Role of Intraocular Leptospira Infections in the Pathogenesis of Equine Recurrent Uveitis in the Southern United States

Abstract

The results of our study identified a population of ERU cases with an active intraocular Leptospira infectious process in the Southern United States. The diagnosis of intraocular leptospirosis required ocular fluid sampling for PCR or culture. Twenty-one percent of ocular fluid samples were positive by culture and forty-five percent by PCR; no control horses were positive by either culture or PCR. These findings are in contrast to a recent study from the Southeastern US that showed no evidence of bacterial DNA by PCR and supports the conclusion that a regional variation in Leptospira infections exists. The most common culture isolate was the serovar pomona; additionally, we report the first cases of serovar grippotyphosa outside of Europe. Title Role of intraocular Leptospira infections in the pathogenesis of Equine Recurrent Uveitis in the Southern United States.Abstract: Equine Recurrent Uveitis (ERU) has been linked to leptospirosis in Europe, however regional differences exist in reports from the United States. The objective of this study was to investigate the role of intraocular leptospiral infections in horses with ERU in the Southern United States. Blood and ocular fluid samples were collected from horses with ERU as well as normal controls. Leptospira serology was performed using microscopic agglutination test (MAT). Aqueous and vitreous humor samples were obtained and submitted for aerobic and Leptospira culture, PCR and MAT. Twenty-one control horses (40 eyes) and 31 ERU horses (46 eyes) were available. Serology was available for 48/52 horses: 16/21 control and 23/27 affected horses were positive for at least one serovar; bratislava was the most common serovar identified. Bacillus sp. and Micrococcus sp. were cultured from one control eye; Streptococcus sp. (n=1) and Leptospira (n=6) from the eyes of 6 ERU horses. Leptospira isolates belonged to serogroup pomona (n=4) and grippotyphosa (n=2). PCR results were positive in 14/31 (45%) horses with ERU; no control horses were positive by PCR (p=0.0001). MAT was positive for 17/24 of ERU horses (71%) and 1/21 (4.7%) of normal horses (p<0.0001). Horses with ERU had a high prevalence of Leptospira infection based on PCR and MAT results from intraocular fluids compared to controls. The diagnosis of intraocular infections was not aided by serology and required specific, invasive sampling of ocular fluid. Leptospira infection should be considered as a cause of ERU in the Southern United States.

Detection of intraocular leptospiral DNA, antibodies and Leptospira spp. in horses with equine recurrent uveitis in different laboratories

“…and ERU (Brandes et al 2007, Bryans 1955, Davidson et al 1987, Polle et al 2014, von Borstel et al 2010, Wollanke et al 2000, Wollanke et al 2001. In these studies, the amount of positive results for intraocular leptospiral antibodies ranged between 35 and 94 % (Brandes et al 2007, Dorrego-Keiter 2016, Gerding et al 2015, Gilger et al 2008, Polle et al 2014, von Borstel et al 2010, Wollanke et al 2001) of the eyes tested. In the present study the positive MAT-results ranged between 41 and 51% in L1 and L3.…”

“…But it was shown that these intraocular leptospiral traces can be detected in aqueous humor, too (Faber et al 2000, Polle et al 2014, Schwink et al 1989, Tömördy et al 2010. A steady-state passive diffusion between the vitreous body and the aqueous humor has been described in rabbits.…”

“…They categorized ERU into a painful "anterior uveitis/iritis", an almost painless "intermediate uveitis/cyclitis/pars planitis" and a "posterior uveitis/choroiditis" or rather "panuveitis", because not only the choroid, but also the ciliary body is usually involved during inflammation (Spiess 2010, Tömördy et al 2010, Wollanke et al 2009). There are numerous aetiological theories for the causes of ERU, but to date, the "classic ERU" is most commonly associated with an intraocular leptospiral infection (Alexander 1990, Brandes et al 2007Faber et al 2000, Frellstedt 2009, Gerding et al 2015, Gilger et al 2008, Halliwell 1985, Heusser 1948, Niedermaier et al 2006, Pearce et al 2007, Polle et al 2014, Rimpau 1947, Schwink et al 1989, Sillerud et al 1987, von Borstel et al 2010, Wiehen 2012, Wollanke et al 2000, Wollanke et al 2001. Involvement of Leptospira spp.…”

“…Positive results in the literature vary between 43 and 94 % when performing the MAT on the vitreal material of affected eyes (Brandes et al 2007, Gerding et al 2015, Gilger et al 2008, Polle et al 2014, von Borstel et al 2010, Wollanke et al 2001. The PCR is able to detect leptospiral DNA in 40 to 100 % of the eyes tested in the literature (Brandes et al 2007, Faber et al 2000, Polle et al 2014, von Borstel et al 2010. The rate for successful leptospiral culturing ranges between 21 and 53 % (Brandes et al 2007, Faber et al 2000, Wollanke et al 2001.…”

Haemolytic anaemia and bilateral uveitis associated with leptospirosis in a 6‐year‐old Quarter Horse gelding

“…Other possible diagnostic tests to determine the cause of uveitis include evaluating aqueous humour leptospiral titres, aqueous humour leptospiral PCR and aqueous humour culture (Gerding and Gilger ; Polle et al . ). It was not performed due to concerns for complications such as causing more inflammation (Featherstone and Heinrich ).…”