The infection caused by canine distemper virus is widely spread throughout the world and is associated with high morbidity in unprotected animals and also a high mortality rate as a result of the development of respiratory, gastrointestinal and/or neurological problems. The prevention of distemper is mainly medical and is based on vaccination. Live attenuated vaccines give effective protective immunity, but their quality differs depending on the strain used (strains attenuated on canine cells or avian strains). The standard dead vaccines have a more limited efficacy in dogs, but can be used without any risk in other species (ferrets and wild carnivores), for which the live vaccines are not sufficiently attenuated.
It is good practice to vaccinate all puppies and give boosters to adult dogs. When an animal’s history is not known, it should be considered at risk and vaccinated, and periodic boosters also planned.
Vaccination against distemper is usually performed together with the administration of other antigens starting from 8 weeks of life and using a live attenuated virus vaccine, with boosters at intervals of 3 to 4 weeks. If a puppy is at high risk, the first vaccination can be given at 6 weeks of age and then boosters administered at 9-11 and at 12-14 weeks, because of the risk that the contemporary presence of maternal antibodies could interfere with the vaccination. The most widely used vaccines do, however, seem able to overcome maternal immunity starting from 12 weeks.
A booster should be given after 1 year and should provide long-term immunity. The current recommendations of the American Veterinary Medical Association (AVMA) indicate that boosters should be administered every 3 years (following the initial booster after 1 year), whereas annual boosters are recommended in the product information leaflets of most vaccines. In fact, the minimum duration of immunity following vaccination is variable and it is, therefore, necessary to adapt the protocols depending on the type of vaccine used and the lifestyle of the patient. The minimum duration of immunity with the Rockborn and Onderstepoort strains is 7 and 5 years, respectively, while that following vaccination with a vaccine based on a recombinant canaripox vector is only 1 year. In conclusion, with live attenuated virus vaccines, 3-yearly boosters following the first booster at 1 year can be considered protective, whereas if vaccines based on a recombinant vector are used, the boosters should be given at shorter intervals (1 year). Early immunisation can be established by administering the vaccine (only the distemper valence) by the intravenous route in non-vaccinated animals.