Animals exposed to Leptospira Serogroups not included in bacterins in the United States and Puerto Rico

Authors: ANDERSON, TAMMY - US Department Of Agriculture (USDA); HAMOND, CAMILA - US Department Of Agriculture (USDA); HALUCH, ANDREA - US Department Of Agriculture (USDA); TOOT, KARI - US Department Of Agriculture (USDA); Nally, Jarlath; LECOUNT, KAREN - US Department Of Agriculture (USDA); SCHLATER, LINDA - US Department Of Agriculture (USDA)

Submitted to: Tropical Medicine and Infectious Disease
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/14/2023
Publication Date: 3/22/2023
Citation: Anderson, T., Hamond, C., Haluch, A., Toot, K., Nally, J.E., LeCount, K., Schlater, L.K. 2023. Animals exposed to Leptospira Serogroups not included in bacterins in the United States and Puerto Rico. Tropical Medicine and Infectious Disease. 8(3). https://doi.org/10.3390/tropicalmed8030183.
DOI: https://doi.org/10.3390/tropicalmed8030183

Interpretive Summary: Leptospirosis is a worldwide zoonotic disease caused by a group of unique bacteria, pathogenic Leptospira. These bacteria are classified in two ways: 1) according to their genotype (species) and 2) according to their phenotype (serogroup and serovar). Animal leptospirosis can be caused be multiple different serogroups. In this study, sera samples were screened to identity serogroups of Leptospira that are associated with animals in the U.S.A. and Puerto Rico. A total of 568 sera were submitted for diagnostic, surveillance, or import/export testing from the U.S. and Puerto Rico. Overall seropositivity was 51.8% (294/568), with agglutinating antibodies found in 115 (39.1%) cattle, 84 (28.6%) exotic animals, 38 (12.9%) horses, 22 (7.5%) goats, 15 (5.1%) dogs, 11 (3.7%) swine, and 9 (3.1%) sheep. The serogroups with highest levels of detection were Australis, Grippotyphosa and Ballum. Results showed that animals were exposed to serogroups that are not included in commercial bacterin vaccines, including Ballum and Tarassovi.

Technical Abstract: Leptospirosis is a worldwide zoonotic disease. Pathogenic leptospires colonize the renal tubules and genital tract of animals and are excreted via urine. Transmission occurs via direct contact or through contaminated water or soil. The microscopic agglutination test (MAT) is the gold standard for the serodiagnosis of leptospirosis. The present study aims to evaluate animal exposure to Leptospira in the U.S. and Puerto Rico during 2018-2020. The presence of antibodies against pathogenic Leptospira spp. was assessed with the MAT according to the standards of the World Organisation for Animal Health. A total of 568 sera were submitted for diagnostic, surveillance, or import/export testing from the U.S. and Puerto Rico. Seropositivity was 51.8% (294/568) with agglutinating antibodies found in 115 (39.1%) cattle, 84 (28.6%) exotic animals, 38 (12.9%) horses, 22 (7.5%) goats, 15 (5.1%) dogs, 11 (3.7%) swine, and 9 (3.1%) sheep. The most detected serogroups were Australis, Grippotyphosa and Ballum. The results showed that animals were exposed to serogroups/serovars not included in commercial bacterins such as Ballum, Bratislava (only in swine vaccine) and Tarassovi. Our findings suggest that more studies should include culture and concomitant genotyping to reduce animal disease and zoonotic risk through efficacious vaccine and diagnostic strategies.