Pathology of equine pneumonia associated with transport and isolation of Streptococcus equi subsp. zooepidemicus.

This research investigates the cause of pneumonia in horses that is related to transportation, identifying the bacteria Streptococcus equi subsp. zooepidemicus as a primary culprit and illustrating two different types of lung damage it causes. The study also highlights the possible role of severe tonsillitis in beginning this pneumonia.

Streptococcus equi and its Role in Equine Pneumonia

• The study started with seven horses that had died of pneumonia after transportation. Lung samples from these horses were analyzed and a bacterium called Streptococcus equi subsp. zooepidemicus (S.z) was discovered in all animals’ lung wounds or lesions.
• This bacterium is being associated with the pneumonia that caused the death of the horses. The relation between horse transportation and the onset of pneumonia has been made, indicating the stress or environmental changes might have facilitated the bacteria’s impact.

Two Types of Lung Lesions

• There were two general categories of lung injuries found during this study: serous haemorrhagic pneumonia and multiple foci of coagulative necrosis. These types are believed to demonstrate different stages in the progression of the disease, implying a temporal difference in lesion formation.
• Serous haemorrhagic pneumonia is characterized by the accumulation of serum, a yellowish fluid that typically exudes from inflamed tissues, accompanied by bleeding into the lungs.
• Multiple foci of coagulative necrosis, on the other hand, refers to localized areas of tissue death within the lungs, resulting from restriction or loss of blood supply, typically caused by a bacterial infection such as S.z.
• Immunohistological methods were used to identify the presence of S.z antigen in both these types of lung lesions. An antigen is a substance that stimulates an immune response, particularly the production of antibodies.

Importance of Tonsillitis in the Onset of Pneumonia

• The study suggests acute necrotic lacunar tonsillitis played a crucial role in the onset of pneumonia. This condition refers to severe inflammation and cell death in the tonsils, which are strategically positioned in the throat to act as a first line of defense against inhaled or ingested pathogens like S.z.
• While the mechanism by which tonsillitis facilitates the onset of lung lesions leading to pneumonia is not explicitly mentioned, it is implied that compromised tonsil health might make horses more susceptible to more severe respiratory infections.