Seroprevalence of Leptospira spp. in Horses in Israel

Abstract

Leptospirosis has been reported in both humans and animals in Israel but has not been reported in horses. In 2018, an outbreak of Leptospira spp. serogroup Pomona was reported in humans and cattle in Israel. In horses, leptospirosis may cause equine recurrent uveitis (ERU). This report describes the first identification of Leptospira serogroup Pomona as the probable cause of ERU in horses in Israel, followed by an epidemiological investigation of equine exposure in the area. Serologic exposure to Leptospira was determined by microscopic agglutination test (MAT) using eight serovars. In 2017, serovar Pomona was identified in a mare with signs of ERU. Seven of thirteen horses from that farm were seropositive for serogroup Pomona, of which three had signs of ERU. During the same time period, 14/70 horses from three other farms were positive for serogroup Pomona. In 2015, two years prior to this diagnosis, 259 horses from 21 farms were sampled and one horse tested seropositive for serovar Icterohaemorrhagiae. In 2018, one year later, 337 horses were sampled on 29 farms, with none testing seropositive. Although horses are not considered a major host of Leptospira spp., it appears that horses may be infected, and clinically affected, in the course of an outbreak in other species. The identification of leptospirosis in stabled horses may impose a significant zoonotic risk to people.

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

“…Serum tests for anti-Leptospira antibodies have been frequently performed in ocular healthy horses and horses suffering from ERU [5,41,48,61,64]. Most of these studies used MAT, which has long been considered the gold standard in serum diagnostics [70,76,77], is cited in almost all studies as the reference method for the humoral immune response to leptospiral infection, and is still listed by WHO as the only reference method for screening tests [75,78].…”

“…In other cases, where the history is suggestive of ERU but the ophthalmologic findings are questionable, the indication for vitrectomy cannot be reliably established by ophthalmologic examination. Examination of serum by micro agglutination test (MAT) unfortunately does not allow a reliable statement about a local leptospiral infection in the eye, because too many healthy horses in Europe [5,6,10,[41][42][43][44][45][46][47][48] as well as in other parts of the world [24,27,[49][50][51][52][53][54][55][56][57][58][59][60][61] have agglutinating antibodies in the serum.…”

Serological Survey of Leptospira Infection in Arabian Horses in Poland

“…Additionally, very high seropositivity has been reported in Switzerland and Colorado in the US, where almost 60% and 82% respectively of clinically healthy horses were positive for one or more Leptospira antigens [22,27]. On the other hand, in Israel, seroprevalence was low and only individuals out of hundreds investigated horses were seropositive [28]. The risk of Leptospira infection may be related to the rainfall during the studies, rodent population increases or decreases or other, sometimes not recognized factors that have to be taken into consideration to interpret and compare reported data properly.…”

Neutrophil Extracellular Traps (NETs) in Ocular Diseases: An Update

“…These pro-inflammatory cytokines mediate the formation of NETs and the production of adenosine monophosphate (AMP), resulting in the occurrence of ERU. Leptospira, which induces NETs in a concentration-dependent manner in the VBF of ERU-diseased horses, is another contributor to the pathogenesis of ERU [ 93 , 96 ]. However, little is known about whether NETs contribute to the pathogenesis of ERU.…”