Seroprevalence of Leptospira spp. in Horses in Israel

Serological surveillance of equine leptospirosis in Croatia in the period from 2012 to 2022 - a key insight into the changing epizootiology

Leptospirosis is re-emerging zoonotic bacterial disease of global importance that affects domestic and wild animals and humans. Due to the public health importance, control of disease in Croatia is being implemented by monitoring the seroprevalence of equine leptospirosis and it is regulated by the law. In the period from 2012 to 2022, a total of 61724 serum samples from apparently healthy horses were admitted to the Laboratory for leptospires, Faculty of Veterinary Medicine University of Zagreb. Serum samples were tested for Leptospira spp. antibodies using the microscopic agglutination test (MAT). Samples were considered seropositive with a cut-off titre 1:200 for Bratislava and 1:400 for other Leptospira spp. serovars. Out of 61724 serum samples tested, 6665 (10.80%) were found seropositive for at least one Leptospira serovar. In the studied period, seroprevalence varied between 5.00% and 15.94%. The highest seroprevalence was found for serovar Pomona (41.98%) and serovar Grippotyphosa (31.34%), followed by Sejroe (8.03%), Icterohaemorrhagiae (7.05%) and Bratislava (6.47%). Results indicated that horses in Croatia are particularly exposed to Leptospira spp. infections. The most prevalent presumed infective serovar was Pomona increasing each year. Investigated horses were randomly selected and healthy and most seropositive horses have anamnestic titre due to previous infection. This is the first study in Europe reporting such high seropositivity for the serovar Pomona in apparently healthy horses. According to the results of the present study, the question arises of the possible evolutionary adaptation of the pathogenic serovar Pomona as dominant for horses.

Seroprevalence of anti-Leptospira antibodies in equines and associated workers-Isolation of Leptospira interrogans serogroup Canicola from equine urine

To investigate seroprevalence of anti-Leptospira antibodies in equines and associated workers in Uruguay, 891 equine and 150 human sera were drawn; 212 equine urine samples were also taken for culture. Environmental conditions and equine raising or managing practices were recorded in all 72 visited establishments; epidemiological information was obtained from each worker. Microscopic agglutination technique (MAT) was performed with 10 Leptospira strains for equines and 18 for human sera, that were also studied with IgM indirect immunofluorescence (IgM-IIF). Equine titres ≥100 were considered positive, and human sera titres ≥200 suggested probable recent or past infection. Urines were cultured in Ellinghausen-McCullough-Johnson-Harris (EMJH) media; local identification of one obtained isolate with lipL32 PCR, Multiple Locus Variable number tandem repeat Analysis and partial rrs gene sequencing, were completed at Institut Pasteur, Paris. Estimated reactivity was 61.3% for equines, which was higher than the studied bovine national levels (21%) and mainly observed with Icterohaemorrhagiae serogroup (40.3%), Sejroe, Canicola, Pomona or Ballum. Aged animals from slaughterhouses and cattle farms were the most frequently positive. Multiple regression analysis confirmed a significant association between seropositivity and equine age. Only one positive culture could be fully studied, and confirmed to be Leptospira interrogans serogroup Canicola; it was added to the MAT antigen panel and revealed fairly frequent reaction with equine and human sera. Three workers (2%) showed titres = 200 with Icterohaemorrhagiae or Canicola serogroups, without recent clinical manifestations. Their attended equines reacted with the same serogroups, suggesting common source infections or infection transmitted by equines. Three other humans yielded titres = 100, and none of the 150 showed an IgM-IIF-positive result. Equines seem not to be an important origin of regional human leptospirosis, except perhaps during acute animal infection. More culture work is required to study intensity and lapses of leptospiruria, as well as to further identify circulating strains.

Detection of Anti-LipL32 Antibodies in Serum Samples from Horses with Chronic Intraocular Infection with Leptospira spp

Equine recurrent uveitis (ERU) is typically caused by chronic intraocular leptospiral infection in warm-blooded horses in central Europe. The most effective therapy for leptospiral-induced ERU is the surgical removal of diseased vitreous (vitrectomy). Since vitrectomy is a highly specialized and invasive surgery, the indication must be determined very carefully. In order to obtain evidence of intraocular leptospiral infection by laboratory diagnostics in questionable leptospiral ERU-cases, sampling of aqueous humor is required, because serum tests using microscopic agglutination test (MAT) are too unspecific. The SNAP Lepto is a cross-species rapid test for the detection of anti-Lipl32 antibodies that has a high sensitivity (0.97) and specificity (1.00) for the detection of anti-leptospiral antibodies using aqueous humor or vitreous samples, which is comparable to MAT. To evaluate sensitivity and specificity of SNAP Lepto using serum, serum samples from 90 horses with confirmed leptospiral ERU and from 103 ocularly healthy horses were tested by both MAT and SNAP Lepto. Sensitivity was similar for both tests (0.82 vs. 0.79), but specificity was lower for MAT (0.52 vs. 0.95). Sensitivity and specificity are therefore lower in serum samples compared to intraocular samples, however, the SNAP Lepto is far superior to MAT and suitable as a screening method using equine serum.

Serological Survey of Leptospira Infection in Arabian Horses in Poland

Leptospirosis is one of the most common zoonotic infections worldwide, including in most livestock, some companion animals, horses, wildlife, and humans. Epidemiological estimation of its prevalence in all species is difficult due to the variety of clinical presentations and challenges regarding laboratory diagnosis. The purpose of this study was to measure the seroprevalence of leptospiral infection in Arabian horses kept in the largest breeding farms in Poland, representing over 15% of the Polish Arabian horse population. Leptospira antibodies were detected by MAT (cut-off 1:100) in 33.2% of serum samples (204 of 615 animals) (CI 95%: 29.6–37.0%), most frequently reacting with the serovar Grippotyphosa, similar to previous reports in populations of randomly selected horses. These results indicated high Leptospira seropositivity, thus, although any form of clinical leptospirosis is rare, it may be postulated that the leptospiral exposure is widespread.