Imperfect Vaccination Can Enhance the Transmission of Highly Virulent Pathogens

• DOI: 10.1371/journal.pbio.1002198
• Publication Date: 2015-07-27T17:44:05Z
• Authors: Andrew F. Read; Susan J. Baigent; Claire Powers; Lydia B. Kgosana; Luke Blackwell; Lorraine P. Smith; David A. Kennedy; Stephen W. Walkde...; Venugopal K. Nair
• Keywords: 2. Zero hunger; Mardivirus; QH301-705.5; Marek Disease; Animals; Marek Disease Vaccines; Biology (General); Selection, Genetic; Chickens; Research Article; Virus Shedding; 3. Good health

Could some vaccines drive the evolution of more virulent pathogens? Conventional wisdom is that natural selection will remove highly lethal pathogens if host death greatly reduces transmission. Vaccines keep hosts alive but still allow transmission could thus very strains to circulate in a population. Here we show experimentally immunization chickens against Marek's disease virus enhances fitness strains, making it possible for hyperpathogenic transmit. Immunity elicited by direct vaccination or maternal prolongs survival does not prevent infection, viral replication transmission, extending infectious periods otherwise too persist. Our data anti-disease do can create conditions promote emergence pathogen cause severe unvaccinated hosts.