Evidence of Equine Genital Leptospirosis (EGL) syndrome in a mare with chronic placentitis

Abstract

Leptospirosis is an important disease in equine reproduction. Recently, a specific genital syndrome, named Equine Genital Leptospirosis (EGL), distinct from renal/systemic disease, was described (Di Azevedo & Lilenbaum, Theriogenology. 2022; 192:81-8). Herein we present a typical case of EGL in a pregnant mare diagnosed in the northeastern region of Brazil. A mixed-breed mare of 436kg at 243 days of gestation, presented with hyperechogenic allantoic fluid, placental edema, and fetal tachycardia in a routine obstetrics examination. Serum progesterone and estradiol (RIA) were normal (6.26ng/mL and 1404.76pg/mL, respectively). The serology for equine herpes virus1 or –4) was negative. Placentitis treatment was started with flunixin meglumine (1.1mg/kg, IV, SID, 5 days) and trimethoprim-sulfamethoxazole (30mg/kg, PO, BID). On subsequent evaluation (272 days of gestation), the placenta was heterogeneous, showing mild edema, with multiple folds in the cervical star region and placental detachment was suspected. The fetal evaluation did not show any abnormalities. Serum progesterone and estradiol were 9.86ng/mL and 872.73pg/mL, respectively. Cervicovaginal mucous (CVM) cytology did not show any abnormalcharacteristics. A PCR for leptospirosis was conducted from urine (negative) and from CVM (positive). Serology (Microscopic Agglutination Test) for Leptospira spp was positive (titre 200) for serogroup Australis. The low titers against this Leptospira serogroup (which includes serovar Bratislava), together with a negative PCR on urine and positive PCR on CVM, strongly supports a diagnosis of EGL syndrome. Trimethoprim-sulfamethoxazole was then substituted with doxycycline (10mg/kg, PO, BID) until parturition, which was uneventful at 332 days of pregnancy. The placenta had mild macroscopic lesions on the cervical star and at the tip of the gravid horn. The foal had normal general clinical parameters at birth, but physical signs of immaturity and leukopenia with a shift to the left. Treatment with amikacin (25mg/kg, IV, SID) and one liter of plasma was established and the foal made a full recovery. EGL is primarily a reproductive syndrome and is characterized by a chronic, silent, and genital-focused disease, distinct from renal or systemic syndromes. It is vastly underdiagnosed, and the disease is little studied and underestimated. This is the first case fully reported.