Canine Parvovirus

Canine Parvovirus    

  • Canine parvovirus (CPV) is a highly contagious diseases of young dogs characterized by acute hemorrhagic enteritis, leukopenia and occasionally  myocarditis

ETIOLOGY

  • Canine parvovirus – SS DNA
  • Several antigenically different serotypes:
    • CPV-1: Minute virus of canines – causes myocarditis and respiratory diseases and intestinal enterocyte hyperplasia with eosinophilic to amphophilic INIB
    • CPV-2: Subtypes CPV-2a, and CPV-2b – causes parvovirus enteritis
  • Genus:  Protoparvovirus
  • Family: Parvoviridae
  • Parvo: from Latin, ‘small’

Host

•       Young (less than 6 month), unvaccinated or incompletely vaccinated dogs are most susceptible.

•       Cat, mink, calves can also affected

Transmission

•       Direct contact 

•       Virus shed in feces of infected dogs

•       Contaminated food, water, fomites

Pathogenesis

•       Virus reach to nasopharyngeal mucosa→ viral uptake by epithelium over tonsils and Peyer's patches → Virus (1-2 days) → Lymphoblast dissemination to many tissues (3-4 days) → Lymphocytolysis (Leukopenia) → releases virus, causing viremia → neutralizing antibody - terminating viremia (5-7 days) →Infection of GI crypt epithelium and Peyer's patches (5-9 days)

•       Further diseases development depends on amount of virus ,  lymphocyte lysis  and the rate of cell proliferation in the crypts of Lieberkuhn (Lieberkuhn  is the pit between the villi in the small intestine)

•       Virus reach to crypts of Lieberkuhn→  Replication of virus in actively dividing enterocyte ( Enterocyte : intestinal absorptive cells, are simple columnar epithelial cells which line the inner surface of the small and large intestines.) → Lysis, necrosis and sloughing of enterocyte → Villus atrophy, erosion or ulceration →  Hemorrhages and malabsorption → bloody diarrhea → Dehydration

•       Epithelium regeneration → Facilitate virus replication → more destruction If stem cells present  - Regeneration occurs 

•       Cytolysis of proliferating cells in the bone marrow causes myeloid and erythroid hypoplasia (Megakaryocytes are the least sensitive to lysis)

•       In new born puppies → Cardiac myocytes  are actively dividing cells up 15 day age → Replication of virus in actively dividing cardiac myocytes → Lysis and necrosis of  cardiac myocytes → Myocardial necrosis → arrhythmia and unexpected Death

Clinical Signs

•       Three forms of disease:

❶ Generalized: 

•       Pups less than 2 weeks  - Found Dead – Rare

❷Cardiac form:

•       Pups 2-8 weeks  - sudden death from cardiac arrhythmias

•       Survivors usually die by 5 months of age from chronic myocardial fibrosis and resultant cardiac arrhythmias.

❸Leukopenia/enteritis:

•       Common form in pups 8 weeks and older

•       Vomiting, anorexia, pyrexia, dehydration, lethargy, bloody diarrhea.

•       Leukopenia, with relative or absolute lymphopenia, hypoproteinemia, and anemia.

•       Myocardial and enteric forms rarely occur together.

Macroscopic  Pathology

Leukopenic/enteric form :

•       Segmental to diffuse hemorrhagic gastroenteritis with mucoid/bloody intestinal contents and fibrinous serosal exudate

•       Peyer's patch necrosis

•       Enlarged, congested, edematous mesenteric lymph nodes

•       Semiliquid, yellow-gray bone marrow

•       Thymic atrophy

Myocardial form:

•       Pale streaks in myocardium, pale, flabby

•       Pulmonary edema with white frothy fluid in trachea and bronchi


Canine small intestine dilatation, luminal hemorrhage

Segments of the small intestine are diffusely reddened (active hyperemia of the mucosa), and the serosal surface is roughened, faintly granular, and petechiated.

Note the multifocal pale areas (arrow) in the ventricular myocardium

Microscopic  Pathology

•       Severe necro-hemorrhagic gastroenteritis; crypt necrosis; blunting; fusion

•       Basophilic intranuclear inclusion bodies in GI epithelium are variably evident.

•       Necrosis and depletion of lymphoid tissues

•       Bone marrow depletion

•       Focal myocardial necrosis with intranuclear basophilic inclusion bodies in cardiomyocytes

Parvovirus infection, section of myocardium. An intranuclear basophilic inclusion body is in a myocyte (arrow)


Diagnosis

•       Clinical signs

•       Histopathology

•        Laboratory tests

•       Virus neutralization tests   

•       Enzyme-linked immunosorbent assay (ELISA)

•       Polymerase chain reaction

•       Serological tests

Canine Parvovirus Antigen Test Kit 

Sample Information

● Samples must be at room temperature (18-25°C) before beginning the test procedure.

● Canine fecal matter is required for this test. Swabs are provided for sampling.

● Fecal samples can be stored at 2-8°C for 24 hours. If longer storage is required, samples should be frozen.

Test procedure

1. If stored in a refrigerator, allow all components to equilibrate at room temperature (18°C-25°C) for 30 minutes. Do not heat.

2. Obtain a sampling swab and a SNAP device for each sample to be tested. Pull and twist the tube covering the swab tip to remove the tube from the swab/reagent bulb assembly (A). Using the swab, coat the swab tip with fecal material. Then, return the swab to the tube (B).

3. Break the purple valve stem inside the bulb assembly by bending the assembly at the narrow neck (C), rebending the opposite way may be helpful. Squeeze the reagent bulb three times to pass the blue solution through the swab tip and mix it with the sample (D).

4. Place the SNAP device on a horizontal surface. Using the swab as a pipette, dispense 5 drops of the fluid into the sample well, being careful not to splash contents outside of the sample well.


The sample will flow across the result window, reaching the activation circle in 30-60 seconds. Some sample may remain in the sample well.

5. When color FIRST appears in the activation circle, push the activator firmly until it is flush with the device body.

NOTE: Some samples may not flow to the activation circle within 60 seconds, and, therefore, the circle may not turn color. In this case, press the activator after the sample has flowed across the result window.

6. Read the test result at 8 minutes.

Interpreting Test Results

To determine the test result, read the reaction spots in the result window and compare the color intensity of the sample spot to that of the negative control spot.

Positive Results

Color development in the sample spots that is darker than the negative control indicates a positive result, and the presence of parvovirus antigen in the sample.

Negative Results

Color development only in the positive control spot indicates a negative result.


TREATMENT


  • Intravenous fluids (a drip) to treat shock and correct dehydration and electrolyte abnormalities
  • Anti-sickness medication
  • Plasma transfusions and/or blood transfusions to replace proteins and cells
  • Antibiotics to treat or prevent secondary infections as a result of the effects of parvovirus infection like The most common antibiotics used include ampicillin, cephalexins, and flouroquinolones
  • Tube feeding
References : 
 

Pathologic Basis of Veterinary Disease Expert Consult

6th edition


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