How Do They Check Animals for Rabies?

The definitive test for rabies in animals involves tissue samples of the brain. Animals must be euthanized to conduct this check for rabies.

In the case of pets and other domestic animals a vet may choose to observe the animal for 10 days, says the Mayo Clinic. If an animal is rabid; it should exhibit symptoms during this time frame.

A doctor can check for rabies in humans by taking a tissue sample from the neck or looking for evidence of the virus in the saliva or spinal fluid, reports the National Health Institute (NHI).

What the Vet Looks For

• Rabies symptoms can also include depression.

  Animals may not exhibit rabies symptoms for up to two weeks or even many months after being infected.

  Although we may think of foaming at the mouth and wildly abnormal behavior as typical rabies symptoms: the Michigan Department of Agriculture explains that there are also rabies symptoms known as "dumb" or "furious" rabies.

  In cases of dumb rabies, animals may seem depressed and isolate themselves and wild animals lose their natural caution and fear around humans. Dumb rabies symptoms also include signs of paralysis such as strange facial expressions, dragging hind limbs, or a drooping jaw or head.

  In furious rabies, animals may bite or gnaw at themselves or attack other animals and even stationary objects. Furious rabies symptoms, says the Michigan DOA, often alternate with periods of depression.

The Direct Fluorescent Antibody Test (DFA)

• Brain tissue samples are needed to check animals for rabies.

  In the direct fluorescent antibody test, tissue samples are taken from the brain stem and cerebellum of an animal to check for rabies. The animal must be euthanized.

  The tissue samples are checked for rabies virus antigens. The rabies virus exists within nervous tissue and not the blood.

  The test takes about 2 hours and lab results are usually available within 24 to 72 hours according to the Centers for Disease Control and Prevention (CDC).

Histologic Examinations

• Brain tissue can be checked for specific rabies reactions

  Before the development of the DFA, tissue samples were studied under the microscope for specific evidence of rabies infection in the brain.

  There are certain lesions and inflammation of cells and structures that occur with rabies infections, but this method is not considered diagnostic says the CDC.

Tests of the Saliva

• Tests haven't evolved enough to test the saliva of live animals.

  The rabies virus does present itself in the saliva says the CDC, but only intermittently. Any such test on a living animal would have to be extremely sensitive to pick up the tiny amounts of protein or nucleic acid and to check for rabies, many saliva tests would be necessary.

Diagnosis in humans

• Many and repeated tests are needed to check for rabies in humans.

  To check for rabies in humans, multiple tests are required according to the NIH. Saliva is repeatedly tested; hair follicles taken by skin biopsies are checked for rabies antigens; the serum and spinal fluid are also tested for antibodies to the rabies virus.

Symptoms in Humans

• A bite isn't necessary to transmit rabies.

  It's not only the bite of a rabid animal that can transmit the rabies virus to humans: the loving lick of an infected pet around open wounds or the mucous membranes can also cause infection in humans say Penn State scientists.

  Rabies symptoms in humans begin 30 to 50 days after infection and include aches, diarrhea, fever, nausea and restlessness. The symptoms then worsen to agitation, irritability and uncontrollable excitement, muscle spasms and paralysis and confusion or hallucinations.

  Once symptoms occur, the rabies virus has infected the brain and there is no treatment. Humans die within 3 to 20 days.