Rift Valley fever (RVF) virus (RVFV) is a mosquito-borne pathogen that causes explosive outbreaks of severe human and livestock disease in Africa and Arabian Peninsula. The rapid evolution of RVF outbreaks generates exceptional challenges in its mitigation and control. A decision-support tool (DST) for prevention and control of RVF in the Greater Horn of Africa identifies a series of events that indicates increasing risk of an outbreak and matches interventions to each event (RVF-DST, 2010). This poster presents information from a study that assessed the effectiveness of targeted vaccination in mitigating the impacts of RVF outbreaks.

1. Mi#ga#on
of
the
impacts
of
Ri2
Valley
fever
through
targeted
vaccina#on
strategies
John
Gachohi
and
Bernard
Be.
IntroducDon
• Ri#
Valley
fever
(RVF)
virus
(RVFV)
is
a
mosquito-­‐borne
pathogen
that
causes
explosive
outbreaks
of
severe
human
and
livestock
disease
in
Africa
and
Arabian
Peninsula.
The
rapid
evoluDon
of
RVF
outbreaks
generates
excepDonal
challenges
in
its
miDgaDon
and
control.
• A
decision-­‐support
tool
(DST)
for
prevenDon
and
control
of
RVF
in
the
Greater
Horn
of
Africa
idenDfies
a
series
of
events
that
indicates
increasing
risk
of
an
outbreak
and
matches
intervenDons
to
each
event
(RVF-­‐DST,
2010).
• This
study
assessed
the
effecDveness
of
targeted
vaccinaDon
in
miDgaDng
the
impacts
of
RVF
outbreaks.
Pictures
Materials
and
methods
Figure
1:
Incidence
curves
upon
vaccina#ng
50%
and
75%
of
each
host
species
at
different
#me
points
iden#fied
in
the
RVF-­‐DST.
John
Gachohi
j.gachohi@cgiar.org
●
P.O.
Box
30709-­‐00100
Nairobi,
Kenya
●
+254
20
422
3000
h]p://aghealth.wordpress.com
●
www.ilri.org
• Predicted
impacts
higher
in
ca]le
relaDve
to
sheep
(Fig.1)
• No
September
2014
major
differences
in
vaccinaDng
hosts
during
the
period
prior
to
and
at
outbreak
onset
parDcularly
in
ca]le.
• VaccinaDng
hosts
3
weeks
a#er
outbreak
onset
has
li]le
or
no
impact
parDcularly
in
sheep.
• Similar
pa]erns
in
both
scenario
with
moderate
reducDons
in
the
AUC
upon
vaccinaDng
75%
of
hosts
(Table
1).
• Differences
in
impacts
dependent
on
species
is
a]ributed
to
higher
populaDon
turn-­‐over
and
higher
disease
suscepDbility
among
sheep
relaDve
to
ca]le.
Acknowledgements:
The
CGIAR
Research
Program
on
Agriculture
for
NutriDon
and
Health
(A4NH)
and
the
InternaDonal
Livestock
Research
InsDtute
(ILRI)
Funding:
European
Community’s
Seventh
Framework
Programme
(FP7/2007-­‐2013)
under
grant
agreement
no
266327.
This
document
is
licensed
for
use
under
a
CreaDve
Commons
A]ribuDon
–Non
commercial-­‐Share
Alike
3.0
Unported
License
September
2014
• We
used
a
2-­‐host
(ca]le
and
sheep)
and
2-­‐
vector
(Aedes
and
Culex
species)
RVFV
transmission
model
to
assess
the
impact
of
vaccinaDng
either
50%
or
75%
of
each
host
species
populaDon
at
different
Dme
points
idenDfied
in
the
DST.
• The
impact
is
measured
by
esDmaDng
the
area
under
incidence
curve
(AUC)
for
the
different
scenarios.
Results
Research
into
use
DST
#me
points
included
in
the
model
and
their
lead
#mes
based
on
recent
outbreak
in
2006/2007
in
Kenya
1. Issuance
of
RVF
early
warning
based
on
naDonal
meteorological
forecasts
-­‐-­‐
11
weeks
to
the
outbreak.
2. Onset
of
heavy
rains
-­‐-­‐
6
weeks
to
the
outbreak.
3. Occurrence
of
mosquito
swarms
and
first
RVF
cases
in
livestock
-­‐-­‐
at
outbreak
onset.
4. Laboratory
RVF
virus
confirmaDon
-­‐-­‐
3
weeks
following
outbreak
onset.
• Targeted
vaccinaDon
can
be
effecDve
in
miDgaDng
the
impacts
of
RVF
outbreaks.
• However,
challenges
associated
with
predicDon
of
the
outbreak,
availability
and
delivery
of
vaccines
need
to
be
addressed.
• Impacts
appear
to
depend
on
host
diversity,
with
sheep
potenDally
requiring
more
intensive
vaccinaDon
coverage.
Table
1:
Impact
of
caOle
and
sheep
vaccina#on
measured
as
propor#onal
reduc#on
(%)
in
the
area
under
incidence
curves
rela#ve
to
baseline
(no
interven#on)
Reference
Decision-­‐Support
Tool
for
PrevenDon
and
Control
of
Ri#
Valley
Fever
EpizooDcs
in
the
Greater
Horn
of
Africa.
Am.
J.
Trop.
Med.
Hyg.,
83(Suppl
2),
2010,
pp.
75–85