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Advice on Mareks in a vaccinated flock.

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Hi I have the results of PM done on one of my birds we have lost 4 recently and it turns out it was mareks. All my birds have come from the same breeder, although in two batches so not all at once and all are supposedly vaccinated. All the birds I have lost have been pure breeds- all my hybrids appear fine. I only have two pure breeds left in my flock - so I guess I am most worried about those.




This is the reply I have had from the breeder is this:


"The mareks vaccine can be threatened if the field challenge around it is threatened. this could be due to stress or disease of some sort.

The hybrids have been vaccinated for mareks twice (they are mechanically done in belgium as we buy them as day olds)"

"Birds can only catch mareks when they are young (normally before they lay) IF there was a huge case of mareks in your area the vaccine may not protect them(or that particular vaccine may not protect them.) within your birds there have been two vaccines used. the pures were with poulvac md vac and the hybrids had Mareks respins vac. It could be the the Poulvac is not as affective in your area."



Just after any advice about things to look for and how others have managed it- as far as I know there have been no outbreaks of Mareks in my village- Just looking for any wise words from any of you who have dealt with this horrible disease before and experiences of adding birds to a flock where others probably carry the virus.


Thanks for reading

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Oh lots of sympathy from me! I' just lost my beautiful pekin cockerel to this horrible disease :( I am also worried about the girls. But I knew they were'nt vaccinated as I got them from a hobby breeder. I was very naive when I got my originals, I have been on a steep learning curve ever since!!!!! I think the info i have found since is that it is quite rare, can surface in times of stress (moult, that kind of event) but some breeds like silkies are more prone.


I read that chicks reared by a broody hen are less likely to develop it, I think they build up an immunity. But don't quote me!!!The vaccine is given as day old chicks or a close to that as poss and can only be bought in large quantities so my vet informs me.


It seems as a hooby chicken keeper we have a harder time, but really small flocks can be very healthy, it depends on where the stock comes from and of course husbandry. I would never use my original breeder again as I've lost 2 out of my original 4 (1 to mareks, his sister to a mystery illness) but did hatch myself this year and will say thay you know EXACTUALLY what you've put in and also what they have been exposed to. If that makes sense? Time will tell?!


Hope your remaining girls do well, winter is so hard!! We all need some sunshine!!!!


Best wishes

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Hi I know hence i searched high and low to find a breeder who did- they are not a hobby breeder but quite a large company.


Thats why I am so annoyed I guess they should have all been vaccinated against mareks, ib and newcastles, then finally salmonella.


Not sure if this did happen or if the breeders telling the truth- I have emailed my vet the reply from the breeder( who is a specalist poultry vet and will see what he thinks).


I am not looking to expand until i know the truth or until I know which of my girls are immune, I may also ask my vet to take blood from my two pure breeds to see if they have been given the vaccine - not sure if this is possible but I will ask.


I will say my Cock showed none of the classic signs apart from a mild limp so unless I had the PM I would be none the wiser.

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As far as I understand it the situation with Mareks and vaccination is as follows


Vaccination does not prevent Mareks, but it does, in most, though not all of the cases, alleviate some or all of the symptoms

]vaccination does not prevent infection with the virus, and the Marek's Disease virus has evolved increased virulence and resistance to this vaccine


It also reduces the amount of infected dander shed by the birds, so vaccination is imperitive in commercial situations where buildings contain thousands of birds in close proximity which would mean huge finacial losses for the business concerned


Birds still have the potential to succumb when under stress, which could be when moved to new surroundings and introduced to established birds. Similarly the resident birds may be stressed by the change in pecking order when new fowl arrives.


POL is a particularly stressful time in any case so this is a natural time when Mareks will manifest. Any other stressors, such as change of routine ie attendents and type of feed, adverse weather conditions, and illnesses of any sort may also have an effect. Also potenial infections by lice and mites, and disturbance by rats or other vermin should be looked to as all these will weaken the birds.


It is a horrible disease, though one that (at least in my liftetime) has always been around. Personally it is my experience that strong healthy birds bred for a degree of natural immunity survive and perform without problems even when not vaccinated. But it will be interesting to hear what your vet says

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I know that there's another recent thread from Suebee on the "chickens" part of the forum. She lost a girl suddenly from suspected Mareks and still has her 2 remaining sisters, which leaves her in a quandary about wether to get vaccinated birds to add to her flock, as potentially the remaining 2 could be carriers.


My vet told me that the cost of the large batch of vaccine would be prohibitive when I asked :( I do understand that Mareks in everywhere in the poultry world, with resistance to the vaccine becoming a worry. Difficult to know what to do for the best.

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my Flock was apparently vaccinated with 2 different Vaccines.


The Hybrids were Vaccinated with a diffrent vaccine at day old in Belguim where the breeder purchased them, the pure breeds were apparently vaccinated with Poulvac Md- made by pfizer.


My vet has informed me that the vaccine would have prevented Mareks developing in to a fatal disease and would have prevented the tumors if it had been given or given correctly, I have lost none of my Hybrids so this fits with the theory. - they can still catch and carry it but not die from it.


Also if they have Mareks and are just carriers they are more prone to viral and bacterial illnesses when under stress.


I have emailed Phizer to see if they feel it could be a new strain of Mareks or if has mutated - however both myself and my vet feel that this is unlikely as there would be more reported cases and Poultry farms would not use that vaccine- also it is the classic type that the vaccine was made to stop.


I have emailed the breeder again asking for vial details and batch numbers to see if they exist - when I contact Pfizer.



My hybrids will probably be carriers- so I would need to cull them all and wait a year ( the virus can survive for a yr)- or ensure that if I add any more birds they have to have been vaccinated - due to my luck - I no trust no one, and I am not willing to cull my chickens if they are showing no signs so vaccination is the only way forward for me if I ever choose to expand.


I am very lucky that if I was to pay my vet to purchase the vaccines he would not charge me or only charge me a £10 to administer them- the vaccines themselves are only £12-20 per 1000, so not that bigger expense if you have a farm vet.


My vet is a farm Vet who's expertise is poultry game and dairy. I would recommend if possible to use a farm vet as the prices they charge are pennies - when placed against small animal vets- If anyone lives near High Wycombe/thame/Aylesbury Pm and I will give you his details- though he mainly deals with dead birds.

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Hi there,


As mimi said earlier, I have - (as she has) - just lost a bird with suspected Mareks, and wonder what to do regarding replacements, where new birds will be exposed to the virus which is more than likely being shed by the survivors.


Below, is what I have gleaned, over the last couple of weeks of wading through the internet for advice....


I thought the virus could survive for a lot longer than a year.


I wonder if the vaccination of your pure breeds may have been ineffective due to expired vaccine, or incorrect administration... I gather it's a bit hit and miss. Or, it could still have been down to exposure to Mareks from other birds, earlier on, before they had built up resistance.


Once the chicks have been vaccinated, I gather their resistance still needs to build up, without exposure to Mareks challenges, so for a few weeks after vaccination, good biosecurity apparently still needs to be in place. I wonder if some breeders are (probably understandably) thinking the Mareks problem is solved once the chicks have received their vaccination. The vaccination is only for resistance to Mareks, it seems, rather than immunity. Also, it is still only about 90% effective.


Whether the above information is correct or not, I am not sure. There is lots of conflicting advice, one breeder says one thing.... another says another. The veterinary information is somewhat in depth and a little difficult to get your head round, as it's written for professionals with a good grounding in 'vet speak'.


One more thing I gathered, which may interest you (with access to blood testing)... Apparently, you could ask for a 'B type' blood test. Apparently, 'B factor' birds have better resistance to the virus.


Please let us know what happens next, and good luck.

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I agree with some of the points raised above.


Unless you are buying hybrids, I think it would be best to assume that your birds haven't been vaccinated. It can strike at any age, not just in immature birds; I have recently lost a 7 year old to it, no surprise really as she was a bit infirm. The wild birds will be introducing it into your garden, whilst it isn't possible to stop this point of contact you'd be best not to set up wild bird feeding stations in your garden.


My farm vet in nth Oxfordshire is the country's leading poultry expert; he can provide a vaccination programme for backyard poultry keepers.

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Hi thanks for the replies. My vet has said the uptake to the vaccine would be poor if it was not given correctly, or if the other vaccinations were given too close together or if the chicks were ill when they were given it.


He has also advised me to not introduce Any chickens to the existing flock- I am awaiting a reply to see if there is a way I can test to see if my two remaining pures have had the vaccine, or if there is a way to test if the others are carriers.


My vet is also worried as the breeder has informed me she can sell vaccines and my vet wants to speak to the breeders vet to check some details.


Its interesting about the wild birds- I don't encourage them due to all the mites/lice and illness they can bring to flock, however in our back garden in a tree, we have a Red Kite that roosts due to injured leg/wing and his mate brings him food- probably nothing but it did cross my mind.

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I would assume that all your flock will be carriers whether they have exhibited any symptoms or not; I am not saying that they are, but it is likely. As I've said before, it is a herpes virus which remains dormant in the background until any stressful situation or old age compromises their immune system and they succumb. Much like cold sores or shingle in humans.


I have added to my flock over many years and hardly been troubled by Marek's; as son as one exhibits any symptoms, I will cul it as a matter of course.

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