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Contents lists available at ScienceDirect
Preventive Veterinary Medicine
journal homepage: www.elsevier.com/locate/prevetmed
Assessing the impact of East Coast Fever immunisation by the infection
and treatment method in Tanzanian pastoralist systems
S. Babo Martins a,∗ , G. Di Giulio b , G. Lynen b , A. Peters c , J. Rushton a
a
b
c
The Royal Veterinary College, Hawkshead Lane, North Mymms, Hatfield, Hertfordshire AL9 7TA, UK
VetAgro Tanzania Ltd, PO Box 13188, Arusha, Tanzania
Global Alliance for Livestock Veterinary Medicines (GalvMed), Pentlands Science Park, Bush Loan, Edinburgh EH26 0PZ, UK
a r t i c l e
i n f o
Article history:
Received 23 December 2009
Received in revised form
21 September 2010
Accepted 22 September 2010
Keywords:
East Coast Fever
Infection and treatment method
Pastoralist systems
Partial budget analysis
Decision analysis
a b s t r a c t
A field trial was carried out in a Maasai homestead to assess the impact of East Coast Fever
(ECF) immunisation by the infection and treatment method (ITM) with the Muguga Cocktail
on the occurrence of this disease in Tanzanian pastoralist systems. These data were further
used in partial budgeting and decision analysis to evaluate and compare the value of the
control strategy. Overall, ITM was shown to be a cost-effective control option. While one ECF
case was registered in the immunised group, 24 cases occurred amongst non-immunised
calves. A significant negative association between immunisation and ECF cases occurrence
was observed (p ≤ 0.001). ECF mortality rate was also lower in the immunised group. However, as anti-theilerial treatment was given to all diseased calves, no significant negative
association between immunisation and ECF mortality was found. Both groups showed an
overall similar immunological pattern with high and increasing percentages of seropositive calves throughout the study. This, combined with the temporal distribution of cases in
the non-immunised group, suggested the establishment of endemic stability. Furthermore,
the economic analysis showed that ITM generated a profit estimated to be 7250 TZS (1
USD = 1300 TZS) per vaccinated calf, and demonstrated that it was a better control measure
than natural infection and subsequent treatment.
© 2010 Elsevier B.V. All rights reserved.
1. Introduction
East Coast Fever (ECF) is a disease of cattle caused by the
protozoan parasite Theileria parva and transmitted by the
three-host tick Rhipicephalus appendiculatus (Norval et al.,
1992). The disease occurs in 11 countries in eastern, central
and southern Africa (Mukhebi et al., 1992), with a heterogeneous distribution and prevalence strongly related to its
vector dynamics, host susceptibility, grazing system and
tick control practices (Deem et al., 1993; Kivaria, 2007).
In all affected areas, ECF has a considerable epidemiological and economic significance. In Tanzania, the disease
∗ Corresponding author. Fax: +44 1707666574.
E-mail addresses: [email protected], [email protected]
(S. Babo Martins).
is the main cause of reported livestock deaths, accounting
for 43.7% of annual mortality between 1981 and 1992/1993
(Mtei and Msami, 1996) and was estimated to have an overall annual cost of 43 million USD (McLeod and Kristjanson,
1999). In unvaccinated Zebu (Bos indicus) calves kept under
pastoralist management, ECF is responsible for annual mortality rates of 40–80% (Homewood et al., 2006; Di Giulio et
al., 2009).
Although ECF control has traditionally relied on intensive acaricidal application (Norval et al., 1992), this practice
has been progressively abandoned due to factors including
logistical and financial constraints, development of resistance by vector ticks, disruption of endemic stability and
environmental impact (deCastro, 1997; Ministry of Water
and Livestock Development, 2004).
Immunisation of cattle by the infection and treatment
method (ITM) offers a valuable alternative for ECF control
0167-5877/$ – see front matter © 2010 Elsevier B.V. All rights reserved.
doi:10.1016/j.prevetmed.2010.09.018
Please cite this article in press as: Babo Martins, S., et al., Assessing the impact of East Coast Fever immunisation by the
infection and treatment method in Tanzanian pastoralist systems. PREVET (2010), doi:10.1016/j.prevetmed.2010.09.018
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(Oura et al., 2004). The method involves the inoculation of
a known strain(s) of T. parva with a concurrent administration of an antibiotic, resulting in an attenuate infection but
in a long-lasting efficient immune response (Di Giulio et al.,
2009; McKeever, 2009). Broad protection against most field
isolates can be accomplished by combining different strains
(Uilenberg, 1999; McKeever, 2009), as occurs with the
trivalent formulation known as the Muguga Cocktail, composed of Muguga, Kiambu 5 and Serengeti-transformed
stocks (Ruheta, 1999; McKeever, 2007).
As the Muguga Cocktail is a live vaccine, disadvantages of the technique include the requirement of a cold
chain and the establishment of a persistent carrier status
(Uilenberg, 1999; Di Giulio et al., 2009). Concerns extend to
the possibility of introduction of vaccine parasite strains (or
specific alleles) into the field, resulting in genetic recombinations with local parasite populations (Oura et al., 2007)
or introduction of the disease in previously free areas
(Uilenberg, 1999; McKeever, 2007).
Results achieved in studies carried out in Zambia to
assess the impact and financial implications of ITM in traditionally managed Sanga (cross between B. indicus and
Bos taurus) cattle showed that it is a cost-effective strategy for ECF control (Minjauw et al., 1999). For pastoralist
cattle in Tanzania, information on ITM economic impact
is scarce but informal assessments and modelling have
already provided encouraging results (Kimera, 1997; Sudi,
1998; Homewood et al., 2006).
This study reports the epidemiological and economic
results of a 12-month field trial carried out in a Maasai herd
in the Ngorongoro Region, Tanzania. The aim was to formally evaluate the effect of ECF vaccination through ITM
using the Muguga Cocktail on ECF-disease occurrence in
pastoralist cattle and, through an economic analysis, assess
its value in the context of the pastoralist production system.
2. Materials and methods
Calves within the immunised group were vaccinated at
the start of the study (day 0) by ITM with Muguga Cocktail,
FAO batch 2 (Di Giulio et al., 2009), and using a long-acting
oxytetracycline (20 mg/kg). No placebo treatment was used
in the control group. Both groups grazed together, leaving the homestead in the morning and returning in the
night, and were subjected to similar management practices
including acaricidal treatment.
Clinical monitoring of all calves was carried out daily
in the first month and then bi-monthly for the remaining 11 months of the study. Since immunised calves were
identified by double ear tags, blinding was not possible.
The livestock owner was also trained in early recognition of ECF clinical signs, to prepare thin blood and
parotid lymph node biopsy (LN) smears and to report
and take blood, LN and impression smears of dead calves
between visits. Cases of ECF were diagnosed on the basis of
clinical assessment (predominantly acute respiratory distress, swelling of parotid and prescapular lymph nodes
and fever (temperature above 39.5 ◦ C) for more than 3
consecutive days) and the presence of a macroschizont
index ≥5% on collected smears (Norval et al., 1992). An
immunisation reactor was considered as a calf developing
clinical ECF due to ECF vaccination between day 14 and
28 post-vaccination (Di Giulio et al., 2009). All diseased
calves were treated using buparvaquone (2.5 mg/kg) and,
in case of death, post-mortem examination was performed
whenever possible. All information was recorded on field
sheets.
Blood samples were collected monthly and sera were
tested for antibodies to T. parva using the PIM-based T.
parva ELISA method (sensitivity > 99%, specificity 94–98%)
(Katende et al., 1990). A percent positivity ≥20% was used
as the cut-off value.
Live weights of all calves were measured and recorded
monthly by the same person using a weight-band (Dalton
Supplies Ltd).
2.1. Study area
2.3. Data analysis
The field trial was conducted in Endulen (1993 m altitude, 03◦ 10 32 S, 035◦ 16 96 E), Ngorongoro Conservation
Area, Tanzania. The region is classified as sub-humid highland, recording overall high tick numbers, and considered
to be endemic for ECF. High mortality in the indigenous
Zebu calf population is usually observed (Lynen et al.,
2005).
Data recorded on field sheets was stored and edited
using Excel® (Microsoft). Statistical hypothesis testing was
performed using SPSS Statistics 17.0 ® (SPSS Inc.).
All epidemiological parameters were determined as
described in Thrusfield (1995), including vaccine efficacy
calculated as:
2.2. Data collection
efficacy of vaccination =
A total of one hundred Zebu calves, aged between 1 and
7 months, from a study Maasai homestead were randomly
allocated, by simple random sampling, to two groups of 50
calves, one immunised (I) and one non-immunised (NI).
The sample size was determined by the availability of
calves grazing together and not previously treated against
ECF.
All calves were individually identified by ear tags and
information on date of birth and live weight was recorded.
Non-immunised calves were identified with one ear tag
and double ear tagging was used for immunised calves.
(incidence rate NI group−incidence rate I group)
incidence rate NI group
Daily weight gain was calculated as:
daily weight gain =
weight gain by the end of the trial
number of days in the trial
Chi-squared tests were performed to explore possible
associations between immunisation and ECF cases occurrence, ECF specific mortality and overall mortality. Fisher’s
exact test was used to compare proportions of seropositive
calves in the immunised and non-immunised groups and
a two-sample t-test was used to compare the mean daily
weight gains between the two groups. A critical p-value of
Please cite this article in press as: Babo Martins, S., et al., Assessing the impact of East Coast Fever immunisation by the
infection and treatment method in Tanzanian pastoralist systems. PREVET (2010), doi:10.1016/j.prevetmed.2010.09.018
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Table 1
Inputs used in partial farm budget analysis of the financial benefits of East Coast Fever immunisation by the infections and treatment method in Tanzanian
pastoralist systema .
Parameter
Number of calves (NoA)
Number of females (NoF)
Market value of a calf (TZS per head) (CP)
ECF cumulative incidence (CumInc)
ECF cumulative mortality (CumMort)
Daily milk yield (l per cow) (DMY)
Lactation length (LL)
Milk price (TZS per l) (MP)
Vaccine cost (TZS per calf) (VC)
Cost of treatment (TZS per calf) (TC)
Percentage of reactors to vaccination (R)
Extra calves available to sell (ECS)
a
b
Value
Source
NI group
I group
50
21
Uniform (70,000;100,000)
0.48
0.1
Lognorm (0.891;0.491)
Lognorm (372;7.96)
500
50
21
Uniform (105,000;150,000)
0.02
0.02
Lognorm (0.891;0.491)
Lognorm (372;7.96)
500
7900
19,700
6%
RiskIntUniform(0;4)
19,700
Study data
Study data
Expert opinion
Study data
Study data
Roderick et al. (1999)
Roderick et al. (1999)
Expert opinion
Market priceb
Market price
Study data
Study data
TZS – Tanzanian shilling.
The cost of the vaccine is not subsidised.
0.05 was used to interpret statistical results. In addition,
survival analysis (Kaplan–Meier survival curve) was conducted to evaluate and compare the distribution of time to
effect (ECF case) for the two groups.
Partial budget analysis was used to estimate the herdlevel profitability of ECF vaccination. It was assumed that,
as a consequence of ECF vaccination, calf trade would
increase (Homewood et al., 2006); calves would command
a price 50% higher in the market (Di Giulio et al., 2009;
Norval et al., 1992; expert opinion) and that, as the presence
of the calf is required to stimulate milk let-down process,
a higher milk production would be observed (Roderick et
al., 1999). A stochastic analytic approach was used to take
into account uncertainty associated with some inputs using
@Risk for Excel 5.5® (Palisade Inc). Five thousand iterations using Latin Hypercube sampling were run considering
the inputs shown in Table 1. Outputs such as net impact
and marginal return were then calculated according to
Dijkhuizen et al. (1995), using the parameters presented
in Table 2. Sensitivity analysis was carried out within
@Risk, using a multivariable stepwise regression technique
and Spearman’s rank correlation, to access the impact of
changes in the inputs in the final output.
Decision tree analysis was carried out following the
methodology described by Ngategize et al. (1986) and using
decision analysis software Precision Tree 5.5® (Palisade
Inc). The analysis considered two decisions on ECF control:
(1) immunisation through ITM and (2) natural infection
combined with anti-theilerial treatment with improved
detection and management. Inputs used in the analysis are
shown in Table 3.
3. Results
A total of 25 cases of ECF occurred between May
(day 0) and October 2000, of which 96% occurred in the
non-immunised group. The highest number of ECF cases
occurred in July (Fig. 1). Calves that developed ECF were
aged between 1 and 5 months, with a mean age of 2.6
months (SD = 1.13). In the immunised group, 6% of the
calves reacted to vaccination. The epidemiological findings
of the study are summarized in Table 4.
A significant negative association between immunisation and the occurrence of ECF cases was observed,
chi squared (1, n = 100) = 25.8, p < 0.001. Furthermore,
Kaplan–Meier analysis (Fig. 2) showed significant differences between the two groups (p < 0.001). An immunised
calf had an annual probability of not developing ECF disease close to 100%, compared to approximately 50% for the
non-immunised calves.
Despite prompt treatment of all ECF cases, 5 deaths
due to the disease were recorded in the non-immunised
group (21% case fatality). In the immunised group the one
ECF case was fatal. However, no significant negative association between immunisation and mortality due to ECF
mortality was found, chi squared (1, n = 100) =1.5, p = 0.2.
Table 2
Parameters and components considered in partial budget analysis of the financial benefits of East Coast Fever immunisation by the infection and treatment
method in Tanzanian pastoralist systemsa .
Parameters
Components considered
Additional returns
1. Extra milk production = ((LL × DMY × CumMort NI × NoF NI) − (LL × DMY × CumMort I × NoF I)) × MP
2. Extra calves sold = ECS × (CP NI group − CP I group)
Additional costs incurred
1. Cost of vaccination = VC × NoA I group
2. Cost of treatment of reactors = TC × (R × NoA I group)
3. Cost of treatment of infected calves = TC × CumInc I group × NoA I group
Costs no longer incurred
1. Costs with treatment of diseased calves = TC × CumInc NI group × NoA NI group
Foregone returns
None (reported that calves that die do not have salvage value)
a
Please refer to Table 1 for abbreviations.
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Table 3
Inputs used on the decision tree analysis of East Coast Fever immunisation by the infection and treatment method in Tanzanian pastoralist systemsa .
Parameters
Values
Source
Probability of a calf being a reactor
Probability of survival after ECF infection (with anti-theilerial treatmentb )
Probability of developing ECF I
Probability of developing ECF NI
Cost of the vaccine
Cost of the treatment for a calf
Mean market value of a vaccinated calf
Mean market value of a non-vaccinated calf
0.06
0.76
0.02
0.48
7900 TZS
19,700 TZS
127,500 TZS
85,000 TZS
Study data
Study data (overall survival, data not shown)
Study data (cumulative incidence group I, Table 4)
Study data (cumulative incidence group NI, Table 4)
Market price
Market price
Expert opinion
Expert opinion
a
b
TZS – Tanzanian shilling.
Treatment performed using buparvaquone (2.5 mg/kg).
Fig. 1. Evolution of the number of East Coast Fever cases per group throughout the study, where May-00 corresponds to day 0 in a field trial conducted at
Endulen, Tanzania, 2000.
Table 4
Measures of disease occurrence and vaccinal efficacy for two groups of
calves in a study of East Coast Fever, Endulen, Tanzania, 2000.
Fig. 2. Kaplan–Meier analysis survival curve showing time to effect
(developing an East Coast Fever case) in both groups (Y – immunised
group; N – non-immunised group) in a field trial conducted at Endulen,
Tanzania, 2000.
Parameters
I group
NI group
No. calves at the
beginning of the study
Mean age at the
beginning of the study
(months)
Mean weight at the
beginning of the study
(kg)
ECF cases
Overall deaths
ECF deaths
Incidence rate
Cumulative incidence
Case fatality
Survival
ECF cumulative mortality
ECF mortality rate
Vaccine efficacy
50
50
3.48 (SD = 1.68)
3.4 (SD = 1.93)
51.44 (SD = 18.03)
50.06 (SD = 19.02)
1
6
1
0.02
0.02
1.00
0.00
0.02
0.02
24
10
5
0.77
0.48
0.21
0.79
0.10
0.16
0.97
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Fig. 3. Evolution of seroprevalence levels (expressed as a percentage) by group over the period of the study in a field trial conducted at Endulen, Tanzania,
2000.
Similarly, no significant negative association was found
between immunisation and overall mortality, chi squared
(1, n = 100) =0.81, p = 0.37.
At the beginning of the study, 60% of the calves in the
immunised group, and 65% in the non-immunised group,
were positive for T. parva antibodies. At the end of the study
both groups presented a similar immunological pattern,
with only 7.3% and 8.11% of the calves seronegative in the
immunised group and non-immunised group, respectively
(Fig. 3).
Seroprevalence in calves aged 1–2 months in the nonimmunised group fell sharply from 80% at day 0 to 11%
at day 60. Overall, older calves showed higher seroprevalence levels. Evolution of the percentage of seropositive
calves per age group during the first 180 days of the study
is presented in Table 5.
There was no significant association between immunisation and seroprevalence at 6 and at 12 months of the
study (p = 0.23 and 0.45, respectively). Also, no statistically significant difference in daily weight gain between
immunised (mean = 0.11 kg, SD = 0.03) and non-immunised
(mean = 0.10 kg, SD = 0.04) calves was observed, t = 0.48,
p = 0.63 (two-tailed).
Immunised calves were estimated to generate a net output of 362,497 TZS (SD = 165,450) and ITM intervention
was estimated to have a mean marginal return of 7250 TZS
(SD = 3309) per vaccinated calf, with a minimum value of
1085 TZS and a maximum value of 38,564 TZS. Sensitivity
analysis showed that marginal returns were most strongly
affected by daily milk yield followed by the number of extra
calves sold as a consequence of vaccination and then by
market value of immunised calves.
Decision tree analysis (Fig. 4) showed that ITM was the
better economic option for ECF control, considering the
probability of occurrence and the value of the outcome. A
break-even analysis showed that the price of the vaccine
would have to double to make natural infection and antitheilerial treatment a better control option. Alternatively,
efficacy of the treatment of clinical cases would have to
increase to 100%.
4. Discussion
ITM adoption by pastoralists in northern Tanzania has
been gradually increasing (Lynen et al., 2005; Di Giulio et
al., 2009), suggesting a growing perception by the farmers
of the benefits associated with the method. Currently, the
pastoral sector accounts for over 95% of the immunisations
carried out in the country (Lynen et al., 2005).
In this study the number of ECF cases in the immunised
group was significantly lower than in the non-immunised
group, clearly showing that ITM is an effective ECF control
method with a vaccine efficacy of 97%.
However, since all ECF cases were promptly treated, no
significant statistical differences in ECF specific mortality
rates between both groups were observed and a relatively
low ECF-specific mortality rate in the non-immunised
group was reported. Treatment efficacy is dependent on
the speed of diagnosis and early implementation of treatment of cases (Muraguri et al., 1999). Thus, in a situation
where the farmer is not trained to recognize the clinical
signs of ECF, anti-theilerial drugs are not readily available,
the quality of available products is unreliable or underdosing is applied, differences in mortality between groups are
expected (Lynen et al., 2005; Homewood et al., 2006).
The lack of significant differences in terms of daily
weight gain between the two groups may also reflect
the efficacy of ECF treatment and the drought conditions
observed during the year of the study (2000).
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Table 5
Evolution of seroprevalence levels (expressed as a percentage) in the first 180 days, by age and group, in a study of East Coast Fever, Endulen, Tanzania,
2000.
Time post-immunisation
Day 0
30 days post-immunisation
60 days post-immunisation
90 days post-immunisation
120 days post-immunisation
n
1–2 months
≥7 months
3–6 months
I
NI
I
NI
82.4
52.9
60.0
40.0
75.0
17
80.0
75.0
11.1
18.2
62.5
20
46.7
50.0
56.3
56.3
75.0
30
57.1
42.9
33.3
40.0
69.2
28
The number of ITM reactors in this study is above the
average percentage presently recorded in Tanzania (Lynen
et al., 2005; Di Giulio et al., 2009). This is probably due to
the current use of a higher concentration of OTC (30 mg/kg)
in ITM, which has shown to reduce the occurrence of ECF
immunisation reactors (Di Giulio et al., 2009).
As the number of ECF cases declined, seroprevalence increased. Both groups presented an overall similar
immunological pattern with high seroprevalence levels
6 months after the beginning of the study, indicative of
severe field challenge. These levels of seropositivity and
low number of clinical cases strongly suggest the establishment of endemic stability to T. parva infection (Norval
et al., 1992; Deem et al., 1993), an epidemiological situation
where little or no clinical disease is detected in the cattle
population since the majority of calves become infected
and immune by 6 months of age (Norval et al., 1992).
Although immunity to ECF is cell-mediated (McKeever,
2007), results show that ECF cases mainly occurred in
an age-group and timeframe where the percentage of
I
NI
66.7
66.7
100.0
100.0
100.0
3
50.0
50.0
100.0
100.0
100.0
2
seropositive calves fell sharply from 80 to 11%. This could be
could be a reflection of current calf management practices,
since calves only leave the homestead for grazing after
reaching 6–8 weeks of age, delaying contact with field challenge and allowing for maternal antibody decline (Gitau et
al., 1997, 2000).
Sixty percent of the calves vaccinated between 1 and 2
months of age were seropositive by 180 days after immunisation, whereas for calves vaccinated over 2 months of
age this percentage reached 80%. Results from other studies conducted in Zambia found a similar pattern in young
calves, showing that even though maternal antibodies do
not hinder ITM efficacy, they might interfere with seroconversion and reduce the utility of serology as a tool
to monitor immunisation performance in this age group
(Marcotty et al., 2002).
The possible transmission of Muguga Cocktail components from vaccinated ECF carriers to non-immunised
co-grazing animals (Oura et al., 2004, 2007; De Deken
et al., 2007; Geysen, 2008), could mean that non76.0%
Survives
0
2.0%
ECF
-77900
-19700
24.0%
Dies
-127500
76.0%
Survives
-28606
98.0%
No ECF
0
Reactor
-174800
Chance node value
0
6.0%
-47300
Chance node value
-27600
Chance node value
-58964.56
-19700
24.0%
Dies
-155100
-127500
Chance node value
ITM
-11909.5136
-7900
76.0%
Survives
0
2.0%
ECF
-58200
-19700
24.0%
Dies
-127500
No reactor
94.0%
-8906
98.0%
No ECF
0
-7900
76.0%
Survives
0
48.0%
-155100
Chance node value
0
ECF
-27600
Chance node value
-19700
Chance node value
-40100
-19700
24.0%
Dies
-85000
-104700
Chance node value
-19248
No ECF
52.0%
0
Fig. 4. Decision tree for East Coat Fever control, displaying baseline probabilities and outcome values. Cost and probability of each branch is given before
the following chance or terminal node.
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immunised calves faced a heavier ECF challenge. However,
serology results in this study suggested that nonimmunised calves were already experiencing a severe field
challenge. Furthermore, in previous experiments in traditionally managed production systems, where cases mainly
occurred just after immunisation, transmission as a result
of a carrier state was ruled out (Minjauw, 1996). The
mid to long term ECF incidence in the non-immunised
calves decreased, suggesting a positive effect on rapidity
of the development of endemicity in previously unstable
areas (Minjauw et al., 1998). In this study, similar results
were observed. All ECF cases occurred between May and
October.
While treatment of ECF clinical cases might be seen as
a reasonably successful strategy provided there is an early
diagnosis, the economic analysis demonstrated that ITM is
still the most attractive option. Partial budgeting showed
that the intervention carries an approximate profit of 7250
TZS (5.5 USD) per vaccinated calf, while decision tree analysis indicates that vaccination is a better control option
than natural infection and improved diagnosis and treatment. It has been shown previously that ITM in traditionally
managed Sanga cattle in Zambia offers the most profitable
option (Minjauw et al., 1999). In fact, although the cost of
vaccine is significant for pastoralists, representing a substantial part of the household income (Homewood et al.,
2006), uptake of the vaccine has been increasing (Lynen et
al., 2005), showing that livestock owners are prepared to
invest 8% of the value of a calf in this intervention.
The alternative decision to ITM, natural infection and
anti-theilerial treatment, would only be a better economic
option where vaccine cost increased or with enhanced efficacy of the treatment to a level where no deaths occur.
However, the results achieved here portray a management
system with good detection of ECF clinical cases, suggesting
that they represent the best scenario in terms of treatment
efficiency. Higher treatment costs and lower survival rates
in farms without early detection capacities can be expected,
marking ITM the most favorable choice. In fact, in the scenario where no medical treatment is available and all ECF
cases result in death, ITM carries a mean profit of 32,704
TZS (SD = 19,216) per vaccinated calf (data not shown).
Sensitivity analysis showed that returns to ITM are
strongly affected by changes in daily milk yield, number
of extra calves sold by the herdsman as a consequence of
reduced mortality due to ECF vaccination, and market price
of calves. The number of calves sold is dependent on the
households’ need for money to meet imminent expenses
such as education (Cleaveland et al., 2001; Homewood et
al., 2006). The model showed however that ITM is profitable even in the scenario where no extra calves are
sold. Similarly, milk off-take varies according to the milk
requirements of the family. Production is also dependent
on the availability of grazing and drinking water and disease prevalence (Roderick et al., 1999). Moreover, the
market price of calves is strongly influenced by seasonality.
Partial budgeting provides a simple economic description and comparison of different disease control measures
(Dijkhuizen et al., 1995) and a broader economic analysis
could prove useful to assess the potential benefits of ITM to
society as a whole. It is important to note that adding to the
7
above quantified economic benefits are also the intangible
benefits related with reduced calf mortality in communities where milk provides the major source of nutrition and
an increased herd size adds to social capital.
Acknowledgments
The field work conducted was partially funded by The
Netherland Cooperation and by VetAgro Tanzania Ltd. The
write-up of this paper was made possible through Global
Alliance for Livestock Veterinary Medicines (GalvMed) and
the Royal Veterinary College (RVC). We would like to thank
the Government of the United Republic of Tanzania to have
allowed the use of the data and acknowledge Mrs. Kim
Stevens, Dr. Peter Russell and Professor Decklan McKeever
for their useful contributions to the analysis and discussion.
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