Control and prevention of rabies in animals: paradigm shifts

Abstract

Animal management is the keystone of any modern programme for the prevention and control of rabies. Historically, "animal control" for local elimination of disease was largely equated with population reduction. However, with relatively few exceptions, culling alone has not led to effective control of rabies. In most documented examples of effective control of rabies in the 20th century, an integrated management approach was used that included public education, responsible stewardship of animal populations, manipulation of the population carrying capacity of the local habitat, and vaccination strategies. Globally, the greatest burden on human health that is attributable to this zoonosis is caused by uncontrolled rabies in dogs. Where political willingness, biomedical infrastructure, and economic stability permit the sustained use of control measures (e.g. stray animal removal and mandatory parenteral vaccination), canine rabies has been significantly suppressed and even eliminated over large geographical areas. Examples include many island nations, most of North America, Europe, and increasingly in South America. Despite the effectiveness of such proven control techniques, however, their implementation in parts of Asia, Africa, and elsewhere has been limited, primarily because of a lack of dedicated resources and intersectoral cooperation, and also because of the burden of high-density populations of dogs. Implementation is often complicated by cultural and social factors, e.g. reluctance to cull apparently ownerless, nuisance animals that are suspected to have been exposed to rabies, partly on the basis of religious beliefs). Attempts to modify animal fertility (such as the encouragement of voluntary spay-neuter programmes or individual chemical contraception, and the extension of such actions to animals in the community) may provide ancillary support in line with other traditional methods of control of canine rabies. With the identification of complex situations in which wildlife rabies persists despite the elimination of canine rabies, e.g. in North America and Europe, cats can pose a significant public health risk requiring consideration of alternative approaches. In any model system, the threat of translocation of infected animals, unintentional or otherwise, provides a strong rationale for the creation of barriers to prevent reintroduction or exacerbation of the disease, and the maintenance of a minimum body of expertise related to surveillance, diagnosis, and the enactment of mitigating measures. While control activities have traditionally focused upon certain Carnivora species, bats represent another worldwide rabies reservoir. Indiscriminate killing of bats and destruction of roosts was once the norm, but such activities are not sanctioned by reputable organizations today. Even vampire bats, responsible for substantial effects on health and agricultural losses in the New World (Mexico to Argentina), should be targeted only by specific control applications, rather than by more widespread, unconventional, non-specific methodology. Bats should be excluded from human living quarters. Implementing measures to prevent bats from gaining access to homes should occur at an appropriate time when the bats are absent, especially to avoid sealing the non-flying young within a building. Although great progress has been made during the past four decades in the induction of herd immunity among free-ranging carnivores via oral vaccination against rabies, similar novel solutions have not been readily applied to bat populations. Given these challenges, new paradigm shifts are eagerly anticipated as additional biotechnological applications (including contraceptives and anticoagulants) are developed to deal with domestic animals and wildlife.