Inadequate measures taken to prevent the spread of animal diseases may result in epidemics and heavy losses, spreading the risk of zoonoses. Such inadequate measures may include lack of quarantine; lack of development of effective vaccine or immunization for certain diseases; lack of research; lack of availability of vaccine or other means of immunization; lack of knowledge of an outbreak; lack of knowledge of the way in which disease can be transmitted; lack of monitoring of wild vectors of disease; inadequate international information on current outbreaks; inadequate international legislation on the traffic in animal products, edible or inedible (such as hides, wool, bones); lack of disinfection measures for animal housing, equipment, pastureland and human beings; inadequate means of disposal of infected carcasses; confusion of symptoms; ignorance concerning identification of animal diseases; negligence; high cost of adequate means of controlling certain diseases; and difficulty in controlling disease in wild animals because of inaccessibility.
Diseases of farm animals are widespread; in addition to diminishing animal yields, diseased animals may also cause illnesses in humans. Furthermore, the extent of certain diseases in developing countries may be so great that the modernization of livestock production is prevented. The destruction of large populations of animals by disease is not a new problem, but only recently have some countries begun to develop extensive programmes to minimize communicable livestock diseases.