A diagnosis of rabies Ag can be made after detection of the rabies virus in any part of the affected brain, but to rule out rabies, the test should include tissue from at least two locations in the brain, preferably the brainstem and cerebellum. The test requires that the animal be euthanized. The test itself takes about 2 hours, but it takes time to extract brain samples from an animal suspected of having rabies and send these samples to a state public health or veterinary diagnostic laboratory for diagnosis.
In the United States, the results of a rabies test are generally available within 24 to 72 hours after an animal is collected and euthanized. Because rabies exposure of suspected animals is a medical emergency, but not an emergency, testing within this period is more than adequate to determine if a person was exposed to a rabid animal and requires rabies vaccinations after The exhibition.
Approximately 120,000 or more animals are tested for rabies each year in the United States, and approximately 6% are found to be rabid. The proportion of positive animals is highly dependent on the animal species and ranges from <1% in domestic animals to >10% in wild species.
Based on routine public health surveillance and pathogenesis studies, we have learned that it is not necessary to euthanize and test every animal that bites or potentially exposes a person to rabies. For animals with a low probability of rabies such as dogs, cats, and ferrets, observation periods (10 days) may be appropriate to rule out potential exposure risk to human rabies. Consultation with a local or state health official after a potential exposure can help determine the best course of action based on current public health recommendations.
Several tests are needed to diagnose rabies antemortem (before death) in humans; no proof is enough. Tests are performed on samples of saliva, serum, cerebrospinal fluid, and skin biopsies from hair follicles at the nape of the neck. Saliva can be analyzed by virus isolation or reverse transcription followed by polymerase chain reaction (RT-PCR). Serum and cerebrospinal fluid are tested for antibodies to the rabies virus. Skin biopsy samples are examined for rabies antigen in the cutaneous nerves at the base of the hair follicles.