CANINE PARVOVIRUS 

Nature of the disease
Canine parvovirus is a highly contagious infection of dogs caused by a Parvovirus and characterised by sudden onset of vomiting, diarrhoea, dysentery, depression, anorexia, pyrexia, severe dehydration, leucopaenia and death. Sudden death from myocarditis occurs in very young puppies.
Classification
SPC List D disease
Susceptible species
Dogs. Canine parvovirus is primarily a disease of young dogs. Rottweilers, American Pit Bull Terriers, Doberman, Pinschers and German Shepherd are more susceptible.
Distribution
Canine parvovirus appeared suddenly right around the world, including Australia and New Zealand, in 1978.
Clinical signs 
Clinical signs are very variable with puppies the most severely affected.Mortality rates can be high. 

There are two main clinical syndromes associated with canine parvovirus infection — enteric form, and myocardial or heart form

Enteric form 

  • Sudden depression
  • Loss of appetite
  • Fever especially in puppies
  • Vomiting and diarrhoea (in up to 50% of cases, diarrhoea may be haemorrhagic)
  • Rapid dehydration
  • Shock and death (in acute cases)

If the dog survives the enteritis and dehydration, it becomes immune, but recovery may be slow.
Myocardial form or heart form 
The first form is associated with sudden death. The puppy appear normal, then gasps, mucous membranes turn pale and then cyanotic, with death occurring in about two hours due to acute non-suppurative myocarditis.
The heart form is associated with congestive heart failure. There is slower onset of clinical signs:

  • Dyspnoea
  • Depression
  • Cough
  • Ascites
  • Death typically at 12–16 weeks of age
Post-mortem findings 
In the enteric form the following are seen:
  • Lower and middle small intestine is dilated — contents are watery and flocculent
  • Bone marrow is depleted

In the myocardial form the following is seen:

  • Lungs are heavy and oedematous, grey-pink in colour with focal congestion
  • Heart is dilated will ill-defined pale areas in the myocardium
  • May be haemorrhages in the pancreas
  • Clear watery fluid in the thorax and abdomen
  • Pale, flabby heart with myocardial fibrosis in more chronic cases
Differential diagnosis 
Other cause of enteritis to be considered include:
  • Canine distemper
  • Infectious canine hepatitis
  • Canine coronavirus
  • Salmonellosis
  • Campylobacteriosis
  • Haemorrhagic gastro-enteritis
  • Poisonings

Other cause of myocarditis include:

  • Canine distemper
  • Infectious canine hepatitis
  • Canine herpesvirus
  • Streptococcal infection
  • Congenital heart anomalies
Specimens required for diagnosis 
Canine parvovirus can be suspected on clinical grounds in severe cases. In less severe cases, laboratory assistance may be required.
Faecal material should be collected from suspect cases for attempted virus isolation and/or virus detection.
At post-mortem, fresh samples of mesenteric lymph nodes, tonsils, small intestine and intestinal contents should be collected and forwarded chilled, on water ice or frozen gel packs, to the laboratory.
Serum samples from recovered or older in-contact animals can be collected for serology.
Transmission   
Animals are infected by contact with infected faeces, usually by ingestion — via feeding utensils, licking infected dogs, etc. Virus can survive for up to 12 months in faeces. The virus is also present in urine.

Infection is spread directly and indirectly by anything contaminated by faecal material (shoes, coats, hands, equipment).

Risk of introduction   
Canine parvovirus has shown the ability to spread widely and rapidly. The virus can survive for long periods. The disease could be introduced with an infected dog or via clothing or equipment contaminated with faecal material.
Control / vaccines  
With the enteric syndrome, supportive therapy is important. Treatment should include electrolyte fluid replacement, gastric sedatives and anti-emetics.
With the myocardial form, treatment is ineffective.

Vaccines are available. If the bitch has been vaccinated, puppies will have some passive immunity that will decline over the first 3 months of age. To be protected, puppies need to be first vaccinated at 6 weeks with repeat doses at 12-14 weeks and 16-18 weeks. Annual boosters are recommended.
For dog breeders, there should be careful attention to hygiene and disinfection of kennels.

References
  • Canine Parvovirus, In Merck Veterinary Manual, National Publishing Inc. Eight ed, 1998, Philadelphia, p 285-286
  • Parvovirose du chien, In Dictionnaire Pratique de Thérapeutique Canine et Féline, Masson, Forth ed, 1997, Paris, p 401-402