The severity of enteric disease caused by canine parvovirus is very variable. Many natural infections appear to be subclinical, and severe disease is difficult to reproduce experimentally. However, CPV-2 has been reported to account for between 25% and 50% of acute diarrhoea cases in dogs.
The diarrhoea results from loss of absorptive and digestive capacities but an inflammatory response may contribute a secretory component if a secondary bacterial infection occurs.
Mortality rates may be as high as 7-10% in pups but in adults they are generally less than 1%, although in an outbreak at one rescue kennel, 92% of dogs older than eight months of age were reported to die of CPV-2 enteropathy.
Clinical features include:
- Incubation period of 4-7 days.
- Initially see acute onset, protracted and severe vomiting with depression and anorexia.
- Watery, often haemorrhagic diarrhoea developing 6-24 hours later.
- Pyrexia is common.
- Haematological investigation may show a lymphopenia, associated with viral of lymphoid tissue, and an increased packed cell volume as a result of dehydration.
- Weight loss may be dramatic.
- Death may occur within 72 hours of the onset of clinical signs.
- Myocardial disease associated with CPV-2 infection is no longer at all common as most pups are protected during the first few weeks of life by maternally derived antibody.
Clinical features reported with myocardial CPV-2 infection include:
- Clinical signs of myocardial disease develop 3-7 weeks after CPV-2 infection.
- Death in up to 70% of affected pups by 8 weeks of age. Of the remaining 30%, many will die some months or years later of acute or chronic cardiac failure.
- Most affected pups collapse and die rapidly within minutes of acute cardiac failure
- Premonitory signs are not often observed, but on occasions dyspnoea, crying and retching have been recorded.
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