FINAL DIAGNOSIS
Feline Panleukopenia and Bordetella bronchiseptica bronchopneumonia
History: A male domestic shorthaired cat, reportedly 3 months of age, was submitted for necropsy to the Purdue Animal Disease Diagnostic Laboratory. Upon presentation to the referring veterinarian, the kitten was recumbent and severly dehydrated with pale mucus membranes and a temperature of 96° F. The owner reported a one day history of vomiting and anorexia.
Gross findings: The small and large intestinal serosa was roughened and pale grey. Both the small and large intestine had thickened walls and contained a small amount of yellow mucoid material. Cranioventrally, the lungs were mottled dark red and firm. The thymus was reduced in size.
Histopathologic findings: The small intestinal villi were severely blunted or absent, and there was destruction of crypts. The majority of crypts that remained contained either no crypt epithelium or epithelial cells that were polyhedral with a large nucleus (hypertrophy). Peyer's patches contained reduced numbers of lymphoid cells. In the lungs, therre was infiltration of macrophages and neutrophils into alveolar spaces and pulmonary interstitium. Eosinophilic fibrinoid material, cell debris, and numerous finely basophilic coccobacilli filled many air spaces. Both the spleen and examined lymph nodes contained reduced numbers of lymphoid follicles. The morphologic diagnoses were necrotizing enteritis, lymphoid depletion, and bronchopneumonia.
Discussion: Feline panleukopenia virus, a parvovirus, is cytolytic and targets rapidly dividing cells such as lymphoid cells and crypt epithelium. The virus is also capable of altering the differentiation of the layers of the cerebellum during fetal development, producing cerebellar hypoplasia.
Panleukopenia virus is highly contagious and transmission is commonly fecal-oral. However, fomites are also an important source of transmission. The virus is very resistant to extreme temperatures and conventional cleaning agents. All of these factors contribute to the common occurrence of feline panleukopenia virus infection in animal shelters and humane societies.
Early in the course of the disease, the virus infects the bone marrow, lymphoid tissue, and thymus, resulting in lymphoid depletion, thymic involution, leukopenia, and enteritis. Grossly, intestinal serosa may be roughened and intestinal walls may be segmentally thickened and hemorrhagic. Peyer's patches may be depressed. Thymic atrophy and lymph node edema may also be present.
As the virus destroys the rapidly dividing crypt cells, villi are lost to attrition and nonabsorption results. This contributes to the diarrhea often noted in feline panleukopenia patients. Histologically, villi may be shortened or absent. Crypt epithelium may be hypertrophic, attenuated, or absent and crypts may be dilated with mucus and necrotic cell debris. Peyer's patches may be hypocellular. Enterocytes and lymphocytes may contain basophilic intranuclear inclusion bodies, although these are not commonly seen.
As the name suggests, panleukopenia virus infection causes depletion of all lymphoid cells. The resulting immune compromise increases susceptibility to other infections, such as respiratory disease or bacterial enteritis. Also, loss of the gastrointestinal mucosal barrier can increase susceptibility to bacterial infections. In this case, the gross and histopathologic findings of broncho-pneumonia correlate with the culture of Bordetella bronchiseptica from the lung. Panleukopenia virus infection may have contributed to the incidence and/or severity of this respiratory infection by causing immune compromise.
Common postmortem ancillary tests performed when feline panleukopenia virus infection is suspected include virus isolation and fluorescent antibody (FA) testing or immunohistochemistry of the ileum, distal jejunum, spleen, lung, and tongue. These results, in addition to clinical history and gross and histopathologic findings, aid in a diagnosis of feline panleukopenia virus infection. In this case, the tongue and small intestine were positive for feline panleukopenia by virus isolation and FA. The final diagnosis is feline panleukopenia and Bordetella bronchiseptica bronchopneumonia.
From July 29,2004 to August 31, 2004, there have been at least 19 diagnosed cases of feline panleukopenia at the ADDL. This is one of the largest outbreaks of panleukopenia in recent ADDL history. It is important for area clinicians to be aware of the increasing number of cats diagnosed with this disease.
-by Dr. Sarah Janke, ADDL Graduate Student
References:
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Animal Disease Diagnostic Laboratory. Retrieved September 5, 2004 from http://www.addl.purdue.edu
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Armed Forces Institute of Pathology, Veterinary Systemic Pathology, Feline panleukopenia virus infection-small intestine, lymph node-cat (n.d.). Retrieved September 26, 2004 from http://vetpath4.afip.org/systemic/index.php
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Jones, Hung and King: 1997. Veterinary Pathology, 6th ed. Baltimore: Lippincott Williams & Wilkins.
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McGavin, Carlton and Zachary: 2001. Thomsons's Special Veterinary Pathology, 3rd ed. St. Louis: Mosby
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