Can a dog seam happy and very active suddenly drop dead from disease?

Unfortunately, yes. Sudden death in dogs can occur due to various underlying health conditions that may not always present obvious symptoms. Some diseases or conditions that can lead to sudden death in dogs include:

1. Heart Disease: Certain heart conditions, such as arrhythmias or cardiomyopathy, can cause the heart to stop functioning properly, leading to sudden cardiac death.

2. Respiratory Issues: Severe respiratory problems, like laryngeal paralysis or tracheal collapse, can obstruct the airways and cause sudden death due to lack of oxygen.

3. Neurological Conditions: Neurological disorders like epilepsy or brain tumors can lead to seizures, which can sometimes be fatal if they cause respiratory or cardiac complications.

4. Liver Failure: Acute liver failure can cause a rapid decline in the dog's health and lead to sudden death if left untreated.

5. Hemorrhage and Trauma: Severe internal bleeding or trauma due to accidents or injuries can result in sudden death if not promptly addressed.

It's essential to note that while these conditions can cause sudden death, they often have underlying signs or symptoms that may not be immediately noticeable to pet owners. Regular veterinary check-ups, early detection of health problems, and prompt medical intervention can help reduce the risk of sudden death in dogs. If you suspect your dog is experiencing a medical emergency, it is crucial to seek veterinary attention immediately.