Wild life and CDV.
CDV spread from unvaccinated village dogs to lions inside the Serengeti reserve. The lions showed grand-mal roaring and died. Free CDV (and rabies) vaccination of the village dogs helped control it.
Distemper also spread from huskies to seals at Lake Baikil.
UK common seals recently have died from a phocid paramyxovirus. This is related to CDV. The virus originated from USA Harp seals which migrated to Europe in search of fish and infected the grey seal (minimal symptoms) and the common seal (fatalities). Less disease now, why?, maternal antibody.
Control: Most current vaccines are live virus which has been attenuated by egg passage and then grown in canine monolayers. They evoke antibody against both F and H antigens and are protective. Two doses are given at 10 and 12 weeks old because of passive immunity. However some live vaccines are now given at 7 and 10 weeks to permit more puppy socialisation before 4m.
Homeopathic vaccines or no vaccination are not recommended. In Finland an outbreak was associated with the market-leader vaccine (Dohyvac from Solvay Animal Health) being useless.