Lack of Th1 or Th2 polarization of CD4+ T cell response induced by particulate antigen targeted to phagocytic cells

Viral haemorrhagic disease (VHD) of rabbits was introduced into Mexico from the United States of America in November 1988, following the importation of infected carcasses from China. In February 1989, the National System for Animal Health Emergencies was created, and an eradication programme was implemented at that time. The VHD virus was eradicated in 1992, by means of disease control procedures which included active epidemiological surveillance, publicity campaigns, slaughter, cleaning and disinfection of affected premises, the use of sentinel animals, serological monitoring and repopulation. The eradication programme involved the serological sampling of 39,727 rabbits (revealing an incidence of 1.4%) and the slaughter of 121,275 affected rabbits and rabbits at risk of exposure to infection. The final outbreak of the disease was recorded in April 1991. The country maintained strict epidemiological surveillance through serological testing, certification of premises free from the disease, and control of movement of animals and animal products. Mexico was declared free from the disease on 20 January 1993, becoming the first country to have eradicated VHD. The authors propose a model to evaluate the risk of introducing VHD through the importation of animals and animal products. A guide is provided to evaluate each branch of the relevant scenario tree and the principal criteria which indicate the event at each parameter.