Feline Panleucopenia

Introduction

Feline Parvovirus, also known as feline infectious enteritis (FIE) or feline panleukopenia is a non-enveloped virus, capable of persisting for long periods of time in the enviroment.

It infects the lymph nodes of the oropharynx and the nasopharynx, and the spreads to other tissues. It infects and kills actively replicating cells. Kittens are most susceptible, but unvaccinated older cats can also become infected.

Hosts

Feline Parvovirus is most commonly seen in cats, but is may also be seen in minks, racoons, and pandas.

Pathogenesis

Feline Parvovirus kills the stem cells of the villi. The villi tip cells turnover normally but are not being replaced, leading to stunted villi and malabsorption. Clinical signs include pyrexia, severe enteritis (often bloody), dehydration, leukopenia, anemia Neonatal kittens less than 2 weeks show cerebellar hypoplasia

• Kittens more susceptible than cats
• Oral infection
• Initial replication in pharyngeal lymphoid tissue
• Viremia
• Virus targets rapidly dividing cells: lymph nodes, bone marrow, crypts of small intestine

Epidemiology

• Infection by direct contact and fomites
• Subclinical infections occur
• Virus excretion can be persistent
• Endemic worldwide

Diagnosis

• Clinical signs
• Hematology: leukopenia
• Can be confirmed by haemagglutination (HA) or ELISA using feces

Control

• Inactivated vaccines are available and essential for boarding
• Administered parenterally post-weaning to induce a systemic immune response to neutralize viremia
• Annual booster

Parvovirus Enteritis

• Parvovirus enteritis is also know as feline infectious enteritis or feline panleucopenia
• Since a vaccine is available, this disease is now uncommon.
• Over the last 10/15 years this has been seen primarily in the cat, but it is now also seen in the dog.

Clinical

• Manifests mainly in cats under 6 months old.
• Common in groups of unvaccinated cats.
  • Produces big outbreaks, with vomiting and pyrexia.
• Severe vomiting and diarrhoea occur.
  • diarrhoea is thin, watery and foul-smelling, and may also be blood-tinged.
    • Animals usually die despite treatment- die from dehydration.
• Animals suffer from fever.
• Pancytopaenia also occures.
  • White blood cell count drops very low so as to become almost non-existent.
    • Drops to 1/ml from 10000/ml.
  • Animals may therefore also die from other infections.

Pathology

Gross

• Virus targets crypt cells and lymphoid areas.
  • Causes villus atrophy.
• In the cat, the intestine is thickened, turgid and swollen.
  • Has a pale, dull and mottled appearance.
  • The contents are rather dry - this gets worse lower down the gut.
• Areas of depression in the mucosa can be seen in the upper small bowel.
  • Due to necrosis of tissue overlying Peyers patch.
• Lower down in the gut, enteritis is apparent.
  • Cat- fibrinous.
  • Dog- haemorrhagic.
    • Blood in lumen.
  • Inflammation sometimes doesn't appear very severe.
• There may be very few lesions
  • Histology is usually required for diagnosis.
• A radiomimetic virus.
  • Affects all rapidly dividing cells and destroys them.
    • E.g. epithelium in the base of the crypts of small intestine are killed.

Histological

• The crypt lining cells undergo complete necrosis, but very little inflammation occurs.
  • Collapse of villous architecture.
• May be fibrinous exudates on surface of mucosa.
• The submucosa and lamina propria are not affected and are left intact.
  • Many neutrophils in the lamina propria.
• Cyst-like structures are seen in the deepest parts of the glands of the intestinal mucosa, if the animal survives for more than a few days.
  • Flattened epithelial cells line these cystic glands.
    • Are enterocytes trying to repair the damage.
    • However, animals usually die from dehydration or secondary infection before the mucosa recovers.
• Inclusion bodies may be seen, but these are very hard to find.
• May get lymphocyte invasion of mucosa.
• Lymph nodes appear pale and oedematous, and almost aplastic.
• Bone marrow appears pale and fatty looking and is depleted of cells.