What is the earliest age at which an animal can be safely vaccinated?
In general, six to nine weeks is the earliest age at which a routine vaccination program should be started. Exceptions occur for animals who are in environments which would likely expose them to disease, e.g., humane shelters, breeding facilities, etc. These animals may benefit from earlier vaccinations. Vaccination with a parvovirus vaccine in puppies 5 weeks of age is recommended by some. Vaccinating puppies and kittens less than 4-5 weeks of age is generally not recommended.
Distemper
Canine distemper is a contagious and serious viral illness with no known cure. The disease affects dogs, and certain species of wildlife, such as raccoons, wolves, foxes, and skunks. The common house pet, the ferret, is also a carrier of this virus. Canine distemper belongs to the
Morbillivirus class of viruses, and is a relative of the measles virus, which affects humans, the
Rinderpest virus that affects cattle, and the
Phocine virus that causes seal distemper. All are members of the
Paramyxoviridaefamily. Young, unvaccinated puppies and non-immunized older dogs tend to be more susceptible to the disease.
Symptoms and Types
The virus, which is spread through the air and by direct or indirect (i.e. utensils, bedding) contact with an infected animal, initially attacks a dog’s tonsils and lymph nodes and replicates itself there for about one week. It then attacks the respiratory, urogenital, gastrointestinal, and nervous systems.
In the initial stages of Canine Distemper, the major symptoms include high fever (≥103.5 ° F, or 39.7° C), reddened eyes, and a watery discharge from the nose and eyes. An infected dog will become lethargic and tired, and will usually become
anorexic. Persistent coughing,
vomiting, and
diarrhea may also occur. In the later stages of the disease, the virus starts attacking the other systems of the dog’s body, particularly the nervous system. The brain and spinal cord are affected and the dog may start having fits, seizures, paralysis, and attacks of hysteria.
http://www.petmd.com/dog/conditions/respiratory/c_dg_canine_distemper