How are rats tested for rabies? - briefly
Rats suspected of rabies infection are usually euthanized, and their brain tissue is examined with a direct fluorescent antibody (DFA) test or a reverse‑transcriptase PCR assay to detect viral antigens or RNA. These laboratory methods provide a definitive diagnosis within a few hours.
How are rats tested for rabies? - in detail
Rats suspected of rabies infection undergo a series of laboratory procedures designed to detect viral antigen or genetic material in neural tissue. The process begins with humane euthanasia, typically by overdose of an anesthetic agent, to comply with animal welfare regulations. After death, the skull is opened and the brain is removed, focusing on regions where rabies virus concentrates, such as the hippocampus, cerebellum, and brainstem.
The primary diagnostic test is the direct fluorescent antibody (dFA) assay. A thin slice of brain tissue is placed on a slide, fixed, and incubated with a fluorescently labeled anti‑rabies immunoglobulin. Under a fluorescence microscope, the presence of specific orange‑green fluorescence indicates viral antigen. Positive results are reported immediately; negative samples may be subjected to additional testing.
If the dFA result is inconclusive, a reverse transcription polymerase chain reaction (RT‑PCR) is performed. RNA is extracted from the same tissue, reverse‑transcribed into cDNA, and amplified using rabies‑specific primers. Amplified products are visualized by gel electrophoresis or real‑time detection, providing a highly sensitive confirmation of viral nucleic acid.
For epidemiological purposes, virus isolation in cell culture or mouse inoculation may be employed. Homogenized brain material is inoculated onto susceptible cell lines (e.g., murine neuroblastoma cells) or intracerebrally injected into laboratory mice. Observation of cytopathic effects or development of clinical signs confirms the presence of viable virus.
All procedures are conducted in biosafety level 2 or higher facilities, with personnel wearing appropriate personal protective equipment. Documentation includes animal identification, clinical history, collection date, and test results, recorded in a laboratory information management system compliant with national rabies surveillance guidelines.