Vaccines for Marek's disease

I am happy that we now all agree that vaccination failure to Marek's disease do occur despite bivalent vaccination strategy as it is widely practiced, and this confirm our field advise that the hatchery vaccination is not a full proof guarantee for solid immunity 

You raised important factor of hygiene as a probable aetiology for vaccination failure and this seem to agree with my view of exogenous potentiating factors that include contaminated feed with mycotoxin.I strongly believe that in view of the recent knowledge on the immuno pathology of mycotoxin, certain groups of Toxin like DON and Fuminoxin may AFFECT Cytokins functions and trigger the production of non specificity to antibodies which may allow emergence of DNA of virulent MDV strain 

This is why I strongly recommend that in endemic region revaccination with HVT must be syn energized with the administration of Nanotechnology Toxin Binder to maintain the integrity and functionality of the immune system.it is worthwile to look at this challange of our field experience as a laboratory trial and this will be a good collaboration between the lab and the field for the benefit of the industry 

Stephen Adejoro 

Double vaccination is very interesting.

Double dose - 

Single dose applied twice (to cover missed ones). The dutch like to give Rispens in the leg muscle using data showing protection one day earlier than intramuscular 

Revaccination at one or two or three or four weeks. There are many examples where birds that are stressed (no water, or no feed [double brooding without hiting growth curves], high mortalities in the first two weeks) can not respond to vaccination and break under challenge. 

In most cases where you are having marek's disease despite vaccination concentrating on reducing early challenge can pay dividends - for example moving rearing off production farms. Had a nice example of this in Russia where all the flocks reared off farm had very little mareks while contempories reared on farm had problems. This is often more useful than double vaccination uinless there is a systematic problem with the vaccinatiion. 

Good article about vaccines for marek's disease. In my experience we must and do vaccinate on 1st day with HVT+SB1 and booster with HVT monovalent gives better result.

Thank you for your all your valuable opinions. I like the new vision of dr Adejoro of the influence of mycotoxins on immune system function. According to reply of dr Chris Morrow indeed the best idea is rearing off of farms, However it is obvious that in many cases the main goal is highly profitable and fast production without rearing off farms. However I am thankful for your opinion and I always refer your data regarding economic impact of MD in my papers as well as PhD thesis. I am also thankful for the opinion of dr Suresesh. Unfortunately SB-1 in forbidden to apply for vaccination in many EU countries due to higher risk of the incidence of lymphoid leucosis in chickens. I know the practice of boosting with HVT but since the new very virulent plus variants of MDV appeared it may be not enough to protect chickens.
Another question: Do you think that revaccination with bivalent vaccine may cause overloading of immune system of birds so they are more susceptible to infection with very virulent MDV?

In spite of bivalent vaccination against Mareks disease, I agree that some cases appears and we can summarise the main causes as follows:
1. Improper handling and storage of vaccines.
2. Delay or insufficient vaccination.
3.Bad hygiene either in hatcheries or in poultry farms.
4.stressed birds e.g overcrowding,bad ventilation,omphalitis and vertical transmitted diseases.
5.Immunosuppressor factors either from food, causative agents...
6.Genetic susceptibility of some breeds especially some native breeds.
7.Revaccination may correct missing unvaccinated birds.

I think they Mosqsood Jaffery and Nabil Tanios completely right about what the main reason for the occurrence of Marek's disease vaccines are considered improper handling and respect for the biosecurity measures in the process of keeping poultry.
Farms where Marek's disease occurred in one or two times you should not settle for a longer period (six months) and the next two times done disinfection.
A large number of different vaccination certainly conditioned by weaker immune response.

Dear G. Wozniakowski,

Thanks for forum on Marek's disease. I have seen many cases of Marek’s in broiler breeders. I feel the first vaccination at hatchery is very important. Proper vaccination at hatchery before chicks goes in to other environment is important. The vaccination method is equally important specially vaccinator needle guaze ,mixing, keeping vaccine cool. I had seen lapses in above leads to improper vaccination. We need to make sure that every chick is vaccinated. Amongst various types we used 2doses HVT +1 dose SB1 commonly , in some cases 2 HVT + 1 dose Rispens in case of non availability of Rispens we tried 2 doses of HVT + 301 Marek’s vaccine at day old. I have seen first vaccination at Day old is important. I saw few farmers are repeating vaccine on 5th day or 18th day and claiming they are getting good response. However I did not see and advantage of doing 2nd vaccination in filed. It is very difficult to see response in multiage group farms. Proper IBD immunized flocks less problem noted. Similarly we have seen problems in coccidiosis out break flocks. Flocks brooded till 8 weeks in isolated new premises proven good results if flocks grown in minimal stress conditions. Doing double dose SB1 , we noticed cancers lesion in few cases around 4o week age. Many times the problem I had seen is due to improper vaccination or missing few chicks while vaccinating at hatchery at day old.

Dr Mahendra Chaudhari

Dear Grzegorz Wozniakowski ,

Thanks for posting such wonderful topic for discussion. All experts in this field have expressed their views and i also supports the same. The main reasons for any vaccine failure including Marek's disease vaccines on field are closely related to...
1) Hygiene
2) Biosecurity
3) Feed Toxins
4) Drinking Water Quality
5) Environmental factors.
6) Improper storage & handling of vaccines.
7) Improper Nutrition etc.

Regards,

Dr Jaydip

I am fully agrre with the coments of Dr AD Anjum, important thing which i want to discuss here is vaccination prepartion at the Hatchery Level, as the water Bath Temp should not be high and the time period for the vail of vaccince vail may be less than 1 minute time , as most of the vaccince lost its efficay before applying .
2nd thing is that if the Farm has a history of MD than a proper cleaning and disinfection must be done the chicks arrived there.
3rd thing is that the only way for the Virus infection is the wk of life if there is any chances of fielf infection so at the First 2 wks a good bio security is important and even latter is important.
3rd thing is provide Toxin Free Feed for the first 5-7 wks so that less imune supersion.
4th is that preven the flock from some very imune supresive disease in 5wks like IBD/CAV/COCCI etc.
5th is that provide some good vitamins suplelments at the start of the flock with additionaly added of Vit E& Sel in feed and in D/W.
I hope that by Following some of the nice coments from the Group one can easily protect his Flock from the Marek's disease.
Thanks

Several of the possible causes of the MDV failures have been put forward.I would like to add some comments re possible failures.
In several cases the Marek's disease vaccines are simulteneously applied with other vaccines ,one has to make sure that these vaccines do not interfer with the MD vaccine (only use these vaccines as recommended by the vaccine manufactory),in addition in most cases antibiotics like gentamycin are added extra to the diluent ,one has to be carefully with the dose since we have shown that incresed doses of antibiotics have an effect on the MD titer,
MD vaccines like basically all vaccines will not even if applied properly provide 100% protection further on a vaccination will not provide immediate protection ,it will take some days to provide full protection (see also comment Chris Morrow).In ovo vaccination may reduce the delay in onset of immunity.
Maternal antibodies specific for MDV type 1 ,2 and 3 have shown in laboratory trials to interfere with the onset of immunity however it is not known how far this plays a role in the field.Use only low passage vaccines since it has been clearly shown that high passage levels of HVT and CVI988(Rispens) will reduce its efficacy despite it will induce higher vaccine (PFU) titers.

Possible cause of Marek's disease virus spresd through feathers. So that we should take care to complete burning of feather before placing chicks.

Few years back, we compared performance (live weight, FCR, etc) of HVT vaccinated broilers with non-vaccinated broilers EXPERIMENTALLY. HVT vaccinated broilers had better performance BUT the difference was not statistically significant. So the use of Marek's disease vaccine did not become popular for commercial broilers in Paksitan.

All the participants covered the topic very well especially Mr. Nabil tanious and Mr Ahmad froM Egypt and Saudi Arabia.

In Jordan the main problems of Marek's disease detected due to failure of vaccination (due to improper cold tranefer of the vaccine from the country of origin) so all the companies now vaccinating their layer twice in Hatchary with different source of MD vaccines and Rispin approved to give good protection against MD.

But i believe the fear from Lymphoid leukosis due to MD is not very clear unless you have reliable publication?!

Marek's disease vaccination in broiler , i think due to genitic potential and the age of Marketting is reduced from 48/42 to up to 35 days in some countries and also in these countries the live weight is not even more than 1.5kg so for this case i will say that using of the MD alone is not good , how ever if using with some vaccince like IBD at DO may be good , but the cost will be higher and now if some one take care for the cost reduction in this instances no need for it just IBD alone is also available if there is a real thread in the area , and if not than Normal IBD vaccination will protect the birds .
How ever i did not seen / notice any much difference in the weight for the DO MD vaccinated and un vaccinated chicks .
For the Failure of MD due to Transportation or storage is always Q mark .
Yes it is good to vacciante twice so that it will give more protection and also if any chicks were miss in first short may get the vaccince in second one , how ever it need some rest period between the two shorts of vaccinations which may be about 2-3 hrs .
Thanks