Fatal canine adenovirus type 1 acute infection in a Yorkshire Terrier puppy in Portugal: a case report

This study reports the diagnostic algorithm followed for the identification of a fatal canine adenovirus type 1 (CAdV-1) infection in an unvaccinated 56 day-old puppy to overcome the limitations imposed by inconclusive histopathology hampered by body freezing. The animal was submitted to necropsy after a clinical history of lethargy, dehydration, vomiting and haemorrhagic diarrhoea. Pathological features, suggestive of infectious illness, included generalised gelatinous subcutaneous oedema, petechial, ecchymotic haemorrhages of the subcutaneous tissues and a friable uniformly yellow mottled liver. Differential diagnosis based on PCR ruled out the presence of most common gastrointestinal canine viruses and bacteriology and coprology confirmed that pathogenic bacteria and intestinal parasites did not account for the puppy's death. Strong amplification of CAdV-1 DNA was obtained from liver samples. Isolation of CAdV-1 in MDCK cells was subsequently demonstrated and sequencing analysis showed high similarity with CAdV-1 isolates from Europe. In the absence of serum, antibodies against CAdV-1 were investigated in lung tissue extracts. The presence of CAdV-1 infectious particles and absence of immune response was consistent with rapid progression of the infection and death of the animal two days after the onset of clinical signals, allowing a final diagnosis of the acute form of ICH. Antibodies against CAdV-1 were detected in sera collected from clinically healthy dogs from the same premises, 14-months after the index case, suggesting that the virus had circulated in the breeding kennel. We believe this to be the first report of CAdV-1 in Portugal where canine infectious hepatitis is considered a rare infection.