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Doctoral thesis

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sabina seric

on 27 October 2015

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Transcript of Doctoral thesis

entries from 2009 - 2011
flock identifier - owner
duplicate entries
entry for replacement animal vaccination
removed
sheep and goat flocks
merged
into one flock
flocks with less than 10 animals
excluded










Final population database used in analysis
1.097.743 animals
19.421 flocks

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%
Results
- 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)
Discussion
Methods
- effectiveness of surveillance strategies-
Considered cost:
sampling and testing
animal removal and compensation
twofold retesting of positive flocks
vaccine, vaccine administration
immunity checks for vaccinated animals

Multipliers:
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
Methods
- estimation of costs -
Brucellosis
Herculaneum and Pompeii 79 n.e.
Effectiveness and economic assessment of different surveillance strategies for small ruminant brucellosis in Bosnia and Herzegovina
Methods
- 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)

Sensitivity analysis
ranking inputs by impact on outputs
measuring (%) pos./neg. impact-"tornado" charts

Prevalence trends compared by ANCOVA
T&S in Portugal
(Neto, 2002.)
, Spain
(Lithg-Pereira, 2004.)
, Greece
(Minas,2007.)
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
REQUIRES
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
Brucellosis
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
Unapparent/latent carriers!?!
>90% DNA genus homogeneity -> challenges for diagnosis:
by symptoms
by serology
by culture/molecular methods
Brucella melitensis
Small ruminants, humans!!!, cattle!?
Endemic in Bosnia and Herzegovina

Disease management strategies:
test and slaughter
abortion investigation
vaccination
Objectives of the study
Methods
- Questionnaire administration-
- doctoral thesis -
Sabina Šerić-Haračić, DVM, MS

Investigated strategies:
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

Materials
-data and data sources-
small rum.pop. in BiH

small rum. bruc. in BiH

Brucellosis surveillance/control
B.melitensis
epidemiology

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
Methods
- national small ruminant data base -
Results
- effectiveness of surveillance strategies-
Results
- 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
Results
- Prevalence trends for T&S all 3 starting prev.levels -
Results
- Prevalence trends for RB T&S all 3 starting prev.levels -
Results
- Prevalence trends for Vacc+T&S all 3 starting prev.levels -
Results
- estimation of cost-
Results
-estimation of costs-
Estimated costs fort all 8 years
(in KM)
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
Discussion
Modeling today common decision making support tool for animal health programs

Modeling studies

(Roth, 2003., Zinsstag, 2005.)
-
vaccination without active removal of diseased animals
insignificantly/variably
influences brucellosis prevalence in animals

Empirical results
(Minas, 2004., EU 2009.)
-
positive effect of animal vaccination on reduction of human brucellosis incidence (Roth, 2003. - estimated saving for PH sector 85,6%)
Concussions
Average estimates of flock prevalence after 8 yrs.
Start
T&S

Vacc+T&S

RB T&S
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%
Concussion
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?!?



study questionnaire
national registry (AIMCS BiH)
reports on bruc. occurrence (SVO BiH +OIE - WAHID)
brucellosis surveillance/control requirements in BiH

scientific papers


study questionaire
SVO BiH
Full transcript