Evidence of Leptospira Interrogans Infection in California Sea Lion Pups From the Gulf of California

Abstract

Forty-two urine and 96 blood and serum samples were obtained from California sea lion (Zalophus californianus) pups from the Gulf of California during the 2000 reproductive season. Antibody prevalence to 13 serovars of Leptospira interrogans was determined by microagglutination tests (MAT); presence of pathogenic leptospires was detected by polymerase chain reaction (PCR). Samples with antibody titers > or = 1:25 or 115 bp fragments on ethidium bromidestained 1.5% agarose gels were considered positive. Antibody prevalence was 54% overall with highest prevalence against serovar cynopteri (50% of all positive reactions). Highest antibody titers (1:50) were detected against serovars cynopteri and pomona. Polymerase chain reaction products were observed in two of 42 urine samples, six of 96 blood samples, and one of 96 serum samples. Presence of PCR products in blood and serum was demonstrated in pups that were seronegative. Kruskall-Wallis tests and corresponding post hoc Tukey tests (alpha = 0.05) showed that prevalence of leptospirosis was significantly different among all rookeries. The high seroprevalence (54%), low antibody titers (maximum 1:50), absence of pups showing clinical signs indicative of the disease, and lack of recent reports of increased mortality of sea lions in the Gulf of California are suggestive of the presence of enzootic host-adapted serovars. Crowding in rookeries as well as the presence of bats and rodents on some of the islands may explain infection by L. interrogans (sensu lato) and some of the differences in seroprevalence among reproductive rookeries.

Variable Nucleotide Tandem-Repeat Analysis Revealing a Unique Group of Leptospira interrogans Serovar Pomona Isolates Associated with California Sea Lions

“…California sea lions are persistently exposed to serovar Pomona during nonoutbreak years (15). Intermittent exposure of California sea lions to the same L. interrogans serovar Pomona clonal population from another host species through accidental exposure over a 37-year period is unlikely (1,4,6,7,(10)(11)(12)(13)23). We conclude that California sea lions are maintenance hosts of L. interrogans serovar Pomona.…”

“…California sea lion isolates are distinguished by the presence of 10 to 12 repeats at VNTR locus 4, compared to 3 to 7 repeats in all other isolates (Table 1). Isolate Po048, which is unique among California sea lion isolates at VNTR locus 4, was obtained in 1970 during the earliest reported leptospirosis outbreak along the California coast (23); other isolates obtained during subsequent outbreaks (1,4,13) were identical to each other. California sea lions are persistently exposed to serovar Pomona during nonoutbreak years (15).…”

Seroprevalence of Leptospirosis in Korean Municipal Zoo Animals

“…It is difficult to clarify the infecting serovars without isolates, however, the MAT data can give a general impression about which serovars are present in herds. Although a higher cutoff value of the MAT was necessary for defining cases of leptospirosis [2], a low cutoff value has been widely used in wild animals [1,6,7,14]. Hence, titers of 1:25 or higher were considered as a positive reaction in the present study.…”

“…The serum samples were incubated overnight at 4°C and examined under a dark field microscope [16]. Serum samples with agglutination of at least 50% of the leptospires at a ≥1:25 titer were considered positive [1]. For serum samples showing positive reactions against more than two serovars, the serovars that gave lower dilution steps than the highest recorded titer were considered as cross-reactions and excluded from further analyses.…”

Pathological and Parasitological Findings in South American Fur Seal Pups (Arctocephalus australis) in Uruguay

“…The coastal ecosystems of Cabo Polonio, Isla de Lobos, and other pinnipeds settlement areas are strongly influenced by anthropogenic factors (sewage from cities and small towns near seal colonies, presence of domestic animals and plague species) that could promote the development of different infectious or parasitic diseases diagnosed in other marine mammal populations [3,6,[37][38][39][40]. In this context, an initial serological survey conducted in cats from Isla de Lobos (n = 3) resulted in high antibody titers against Toxoplasma spp., consistent with active infection (H. Katz, unpublished data), being a potential risk of infection for pinnipeds and other marine mammals.…”