Forum: Cause of vaccination failure against Marek's disease
Published:November 4, 2011
By:Grzegorz Wozniakowski
Dear poultry scientists, I would like to start with the new subject regarding possible vaccination failure in MD prophylaxis. From my actual experience nowadays in spite of frequent use of bivalent vaccines against MD (Rispens+HVT) or (SB1+HVT) the MDV strains with raised virulence are isolated from field cases of the disease. I know in some cases this may be due to the low hygiene conditions in farms. However I also consider in some cases farmers apply double vaccination with bivalent vaccines at the 1st and 7th day of chickens life. From my own study I found that in such cases I commonly detect DNA of virulent MDV strain and HVT strain but not Rispens in spite of proper vaccination of chickens. Therefore I am curious about your experience and explanations of this problem. Please fell free to add comments. Thank you.
Dear Dr. Kashif,
There are many causes of failure of MD Vaccination.
Improper storage of cell associated vaccine in liquid nitrogen ( Tepm. -196 degree C) is one of them.
No doubt MD is a horizontally transmitted disease, but because vaccination is always done in DOC in the hatchery, this is why the commercial farmers mostly concentrating on this part.
The 2nd most important part is the proper cleaning & disinfection of rearing area required to get immunity from vaccine particularly during 1st 2 weeks. I & other writers has already explained this part in details.
Dr. M. Akram, Ph.D.
Marek disease vaccination should be brought into practice either in 18 th day to the embryos or else in the very first week after coming out of hatcheries and of course after pursuing all safety protocols prior vaccinating the flock. Commercialy the task is carried out through fine sprayer to enable fine droplets of live attenuated vaccines gain access through nostrils of chicks running on a conveyor.
Any mis executions in above step may bring the task to be an abortive and that invite stress to precipitate infection in subsequent phases as highlighted now. It should be certain that the live attenuated virus should ensures it's process of attenuation or else same may act like a pathogen with full virulence only during application.
Dr. R. P. Chakraborty
The dose is fixed by the manufacturer. no point in doubling it. Slips in vaccination is a problem associated with large flock size and hurrying man power. repeating the vaccination will be better.
Mareks vaccine is never done by spray. All vaccines are to be administered by injection either 18thday or day one.
Mareks vaccine works by blocking specific receptors. Better we vaccinate early and give lead to vaccine virus before the field virus ( in broader houses) races to the receptors
Sir very much important and valuable comment on vaccine. Please keep on delivering this type of facts of which many people are not aware of.
Thank you so much
MD vaccination failures may occur due to several factors
This will also an important fact in the failures of the response to the immune foreign gene inserts. using recombinant HVT vector vaccines
Rudolf Hein, the use of vectorized HVT does not interfere with the vaccine response because the insert is in a domain that does not constitute a primordial antigenic portion.
Bouayad, I have def. never implicating that the insert does always interfere with HVT protection, However myself involved in RD HVT vector development have shown that in several cases depending on the construct of rHVT efficacy is less than the parent HVT. Particularly in early challenge in those cases it is recommended to add SBB 1 or CVI 988. In this forum we should focus on administration failures on the MD vaccines (including the rHVTvaccines)
Rudolf Hein, even without HVT vectorial I vaccinate HVT+CVI 988 because we are in a context MDV vv+ we don't vaccinate anymore with HVT alone or HVT +SBI. Of course, it is necessary to concentrate on all the steps of the vaccine itself to avoid immunosuppressive diseases- biosecurity-' chain of custody- hygiene in the hatchery- mycotoxin sensors and verification by PCR the presence of the vaccine at D21.
Two different vaccination proceedings “in Ovo” and day old s.c hatchery vaccination Can draw a list of application problems,of coarse quality of vaccine (e.g PFU titer etc) May play a role
DR Grzegorz Wozniakowski When vaccinating, we never eliminate Marek's virus: the hen remains a carrier without having tumors or lymphocyte infiltrations.
Hi ; Grzegorz Wozniakowski
your question is why you dont find DNA of Rispens vaccine ; I have experience using many bivalent vaccine from different company vaccine making . in one experiment compared the replication ability of tow by testing the DNA in feather papilla in weeks 1-2-3 after vaccination
after 1 week in one product only 30% was positive and another 100% . in 2 week 70 and 100 respectively .
The reason for test was because of using new brand of vaccine saw Marek disease in pullet and after that . all of work in managing vaccine handling was as before the only difference was changing the brand of vaccine .
I believe that seed and process that vaccine making technology in not similar and hence the quality of vaccine are not the same .and not founding DNA you mentioned be because of vaccine quality.
As you know Marek virus is in every poultry houses and near 100% of commercial chicken even those that have no any mortality shed it in their life . and infection whit it ocurre in fist week of life , proper vaccination by good quality vaccine and good clean house is needed to prevent it .
My speculations are that birds may get exposed to the virus before protective immunity is developed especially following sc MDV inoculation at day one and less so with the inovo approach. The vvMDV in circulation in many places may not respect the present vaccines in use.
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