THE GOAT VETERINARY SOCIETY |
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Transplacental transmission
One of the reasons for Chris Oura taking his standpoint is that we now know more about transplacental transmission of disease than we did even 3 months ago, and this was backed up by a presentation by Linda van Wuiijckhuise from Holland, who has been involved in similar work.
It is now known that embryos whose dams are infected early in pregnancy, tend to be aborted early. Those infected in the last 3 months of pregnancy tend to be unaffected, or relatively so. It is the ones in the middle that are interesting. they can survive to full term, and while some may be stillborn, many will live, but have the condition called hydroanencephaly, where the cerebral hemispheres are replaced by fluid, leaving them as Chris called it, “Intellectually challenged”, and as Linda called them, “Dummy calves”. They can suck, but not for long, are strong candidates for stomach tubing with colostrum, and then display the characteristics of the bovine equivalent of having learning difficulties. I think we can assume that this might apply to lambs and kids as well, but to what extent we do not as yet know.
Apparently, these calves are born potentially viraemic, (and again here read lambs, and probably kids as well). If they get a good feed of colostrum, whether naturally or by stomach tubing, the virus rapidly disappears, and so cannot be picked up by midges and circulated. The neonatal that might be a threat is the one who failed to get colostrum, and could therefore be inadvertently targetted by midges, for as long as it survived, which can be quite a variable time.
Importantly, if these neonates, infected during pregancy, receive colostrum, the disease seems not to progress and not to be a threat, other than transiently, of causing circulation of virus in the local midge population. It is those few who are born viraemic, and who did NOT receive colostrum, that could potentially lead to virus circulation.
The possible mechanisms for “Overwintering” of virus were discussed, and while translplacental transmission is still an obvious method, the possibility of what might be called virus hibernation in non ruminant species cannot be ruled out. I think that shows that ths is a disease where we are still learning fast. It is essential that all involved, including politicians, accept that as we advance scientific frontiers we need to adapt to the implications, whether as Scientists, politicians, AH personell, or even Secretaries of the various breed veterinary societies in the UK and elsewhere.
This is a debate which is still open, and another possible mechanism of transmission, Oral transmission, is under investigation.
Eradication ofVirus and Current International State
Vaccination Transmission Transplacental Eradication Current situation