Pneumonia in a Paso-Fino mare.

The research paper delves into the case of a 5-year-old Paso-Fino mare with severe respiratory distress, which was later diagnosed as Pneumocystis carinii pneumonia after thoracic radiographs and microscopic identification of the pathogen in bronchoalveolar lavage (BAL) fluid. The horse’s condition worsened after foaling, marked by poor body condition, dull hair coat and mild fever, while decreased levels of certain immunoglobins were noted, revealing affected immune status. Significantly, the paper emphasizes that an ideal diagnostic method is yet to be developed for P carinii infection in horses.

Presentation of the Horse

• The subject of the research was a 5-year-old Paso-Fino mare that had been experiencing severe respiratory distress. She had given birth just two months prior to her symptoms manifesting.
• Medical hallmarks included a poor body condition and dull hair coat, implying a significant decline in the mare’s overall health.
• Upon physical inspection, the mare had a mild fever; a clear indication that her body was fighting off an infection of some kind.

Physical Examination and Diagnosis

• During auscultation, increased bronchovesicular sounds were discovered, suggesting the presence of air or gas in significant quantities around the horse’s respiratory tract.
• Thoracic radiographs were conducted, revealing an interstitial pattern and an alveolar infiltrate with distinct air bronchograms, indicating inflammation or swelling of the lung tissues.
• A substantial amount of mucus and certain phagocytes consistent with Pneumocystis carinii, a specific type of fungal infection, were found in the bronchoalveolar lavage (BAL).
• Despite the significant findings, no infectious agents could be conclusively pointed out in the tracheal wash fluid.

Immunophenotyping and Histology

• The mare’s immune status was also analyzed. Substantially reduced levels of immunoglobulin M (IgM) and immunoglobulin G (IgG) were found in the serum, both crucial for the immune response.
• Decreased expression of major histocompatibility complex (MHC) class II molecules was revealed through immunophenotyping. MHC are proteins that are essential for the immune system to recognize and respond to foreign substances.
• A deep examination of the lung tissue found hyperplasia of type II epithelial cells. However, the fungal pathogens were not visible.

Diagnosis and Sensitivity

• The paper highlights that a highly effective culture system for diagnosing P carinii infection is yet to be developed.
• Currently, the detection of P carinii pneumonia relies on microscopic identification of the pathogen’s characteristic features.
• In humans, diagnosis usually involves examination of BAL fluid, a process which is thought to also apply to horses. It’s noted that in human cases, this method is often more accurate than histopathological examination of lung biopsies.