How is rabies diagnosed in an asymptomatic cat?

Diagnosing Rabies in Asymptomatic Cats

Definitive diagnosis of rabies in an asymptomatic cat is not possible without euthanizing the animal and testing its brain tissue using the Direct Fluorescent Antibody (DFA) test, which is the gold standard for rabies diagnosis. 1

Diagnostic Process for Suspected Rabies in Cats

Laboratory Testing Requirements

The DFA test requires brain tissue samples and must be performed by a qualified laboratory designated by local or state health departments. This process involves:

1. Euthanasia of the cat in a way that maintains brain integrity 1
2. Submission of the head or brain (including brain stem) to the laboratory 1
3. Proper specimen handling - samples should be:
   • Stored and shipped under refrigeration (not frozen)
   • Not chemically fixed (as this delays testing)
   • Submitted promptly to facilitate testing 1

When to Consider Testing an Asymptomatic Cat

Since testing requires euthanasia, the decision to test an asymptomatic cat should be based on:

• Exposure history - whether the cat was bitten or scratched by a wild carnivorous mammal (especially raccoons, skunks, foxes, coyotes) or bat 1
• Vaccination status - unvaccinated cats exposed to rabid animals are at higher risk 1
• Risk to humans - if the cat has bitten or scratched a person 1

Management of Asymptomatic Cats with Potential Rabies Exposure

For Unvaccinated Cats

• Primary recommendation: Euthanasia if exposed to a rabid animal 1
• Alternative if owner refuses euthanasia: Strict isolation for 6 months and vaccination 1 month before release 1

For Vaccinated Cats

• Immediate revaccination against rabies
• 45-day observation period under owner's control 1

Management of Cats That Bite Humans

• 10-day confinement and observation for healthy cats that bite a person 1
• Veterinary evaluation at first sign of illness during confinement 1
• Immediate reporting of any illness to local health department 1
• Euthanasia and testing if signs suggestive of rabies develop 1
• Stray or unwanted cats that bite humans may be euthanized immediately and tested 1

Important Caveats

1. No antemortem test exists for definitively diagnosing rabies in asymptomatic cats
2. Observation period limitations - cats may shed rabies virus in saliva before showing clinical signs 1
3. Vaccination is not 100% protective - though rabies is rare in vaccinated animals 1
4. Incubation period variability - can range from 2 weeks to several months in cats 2

Prevention Strategies

• Regular vaccination of all cats against rabies 1
• Avoiding contact between cats and wildlife, especially known rabies reservoirs 1
• Prompt veterinary care for any cat with potential rabies exposure 1

Remember that rabies is invariably fatal once clinical signs develop, and cats represent a significant vector for human rabies exposure, with more reported rabies cases in cats (274 in 2009) than dogs in the United States 1. This underscores the importance of proper vaccination and management of potential exposures.