Dear moderator, respected colleagues,
may I raise a note of caution here, please. I would argue strongly against equating the discovery of viral RNA by RT-PCR with the presence of infectious virus, especially in late infection, or infection of vaccinated animals.
My observations are that infected cells produce vast amounts of viral RNA and protein, but much, much, less infectious virus (this overproduction of viral protein etc is a natural consequence of life as an RNA virus, but that is much too long a story). During recovery from infection, even abortive infection of a vaccinated animal, the shedding of dead cells from the gut lining, or the mucosae, may include cells containing viral genome, or virus that has already been inactivated. The material will be positive by PCR. In agreement with the observations made by my colleague Satya Parida, I have also observed virus material in nasal swabs of vaccinated-infected animals, despite the fact that we know from prior observations that vaccinated animals do not pass on vaccine to other animals, nor do they pass on infection (shed infectious virus).
Similarly, there is nothing in the literature to say that the vaccine gives totally sterile protection: if the detection system is sensitive enough, we can detect even the very small amount of replication that happens before the immune response kicks in and protects the animal.
We do need to do functional tests: on what days post infection is there transmission of infection to a naïve bystander animal?
best regards,
Michael
This why I asked Dr Aamer the following: " Dear Dr Aamer, I am sure many readers would like to know how you detected the virus in the faeces of the recovered animals- was it live virus recovered in cell-culture or virus antigen or RNA? Have you been able to carry out experiments to see if you can transmit infection to susceptible stock kept in-contact with these "recovered" animals? And what species were these animals? Kind regards,
Hopefully Dr Aamer will soon report back with the details.
Moderator.