Response to and efficacy of vaccination against eastern equine encephalomyelitis virus in emus

Objective - To evaluate humoral immune responses of emus vaccinated with co mmercially available equine polyvalent or experimental monovalent eastern e quine encephalomyelitis (EEE) virus and western equine encephalomyelitis (W EE) virus vaccines and to determine whether vaccinated emus were protected against challenge with EEE virus. Design - Cohort study. Animals - 25 emus. Procedure - Birds were randomly assigned to groups (n = 5/group) and vaccin ated with 1 of 2 commercially available polyvalent equine vaccines, a monov alent EEE virus vaccine, or a monovalent WEE virus vaccine or were not vacc inated. Neutralizing antibody responses against EEE and WEE viruses were ex amined at regular intervals for up to 9 months. All emus vaccinated with th e equine vaccines and 2 unvaccinated control birds were challenged with EEE virus. An additional unvaccinated bird was housed with the control birds t o assess the possibility of contact transmission. Results - All 4 vaccines induced detectable neutralizing antibody titers, a nd all birds vaccinated with the equine vaccines were fully protected again st an otherwise lethal dose of EEE virus. Unvaccinated challenged birds dev eloped viremia (> 10(9) plaque-forming units/ml of blood) and shed virus in feces, oral secretions, and regurgitated material. The unvaccinated pen-ma te became infected in the absence of mosquito vectors, presumably as a resu lt of direct virus transmission between birds. Conclusions and Clinical Relevance - Results indicate that emus infected wi th EEE virus develop a high-titer viremia and suggest that they may serve a s important virus reservoirs, infected emus shed EEE virus in secretions an d excretions, making them a direct hazard to pen-mates and attending humans . Commercially available polyvalent equine vaccines protect emus against EE E virus infection.