Adenovirus pneumonia in an Arabian foal.

The research presents findings of a case of adenoviral infection in an Arabian foal, evidencing that a genetic trait may increase susceptibility to this disease.

Case Background

• The case revolves around a four-week-old Arabian foal which showed signs of dullness and depression before developing extreme respiratory distress and eventually dying.
• The initial assumption was an immunodeficiency, which is an inherited trait in Arabian foals, was what made this foal susceptible to the adenoviral infection.
• The foal’s dam was recently imported from California, and the effect of its geographical origin on the susceptibility of the foal to the infection is unmentioned.

Gross Pathology and Clinical Symptoms

• The physical inspection of the foal’s lungs showed dark red, firm areas in the anterior ventral one-third of both lungs. A checkerboard-like appearance resulted from alternating affected and normal lobules. Purulent exudate was found in the airways of affected lobules.
• Small yellow foci were scattered throughout the affected portion of the lungs, indicating inflammation or infection.
• The spleen of the foal was small and lacked visible lymphoid follicles, further supporting a potential immuno-deficiency.
• The foal developed severe respiratory distress before death, which corresponds with the pulmonary artery issue noted in the gross pathology.

Histopathology Findings

• The bronchi and bronchioles of the foal were filled with a purulent exudate, which consisted of sloughed bronchiolar epithelial cells and large numbers of leucocytes, indicating an acute response to infection.
• The thickness of the bronchiolar epithelium was noted to be 8-10 cells, which is indicative of hyperplasia, or abnormal cell proliferation. This could be a body response to the infection.
• In the nuclei of many of these cells, large, amphophilic inclusion bodies were found, which are typically associated with infected cells in viral diseases such as adenovirus.
• Most of these inclusions were found in cells located at or near the lumen, suggesting that the respiratory tract was majorly affected.
• The alveoli were atelectatic, indicating a collapse or closure of a lung, causing a loss or reduction of medical gases exchange.