Leptospirosis in equine fetuses, stillborn foals, and placentas.

The research article discusses a study focusing on the occurrence and impact of leptospirosis in horse fetuses, stillborn foals, and their placentas, demonstrating that this bacterial infection can cause significant health issues and death in horses.

Investigation Methodology

• The researchers diagnosed leptospirosis based on various tests and observations, such as positive fetal antibody titer, fluorescent antibody test and high leptospiral titers in aborting mares. They also used the Warthin-Starry technique to identify the spirochetes bacteria that causes leptospirosis in kidney and placental samples.
• The assessed samples were from 51 equine fetuses and 16 stillborn foals with different gestation periods ranging from 3.5 to 11 months. Another criterion for diagnosis was if Leptospira spp. bacteria were isolated from the fetuses’ organs.
• The researchers also conducted visual examinations of the fetuses, foals, and placentas to identify any gross lesions, which were found in 80.3% of the cases.

Evidence of Leptospirosis

• Common findings included nodular cystic allantoic masses, edema, necrotic areas in the chorion, and a necrotic mucoid exudate coating the chorion in the placenta. Affected organs in the fetuses, like the liver and kidneys, showed characteristics such as being enlarged, mottled, pale to yellow, swollen, and edematous.
• Microscopic investigation revealed lesions in 96% of the examined samples. In placentas, the lesions resulted in thrombosis, vasculitis, mixed inflammatory cell infiltration, cystic hyperplasia of allantoic epithelium, and necrosis and calcification of villi.
• Fetal lesions consisted of hepatocellular dissociation, mixed leukocytic infiltration, giant cell hepatopathy, suppurative and nonsuppurative nephritis, pulmonary hemorrhages, pneumonia, and myocarditis.

Pathogens Isolation and Identification

• The researchers used the Warthin-Starry staining method, which revealed the presence of spirochetes, the bacteria causing leptspira, in 69 of the 71 cases. Additionally, the direct fluorescent antibody technique validated the presence of leptospires in 56 out of 60 tested cases.
• Confirmation of leptospires was evidenced by their isolation from fetal tissues in 20 out of 42 cases. Sixteen of these were identified as Leptospira interrogans serogroup Pomona serovar kennewicki, the strain of bacteria causing the disease, using a method called restriction enzyme analysis. Two cases were found to have serovar grippotyphosa, which is another variant of this bacterial infection.