6-month-old alpaca presented for lethargy, failure to thrive and leucocytos
is. Diagnostic procedures, including thoracic ultrasound, radiographs and a
computed tomography scan, were used to document a thoracic mass. Based on
appearance and ultrasound-guided aspiration of purulent material, the mass
was determined to be a large abscess. The abscess was treated with surgical
drainage and long-term antibiotic therapy. The origin of this thoracic abs
cess was felt to be the caudal mediastinum, secondary to bacterial seeding
of the caudal mediastinal lymph nodes. Although an aetiological agent was n
ot definitively determined, the most likely was Actinomyces spp or Arcanoba
cterium pyogenes. The alpaca made a complete recovery following treatment.