Diagnosis and Overview of Foal Interstitial Lung Pneumonia

Vet Radiol Ultrasound
2021 Jul;62(4):490-497.
Diagnostic imaging in acute interstitial pneumonia in foals: High variability of interpretation of chest radiographs and good conformity between ultrasonographic and post-mortem findings

Sophia Punsmann 1, Maren Hellige 1, Judith Hoppe 2, Fritjof Freise 3, Monica Venner 4
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Abstract
Acute interstitial pneumonia (AIP) in foals is a rare but challenging syndrome. Diagnostic imaging is crucial for its diagnosis. While there are some reports on radiographic findings, ultrasound is sparsely described. Variability in the evaluation of radiographs in AIP has been well described in human literature. Part one of this study is a prospective, observational, observer agreement study investigating inter- and intraobserver agreement in the assessment of thoracic radiographs. Part two is a prospective, controlled, descriptive study on thoracic ultrasonography in foals with AIP. Eighteen foals with AIP were examined daily by thoracic ultrasound. Thoracic radiographs were taken on three successive occasions. Blinded radiographs were assessed by three observers based on two semi-quantitative scores (pattern recognition, subjective evaluation). Foals that died underwent postmortem examination (n = 9); postmortem findings were compared to ultrasound findings on the day of death. Ultrasonographic findings were consistent with postmortem findings. Comet tail scores in foals with AIP were significantly higher (p < 0.0001) than in control foals. Interrater agreement for the assessment of radiographs was none to moderate (κ = 0.07-0.65) for pattern recognition and weak to moderate (κ = 0.58-0.62) for subjective scoring. Intrarater agreement varied from minimal to strong (κ = 0.30-0.80) for pattern recognition but was strong (κ = 0.83) for subjective scoring. In conclusion, the diagnostic value of thoracic ultrasound in foals with AIP is high due to good conformity with postmortem findings. The evaluation of thoracic radiographs showed high variability in inter- and intra-agreement. Keywords: ARDS; horse; lung; radiography; thoracic ultrasound.

Equine Vet J
2021 Jul;53(4):718-726.
Acute interstitial pneumonia in foals: A severe, multifactorial syndrome with lung tissue recovery in surviving foals

Sophia Punsmann 1, Judith Hoppe 2, Robert Klopfleisch 2, Monica Venner 3 4
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Abstract
Background: Acute interstitial pneumonia in foals has been sparsely described in literature, and the individual authors disagree on the underlying aetiology. Histopathological follow-up from surviving foals is not available.

Objectives: Description of clinical and histopathological findings in the course of acute interstitial pneumonia and in recovery. Investigating the aetiology and possible triggering factors of acute interstitial pneumonia.

Study design: Case series.

Methods: Post-mortem examination of nine affected foals; seven died during the acute phase, and two had recovered from acute interstitial pneumonia. Data from clinical examinations on the day of death were recorded for all foals. Complete necropsy, special histological staining, virological and microbiological examinations were performed.

Results: Seven foals died during the acute phase with severe respiratory distress, fever and increased numbers of comet tail artefacts in lung ultrasound. In post-mortem examination, a wide variety of possible triggering factors was identified. Microbiology revealed Escherichia coli, Rhodococcus equi and Klebsiella pneumoniae as the most common bacterial pathogens. Equine herpesvirus 2 was detected in all foals by PCR. Those with high viral loads also displayed histopathological changes suggestive of viral infections. Pneumocystis carinii was detected in all acutely affected foals. Histopathological changes in lung parenchyma clearly differed between the foals that had recovered from acute interstitial pneumonia and those dying in the acute phase. While lungs in acute phase featured marked parenchymal collapse and necrosis, the recovered foals revealed nearly normal ventilated lung parenchyma and alveolar structure.

Main limitations: Small number of cases. Because all foals are from the same breeding farm with endemic occurrence of pathogens, it is not certain whether the results of this study can be transferred to other foals without restrictions.

Conclusions: Acute interstitial pneumonia seems to be based on a multifactorial aetiology. Lungs from foals that have survived acute interstitial pneumonia appear to be able to regenerate completely, leaving no permanent changes.

Keywords: ALI; ARDS; bronchointerstitial pneumonia; horse; pathology; respiratory distress.