09/16/2026
Under the microscope: small dark clusters inside a 4-month-old Boxer puppy's monocytes — morulae, colonies of Neorickettsia helminthoeca, the organism behind salmon poisoning disease. This one was caught on a lymph node aspirate.
Salmon poisoning is a good reminder that diagnosis isn't always the same difficulty. Sometimes it's textbook. Sometimes it tries to trick you.
This puppy came in with hives and no GI signs — no vomiting, no diarrhea. That combination is a classic red herring: hives push your differentials toward an allergic or immune-mediated process, and without vomiting or diarrhea, salmon poisoning drops down the list fast. But he was also lethargic and feverish at 104.1°F, with lymph nodes swollen in multiple places — findings that, together, kept salmon poisoning on the table. It's an easy case to get tricked by if you're pattern-matching to the "textbook" presentation instead of working the full picture — history, exam findings, and cytology together.
Reading the lymph node aspirate ourselves settled it: morulae, right there in the monocytes, alongside thrombocytopenia on bloodwork — another piece consistent with the diagnosis. No wait on an outside lab.
Treatment mattered too. Salmon poisoning needs doxycycline, and the IV form isn't something every clinic stocks. RVVE carries specialized injectable antibiotics, so we started IV doxycycline within the hour — no waiting on an oral-only option to take effect in a puppy who couldn't keep food down.
He left the next morning eating on his own, temp back to 102.1°F, with two weeks of oral antibiotics ahead of him.
