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Viral Disease - Feline Parvovirus

Definition:

Feline panleukopenia is a highly contagious, acute enteric disease of young cats, typically accompanied by severe leukopenia and high morbidity and mortality.

In utero or early neonatal infection may cause cerebellar disease.

Etiology

Feline parvovirus (FPV), an SS-DNA virus of the family Parvoviridae, is related to CPV-2, which is rarely isolated from cats with panleukopenia.

Epidemiology

FPV is highly contagious to all domestic and wild members of the family Felidae.

Virus is shed in all body secretions, with fecal shedding being the primary source of infection.

Transmission is from contact with infected animals, contaminated environment, or fomites.

FPV is seldom encountered in vaccinated domestic cats, but is problematic in feral, shelter, and stray cats.

Disease is most common in 3- to 5-month-old kittens, because most cats >1 year old are immune from subclinical infection and younger kittens are protected by maternal Abs.

Pathogenesis

After oronasal exposure, the virus replicates in regional lymph nodes and causes viremia.

FPV preferentially infects rapidly dividing cells (e.g., intestinal epithelial cells, lymph tissue, hematopoietic cells of bone marrow).

Secondary GI bacterial infection, translocation of gut bacteria, and increased susceptibility to bacterial infection and sepsis all contribute to the clinical signs produced.

Clinical Signs

Adult cats: usually asymptomatic

Kittens

  • » Initial signs: fever, lethargy, complete anorexia, vomiting, diarrhea (sometimes hemorrhagic), severe dehydration
  • » Outcome: peracute death or spontaneous recovery, with milder disease in older kittens

Transplacental and early neonatal infection

  • » Early gestational infection: fetal resorption, infertility in apparently healthy queens
  • » Late gestational or neonatal infection
  • » Abortion of mummified fetuses, stillbirths
  • » CNS abnormalities: cerebellar hypoplasia with hypermetria and intention tremors
  • » Other signs of in utero infection: hydrocephalus, hydranencephaly, retinal dysplasia

Diagnosis

Hematological findings

A. Severe leukopenia, neutropenia, variable lymphopenia (early)

B. Rebound leukocytosis (often pronounced) during the recovery phase

C. Anemia: rarely severe with intestinal blood loss

D. Thrombocytopenia

Serum biochemistry profile

A. Increased hepatic enzyme activity

B. Azotemia, electrolyte imbalances

Specific diagnostic testing

  • » Canine parvoviral fecal ELISA kits can detect FPV antigen (imperfect sensitivity).
  • » Virus isolation (fecal material and/or urine) is not routinely used.
  • » A fourfold increase in paired serum Ab titers is diagnostic, but the test is not commercially available.

Histopathologic findings are similar to those with CPV.

Differential Diagnosis

Bacterial enteric infection

Septicemia

Parasitism

FeLV, FCoV

GI obstruction

Treatment

Provide supportive care as for CPV (see Box 112-1).

CNS signs are not treatable but are nonprogressive, and many affected kittens can be functional pets.

Monitoring and Prevention

Passive immunity

A. Colostral Ab prevents infection and interferes with vaccination up to 12 weeks of age.

B. Plasma provides passive immunity (up to 4 weeks) if the kitten is colostrum-deprived.

Active immunity

  • » Inactive (killed virus) vaccine
    • » Requires at least two administrations to be effective
    • » Safe in pregnant queens or young kittens (<4 weeks of age)

  • » MLV vaccines

They provide long-lasting immunity, although yearly booster vaccinations are still recommended by manufacturers.

They are not safe in pregnant queens and potentially cause neurological dysfunction in kittens.

Give kittens at least two vaccines, with at least 1 dose occurring after 12 weeks of age.

For current recommendations,

Natural infection produces lifelong immunity.

FPV is resistant to environmental degradation and to many disinfectants


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