Canine Parvovirus: This is the most commonly contracted virus
amongst dogs. It causes severe vomiting and dysentery (bloody
diarrhoea). Usually fatal unless treated intensively (hospitalisation,
intravenous drips etc.) which is expensive.

Canine Distemper: Is less common in this country nowadays thanks
to the success of vaccination but if contracted is often fatal.

  
Canine Hepatitis: This virus attacks the liver it can cause sudden
fatality in acute cases and if treated can be a very long road to
recovery.

Leptospirosis: This bacteria can cause liver and kidney failure,
Jaundice, acute illness and death. If presented early it is treatable,
but again it is quite a long road to recovery and it is a major zoonosis
(can be transmitted to humans).

  

Canine Parainfluenza: This virus is rarely fatal, however it
can cause a very distressing, harsh cough that can continue for many weeks.
The disease is commonly known as 'Kennel Cough'. Most kennels
will insist on this vaccine being given before they will admit the,
animal as this is highly contagious.

The viral part of Kennel Cough is covered by injection but the bacterial
part of the disease is a separate vaccine which is given Intra Nasally.

Cats:   

The main viruses covered by vaccinations are:-

Panleucopenia: This is also known as Feline Enteritis. This virus can
cause 'rapid onset', vomiting, bloody diarrhoea and listlessness.
It is very difficult to treat and usually fatal in young cats.

Feline Rhinotracheitis/ Feline Calicivirus: Otherwise known as Cat Flu.
These virus attacks the upper Respiratory System causing flu-like
symptoms which if left untreated can become very severe.