Welcome to BYC, so sorry for your loss. 
Unless your drake was exhibiting other duck plague symptoms before the seizures, I don't think you need to worry about duck plague.
Symptoms
"Clinical signs may develop within 3-7 days of exposure to the virus and include depression, ruffled feathers, difficulty breathing, loss of coordination, avoidance of light, extreme thirst, loss of appetite, ocular and nasal discharge (that may be bloody), bloody and watery diarrhea, and a bloody vent."
Source: https://www.northeastwildlife.org/disease/duck-plague
Unless your drake was exhibiting other duck plague symptoms before the seizures, I don't think you need to worry about duck plague.Symptoms
"Clinical signs may develop within 3-7 days of exposure to the virus and include depression, ruffled feathers, difficulty breathing, loss of coordination, avoidance of light, extreme thirst, loss of appetite, ocular and nasal discharge (that may be bloody), bloody and watery diarrhea, and a bloody vent."
Source: https://www.northeastwildlife.org/disease/duck-plague
