Zoonoses and fertility control in wildlife--requirements for vaccines.

This paper reflects on public health considerations on the voluntary release of anti-fertility vaccines for wildlife in the environment. The World Health Organization (WHO) has established a variety of recommendations on safety and efficacy requirements for the voluntary release of rabies vaccines used for oral immunization of animals. These requirements cover aspects of control of rabies and possible biological consequences in the target population. They also deal with the protection of the health of humans and other non-target species that might come into contact with the different oral rabies vaccines used in various parts of the world. These recommendations are laid down in several WHO publications. They are specific to the disease concerned, the target animal reservoir, the relationship and types of contact between humans and target animals, the vaccines and baits used and the respective conditions of oral immunization of wildlife in densely-populated areas. Many of these recommendations also apply to the development and application of contraceptive vaccines for wildlife carnivores. Additional safety requirements concern the transmissibility of the antigen, the reversibility of the intervention within an individual animal and in animal populations, as well as the species specificity of the antigen used. The management of animal populations that are reservoirs for zoonotic diseases is a possible means by which diseases that are transmissible from animals to humans could be prevented. Oral contraception by means of vaccines is an appealing method, provided that requirements for protecting public and animal health, as well as ensuring environmental safety, are precisely defined and strictly adhered to.