Experimental Leptospira interrogans serovar Kennewicki infection of horses.

The paper focuses on an experimental study conducted on horses, wherein they were infected with Leptospira interrogans serovar Kennewicki – a bacteria known to cause the disease leptospirosis. Results revealed both disease-specific and generic responses of the horses against the administered bacterial strains, emphasizing that associated clinical symptoms could either be mild or almost non-existent.

Experimental Design

• The study revolved around an experimental and observational approach wherein four adult horses were selected based on their seronegative status for leptospirosis.
• The selected horses were subject to the bacterial challenge using an equine isolate of L. interrogans serovar Kennewicki. The challenge was administered at two different doses and through different inoculation sites.
• After bacterial challenge, horses were closely observed for a duration of 60 days. During this observation period, samples of blood, urine, and aqueous humor (fluid in the eyes) were collected at different intervals till the 60-day conclusion mark.

Observations and Results

• One of the early observable changes was a spurt in body temperature (39.3-40 degrees C), which was noted as soon as one day following the bacteria challenge. This was specifically observed in two horses who were subjected to an equally divided dosage of Leptospira through topical ocular and intraperitoneal injection.
• Further analysis of collected samples revealed the presence of Leptospira bacteria in the blood and urine but not in the aqueous humor of the two horses exhibiting symptoms of fever.
• Moreover, the study recorded that all four horses developed microscopic agglutination test antibodies post the bacterial challenge, which remained relatively constant for 21 days. Nevertheless, that titer to cross-reactive strains reduced earlier than the titer to the specific challenge strain.

Conclusions

• The study concluded that the signs of the disease in horses infected with Leptospira might either be mild or almost non-detectable. Hence, constant and repeated serologic testing is advised for the recognition of the infecting serovar.
• Additionally, it was noted that in febrile (feverish) horses, Leptospira can be isolated from the blood during active fever period, and from the urine after the subsidence of fever.