Transcript Social costs socioeconomic factors leading to chemoresistence to

Social Costs Socioeconomic Factors
Leading to Chemoresistance to
Trypanosomiasis
By:
D. OUEDRAOGO et al.
Université Polytechnique de Bobo-Dioulasso (UPB)
Institut du Développement Rural (IDR)
Outline
1. Introduction and problem statement
2. Objectives
3. Study design
4. Results and discussion
5. Conclusion
1. Introduction and the problem
Trypanocidal drugs are the most widely
applied method that farmers use to treat and
prevent trypanosomosis in sub-Saharan
Africa.
25 to 50 million doses of trypanocides are
administered each year to the
approximately 45 million cattle at-risk of
trypanosomosis (Kristjanson et al. 1999;
Sones 2001).
The efficacy of trypanocides in cattle appears
to be threatened by the widespread
development of resistance in trypanosomes to
the two drugs licensed for use in WA
(isometamidium, and diminazene; Peregrine
1994).
There is a general lack of information on the
prevalence, distribution and impact of
resistance to trypanocides (Geerts and
Holmes, 1998), and ignorance about the most
important factors leading to the development
of trypanocidal resistance in the field.
On biological side:
Resistance is the loose of the sensitivity
by an organism to a drug it is previously
sensitive (Uilenberg 1998).
On economic side:
Resistance appears like a waste of
resources (many treatments without
success, externalities, source of
transaction costs, …)
Resistance is a big constraint for animal
production in endemic area with induced
effects on agricultural production.
As new trypanocides for use in cattle are
unlikely to be developed in the near future,
field studies to better understand factors
influencing the prevalence, distribution and
impact of drug resistance are required.
This information could support strategies to
improve the use and efficacy of currently
available trypanocides in key production
systems under trypanosomosis risk.
2. Objectives of the study
 Estimate the proportion of trypanosome
infections in cattle due to drug-resistant
strains.
 Analyze the trypanocides market.
 Identify the factors leading to resistance in
trypanosomoses.
 Make recommendations for a better use of
trypanocides in the study area.
3. Study design
To better understand the occurrence, impact
and factors influencing the development of
trypanocidal drug resistance in the cotton belt,
of the sub-humid zone of West Africa (southwestern Burkina Faso, south-eastern Mali and
northern Côte d’Ivoire).
Kenedougou province of Burkina Faso
Team:
Entomologists
Epidemiologists
Biologists
Agricultural / resources economists
Cross sectional studies
Characterization of tsetse challenge and
trypanosomosis risk (“block treatment”)
Mains characteristics of production systems
Longitudinal study
Six villages (low, medium and high level of
resistance)
Modeling resistance factors
Econometric model
RESIS ht  K ht   RESIS h ,t 1   ht
K: Vector of variables
β, η: Vector of parameters
µ: stochastic variables
Market study
Trypanocides demand functions
4. Main results and discussion
Socioeconomic factors: Age of
household head (+), education (+),
production systems [crops producers /
herdsmen] (-), wealth level (+)
Environmental factors: Tsetse flies
infection rate (+), accessibility (-),
previous treatment failure rate (-)
Expenditures of trypanocidal drugs represent about
45% of total animal health cost.
About 60% of trypanocides used are preventive
ones.
Price is higher on official market (high transaction
costs) than on parallel markets (asymmetric
information and hazard moral problems) .
Impact on some parameters:
Mortality: 10 et 26%
Milk production: 10 et 40%
Performance of oxen: 33%
FAO (1994): USD1-1.5 billion of loss for Africa.
5. Conclusion
Field studies undertaken in Kénédougou
province provided valuable information on the
widespread presence, but variable pattern, of
trypanocidal drug resistance and changing
patterns of trypanosome risk.
The resistance cost appears to be high:
Externalities for individual and society
Impact on productivity
Increase of treatment cost (4-5 treatments per year
vs. two treatments without resistance
This information has important implications
for managing tsetse and trypanosomosis risk
in the area.
The results suggest reducing drug use in
areas with very low risk, and helping
livestock keepers to improve tsetse control
and minimize trypanocidal drug use in higher
risk areas.
To tackle the complexity of trypanosomosis, it
is necessary to adopt multidisciplinary
approach.
The results presented here are preliminary
ones. An ongoing study try to evaluate the
total cost of the resistance to trypanosomosis
in the Cotton belt in West Africa.
[CIRDES, ILRI, BMZ, Free University of Berlin,
NARS]