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Parvovirus Variants and Vaccines

These days the news is filled with discussions about the emerging variants of SARS-CoV-2 – the virus that causes COVID-19. Hemopet discussed the occurrence of viral variants approximately nine months ago. We reminded everyone that all viruses and other microbes like bacteria, parasites and fungi must mutate to survive. Mutations spark these questions amongst virologists and other scientists:

  1. Will the mutation processes trigger new and significantly dominant variants?
  2. Will the variants be more transmissible, cause more severe illness, or be more deadly?
  3. Will natural or vaccine-induced immunity to a previous variant protect against new variants?
  4. Has too much antigenic drift occurred from the ancestral strain to impair the effectiveness of vaccines and treatment options such as monoclonal antibodies developed against the new variants?

As we already know that SARS-CoV-2 is a rapidly evolving virus, we thought instead to discuss viral replication in the context of the ubiquitous canine parvovirus and the vaccines that protect against it.

Parvovirus

Parvovirus infection in dogs was first clinically recognized in 1978. It was and is distinct from the B-19 strain of human parvovirus first recognized in Australia in 1974.

It can be spread through direct dog-to-dog contact or contact with contaminated feces (stool) or fomites. Additionally, once parvovirus is exposed to the environment, it can last for years in soil.

The symptoms and effects include:

  • abdominal pain and bloating
  • bone marrow failure (anemia), bruising and pinpoint skin bleeding (petechiae) and very low white blood cell counts
  • fever or low body temperature (hypothermia) in severe cases
  • infertility and early fetal death
  • lethargy
  • loss of appetite (inappetence)
  • severe and often bloody diarrhea
  • vomiting

Parvovirus is deadly because the constant diarrhea and vomiting can lead to dehydration, damage the intestines and immune system, and lead to septic shock.

Researchers have identified the following variants that have evolved since 1978:

  • CPV-2 (original)
  • CPV-2a
  • CPV-2b
  • CPV-2c
  • CPV-2d

CPV-2c appears to be the dominant strain at this time.

Vaccines Against Parvovirus

Do the currently available vaccines such as CPV-2 and CPV-2b work effectively against the newer variants? Yes; they do.

Will the currently available vaccines against parvovirus be effective against a new and significant variant if it emerges? We do not know at this time. We do know that to stop or slow the spread of the disease through effective vaccination will stop viral replication and the emergence of new variants.

Dr. Dodds’ Vaccination Protocol

The following is Dr. Dodds’ latest vaccination protocol from 2016 regarding parvovirus vaccines.

9 – 10 weeks of age
Distemper + Parvovirus, MLV
e.g. Merck Nobivac (Intervet Progard) Puppy DPV

14 – 15 weeks of age
Distemper + Parvovirus, MLV

18 weeks of age
Parvovirus only, MLV
Note: New research states that last puppy parvovirus vaccine should be at 18 weeks old.

1 year old
Distemper + Parvovirus, MLV
This is an optional booster or measure serum antibody titers. If the client prefers not to give this optional booster or plans to retest titers in another three years, giving this optional booster at puberty is wise.

Perform serum vaccine antibody titers for distemper and parvovirus every three years thereafter, or more often, if desired.

Previous Vaccine Protocol

Dr. Dodds’ earlier canine vaccine protocol did not include a parvovirus booster shot at 18 weeks of age; only vaccinations at 9-10 and 14-16 weeks of age. Due to the virulent parvovirus variants and to reach effective protection against the variants based on new research, she now advises an additional vaccination against parvovirus at 18 weeks of age.

References

Canine Parvovirosis. MSD Animal Health Republic of Ireland, 16 June 2020, https://www.msd-animal-health.ie/species/dogs/canine-parvovirosis/.

Canine Parvovirus Type 2c FAQ. American Veterinary Medical Association, Feb. 2013, https://www.avma.org/resources/pet-owners/petcare/canine-parvovirus-type-2c-faq.

De la Torre, David et al. “Molecular characterization of canine parvovirus variants (CPV-2a, CPV-2b, and CPV-2c) based on the VP2 gene in affected domestic dogs in Ecuador.” Veterinary world vol. 11, no. 4 (2018): 480-487. doi:10.14202/vetworld.2018.480-487, https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5960788/.

de Oliveira, Pablo Sebastian Britto et al. “New variants of canine parvovirus in dogs in southern Brazil.” Archives of virology vol. 164, no. 5 (2019): 1361-1369. doi:10.1007/s00705-019-04198-w, https://pubmed.ncbi.nlm.nih.gov/30859474/.

Dodds, W. Jean. “2016 Dodds Vaccination Protocol for Dogs.” Dr. Jean Dodds’ Pet Health Resource Blog, Tumblr, 18 July 2016, https://drjeandoddspethealthresource.tumblr.com/post/147595920886/dodds-vaccination-protocol-dogs-2016#.YDZmPOhKjIW.

Franzo, Giovanni, et al. “Canine Parvovirus (CPV) Phylogeny Is Associated with Disease Severity.” Scientific Reports, vol. 9, no. 1, 2 Aug. 2019, doi:10.1038/s41598-019-47773-6, https://www.nature.com/articles/s41598-019-47773-6.

Larson, Laurie J, and R D Schultz. “Do two current canine parvovirus type 2 and 2b vaccines provide protection against the new type 2c variant?.” Veterinary therapeutics : research in applied veterinary medicine vol. 9, no. 2 (2008): 94-101, https://pubmed.ncbi.nlm.nih.gov/18597247/.

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