LEPTOSPIROSIS IN EQUINE FETUSES, STILLBORN FOALS, AND PLACENTAS

Leptospirosis was diagnosed in 51 equine fetuses and 16 stillborn foal s with gestational ages from 3 1/2 to 11 months. Diagnosis was based o n one or more of the following: positive fetal antibody titer, positiv e fluorescent antibody test, demonstration of spirochetes in kidney an d/or placental sections stained by the Warthin-Starry technique, high leptospiral titers in aborting mares, or isolation of Leptospira spp. from fetal organs. Gross lesions were observed in 80.3% of the fetuses , stillborn foals, and placentas. Gross placental lesions included nod ular cystic allantoic masses, edema, areas of necrosis of the chorion, and necrotic mucoid exudate coating the chorion. The liver (23 cases) was enlarged, mottled, and pale to yellow. The kidneys (seven cases) were swollen and edematous with pale white radiating streaks in cortex and medulla. Microscopic lesions were observed in 96% of fetuses, sti llborn foals, and placentas. Placental lesions consisted of thrombosis , vasculitis, mixed inflammatory cell infiltration of the stroma and v illi, cystic adenomatous hyperplasia of allantoic epithelium, and vill ous necrosis and calcification. Fetal lesions included hepatocellular dissociation, mixed leukocytic infiltration of the portal triads, gian t cell hepatopathy, suppurative and nonsuppurative nephritis, pulmonar y hemorrhages, pneumonia, and myocarditis. Spirochetes were demonstrat ed with the Warthin-Starry stain in the allantochorion and/or kidney o f 69 of the 71 cases. Using the direct fluorescent antibody technique, 56/60 cases tested positively for leptospires. Leptospires were isola ted from fetal tissues in 20/42 cases. Sixteen of the isolates were id entified by restriction enzyme analysis as Leptospira interrogans sero group Pomona serovar kennewicki; case Nos. 36 and 41 were serovar grip potyphosa. The other two isolates were not identified. Microagglutinat ion titers against leptospires were demonstrated in the body fluid of 47/67 cases tested and titers ranged from 1: 50 to greater than 1: 1,6 38,400 against Leplospira interrogans serovars pomona, grippotyphosa, copenhageni, hardjo, canicola, and bratislava. Sixty-two of 71 abortin g mares tested had titers ranging from 200 to greater than 3,276,800. Leptospiral antibody titers in the body fluid and gross and histopatho logic lesions did not differ with age, breed, or sex or between fetuse s and stillborn foals.