Poster prepared by Amos Ssematimba and Jeffrey Mariner for the Fourth International Conference on Infectious Disease Dynamics, Amsterdam, The Netherlands, 19-22 November 2013

1. Modeling the effect of improved diagnostics
and antibiotic treatment on the dynamics of
Contagious Bovine Pleuropneumonia (CBPP)
November 2013
Amos Ssematimba* and Jeffrey Mariner
Epidemics 4 conference, 2013, Amsterdam, The Netherlands, 19-22 November 2013
Methods II: modeling details
Background
CBPP is a livestock disease that has continuously
devastated the industry in the sub-Saharan
Africa.
Control intervention is mainly through
vaccination but seems unsuccessful due to
vaccine- and management-specific factors.
Currently, uninformed use of antibiotics is
rampant in the field; much as it is against OIE
recommendations.
• studies to unravel the “myths” about their use
are in place with hope to guide reconsideration
of the OIE position.
Above: Reported CBPP cases (red) 2010-2013; Below left: Cow
standing legs apart and extended neck, a sign of CBPP; Below
right: A typical encapsulation in the lungs of a CBPP “recovered”
animal
Methods I: The model
Currently, better diagnostic tools are being
sought and antibiotic efficacies being assessed. •
Study aims
•
Given the current CBPP research interests,
there is need for predictive tools to guide
field implementation of the improved
control strategies.
Pictures
• Assumed a gamma-distributed waning of
vaccine induced immunity (i.e. method
of steps); protection=8months.
• A seasonally forced transmission rate:
𝛽 𝑡 = 𝛽0 1 + 𝐴sin 2𝜋𝑡 with 𝛽0 =0.5.
• Effects of pulse vaccination or treatment
scenarios are explored in isolated herd.
• Six year period is simulated in a herd of
500 (S=205, E=10, I=10, R=275) heads.
• Treated animals are assumed 50% less
infectious.
• New recruits are all susceptible to CBPP
and for clarity, between herd mixing is
ignored in the comparison.
Sample graphical results
SVEIRQT compartmental model
implemented stochastically using
Gillespie direct algorithm.
incorporates vaccination and
treatment.
The aim here is to develop mathematical
models to assess how effectively antibiotics
can be used in the field as supplements to
vaccination campaigns.
Preliminary results
Conclusions and next steps
Simulation outcomes for the different interventions
Antibiotic treatment can provide the much wanted
supplement to the current vaccination campaigns and should
be supported.
Synchronizing intervention at regional level is paramount due
to the cross-boarder animal movements.
Cheaper diagnostic tools should be availed to aid CBPP
identification and better antibiotics with higher cure rate are
needed.
Next step: obtain field data to calibrate the models .
Intervention scenario
Cure rate/ detected
Extinction Epidemic
fraction/ vaccination chance
duration
coverage
(%)
(days)
a) Annual pulse
vaccination
30%
72
1194
315
110
90%
100
996
222
77
b) Treatment (default
detected fraction=80%);
different cure rates
1/7 per week
13
1296
526
29
1/2 per week
100
322
18
1
65
937
254
18
77
808
193
8
c) Treatment (default cure 20%
rate = 1/4.5 per week):
different detected fraction 90%
Cumulative
number of
cases
Cumulative
number of CBPPinduced deaths
Amos Ssematimba
a.ssematimba@cgiar.org ● Box 30709 Nairobi Kenya ● +254 20 422 3867
Nairobi Kenya ● ilri.org
This project was funded by BBSRC and partly by BMZ
This document is licensed for use under a Creative Commons Attribution –Non commercial-Share Alike 3.0
Unported License November 2013