7 percent) were positive by rtPCR. Molecular typing indicated that 48 isolates were L. borgpetersenii and 3 were L. kirschneri; the remaining 9 cultures comprised mixed species of leptospires. In the single sample that was culture negative but PCR positive, genotyping directly from the kidney identified L. interrogans. Serotyping of L. borgpetersenii isolates identified serogroup Ballum. This study demonstrates that rodents are reservoir hosts of L. borgpetersenii, L. kirschneri and L. interrogans in the US Virgin Islands and highlights their potential role in the transmission of infection to humans and domestic animals. This study represents a significant contribution to the knowledge of the ecoepidemiology of leptospirosis in USVI. Control and prevention efforts need to be multidisciplinary and multi-sectorial, making it a prime candidate for the One Health approach.