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Transcript of Doctoral thesis
flock identifier - owner
entry for replacement animal vaccination
sheep and goat flocks
into one flock
flocks with less than 10 animals
Final population database used in analysis
active surveillance component - annual testing campaigns
scenario tree models for each evaluated strategy
starting flock prevalence at 2%, 5% and 10%
flock as unit of observation
outputs - number of TP, TN, FP and FN flocks at the end of one year
fixed annual among flocks spread rate - 60%/10%
- sensitivity analysis -
FP flocks predicted only in Vacc+T&S model
Most sensitive outputs :
T&S / RB T&S model - TP/FN flocks
Vacc+T&S model - TP flocks
Most influential inputs :
average flock prevalence (all models)
proportion of sampled flocks (T&S /Vacc+T&S)
RR nomadic flocks (RB T&S model)
- effectiveness of surveillance strategies-
sampling and testing
animal removal and compensation
twofold retesting of positive flocks
vaccine, vaccine administration
immunity checks for vaccinated animals
Average estimates (model) per flock size cat.
annual number of sampled flock
annual number of TP/FP flocks X within flock prev.
Reports on vaccination - actual (1-4yr) and extrapolated (5-8yr)
number of vaccinated animals
number of immunity checks
- estimation of costs -
Herculaneum and Pompeii 79 n.e.
Effectiveness and economic assessment of different surveillance strategies for small ruminant brucellosis in Bosnia and Herzegovina
- scenario tree models -
Assumptions of the model!
Period of 8 yrs. (current vacc. program)
3 strategies - 3 levels of prevalence - every of 8 yrs. = 72 model simulation
Each simulation ran 1000 times (1000 iterations)
ranking inputs by impact on outputs
measuring (%) pos./neg. impact-"tornado" charts
Prevalence trends compared by ANCOVA
T&S in Portugal
etc. - reduced effectiveness when prevalence is low –
risk based approach!?
Targeting “at-risk” population subgroups = improved disease detection (even if disease is endemic – brucellosis in BiH)
Risk based sampling
comprehensive animal population database
Observational studies also found prevalence
(Robinson, 2003.,EU, 2009)
and testing coverage
(England, 2004., Yamamoto, 2008.)
to be the most influential for success of brucellosis surveillance
Pubmed - close to 12 000 published papers
Definition example of zoonosis
Still of high priority
World wide distribution
Who can have brucellosis?
6 host specific causative agent species + 2 to 3 sp.nov
Intracellular agent - Pathogenesis not fully understood
Abortive but abortions not pathognomonic
>90% DNA genus homogeneity -> challenges for diagnosis:
by culture/molecular methods
Small ruminants, humans!!!, cattle!?
Endemic in Bosnia and Herzegovina
Disease management strategies:
test and slaughter
Objectives of the study
- Questionnaire administration-
- doctoral thesis -
Sabina Šerić-Haračić, DVM, MS
Test and slaughter (T&S)
Risk based test and slaughter (RB T&S)
Mass vaccination with test and slaughter (Vacc+T&S)
For each surveillance strategy :
1. Evaluated effectiveness
2. Identified critical influences
3. Estimated implementation costs
4. Compared results of effectiveness and costs
-data and data sources-
small rum.pop. in BiH
small rum. bruc. in BiH
Effectiveness of dg. test
cost of surveillance and control activities
to vet.practices in municipalities > 10.000 small rum.
data relevant to 56,2% of small rum. population in BiH
- national small ruminant data base -
- effectiveness of surveillance strategies-
- questionnaire analysis -
no difference in municipality level population size veterinarian estimate vs. national registry
average male to female ratio in flocks 1:26
in model 1:25
vaccination coverage 70,2% (95%CI range 44,6%-82,9%)
in model Pert dist. (50%,70%,85%)
testing coverage within vacc.program 1-10%
in model Pert dist. (5%,10%,15%)
ANCOVA confirmed difference in prevalence trends for T&S and RB T&S (all start flocks prev.)
Influence of starting flock prevalence on effectiveness of surveillance strategies
- Prevalence trends for T&S all 3 starting prev.levels -
- Prevalence trends for RB T&S all 3 starting prev.levels -
- Prevalence trends for Vacc+T&S all 3 starting prev.levels -
- estimation of cost-
-estimation of costs-
Estimated costs fort all 8 years
2% start Prev. 5% start Prev. 10% start Prev.
T&S 32,5 mil. 41,4 mil. 56,2 mil.
RB T&S 30,4 mil 36,2 mil. 45,7 mil.
Vacc+T&S 19,2 mil. 21 mil. 23,7 mil.
Average annual allocation of public funds in BiH (2008-2012) for ALL ANIMAL and PLANT health systemic activities = 8,5 mil. KM
Modeling today common decision making support tool for animal health programs
(Roth, 2003., Zinsstag, 2005.)
vaccination without active removal of diseased animals
influences brucellosis prevalence in animals
(Minas, 2004., EU 2009.)
positive effect of animal vaccination on reduction of human brucellosis incidence (Roth, 2003. - estimated saving for PH sector 85,6%)
Average estimates of flock prevalence after 8 yrs.
Prev. an. test 55% vacc. 70% (50-85) sample=T&S
(40-70) an. test 10% (5-15) oversampl. at risk flocks
2% 0,48% 2,19% 0,01%
5% 1,25% 5,57% 0,02%
10% 2,44% 11,08% 0,03%
Do we/How will we address brucellosis in BiH?
This study one of possible methods for:
- estimation of effects and costs
- consideration of nationally specific RF
- compensating for lack of precision/availability of data (common in developing countries)
Keep in mind limitations of modeling
Brucellosis is "One Heath" problem - Why not apply "One Health solution?!?
national registry (AIMCS BiH)
reports on bruc. occurrence (SVO BiH +OIE - WAHID)
brucellosis surveillance/control requirements in BiH