Canine parvovirus by wuxiangyu

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									Canine Parvovirus
•Family Characteristics & Structure
•Parvovirus Types
•Signs & Symptoms
•Prevention & Control
•Etiology/ Epidemiology
•Even More Pictures!
•Helpful Links

Created by: Christie Anton, Jason Atkins, Rebecca Morgan &
Bryan Neves
                     Family Parvoviridae

                                 Family Parvoviridae

                    Subfamily Parvovirinae   Subfamily Densovirinae
                      (birds & mammals)            (insects)

                    Genus Parvovirus           Genus Densovirus

                      Genus Erythrovirus
                                                Genus Iteravirus

                     Genus Dependovirus
Genus Parvovirus                               Genus Contravirus         Genus Densovirus

                   Source for pictures:
             General Characteristics of Family
•   Virion is non-enveloped                  Morphology
•   Nucleocapsids are 18-26 nm in                                            crystallograph
    diameter                                                                 y
                                                                             of canine
•   Symmetry is icosahedral with
    capsids (protein coat surrounding
    DNA) made up of 60 molecules of
    overlapping capsid proteins
    designated: VP1, VP2, & VP3

•   Surface projections appear as                      Icosahedron
    small, rough spikes

Source for pictures:

Diagram source:
                                                                     EM of canine parvovirus
           General Characteristics of Family
 •    DNA is single-stranded (– sense or a combination of both + and -), linear, and
      ~5Kb          long.
 •    Palindromic sequences (100-300 nucleotides long) form a hairpin structure,
      which is important for initiation of replication.

  Palindromic sequences resulting
   hairpin structure.

  Diagram source:
                          Parvovirus Types
•  The genus Parvovirus contains viruses that are some of the smallest and hardiest of
   bugs, able to survive in a wide range of climatic conditions in nature.
•  These viruses also have a variable host range, infecting many different mammal & bird
   species in which the viruses have been named accordingly: Canine Parvovirus (CPV),
   Feline Parvovirus (FPV), Porcine Parvovirus (PPV), Bovine Parvovirus (BPV), Goose
   Parvovirus (GPV), etc., etc.
•  CPV in particular is an example of an emerging virus due to its recent appearance
   (1970’s) and rapid spread throughout the world.
•  The evolutionary capabilities of this virus has produced many types to date, and is
   related to the ever-changing virulence of this bug.
Specific Types
•  CPV-1: a.k.a. canine minute virus (CMV). This is the first described canine parvovirus in
   late 60’s / early 70’s that is associated with fetal viral infections, that leads to
   reproductive failure and neonatal respiratory disease. It may also produce enteritis in
   puppies and older dogs. However, it has been shown by DNA sequencing to be more
   closely related to bovine parvovirus (BPV) than canine parvovirus today that is
   descended from feline parvovirus (FPV). [Schwartz et al.]
•  CPV-2: This emerged suddenly in 1978, most likely from FPV, to cause gastroenteritis
   in adult dogs and myocarditis in very young pups. After ‘jumping the species barrier’
   from FPV, CPV-2 was further selected for growth within dog cells, making dogs a better
   and natural host [Strauss p 276].
•  CPV-2 mutated and evolved again in 1979 to give us CPV-2a , in 1984 to produce CPV-
   2b, and finally CPV-2c most recently in Italy, Vietnam, and Spain [Decaro et al.].
          Canine Parvovirus Pathogenesis
•   Incubation: 3-8 days, with shedding of the virus beginning on the 3rd day, before the
    appearance of clinical signs.

•   Transmission is either through direct contact with infected dog’s feces, or indirectly
    through fecal-contaminated fomites. The virus may be shed up to 3 weeks following
    infection and may survive up to 9 months in a contaminated area.

•   Following inhalation or ingestion, the virus will initially replicate within the lymphoid
    tissues of the oropharynx region.

•   Now in the bloodstream, the virus will seek out rapidly dividing cells such as: bone
    marrow cells, lymphopoietic cells, and intestinal epithelium, leading to viremia and further
    replication and lysis of these host cells.

•   Tropism for intestinal epithelium leads to collapse of intestinal villi, epithelial necrosis,
    and hemorrhagic diarrhea—clinical signs of gastroenteritis.

•   Depletion of lymphocytes and compromised gastrointestinal system may lead to
    bacteremia by normal gut flora, i.e. Escherichia coli, which can be fatal.
         Canine Parvovirus Pathogenesis
                                                 Dilated crypt epithelium

                                                 Acute hemorrhagic enteritis

Source for drawings:

Source for pictures:
                         Signs & Symptoms
•   Signs and symptoms are related to usually 2
    disease presentations: gastroenteritis and
    myocarditis. Myocarditis however is rarely an
    issue currently due to immunization practices in
    the mothers [Merck].
•   Initial signs of CPV infection: depression, fever,
    anorexia, vomiting, and severe diarrhea. Feces
    may be yellowish gray due to the presence of
    mucus. The feces may also contain blood due to
    the onset of hemorrhagic enteritis.
•   Dehydration is also common due to the rapid loss
    of fluids from vomiting and loose stools. Some
    very unfortunate puppies may experience
    projectile, bloody diarrhea and vomit until their
    deaths (48-72 hrs following obvious signs).
•   CPV infections have been misdiagnosed,
    unfortunately due to the similarities in symptoms
    to parasitic infections, stress colitis, or perhaps
    the dog’s last meal was disagreeable!
•   So, the correct diagnostic tools are crucial to
    prevent the deaths of such young pups!
             Testing is the only way that you will know for certain if you have a parvovirus problem.
  The following are some common practices performed in veterinary offices or laboratories:
•     Extensive history based upon clinical
•     Positive fecal ELISA result to confirm
•     Newest diagnostic tools

ELISA (Enzyme-Linked Immunosorbent

The ELISA test is the most efficient test to
     use. It takes only 15 minutes and can
     be easily performed in the veterinary

However, ELISA is a very sensitive test and
    can be influenced by some different                               Diagram source:
    factors such as recent vaccination and
    onset of clinical signs, giving false
    positive or false negative results.
Newest Diagnostic Tools

   Parvovirus PCR testing has been shown to be a very effective and sensitive way to detect canine
parvovirus. Dogs that have been experimentally exposed to parvo had positive fecal PCR results from
day three to day fourteen after exposure. This gives you a much bigger window of opportunity to
diagnose the virus. The PCR test will also find the presence of fecal parvo
DNA even when an antigen test (ELISA) showed a negative result.
   Real-time PCR is the newest technology using a minor groove binder (MGB) probe assay to specifically
vaccine strains and field strain types (2a, 2b, and 2c). It is based on the TaqMan technology, and this real
proven to be even more specific, sensitive, and reproducible than other conventional methods such as: he
immunochromatographic tests, viral isolation, and even gel-based PCR [ Decaro, N. et al.].
   Other advantages compared to conventional PCR: less time-consuming, less chance of carry-over con
“However, the molecular assays, especially the real-time PCR method, require expensive equipment, reag
operators; thus, their use as tests for the veterinary practice is not feasible. Nevertheless, there are effor
 to adapt molecular methods to clinical practice, taking advantage of microchip technology that would redu
 of the equipment necessary for on site testing.” [Costantina, D. et al.].
   Electron microscopy is another vital diagnostic tool utilized to view the morphological characteristics o
organisms, like parvoviruses, when standard microscopy will not suffice. Even with all the newest forms o
EM is still extensively used as a reference technique, especially in cases of specimens expected to contain
the virus in diarrheic stool samples.
The WSVL currently uses EM for diagnosis of parvovirus but it is also developing a PCR test for typing of
Supportive care
•   replace lost fluids & monitor electrolyte levels
Control vomiting
•   withhold food and water
•   if persistent, the compound metoclopramide
    can be administered [Merck].
•   once vomiting has subsided, a bland diet such
    as cottage cheese and rice will suffice
•   Gradually reintroduce regular diet

Antibiotic therapy
• in the most severe cases, such as bacteriemia
   and septicemia, antibiotics should be
   administered with a broad spectrum series
      Note: Prevention and control of the virus is the most effective means of
                       Prevention & Control
1.     Vaccination
2.     Decontamination
3.     Isolation

      The most important form of prevention is to vaccinate against CPV-2a and CPV-2b.
      The most effective vaccination available is the live-attenuated canine parvo. It is most
      important to vaccinate puppies, however adult dogs that have been continuously
      vaccinated are at low risk and may not need to be vaccinated so often. To protect
      puppies from infection, a series of vaccine shots should be given every 2-4 weeks
      until they are 16 weeks old. By that time the maternal antibodies will have gone and
      the vaccine will be able to take affect [Mar Vista Animal Medical Center].

      The only absolutely effective disinfectant is bleach at a 1:30 dilution. Use to disinfect
      hands, clothing, food and water bowls, toys, anything that the puppy may come into
      contact with, or has regular contact with [Merck].

        Infected animals must be isolated from healthy animals to prevent the spread of the
        virus. Places of high risk are dog shows, field trials, boarding kennels and public
        spaces reserved for dogs.
                       Etiology/ Epidemiology
    “Canine parvovirus disease is currently the most common infectious disorder of dogs in the United St

•    Canine parvovirus is an extremely
     hardy bug that is able to withstand
     harsh environmental conditions and
     common disinfectants.
•    Highly contagious
•    Mainly affects young puppies that
     are 6-20 wks old due to a limbo
     period of decreased antibody
     protection from the mother and the
     inadequate vaccination protection for
     the young pups [Merck].
•    Adult dogs may be asymptomatic
     carriers and shed the virus
•    Certain breeds seem to be
     particularly susceptible: Rottweilers,
     German Shepherds, Doberman
     Pinschers, and American Pit Bull
     Terriers [Merck].
•    Mortality rate is variable: 16-48%

    The evolution of Canine
   Parvovirus is perhaps one of
      the most important, and
   closely studied, evolutionary
       pathway in diagnostic
    virology. This evolutionary
   map shows in detail how the
     current strains of Canine
     Parvovirus (CPV-2a and
    CPV-2b) came into being.

Diagram source: Uwe Truyen
   (Veterinary Microbiology)
•   Prior to the emergence of Canine Parvovirus, this virus infected the cat
    (Feline panleukopenia virus or FPLV) and mink (Mink enteritis virus or MEV).

•   A mutation of just 2 amino acids enabled FPLV to evolve and make a leap
    between species.

•   At least 11 conserved nucleotide differences (7 nonsynonymous and 4
    synonymous changes) were seen between CPV-2 isolates and FPLV-type
    viruses in the capsid VP2 sequence. However, CPV and FPLV isolates differ
    in <2% of their genomic DNA sequences.

•   In 1978, CPV-2 appeared, quickly spreading worldwide within a couple of
    months, infecting and killing thousands of dogs. This strain of parvovirus
    could not replicate well in cats.

•   Discovered some years later in 1983, a virus isolated from Artic Fox from
    Finland (Blue Fox Parvovirus or BFPV ), while being essentially the same as
    MEV-2, had three synonymous nucleotide changes in the VP2 gene that were
    specific for the canine sequence. This suggests that BFPV may have been an
    evolutionary intermediate between FPLV and MEV, and CPV-2.
•   With the introduction of vaccines, dogs started to develop immunity to CPV-2.
    This forced the virus to mutate once again.

•   The new antigenic type, CPV-2a, became the more commonly seen strain by
    1981. CPV-2 was rarely seen after this point in time. This marked the death
    of the original Canine parvovirus strain.

•   The new strain of CPV-2a differed from CPV-2 in that it had lost at least one
    epitope recognized by monoclonal antibodies (MAbs) and gained a new
    specific epitope.

•   In 1984, yet another new antigenic type, CPV-2b appeared. This strain
    overtook CPV-2a as the parvovirus dogs are most commonly infected with in
    the United States.

•   Both these antigenic types, CPV-2a and CPV-2b replicate effectively in cats.
    In fact, domestic cats and wild felines both present with these viruses today.

•   The newest antigenic type is CPV-2c. This strain, discovered in 1997, has
    only been found in Leopard cats. The virulence of CPV-2c in dogs has yet to
    be determined.
                            Helpful Links
Costantina, D. et al. “Canine Parvovirus Infection: Which Diagnostic Test for Virus?” Journal
    of Virological Methods 126 (2005): 179-185.
Decaro, N et al. “Occurrence of Severe Gastroenteritis in Pups After Canine Parvovirus
    Vaccine Administration: A Clinical and Laboratory Diagnostic Dilemma.” Vaccine (2006),
Ikeda, Y. et al. “Feline Host Range of Canine Parvovirus: Recent Emergence of New Antigenic
    Types in Cats.” Immerging Infectious Diseases, Vol. 8, No.4 (2002): pp 341-346.
Kahn, Cynthia M. ed. The Merck Veterinary Manual 9th edition. Whitehouse Station: Merck
    & Co, 2005.
Parrish, C.R, et. al. “Rapid Antigenic-Type Replacement and DNA Sequence Evolution of
    Canine Parvovirus.” Journal of Virology, Vol. 65, No. 12 (1991): pp. 6544-6552.
Schwartz, D., B. Green, L.E. Carmichael and C.R. Parrish. “The Canine Minute Virus (minute
    virus of canines) is a Distinct Parvovirus That is Most Similar to Bovine Parvovirus.”
    Virology 302 (2002), pp. 219–223.
Strauss, James H., and Ellen G. Strauss. Viruses and Human Disease. San Diego: Academic
    Press, 2002.
Truyan, Uwe. “Evolution of Canine Parvovirus-A Need for New Vaccines.” Veterinary
    Microbiology 117 (2006): 9-13.

Web references:
“Canine Parvovirus.” Mar Vista 2000. Mar Vista Animal Medical Center. 11 Dec.
“Parvovirus.” Pet 2006. Drs. Foster & Smith, Inc. 11 Dec. 2006

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