Blood Test:

A laboratory analysis performed on a blood sample that is usually extracted from a vein in the arm using a needle, or via finger picks. The liquid portion of the blood is called plasma. Blood cells and some proteins turned solid, if there are blood clots outside of the body. The remaining liquid is called the serum, which can be used in chemical tests and in tests to find out how the immune system fights diseases. Viruses can also be identified by growing infectious organisms that cause an illness with blood samples, and view under a microscope.

ELISA:

Enzyme- Linked Immuno-Sorbent Assay (ELISA) is an antibody- Antigen reaction. It detects the presence of antibody or antigen,

It can be used to detect infection with Human Immunodeficiency Virus (HIV). If antibodies to HIV are present, the test is usually repeated to confirm the diagnosis. If the test result is negative, other tests are not usually needed. This test has a low chance of having a false result after the first few weeks that a person is infected.

Haemagglutination- Inhibition (HI):

It is actually haemagglutination conducted in the presence of antibody. Neutralisation of virus inhibits agglutination.

HI is commonly used in chickens for Newcastle disease (Paramyxovirus-1), Infectious bronchitis (Coronavirus), and EDS-76 (adeno-virus). HI tests may also be carried out for Avian Influenza. But due to poor crossing- reactivity between different haemagglutinin groups, AGP is favoured for routine screening. Various serotypes of IBV have been used in HI tests as an aid in suggesting the likely infecting strain. HI tests require inexpensive reagents though they are labour-intensive. The fact that a series of dilutions are separately tested means that the results are highly reproducible.

Plaque assay:

Plaque assay can be used to purify a clonal population of virus or to determine viral titre as plaque- forming units per ml (pfu/ml) so that known amounts of virus can be used to infect cells during subsequent work. Firstly, monolayer cells are infected with low ratio of virus, such that sporadic cells become infected. An overlay of agarose, keeps the cells stable and limits the spread of virus. When each infected cell produces virus and lyses, only adjacent cells become infected. Each group of infected cells is referred to as a plaque. The principle of the assay is, if the concentration of the virus is low enough, it will allow one virus to infect one cell.

PCR:

PCR stands for Polymerase Chain Reaction. It is a technique for amplifying DNA sequences in vitro by separating the DNA into two strands and incubating it with oligonucleotide primers and DNA polymerase. It can amplify a specific sequence of DNA by as many as one billion times and is important in biotechnology, forensics, medicines, and genetic research. Detection and identification of the PCR product is usually carried out by agarose gel electrophoresis, hybridization with a specific oligonucleotide probe, restriction enzyme analysis, or DNA sequencing.

PCR include cycles of three steps, heating, cooling, and increasing temperature.