Carnivora Parvovirus Typing

Reminders

The causative agent for canine parvovirosis is parvovirus type 2 (including subtypes CPV2, CPV2a, CPV2b and CPV2c). The strains currently present on the field are CPV2a, CPV2b and CPV2c (or CPV2-Glu 426). A particular Asian CPV2c strain is also currently circulating in Europe. The CPV2 responsible for parvovirus cases 20 to 30 years ago seems to no longer be circulating on the field.
The main causative agent for feline panleukopenia is feline parvovirus (FPV), and in some cases, canine parvovirus type 2 (2a, 2b, 2c) may be isolated in feces of cats with panleukopenia.

Causative agents

Canine Parvovirosis or panleukopenia vaccination is performed with licensed live viral vaccines (CPV2 or CPV2b for canine parvovirus and FPV for panleukopenia).
All canine vaccines (with high viral titer or not) include CPV2, with the exception of the Zoetis Versican® vaccine (which includes a CPV2b strain).

Vaccines

Typing test characteristics

The test developed by Scanelis allows the distinction of 5 viral types: FPV, CPV2, CPV2a, 2b and 2c. However, FPV cannot be distinguished from 2 genetically closely-related viruses, MEV (Mink Enteritis Virus) and BFPV (Blue Fox Parvovirus) and which are not isolated in cats.
It does not allow the distinction between field and vaccinal strains in FPV and CPV2 (as CPV2 strains seem to no longer be circulating on the field). Gene sequencing analysis of the VP2 capsid protein is necessary to perform this kind of analysis.
The typing test detects polymorphisms on 3 codons (305, 323 and 426) in the VP2 protein gene.

Interest and utilization of the typing test

The typing test must be performed after an analysis has confirmed a parvovirus or panleukopenia.

For further information on the real-time canine parvovirus PCR diagnostic

In that case, the typing of the main strain is enabled in 100% cases (study carried on 57 cases of canine parvovirus and 28 cases of panleukopenia) and shows a 100% correlation with the reference technique (partial VP2 sequencing).
Typing only does not enable a diagnostic because its diagnostic specificity is insufficient (some asymptomatic animals are wild-type strain carriers).
When the viral load is moderate or low, typing can bring an answer in over 90% cases. Cases whose interpretation is hard to establish correspond to mixtures of strains.

When to request typing ?

• To confirm a field strain of parvovirus is in circulation in groups and identify it (notably in a context of recent vaccination).
• To confirm the feline (FPV) or canine (CPV2a, 2b or 2c) origin in groups where cats and dogs live together (e.g: shelters…).
• To confirm results with moderate viral load on a recently vaccinated animal with clinical signs.

How to interpret the results ?