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- #11
Leihamarie
Songster
@froggiesheins , can you clarify for me when the vertical transmissions that you've seen happen, are fertile eggs from a Marek's carrying flock removed and hatched out in an incubator in a clean room that is not touched by anyone other than persons who have sterilized themselves thoroughly???
If not, that's probably how it's happening. Even if it were transfered as @BantamLover21 suggested, there seems to be a modicum of immunity for the first 2 weeks of life.
Marek's (as I'm sure you know) is extremely pervasive and chicks that are hatched out in a Marek's flock under a hen are as likely to succumb to the virus as any non-vaccinated chick. As far as the HVT vaccine is concerned, the chick needs to be kept away from ALL points of contact with the virus for at least 12-16 weeks after hatch. It's best to vaccinate them in-ovo or as a day-old and it's advantageous to vaccinate again at 2 weeks since that is when inherited immunity from the mother seems to dissipate. Basically, if a vaccinated chick is exposed to the virus from anywhere at ANY point in the first 12-16 weeks of life it's unlikely that the HVT vaccine will be effective. Chicks need to be brooded away from the flock in a sterile environment and even then, an open window could blow virus laden dander in. I can see how this would appear to be a vertical transmission though!
In the cases that you've seen, how were the eggs hatched and the chicks raised?
If not, that's probably how it's happening. Even if it were transfered as @BantamLover21 suggested, there seems to be a modicum of immunity for the first 2 weeks of life.
Marek's (as I'm sure you know) is extremely pervasive and chicks that are hatched out in a Marek's flock under a hen are as likely to succumb to the virus as any non-vaccinated chick. As far as the HVT vaccine is concerned, the chick needs to be kept away from ALL points of contact with the virus for at least 12-16 weeks after hatch. It's best to vaccinate them in-ovo or as a day-old and it's advantageous to vaccinate again at 2 weeks since that is when inherited immunity from the mother seems to dissipate. Basically, if a vaccinated chick is exposed to the virus from anywhere at ANY point in the first 12-16 weeks of life it's unlikely that the HVT vaccine will be effective. Chicks need to be brooded away from the flock in a sterile environment and even then, an open window could blow virus laden dander in. I can see how this would appear to be a vertical transmission though!
In the cases that you've seen, how were the eggs hatched and the chicks raised?
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