Livestock diseases contribute to an important set of problems within livestock production systems. These include animal welfare, productivity losses, uncertain food security, loss of income and negative impacts on human health. Livestock disease management can reduce disease through improved animal husbandry practices. These include: controlled breeding, controlling entry to farm lots, and quarantining sick animals and through developing and improving antibiotics, vaccines and diagnostic tools, evaluation of ethno-therapeutic options, and vector control techniques.
Livestock disease management is made up of two key components:
1) Prevention (biosecurity) measures in susceptible herds
2) Control measures taken once infection occurs.
The probability of infection from a given disease depends on existing farm practices (prevention) as well as the prevalence rate in host populations in the relevant area. As the prevalence in the area increases, the probability of infection increases.
Preventing diseases entering and spreading in livestock populations is the most efficient and cost-effective way of managing disease (Wobeser, 2002). While many approaches to management are disease specific, improved regulation of movements of livestock can provide broader protection. A standard disease prevention programme that can apply in all contexts does not exist. But there are some basic principles that should always be observed. The following practices aid in disease prevention:
Surveillance and Control Measures
Disease surveillance allows the identification of new infections and changes to existing ones. This involves disease reporting and specimen submission by livestock owners, village veterinary staff, district and provincial veterinary officers. The method used to combat a disease outbreak depends on the severity of the outbreak. In the event of a disease outbreak the precise location of all livestock is essential for effective measures to control and eradicate contagious viruses. Restrictions on animal movements may be required as well as quarantine and, in extreme cases, slaughter. Figures 1 and 2 are photos illustrating the holistic approaches to livestock disease prevention and control.
The major impacts of climate change on livestock diseases have been on diseases that are vector-borne. Increasing temperatures have supported the expansion of vector populations into cooler areas. Such cooler areas can be either higher altitude systems (for example, livestock tick-borne diseases) or more temperate zones (for example, the outbreak of bluetongue disease in northern Europe). Changes in rainfall pattern can also influence an expansion of vectors during wetter years and can lead to large outbreaks. Climate changes could also influence disease distribution indirectly through changes in the distribution of livestock. Improving livestock disease control is therefore an effective technology for climate change adaptation.
Benefits of livestock disease prevention and control include: higher production (as morbidity is lowered and mortality or early culling is reduced), and avoided future control costs. When farmers mitigate disease through prevention or control, they benefit not just themselves but any others at risk of adverse outcomes from the presence of disease on that operation. At-risk populations include residents, visitors and consumers. The beneficiaries might also include at-risk wildlife populations surrounding the farm that may have direct or indirect contact with livestock or livestock-related material.
Management options may interact, so the use of one option may diminish the effectiveness of another. Another critical issue is the long-term sustainability of currently used strategies. Chemical intervention strategies such as antibiotics or vaccines are not biologically sustainable. Animals develop resistance to drugs used to control certain viruses and with each new generation of vaccine a new and more virulent strain of the virus can arise (FAO, 2003). Small-scale producers may be negatively affected by livestock disease management if the full cost of the disease management programme is directly passed onto them with no subsidy from the government (FAO, 2003b).
Livestock disease management costs include: testing and screening, veterinary services, vaccines, training of livestock keepers and veterinary staff, and perhaps changes to practices and facilities to reflect movement restrictions and quarantines when animals are added to the herd. The costs of a small-scale mastitis control programme in Peru are shown in Box 1.
Prevention and control costs are generally evaluated against expected financial losses resulting from a disease outbreak in a cost-benefit analysis. The assumption is that increased prevention and control costs lower the expected losses by diminishing the expected scale of an infection.
Livestock and animal health policy should be oriented to both the commercial and pastoral sectors and include pro-poor interventions to support the most vulnerable populations. Government investments in infrastructure (including early warning systems, roads, abattoirs, holding pens, processing plants, air freight/ports and so on), systematic vaccination, and in research and development can all contribute to providing an enabling environment for effective livestock disease management. Removing or introducing subsidies for improved management, insurance systems and supporting income diversification practices could benefit adaptation efforts (IFAD, 2002).
In order for producers to make decisions regarding disease management, they must understand the options that they have. These options depend on disease biology, prevention techniques, tests for infection and their costs, treatments available, market reactions, as well as industry and government programs and policies. Disease biology includes transmission modes and rates, disease evolution (for example, length of time to infectious period), production losses associated with the disease, and mortality rate (where applicable).
Practical training for farmers should include:
Modelling disease outbreaks and spread can provide valuable information for the development of management strategies. Modelling involves studying disease distribution and patterns of spread to determine the scale of a problem.This information is used to develop a model that can predict the spread of disease. Disease modelling requires prior knowledge of animal population distributions and ecology, diseases present and methods of disease transmission. Modelling can be used to assess potential disease impacts and develop contingency plans.