Molecular diagnosis of Pneumocystis pneumonia in dogs

Area of Science:

• Veterinary Mycology
• Molecular Diagnostics
• Canine Infectious Diseases

Background:

• Pneumocystis pneumonia (PCP) is a severe fungal infection in dogs, often challenging to diagnose definitively.
• Accurate identification of Pneumocystis carinii f.sp.'canis' (P. canis) is crucial for effective treatment and understanding disease transmission.
• Existing diagnostic methods may lack the specificity and sensitivity required for differentiating infection from colonization.

Purpose of the Study:

• To perform preliminary genetic characterization of P. canis in canine respiratory specimens.
• To develop and validate a reliable molecular protocol for diagnosing canine PCP.
• To differentiate between P. canis infection and colonization in dogs using molecular burden.

Main Methods:

• Investigated P. canis DNA presence in lung specimens from dogs with suspected PCP, non-PCP respiratory issues, and healthy controls using nested PCR.
• Developed and employed a novel real-time quantitative polymerase chain reaction (qPCR) assay targeting specific rRNA loci.
• Correlated molecular findings with cytological/histological detection of Pneumocystis morphotypes and analyzed cycle threshold (CT) values.

Main Results:

• Pneumocystis DNA was detected in 13/16 suspected PCP cases and 4/76 control dogs, suggesting colonization in the latter.
• qPCR demonstrated a significant difference in molecular burden (CT values) between infected (CT ≤ 26) and colonized (26 < CT < 35) dogs.
• Phylogenetic analysis confirmed P. canis as a canine-specific species, validating the qPCR assay's accuracy.

Conclusions:

• The developed qPCR assay is a reliable molecular tool for diagnosing canine PCP.
• The assay effectively distinguishes between Pneumocystis infection and colonization based on molecular burden.
• P. canis is a distinct species specifically associated with dogs, supporting targeted diagnostic and therapeutic strategies.