Microbiologic and pathologic findings in an epidemic of equine pericarditis.

This study investigates an outbreak of pericarditis (heart inflammation) in horses that occurred in central Kentucky in 2001. The researchers found that bacteria, primarily Actinobacillus species, were primarily responsible for the condition, and discovered microscopic damage consistent with bacterial infection in the hearts and surrounding tissue of the afflicted animals.

Study Overview

• The research was carried out following an epidemic of equine pericarditis – inflammation of the heart – in Kentucky during the spring and summer of 2001.
• Of the cases studied, Actinobacillus, a type of bacteria, was the most commonly found culprit in both terminally affected and clinically affected horses.
• The other two types of bacteria cultured were Enterococcus faecalis and Streptococcus zooepidemicus. These were found in the remaining two terminal cases that had not received treatment.

Diagnostic Findings

• No viruses were found in tissue culture from the horse samples indicating that bacterial infection was most likely the key cause of the inflammation.
• Nucleic acid from equine herpesvirus-2 was detected in fluids from the heart and the trachea in several individuals. This suggests that this virus could also play a part in the condition or potentially increase susceptibility to bacterial infection.
• Microscopic observation revealed damage in the heart and adjacent pericardium tissue. The nature of these changes was consistent with chronic fibrinous bacterial pericarditis, a condition where fibrinous strands form due to the inflammation response to bacterial infection.

Research Implications

• This study brought to light the significant role of Actinobacillus species in equine pericarditis and confirmed its role in the epidemic.
• Additionally, this research highlighted equine pericarditis, an infrequent but significant syndrome affecting horses, underlining the need for further studies to understand the factors contributing to such outbreaks and how they can be controlled or prevented.