Objective—To evaluate humoral immune responses
of emus vaccinated with commercially available
equine polyvalent or experimental monovalent eastern
equine encephalomyelitis (EEE) virus and western
equine encephalomyelitis (WEE) virus vaccines and to
determine whether vaccinated emus were protected
against challenge with EEE virus.
Procedure—Birds were randomly assigned to groups
(n = 5/group) and vaccinated with 1 of 2 commercially
available polyvalent equine vaccines, a monovalent
EEE virus vaccine, or a monovalent WEE virus vaccine
or were not vaccinated. Neutralizing antibody
responses against EEE and WEE viruses were examined
at regular intervals for up to 9 months. All emus
vaccinated with the equine vaccines and 2 unvaccinated
control birds were challenged with EEE virus.
An additional unvaccinated bird was housed with the
control birds to assess the possibility of contact transmission.
Results—All 4 vaccines induced detectable neutralizing
antibody titers, and all birds vaccinated with the
equine vaccines were fully protected against an otherwise
lethal dose of EEE virus. Unvaccinated challenged
birds developed viremia (> 109 plaque-forming
units/ml of blood) and shed virus in feces, oral secretions,
and regurgitated material. The unvaccinated
pen-mate became infected in the absence of mosquito
vectors, presumably as a result of direct virus
transmission between birds.
Conclusions and Clinical Relevance—Results indicate
that emus infected with EEE virus develop a hightiter
viremia and suggest that they may serve as
important virus reservoirs. Infected emus shed EEE
virus in secretions and excretions, making them a
direct hazard to pen-mates and attending humans.
Commercially available polyvalent equine vaccines
protect emus against EEE virus infection. (J Am Vet
Med Assoc 2001;218:1469–1473)
Objective—To determine the onset of immunity after
IM administration of a single dose of a recombinant
canarypox virus vaccine against West Nile virus
(WNV) in horses in a blind challenge trial.
Animals—20 mixed-breed horses.
Procedure—Horses with no prior exposure to WNV
were randomly assigned to 1 of 2 groups (10 horses/group). In 1 group, a recombinant canarypox
virus vaccine against WNV was administered to
each horse once (day 0). The other 10 control horses
were untreated. On day 26, 9 treated and 10 control
horses were challenged via the bites of mosquitoes
(Aedes albopictus) infected with WNV.
Clinical responses and WNV isolation were monitored
for 14 days after challenge exposure; antibody
responses against WNV after administration of the
vaccine and challenge were also assessed in both
Results—Following challenge via WNV-infected mosquitoes,
1 of 9 treated horses developed viremia. In
contrast, 8 of 10 control horses developed viremia
after challenge exposure to WNV-infected mosquitoes.
All horses seroconverted after WNV challenge;
compared with control horses, antibody responses in
the horses that received the vaccine were detected
Conclusions and Clinical Relevance—In horses, a
single dose of the recombinant canarypox virus-WNV
vaccine appears to provide early protection against
development of viremia after challenge with WNVinfected
mosquitoes, even in the absence of measurable
antibody titers in some horses. This vaccine
may provide veterinarians with an important tool in
controlling WNV infection during a natural outbreak or
under conditions in which a rapid onset of protection
is required. (Am J Vet Res 2004;65:1459–1462)