Clinical Leptospira interrogans serogroup Australis serovar lora infection in a stud farm in The Netherlands.

This study details the outbreak of Leptospira interrogans infection in a horse farm in the Netherlands. The horses, especially foals, displayed symptoms of respiratory distress, depression, fever, and in some cases, diarrhea, jaundice, and unsteadiness. High antibody titres to serovar bratislava, closely related to serovar lora of the bacteria, were found in most foals and 64% of mares on the farm, suggesting horses may be a natural host for these strains of the bacteria.

Investigation of a Leptospira interrogans Infection Outbreak

• The research focused on a disease outbreak that occurred in a stud farm in the Netherlands over three years, from 1984 to 1986. The causative organism was identified as Leptospira interrogans, belonging to the serogroup Australis and specifically the serovar Lora. The infection presented with a severe clinical course and proved fatal for 12 foals.
• Common symptoms observed in the foals included severe respiratory distress, depression, and pyrexia or fever. Other less frequent symptoms were diarrhea, jaundice, and an unsteady gait.
• Morphological studies of the disease revealed massive pulmonary haemorrhage and serious kidney damage, characterized by haemorrhagic-thrombotic or extracapillary glomerulonephritis, tubulonephrosis, and interstitial oedema.

Serological Findings and Implications

• Serological tests demonstrated high or rising antibody titres against the serovar Bratislava in most foals. One foal even showed direct isolation of the Leptospira interrogans serovar Lora, confirming the infection.
• The research team also conducted a serological examination of all 56 mares present in the stud farm. The results demonstrated antibodies against the serovar Bratislava in 64% of the tested mares.
• The high prevalence of antibodies against the serovar Bratislava in both foals and mares and the successful isolation of the related serovar Lora from a foal suggest that these strains of Leptospira interrogans may be adapted to the horse population. This implies that horses could act as a natural reservoir, maintaining and propagating these bacterial strains within their populations.