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937.e2 Spongiform Encephalopathies

Spongiform Encephalopathies Client Education
Sheet
VetBooks.ir Advanced or Confirmatory Testing

• No transmission of FSE to humans has been
BASIC INFORMATION
identified. Ultimate diagnosis is available only postmortem:
Definition histopathologic lesions showing vacuolation
The spongiform encephalopathies are a GEOGRAPHY AND SEASONALITY in gray matter, and immunohistochemistry
heterogeneous group of diseases that have in FSE was recognized in Europe only at the height demonstrating malfolded prion proteins.
common spongiform change within the brain of the BSE epidemic.
shown on histopathology. This appearance is Clinical Presentation TREATMENT
caused by vacuolation within neurons in gray
matter diseases or within myelin in white HISTORY, CHIEF COMPLAINT Treatment Overview
matter diseases. Use of the term spongiform Behavior changes (timidity or aggression) There is no effective treatment. Confirmation
encephalopathy to describe white matter disease progressing to ataxia, hypermetria, and of gray matter spongiform encephalopathy is
has been discontinued in favor of spongiform leu- hyperesthesia to touch and sound important for public health considerations.
koencephalopathies or spongy degeneration of white
matter to avoid confusion with the transmissible PHYSICAL EXAM FINDINGS Acute General Treatment
spongiform encephalopathies that affect gray Neurologic findings as described above Symptomatic therapy
matter. Recently a number of hereditary diseases
have been identified in dogs with prominent Etiology and Pathophysiology PROGNOSIS & OUTCOME
neuronal vacuolation that can be confused with FSE is caused by prions, which are enigmatic
transmissible spongiform encephalopathies but infectious proteins. Abnormally folded prion FSE is inexorably progressive and fatal.
are not prion diseases. This chapter is limited to proteins act as chaperones to cause misfolding
the transmissible spongiform encephalopathies. of the normal prion proteins found naturally PEARLS & CONSIDERATIONS
Further information on the hereditary diseases in neurons. The misfolded prion proteins are
with neuronal vacuolation can be found in the resistant to degradation, build up in neurons Comments
Suggested Readings. as scrapie-associated fibrils, and ultimately Now that BSE has been controlled, transmissible
lead to cell death. Cats are infected by inges- spongiform encephalopathies should remain
Synonyms tion of meat or by-products from cattle with rare in cats and not occur in dogs. However,
The classic transmissible spongiform encepha- BSE. the spread of CWD in the United States may
lopathy is scrapie in sheep. The more recently increase the risk of future outbreaks. Thus it
identified diseases are named for the species DIAGNOSIS is important to recognize them if they should
affected (e.g., bovine spongiform encephalopa- occur because of the public health implications.
thy [BSE], feline spongiform encephalopathy Diagnostic Overview Necropsy is necessary to confirm a diagnosis
[FSE], transmissible mink encephalopathy). In Diagnosis is confirmed at necropsy. of transmissible spongiform encephalopathy,
deer and elk it is called chronic wasting disease which should be reported to the appropriate
(CWD). As a group, they are also called prion Differential Diagnosis agency. Care must be taken to not confuse the
disease. • Any cause of diffuse forebrain signs in adult hereditary diseases characterized by neuronal
cat vacuolation with the transmissible spongiform
Epidemiology ○ Infectious: rabies, feline immunodeficiency encephalopathies.
SPECIES, AGE, SEX virus (FIV), feline infectious peritonitis
Prion disease has been reported in sheep, (FIP), fungal, protozoal Prevention
cattle, cats, mink, deer, and elk. It has not ○ Metabolic: hepatic, electrolytes, endocrine Risk from deer with chronic wasting disease is
been reported in dogs. Age of onset of FSE in ○ Toxic: organophosphates, heavy metals unknown, but it would be wise to avoid feeding
cats is > 2 years, with a peak incidence at 5-7 • After the recognition of FSE in Europe, deer nervous system tissues or by-products to
years of age. There is no sex predisposition. cats with signs of FSE were screened for cats.
spongiform encephalopathy at necropsy. The
GENETICS, BREED PREDISPOSITION most commonly diagnosed diseases in the Technician Tips
Variants in the prion gene have been associated cats that did not have FSE were nonsup- • Animals with dementia can have unpredict-
with susceptibility to prion disease in sheep and purative encephalitis, neoplasia, and cerebral able behavior. Care should be taken when
humans, but no breed predisposition or variants ischemia. restraining these animals because they may
in the prion gene associated with susceptibility respond aggressively.
to FSE have been identified in cats. In humans, Initial Database • There is no evidence of transmission to
pathogenic variants in the prion gene cause • Neurologic exam (p. 1136): localized lesion(s) humans by bite or scratch wounds.
hereditary spongiform encephalopathy such as • CBC/serum biochemistry profile (including
fatal familial insomnia and Gerstmann-Straussler- bile acids)/urinalysis: rule out metabolic Client Education
Scheinker syndrome, but such hereditary prion disease and look for evidence of infection Clients should be educated about transmissible
diseases have not been identified in animals. • Brain imaging (p. 1132): rule out spongiform encephalopathies so they can make
structural disease. MRI studies have not intelligent choices regarding meat safety rather
CONTAGION AND ZOONOSIS been performed in FSE. Scrapie sheep than being swayed by emotion or politics.
• Ingestion of BSE-contaminated meat or by- show only diffuse atrophy, while humans
products can cause variant Creutzfeldt-Jacob with CJD show T2 hyperintensity in SUGGESTED READING
disease (CJD) in humans and FSE in cats. the striatum and cortex, particularly the Vandevelde M, et al: Prion diseases and feline
Intracerebral inoculation of CWD in cats cingulum. spongiform encephalopathy. In Green CE, editor:
produces disease, but oral transmission has • Cerebrospinal fluid (CSF) analysis (pp. 1080 Infectious disease of the dog and cat, ed 4, St.
not been documented. and 1323): rule out encephalitis/meningitis Louis, 2012, Saunders, pp 862-864.

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