Animal diseases lead to mortality and reduced productivity in dairy herds worldwide, causing substantial economic losses. Production diseases such as mastitis and external and internal parasites do not generally result in the death of the animal, but always reduce the efficiency of the system. Diseases may affect dairy productivity through lowered milk yield, reduced fertility, delays in reaching puberty, reduced milk quality and reduced feed conversion. Diseases of dairy animals may also represent a risk for human health (e.g., tuberculosis, brucellosis).
Small-scale dairy production in developing countries is subject to many risks from disease. This is the result of several factors such as limited knowledge of disease prevention, management and control; high prevalence of pathogens; and the cost, availability or suitability of animal health services. The loss of even one animal to disease may have a substantial impact on the household economy of a small-scale dairy producer with limited resources. Small-scale dairy producers generally make few investments in animal health, especially in disease prevention.
Different dairy species and breeds have different health requirements, depending on their physical and physiological characteristics. Animal health and welfare problems may be significantly reduced by selecting dairy animals that are suited to the local environment. Of particular importance is the dairy animal’s ability to cope with the local climate, to feed on available resources, and to resist endemic diseases and local parasites. Dairy animals that are kept under intensive systems are more exposed to transmissible disease agents, while those in extensive systems are more prone to parasitic infections. When animals are introduced into a new environment they may be vulnerable to endemic diseases of the new location, as they lack acquired immunity.
Of particular importance are transboundry animal diseases. These are defined as those diseases that are of significant economic, trade, and/or food security importance for a considerable number of countries; which can easily spread to other countries and reach epidemic proportions; and where control/management, including exclusion, requires cooperation between several countries.