Leptospirosis is an archetypal One Health problem as described in the companion Currents in One Health article in the October 2022 issue of the Journal of the American Veterinary Medical Association by Sykes et al. A thorough understanding of leptospirosis requires a detailed analysis of the elaborate interplay among pathogenic leptospiral strains, host species, and the environment. Such an understanding is required to inform appropriate preventative measures including vaccine design, prophylaxis efforts, educational programs that help to reduce exposure to pathogenic spirochetes, as well as policy development. Because of the complex epidemiology of leptospirosis, a One Health approach as defined by the One Health Initiative Task Force is critical—an approach that calls for “the collaborative efforts of multiple disciplines working locally, nationally, and globally, to attain optimal health for people, animals and our environment.” Over the last three decades, progressive advances in cutting-edge molecular typing techniques, as well as our ability to rapidly generate and share large amounts of sequence data through establishment and growth of databases, have been central to accelerating a One Health understanding of the epidemiology of leptospirosis. Nevertheless, our dependence on serotype information because of the serovar-specific nature of current vaccines means that laborious serotyping efforts continue. With the advent of new approaches such as mRNA vaccines that are based on lipopolysaccharide immunogens, sequence- and/or proteomics-based typing methods may replace these methods.
Leptospirosis is a quintessential one health disease of humans and animals caused by pathogenic spirochetes of the genus Leptospira. Intra- and interspecies transmission is dependent on 1) reservoir host animals in which organisms replicate and are shed in urine over long periods of time, 2) the persistence of spirochetes in the environment, and 3) subsequent human-animal-environmental interactions. The combination of increased flooding events due to climate change, changes in human-animal-environmental interactions as a result of the pandemic that favor a rise in the incidence of leptospirosis, and under-recognition of leptospirosis because of nonspecific clinical signs and severe signs that resemble COVID-19 represents a “perfect storm” for resurgence of leptospirosis in people and domestic animals. Although often considered a disease that occurs in warm, humid climates with high annual rainfall, pathogenic Leptospira spp have recently been associated with disease in animals and humans that reside in semiarid regions like the southwestern US and have impacted humans that have a wide spectrum of socioeconomic backgrounds. Therefore, it is critical that physicians, veterinarians, and public health experts maintain a high index of suspicion for the disease regardless of geographic and socioeconomic circumstances and work together to understand outbreaks and implement appropriate control measures. Over the last decade, major strides have been made in our understanding of the disease because of improvements in diagnostic tests, molecular epidemiologic tools, educational efforts on preventive measures, and vaccines. These novel approaches are highlighted in the companion Currents in One Health by Sykes et al, AJVR, September 2022.