Antibiotic Efficacy in Eliminating Leptospiruria in California Sea Lions (Zalophus californianus) Stranding with Leptospirosis

Abstract

Stranded California sea lions (Zalophus californianus) along the California coast have been diagnosed with leptospirosis every year since at least the 1980s. Between September 2010 and November 2011, we followed 14 stranded California sea lions that survived to release and evaluated antibiotic efficacy in eliminating leptospiruria (urinary shedding of leptospires). Leptospiruria was assessed by real-time PCR of urine and urine culture, with persistence assessed using longitudinally collected samples. Serum chemistry was used to assess recovery of normal renal function. Microscopic agglutination testing (MAT) was performed to assess serum anti-Leptospira antibody titers, and the MAT reactivity patterns were consistent with L. interrogans serovar Pomona infection frequently observed in this population. Animals were initially treated for 6 to 16 d (median = 10.5; mean = 10.8) with antibiotics from the penicillin family, with some receiving additional antibiotics to treat other medical conditions. All urine cultures were negative; therefore, the presence of leptospiruria was assessed using PCR. Leptospiruria continued beyond the initial course of penicillin family antibiotics in 13 of the 14 sea lions, beyond the last antibiotic dose in 11 of the 14 sea lions, beyond recovery of renal function in 13 of the 14 sea lions, and persisted for at least 8 to 86 d (median = 45; mean = 46.8). Five animals were released with no negative urine PCR results detected; thus, their total shedding duration may have been longer. Cessation of leptospiruria was more likely in animals that received antibiotics for a greater duration, especially if coverage was uninterrupted. Real-time PCR results indicate that an antibiotic protocol commonly used to treat leptospirosis in rehabilitating California sea lions does not eliminate leptospiruria. It is possible that antibiotic protocols given for a longer duration and/or including other antibiotics may be effective in eliminating leptospiruria. These results may have important human and animal health implications, especially in rehabilitation facilities, as Leptospira transmission may occur through contact with animals with persistent leptospiruria.

Detecting signals of chronic shedding to explain pathogen persistence:Leptospira interrogansinCalifornia sea lions

“…This relatively long‐lived infection is consistent with existing data, where sea lions were observed shedding leptospires for at least 12 weeks (Prager et al . ) or 22 weeks (Dierauf et al . ); however, the intensity and intermittency of chronic shedding are unknown for sea lions and most other species (Ellis ).…”

“…; Prager et al . ). Alternative assumptions of 1‐ or 3‐week acute infectious periods did not change qualitative model results (Figs S3 and S4).…”

“…We assumed that chronic shedders suffered no disease‐induced mortality, in line with current understanding of leptospirosis in other maintenance hosts (Ellis ) and the observation of asymptomatic shedders amongst both wild‐caught and stranded sea lions (Prager et al . , ). We assumed that immunity against the same serovar was lifelong (Adler & de la Peña Moctezuma ; Evangelista & Coburn ).…”

“…; Prager et al . , ). With asymptomatic shedders, a long history of disease surveillance, and seasonality in both transmission and susceptible recruitment, the sea lion/leptospirosis system provides a unique opportunity to assess chronic shedding as a mechanism of pathogen persistence in wildlife, and to highlight challenges researchers may face conducting similar assessments in other systems.…”

Mapping the Host-Pathogen Space to Link Longitudinal and Cross-sectional Biomarker Data:LeptospiraInfection in California Sea Lions (Zalophus californianus) as a Case Study

“…This article is a US Government work. It is not subject to copyright under 17 USC 105 and is also of maintenance hosts -occur in sea lions and are the possible mechanism for populationlevel pathogen persistence from one outbreak to another [19,27,28]. Using longitudinal data on antibody titer, disease severity and pathogen shedding, we track the temporal progression of Leptospira infections in California sea lions that experienced either severe illness or subclinical infection.…”