Parvo and panleukopenia: a shelter perspective (Proceedings)


Parvo and panleukopenia: a shelter perspective (Proceedings)

Nov 01, 2009

Canine parvo and feline panleukopenia are closely related viruses that replicate in rapidly dividing cells. The most obvious symptoms of infection are gastrointestinal but the bone marrow is also affected. The virus is transmitted primarily by the fecal-oral route (including indirectly via objects/clothing/hands contaminated with virus from feces). These viruses are unenveloped making them very durable persisting in the environment for months or even years. The incubation period is generally less than 14 days, on average 5-7 days. It tends to be shorter in cats. Control in shelters is dependent on effective vaccination, accurate and efficient diagnosis, effective isolation, and careful cleaning and disinfection. This lecture will focus on these four key outbreak control tools.

Effective shelter vaccination

Vaccination for parvo viruses is highly effective if performed correctly. Shelter vaccination protocols can substantially reduce spread of infection as they are more intensive than those used in private practice. This fact has been recently recognized by both the American Association of Feline Practitioners (AAFP) and the American Animal Hospital Association (AHAA) published vaccine guidelines. Modified live subcutaneous vaccination will provide considerably more rapid protection than killed vaccines. All cats and dogs 4-5 weeks of age and older should receive a modified live parvo/panleukopenia vaccine immediately upon shelter entry. Studies have shown that parvo vaccines can illicit protective immunity within 3-5 days of vaccination in susceptible dogs1. Panleukopenia vaccines have been shown to protect against disease within 72 hrs of exposure. Even injured, pregnant and mildly ill animals should be vaccinated, unless they are certain to be euthanized within a few days.

The emergence of a new canine parvo strain (CPV-2c) has elicited concern about the efficacy of current parvo vaccines that use either CPV-2 or CPV-2b strains. The research and conclusions remain controversial to date but most evidence suggests that all currently available parvo vaccines do protect against CPV-2c

1) Carmichael, L. E., J. C. Joubert, et al. (1983). "A modified live canine parvovirus vaccine with novel plaque characteristics. 1. Viral attenuation and dog response." Cornell Vet 73(1): 13-29.

2) Brun et al. Immunisation against panleukopenia: early development of immunity. Comp Immunol Microbiol Infect Dis. 1979;1(4):335-339.

3) Spibey et al., Veterinary Microbiology 128 (2008) 48–55

4) Larsen et al., Do two current canine parvovirus type 2 and 2b vaccines provide protection against the new type 2c variants. Vet Therap., 2008 9(2):94-101.

Vaccination recommendations
     • Vaccinate all dogs and cats > 4-5 weeks old immediately upon intake with a modified live subcutaneous CPV or FPV vaccine respectively.
     • Revaccinate all puppies and kittens every two weeks up to at least 16 weeks of age while in shelter
     • All animals older than 6 months of age should receive two ML vaccines 2-3 weeks apart.
     • Vaccinate fostered animals at least one week prior to shelter return

Diagnosis may include:
     • Symptoms and exposure history
     • Positive results on a Parvo test
          o weak positive ELISA tests may be caused by recent (within 3 weeks) MLV vaccine) especially in kittens depending on the test used1
          o in spite of rare false positive results it is prudent for shelters to consider positive snap tests in symptomatic animals as real infection.
     • Low white blood cell count on CBC or blood smear
     • Segmental enteritis observed on necropsy

Risk assessment and quarantine
It is important to determine all animals that were in contact, either directly or indirectly, with the infected animal.
     • Low risk: dogs and cats > 4 months old that are either:
          o vaccinated with an MLV SC vaccine at least one week prior to exposure
          o documented history of appropriate vaccination as an adult (>4-5 months of age) prior to exposure.
     • Moderate to high risk: kittens and puppies under 4 months old regardless of number of vaccines given (due to maternal antibody interference)
     • High risk: closely exposed, unvaccinated animals of any age.