Raw, undercooked Pacific salmon and trout can carry Neorickettsia helminthoeca, a parasite-borne pathogen that causes "salmon poisoning disease" in dogs — without treatment, up to 90% of affected dogs die within 7-10 days, so never feed undercooked salmon-family fish. Cats don't appear to develop this disease, but raw fish also contains thiaminase, an enzyme that destroys vitamin B1 and can cause neurological damage with chronic feeding, so it should be avoided for them too.