- Thread starter
- #21
Oh wow, that’s some awesome information! Thank you very much!Marek's is thought to be widespread.
As stated, the vaccine can help to stop the formation of tumors, but does not prevent infection from the virus - birds can still become ill and shed the virus.
And 10% may very well be true. The vaccine may help mask or prevent some symptoms from showing, but birds can still shed the virus and/or spread infection.
This is why research/reading is encouraged. The reader needs to come to their own opinion/conclusion whether vaccinating their flock is something they want to do. There are benefits as well. If adding chicks to a Marek's confirmed flock, the vaccine can offer some form of protection, but those chicks need to be quarantined and good bio-security observed so their immune system can respond to the vaccine.
Again - it's a personal choice/decision that every backyard flock keeper must make for themselves after careful consideration of all the information they can find.
https://www.backyardchickens.com/articles/the-great-big-giant-mareks-disease-faq.66077/
Though the MD vaccines are capable of preventing lymphoma formation and clinical disease, do not prevent superinfection by pathogenic MDV strains [15]. Therefore, detection and elimination of infected birds form the basis for diagnosis and eradication programmes for oncogenic viruses
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6003054/
vaccination does not prevent infection with the virus, Mareks is still transmissible from vaccinated flocks to other birds, including the wild bird population. The first Marek's disease vaccine was introduced in 1970. The disease would cause mild paralysis, with the only identifiable lesions being in neural tissue. Mortality of chickens infected with Marek's disease was quite low. Decades after the first vaccine was introduced, current strains of Marek Virus cause lymphoma formation on throughout the chicken's body and mortality rates have reached 100% in unvaccinated chickens. The Marek's disease vaccine is a leaky vaccine, which means that only the symptoms of the disease are prevented.[11] Infection of the host and the transmission of the virus are not inhibited by the vaccine. This contrasts with most other vaccines, where infection of the host is prevented.
https://en.wikipedia.org/wiki/Marek's_disease
https://www.nationalgeographic.com/...s-enhance-spread-of-deadlier-chicken-viruses/
https://www.pbs.org/newshour/science/tthis-chicken-vaccine-makes-virus-dangerous
Vaccines that keep hosts alive but still allow transmission could thus allow very virulent strains to circulate in a population. Here we show experimentally that immunization of chickens against Marek's disease virus enhances the fitness of more virulent strains, making it possible for hyperpathogenic strains to transmit. Immunity elicited by direct vaccination or by maternal vaccination prolongs host survival but does not prevent infection, viral replication or transmission, thus extending the infectious periods of strains otherwise too lethal to persist. Our data show that anti-disease vaccines that do not prevent transmission can create conditions that promote the emergence of pathogen strains that cause more severe disease in unvaccinated hosts.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4516275/
MD vaccines are considered imperfect because they neither stop infection nor shed-ding of pathogenic MDV from feathers [9–12]. Because MDV remains infectious for weeks in the litters [13], pathogenic viruses can accumulate in the environment of vaccinated birds [12]. Despite the undeniable benefit of current vaccines for chicken health and welfare, the inability of these vaccines to protect from infection and shedding explains the endemic feature of this infection and the difficulty in eradicating it.
https://www.researchgate.net/public...ile_still_carrying_vaccine-induced_antibodies
Any birds who have not received the MD vaccine should never be combined with any chickens who have been vaccinated. This is because the vaccine prevents the formation of tumors, but it does not prevent the chicken from getting infected and shedding the virus into their environment.
http://www.poultrydvm.com/condition/mareks-disease
