Virology, Serology & Electron Microscopy

The Virology/Serology and Electron Microscopy sections test specimens to obtain evidence of viral, rickettsial, fungal and protozoal infection. These sections conduct diagnostic testing for the major viruses of cattle, horses, dogs, and cats, and selected testing for viruses of pigs, sheep, goats, wildlife, llamas, alpacas, amphibians and marine mammals. The sections also conduct fluorescent antibody testing and serological testing for various viral, bacterial, rickettsial, protozoal and fungal pathogens of veterinary importance.

Two main groups of tests are offered:
(1) tests that determine the actual presence of the infectious disease agent or its components (antigens and toxins) including virus isolation (VI), direct fluorescent antibody (FA) examination, electron microscopy (EM), antigen-ELISA, and cytotoxic assays; and
(2) tests that provide evidence of exposure such as various serological assays.

The fluorescent antibody (FA) test is the most widely used antigen detection system for rapid laboratory diagnoses. The test is usually done on frozen sections of fresh tissue; formalin-fixed specimens cannot be used. Fluorescent antibody test results are reliable if fresh, and appropriate tissues are tested. Other rapid diagnostic tests include ELISA and electron microscopy (EM). When at all possible, separate specimens should be submitted for EM.

Specimens

Specimens from live animals may include nasal or ocular secretions, feces, and whole blood. Specimens collected at necropsy should include the organs or tissues affected by the disease process. For details on appropriate specimens to submit for specific tests, please refer to our INTERACTIVE LAB TESTS & FEE SCHEDULE.

Virus Isolation

Specimens collected early in the acute stage of illness are preferred for virus isolation. These should be fresh with no preservative or fixative added. Materials can sometimes be conveniently submitted on sterile swabs if a viral transport medium is used. Tissue samples should be shipped refrigerated on ice packs.

Serology

Serology detects the presence of antibodies in serum samples. Results of serologic tests provide useful information for regulatory and export purposes, and planning herd-health vaccination programs. With the exception of certain life-long viral infections (equine infectious anemia, bovine leukemia, caprine arthritis encephalitis), the presence of antibodies in an animal does not necessarily indicate the animal is infected with that virus at the time of sampling. Therefore, serologic results are of limited use in the diagnosis of most infectious diseases unless the results of acute and convalescent sera are compared. The acute sample should be collected as early in the illness as possible and the convalescent sample 2-4 weeks later. More definitive results can usually be obtained faster if samples are submitted for other tests at the same time, (e.g. fluorescent antibody, electron microscopy, PCR, and virus isolation).

In the event of special requests or large numbers of samples, please contact the laboratory prior to submission. Blood samples for serology should be collected in sterile plain tubes without anticoagulants. Bangs' tubes may contain residues which may be toxic and thus produce non-diagnostic results. Do not freeze blood or allow it to become overheated. Submit serum rather than whole clotted blood if samples will not be received by the laboratory within 48 hours.

Electron Microscopy

Electron microscopy is used to detect and identify viruses in clinical specimens, primarily feces (rotavirus, coronavirus, parvovirus, calicivirus, etc.), but is also used with other specimens such as skin lesions (poxvirus, papillomaviruses) and tracheal or conjunctival swabs and scrapings (herpesvirus). At least 1 ml of feces, more if possible, should be submitted in leak-proof containers under refrigeration. Do not freeze! Do not use plastic gloves or OB sleeves! Plastic bags are acceptable if specimens are double bagged. Fecal swabs are often acceptable for detection of canine parvovirus/coronavirus. Swabs and excised skin lesions should be placed in tightly capped containers with a few drops of sterile saline to prevent drying.

Samples should be collected early in the course of the disease as the concentration of virus shed often decreases rapidly. In the case of herd problems, samples should be collected from more than one animal including an apparently healthy individual and several others in different stages of the disease. Multiple samples will also help in detection of viruses that are shed intermittently, as is frequently the case with infection by rota/reoviruses.

Rabies Suspects

The brain of an animal suspected of having rabies and associated with human exposure should be sent directly to the nearest Georgia Department of Human Resources Laboratory. Most of these laboratories request that only the brain be submitted. The brain should be cut in half longitudinally so each half includes parts of the cerebrum, midbrain, cerebellum, and brainstem. One half should be submitted to the nearest official public health rabies laboratory chilled with ice packs; the other half should be placed in formalin and saved or shipped to one of the diagnostic laboratories. The diagnostic laboratories do not perform the official fluorescent antibody test for rabies.

Note:
In situations where human exposure has occurred, it is suggested that you hand deliver the brain directly to the official public health rabies laboratories. Additionally, all cattle suspected of rabies should be tested for bovine spongiform encephalopathy (mad cow disease) if the rabies result is negative. To accomplish this, a piece of the brain stem (at the level of the obex, as shown below) should be submitted in a 50-ml capped tube in a box with ice packs to the Athens laboratory with the instruction TEST FOR BSE IF RABIES NEGATIVE.


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