Болезнь Марека у птиц и последствия вакцинации цыплят: печальный опыт

Left—normal chicken eye. Right—Eye of a chicken with Marek's disease

<<Смертность цыплят, инфицированных болезнью Марека, была довольно низкой.  Спустя десятилетия после того, как была введена первая вакцина,  существующие штаммы вируса Марека вызывают образование лимфомы по всему  телу цыплят, и уровень смертности среди невакцинированных цыплят достиг 100%. Вакцина против болезни Марека - это неплотная вакцина, а это означает, что предотвращаются только симптомы болезни. Вакцина не подавляет заражение хозяина и передачу вируса.>> 

Vaccination is the only known method to prevent the development of tumors  when chickens are infected with the virus.  However, administration of  vaccines does not prevent transmission of the virus, i.e., the vaccine  is not sterilizing.[3]   However, it does reduce the amount of virus shed in the dander, hence  reduces horizontal spread of the disease. Marek's disease does not  spread vertically.  Before the development of the vaccine for Marek's  disease, Marek's disease caused substantial revenue loss in the poultry  industries of the United States and the United Kingdom. The vaccine can  be administered to one-day-old chicks through subcutaneous inoculation  or by in ovo vaccination when the eggs are transferred from the incubator to the hatcher. In ovo  vaccination is the preferred method, as it does not require handling of  the chicks and can be done rapidly by automated methods.  Immunity  develops within two weeks.[4] 

However, because vaccination does not prevent infection with the  virus, Marek's 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. Under normal conditions, highly  virulent strains of the virus are not selected. A highly virulent strain  would kill the host before the virus would have an opportunity to  transmit to other potential hosts and replicate. Thus, less virulent  strains are selected. These strains are virulent enough to induce  symptoms but not enough to kill the host, allowing further transmission.  However, the leaky vaccine changes this evolutionary pressure and  permits the evolution of highly virulent strains.[12]  The vaccine's inability to prevent infection and transmission allows  the spread of highly virulent strains among vaccinated chickens. The fitness of the more virulent strains is increased by the vaccine. 

The evolution of Marek's disease due to vaccination has had a  profound effect on the poultry industry. All chickens across the globe  are now vaccinated against Marek's disease (birds hatched in private  flocks for laying or exhibition are rarely vaccinated). Highly virulent  strains have been selected to the point that any chicken that is  unvaccinated will die if infected.[citation needed]  Other leaky vaccines are commonly used in agriculture. One vaccine in  particular is the vaccine for avian influenza. Leaky vaccine use for  avian influenza can select for virulent strains.[13] 

В общем, ковидные вакцины не препятствуют заражению, их эффективность где-то 90 процентов или ниже (особенно для нового индийского варианта). Что будет через несколько лет массовой вакцинации — написано выше. 

Биг-фарма знает, что делает, продавливая повальную вакцинацию!


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