Rabies, one of the oldest diseases known to man, remains uncontrolled in many parts of
the world. This is in spite of the availability of safe, effective and economical tools for
its control. The wide-spread distribution and rapid growth of its primary reservoir host
population in the developing world, the domestic dog, together with their ubiquitous
association with human populations, explains why canine rabies is endemic across much
of the globe. However, given that effective dog vaccines are available, and that rabies
has been eliminated from dog populations in many countries (including large, non-island
countries like the United States) through the implementation of these vaccines and other
control measures, why does the disease continue to exact such a toll in other countries?
One reason must be a lack of political and institutional will to tackle the problem. This
in turn is based in part on a lack of awareness of the extent of the problem, coupled with
competing interests for scarce public health resources. Reliance on the reporting of
rabies cases via official channels may lead to underestimation of the true incidence of
the disease by up to one hundred-fold, and a subsequent lack of prioritisation of
resources for its control. This leads to a vicious circle of neglect - low priority means no
resources available for surveillance, which in turn ensures that the true extent of disease
occurrence remains unknown. It is hoped that the quantitative estimates of rabies burden
presented in Chapter 2 will redress this, and provide impetus for policy makers and
donors to tackle the problem. One advantage of the quantitative risk assessment method
used in Chapter 2 is its transparency - as more detailed data become available so the
model can be updated and refined. Knowledge of the estimated burden of the disease, together with preliminary data which shows that, in terms of cost per DALY saved,
rabies is among one of the most cost-effective diseases to target (through the mass
vaccination of dogs), have already encouraged international health agencies and donors
to reconsider their prioritisation of this disease. In this respect, further research is needed
to develop more refined models of cost-effectiveness estimates across different time
horizons and under different epidemiological scenarios.
An additional reason for the lack of rabies control in much of the developing world is
that, while safe and cheap dog rabies vaccines are available, their effective
implementation is often hampered by an incomplete understanding of the demographics
and ecology of dog populations in rabies-endemic areas, and the relative roles of
anthropogenic and non-anthropogenic regulatory factors. Accurate estimates of dog
population numbers are rarely available, and existing estimates often grossly
underestimate actual numbers of dogs. Chapter 3 provides a means whereby such
numbers can be extrapolated for a variety of socio-cultural scenarios in Tanzania
(including national estimates based on composite dog-human ratios), while at the same
time highlighting the difficulties encountered in the estimation process (particularly the
lack of sampling frames for households in the estimation of the owned dog population).
National estimates of the owned dog population, derived from the work presented in
Chapter 3, will be included in the national rabies control policy document currently
being developed by the Tanzanian government, and have also been included in funding
applications to donors to support this programme. These figures can be used to estimate
required resources for rabies control efforts, and to allow the optimal utilisation of those
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resources. They can also serve as targets against which vaccination efforts can be
measured, to assess the vaccination coverage achieved.
Humane dog population management programmes can serve as a valuable adjunct to
vaccination efforts in the control of rabies, by decreasing dog population growth rates
and reducing population turnover. Such stable populations greatly reduce the frequency
of mass vaccination campaigns needed to maintain a given level of vaccination
coverage, in addition to reducing (over time) the total number of dogs to be vaccinated.
Chapter 5 provides valuable baseline data for an humane dog population control
programme aimed at the sterilization of owned dogs in Colombo, Sri Lanka, and
together with Chapter 3 provides a basis for comparison of owned urban dog populations
in Asian and African environments. The characteristics of dog-owning households
identified in these two chapters will enable the effective targeting of education and
awareness campaigns, for both humane dog population programmes and rabies
vaccination campaigns. The strong male bias identified in this study in the sex ratio of
owned dogs, together with the preference for male dogs and the fact that few owners of
female dogs would want to keep a litter, point to the existence of possible anthropogenic
drivers of the population dynamics of both the owned and unowned dog population in
Colombo. Further work is needed to understand the effect of these drivers, and their
interaction with non-anthropogenic regulators. Such studies would need to examine the
fecundity and sex-specific pup survival in both the owned and unowned segments of the
dog population, and migration between the two sub-populations, through adoption or
abandonment. This work is necessary to understand the effect of humane dog population
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control programmes on dog population dynamics, and could be done in conjunction with
studies on the impact of these programmes on the long-term cost-effectiveness of dog
vaccination campaigns.
Human behaviours which impact on the dynamics and welfare of dog populations are
expressed as a result of the underlying attitudes of individuals towards dogs. These
attitudes are in turn modified by socio-cultural conditions and individual experience.
Chapters 4 and 6 present unique research into these attitudes and modifiers in a crosssection
of inhabitants in Tanzania and Colombo. Building on the work done in Tanzania,
the item scale developed in Chapter 5 provides a valuable tool with which these
attitudes, and their relationship to dog welfare and rabies control, can be further
explored. For example, the finding that household heads with more positive attitudes
towards dogs were more likely to have their dogs vaccinated at a central point suggests
the need for integration of programmes on responsible pet ownership into rabies
vaccination planning. Overall, the work suggests a more positive affective attitude
towards dogs in these countries than was perhaps previously supposed, and that this
particular aspect of the human-animal interface may be worthy of further study. The
effect of these attitudes, and the possible changes in attitude occurring as a result of the
implementation of responsible pet ownership programmes, on the uptake and impact of
the humane dog population control programme in Colombo, is a potentially fruitful area
for further research.
The application of the findings presented in this thesis to the refinement of vaccination
campaigns for the control of canine rabies will be of benefit not only to the fields of
public health and animal welfare, but also to the conservation of endangered canids
threatened with spill-over of the disease from sympatric dog populations. The
management strategies discussed in Chapter 7 for the reactive vaccination of Ethiopian
wolf populations following such a spill-over event, although effective, are costly and
potentially high-risk if implemented too late. Targeted vaccination of the dog
population, ideally in conjunction with responsible pet ownership and humane
population control programmes, may be more effective, and have the additional benefit
of improving relations with local communities by reducing the incidence of human bites
from suspect rabid dogs. Once again attitudes of owners towards dogs play a role, as the
uptake and cost-effectiveness of these vaccination programmes is dependent on owner
co-operation and influenced by the ability and willingness of owners to handle their
dogs. Understanding these attitudes and their effects on owner behaviour may improve
delivery of vaccines, possibly through the deployment of new technologies such as bait
formulations containing oral rabies vaccines.