Just as human vaccines have eradicated devastating diseases such as smallpox and polio, pet vaccinations are a vital weapon in the fight against the many diseases that threaten our beloved pets. Take parvo (parvovirus), for example. This horrific virus causes viral gastroenteritis in dogs that literally strips the lining of the intestine. It's hideously painful and often results in death. Parvo is also highly contagious. Just a single gram of faeces infected with parvo can spread the disease to another 1,000 animals. The virus will also stay in the environment for about 12 months, and can even survive on your shoes and clothes for up to six months.