Viral diseases:
* Avian influenza: Highly contagious viral disease that can cause respiratory problems, lethargy, and even death.
* Newcastle disease: Another highly contagious viral disease that can cause respiratory problems, neurological disorders, and death.
* West Nile virus: Transmitted through mosquito bites, it can cause neurological problems and death.
* Botulism: Caused by a toxin produced by bacteria found in stagnant water. It can cause paralysis and death.
Bacterial diseases:
* Salmonellosis: Bacterial infection that can cause diarrhea, lethargy, and death.
* Colibacillosis: Bacterial infection that can cause respiratory problems, diarrhea, and death.
* Fowl cholera: Bacterial infection that can cause respiratory problems, diarrhea, and death.
Parasitic diseases:
* Avian pox: Viral disease spread by mosquitoes or biting insects that causes skin lesions and can lead to secondary infections.
* Avian malaria: Transmitted by mosquitoes, it can cause anemia, lethargy, and death.
* Fungal diseases: Fungal infections can affect the skin, respiratory system, and digestive system.
Other diseases:
* Lead poisoning: Swans can ingest lead shot or fishing tackle, which can cause neurological problems, paralysis, and death.
* Trauma: Swans can be injured by boats, fishing lines, or other human activities.
* Nutritional deficiencies: Lack of essential nutrients in their diet can lead to various health problems.
Note: This is not an exhaustive list, and other diseases may affect swans. If you notice a swan that appears sick or injured, please contact a wildlife rehabilitation center or your local animal control agency for assistance.