Which of the following is a good test to detect rabies virus in the brain of a dog?
a. Agglutination
b. Hemagglutination inhibition
c. Virus neutralization
d. Direct fluorescent antibody

Verified step by step guidance

1. Understand the nature of the rabies virus and where it is typically detected in an infected animal. Rabies virus primarily infects the central nervous system, so testing brain tissue is common for diagnosis.
2. Review the principles of each test option: Agglutination tests detect antibodies or antigens by clumping; Hemagglutination inhibition measures the ability of antibodies to prevent virus-induced clumping of red blood cells; Virus neutralization tests assess the ability of antibodies to neutralize virus infectivity; Direct fluorescent antibody (DFA) test uses fluorescently labeled antibodies to detect viral antigens directly in tissue samples.
3. Consider which test is most suitable for detecting viral antigens directly in brain tissue. The DFA test is widely used for rabies diagnosis because it can detect rabies virus antigens in brain smears quickly and with high specificity.
4. Eliminate options that are more suited for detecting antibodies in serum rather than viral antigens in tissue. Agglutination, hemagglutination inhibition, and virus neutralization are primarily serological tests and less practical for direct detection in brain tissue.
5. Conclude that the Direct fluorescent antibody (DFA) test is the preferred and standard diagnostic method for detecting rabies virus in brain tissue of animals.

Key Concepts

Rabies Virus Detection Methods

Detecting rabies virus in brain tissue requires sensitive and specific tests. Common methods include direct fluorescent antibody (DFA) testing, which identifies viral antigens in tissue samples, and other serological tests that detect antibodies or viral particles. Understanding these methods helps determine the most reliable diagnostic approach.

Direct Fluorescent Antibody (DFA) Test

The DFA test uses fluorescently labeled antibodies that bind specifically to rabies virus antigens in brain tissue. Under a fluorescence microscope, infected cells emit bright signals, allowing rapid and accurate detection. It is considered the gold standard for post-mortem rabies diagnosis in animals.

Limitations of Agglutination and Neutralization Tests in Rabies Diagnosis

Agglutination and virus neutralization tests primarily detect antibodies in serum, not viral antigens in tissues. Hemagglutination inhibition is used for viruses that cause red blood cell clumping, which rabies virus does not. These tests are less suitable for direct detection of rabies virus in brain samples.