Several routes exist for the inoculation of an embryonated chicken egg. The major routes of inoculating an embryonated egg with a virus or clinical sample suspected to contain a pathogenic virus include the chorioallantoic membrane, yolk sac, allantoic cavity and the amniotic sac. Viruses can be inoculated in several sites of an embryonated egg. They can be inoculated into the chorioallantoic membrane (e.g. herpes simplex virus and pox virus); allantoic cavity (e.g. influenza virus and rabies virus); amniotic sac (e.g. mump virus); and yolk sac (avian viruses). Certain areas of the embryonated chicken egg including the allantoic cavity, yolk sac, amniotic cavity and chorioallantoic membrane are chosen for the injection of viruses or viral samples required for virological investigations because viruses can only grow or replicate in certain parts of the embryonated egg. Viral replication outside these designated areas as shall be highlighted in this section is rare and counterproductive. These designated areas of viral inoculation in embryonated chicken eggs contain the necessary materials and substances that will drive viral replication; and thus they are the most preferred sites for viral inoculation when the use of the embryonated chicken egg technique for viral cultivation is anticipated.
- Chorioallantoic membrane: The chorioallantoic membrane is usually used for the cultivation of herpes simplex virus and poxvirus.
- Allantoic cavity: Allantoic cavity is used for the cultivation of avian viruses, yellow fever virus, rabies virus and influenza virus.
- Amniotic sac: Amniotic sac is used for the cultivation and isolation of mump virus as well as influenza virus.
- Yolk sac: Yolk sac is used for the cultivation and isolation of avian viruses; and this region also support the growth of a wide variety of other viruses. Some obligate intracellular parasites like Rickettsia and Chlamydia can also be propagated in this region.
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