Cross-sectional evaluation of multiple epidemiological cycles of Leptospira species in peri-urban wildlife in California

Abstract

OBJECTIVE To perform a cross-sectional survey to estimate prevalence of and potential risk factors for Leptospira spp infection and exposure in peri-urban wildlife throughout California. ANIMALS 723 animals representing 12 wildlife species. PROCEDURES Blood and urine samples were obtained from wildlife in California from 2007 to 2017. Live animals were captured in humane traps, anesthetized, and released. Carcasses were donated by wildlife services and necropsied for urine, blood, and kidney tissue samples. Samples were tested for antibodies against 6 serovars of Leptospira spp with a microscopic agglutination test and for pathogenic Leptospira spp DNA with a real-time PCR assay targeting the LipL32 gene. Potential risk factors for Leptospira spp exposure were assessed by logistic regression. Genetic relatedness of Leptospira spp were assessed with DNA sequencing of the rrs2 gene and multiple locus sequence analysis. RESULTS Statewide Leptospira spp seroprevalence was 39.1%, and prevalence of positive PCR assay results for Leptospira spp DNA was 23.0%. Risk factors for Leptospira spp exposure included being an adult, being from northern California, and being a western gray squirrel, coyote, striped skunk, raccoon, gray fox, or mountain lion. Antibodies against serovar Pomona predominated in most species, followed by serovar Copenhageni. Complete rrs2 sequences were identified as Leptospira interrogans and multiple locus sequence type analysis revealed sequence type 140. CONCLUSIONS AND CLINICAL RELEVANCE Pathogenic Leptospira spp appeared to be common and widespread among peri-urban wildlife in California. Our data highlight the potential for exposure to infectious disease for both humans and domestic animals at the urban-wildland interface.

PathogenicLeptospiraare widespread in the urban wildlife of southern California

“…Skunks, raccoons and coyotes all exhibited moderate levels of infection, while infection prevalence was low in opossums and fox squirrels. Only one opossum was PCR positive, consistent with prior Leptospira surveys of opossums elsewhere in California, which have found no 71 or low infection prevalence 34 . Fox squirrels had the highest seroprevalence of all our target hosts, though no infections were detected in this species.…”

“…We focused on which serovar had the highest titer, though we emphasize that serology cannot conclusively identify the Leptospira strain causing an infection 72 . Coyotes, raccoons, and skunks typically had maximum antibody titers against serovar Pomona, consistent with findings in northern California where serovar Pomona predominated in these mesocarnivores 34 . Conversely, squirrels showed minimal seroreactivity to serovar Pomona and typically had low maximum titers against serovar Icterohaemorrhagiae, which was not highly reactive in other species.…”

“…We used logistic regression to explore potential predictors of Leptospira exposure (as indicated by an antibody titer of 1:100 or higher to any serovar). The following covariates were considered: age class, sex, season (wet Nov-April vs. dry May-Oct) 34 , and composite land category (developed vs. agricultural/open vs. natural). Antibody titers have been identified as significant predictors of Leptospira shedding and PCR status in California sea lions 21,63 .…”

“…In California, one historical wildlife survey reported Leptospira exposure or active infections in multiple species, including coyotes (Canis latrans), Northern raccoons (Procyon lotor) and striped skunks (Mephitis mephitis) 44 , while other surveys detected Leptospira in black bears (Ursus americanus) 45 and feral pigs (Sus scrofa) 46 . A recent survey in northern California reported Leptospira in multiple mesocarnivore and rodent species 34 . Both skunks and raccoons were identified as potential reservoir hosts for Leptospira interrogans serovar Pomona 47 , a serovar which has also impacted California Channel Island terrestrial mammals and marine mammals along the California coast 20,21,[48][49][50][51][52] .…”

“…Since changes to transmission risk are pathogenand host-specific, investigations into pathogen dynamics and host diversity are critical for urban disease management and risk assessment. This is especially true for Leptospira, as most studies in cities have focused primarily on rodents in high-density urban centers 6,[29][30][31][32] , with much less attention placed on other urban-adapted wildlife that may play a significant role in the ecology of this important zoonosis 5,33,34 . Improved knowledge of Leptospira epidemiology in a greater range of susceptible host species, and the diversity of Leptospira strains they carry, would provide valuable context for medical and veterinary clinicians assessing illness in humans and domestic animals.…”