Abstract
BACKGROUND: The diagnosis of certain lungworm infections in dogs relies heavily on bronchoalveolar lavage (BAL) cytology or lesion histopathology, especially in situations in which faecal diagnostics and bloodwork may have limited value. Differentiating morphologically similar parasitic larvae on BAL cytology, such as Oslerus osleri or Filaroides hirthi, may be challenging, and molecular approaches are not yet widely available. OBJECTIVE: Description of two cases of O. osleri infection in young dogs, including (1) representative examples of BAL cytology and lesion-specific histopathologic findings and (2) molecular characterisation, based on targeted gene amplification and sequencing, from cytologic and histopathologic samples of O. osleri. METHODS: Two cases of O. osleri infection were investigated and followed in detail. BAL slides and tracheobronchial biopsy samples were analysed: six primer pairs spanning the ribosomal RNA gene of O. osleri were used to amplify the specific regions of genomic DNA from stained BAL slides (Case 1) and from formalin-fixed paraffin-embedded (FFPE) tracheobronchial biopsy (Case 2). Amplicon sequences were compared to O. osleri nucleotide sequences available in GenBank. RESULTS: The amplicon sequences obtained from both cases were 100% identical, indicating that the infections in both dogs were caused by the same organism. BLAST analysis against the GenBank nucleotide database showed a 100% match with O. osleri, thereby confirming the diagnosis. CONCLUSIONS: PCR testing for O. osleri is feasible on genomic DNA obtained from stained BAL smears and sections of FFPE tissue. Further testing of these primers on other lungworms, such as F. hirthi, is warranted.