A Review of OIE Country Status Recovery Using Vaccinate-to-Live Versus Vaccinate-to-Die Foot-and-Mouth Disease Response Policies I: Benefits of Higher Potency Vaccines and Associated NSP DIVA Test Systems in Post-Outbreak Surveillance

Abstract

To rapidly return to trade, countries with OIE status, FMD-free country where vaccination is not practised, have destroyed emergency vaccinated animals, raising ethical concerns with respect to social values, the environment, animal welfare and global food security. This two-part review explores whether science could support eligibility to return to previous OIE status in 3 months irrespective of vaccinate-to-live or vaccinate-to-die policies. Here, we examine the benefits of higher potency (≥ 6 PD50 ), high-purity vaccines formulated from antigen banks for emergency use, their efficacy and performance in differentiating infected from vaccinated animals (DIVA) assays for post-outbreak surveillance. From an intensive programme of research, we conclude that high-quality, higher potency vaccines are proven to reduce FMD virus (FMDV) subclinical circulation and the risk of carriers. Broader coverage than predicted by serology suggests the potential to hold a few 'key' vaccine strains improving logistics and reducing the financial burden of antigen banks. The OIE should adopt formal definitions for emergency vaccination and emergency vaccines. In terms of supportive tools, we consider that the lack of OIE recognition of DIVA tests other than those of PANAFTOSA in cattle is a shortcoming. There is need for research on maternal antibody interference with DIVA tests and on the use of such tests to establish whether greater purification of vaccines improves performance. We consider that alignment of waiting periods for vaccinate-to-live and vaccinate-to-die in OIE Code Article 8.5.9 1 b. and c. is feasible until an acceptable level of statistical certainty for surveillance or target probability of freedom is established to substantiate the absence of FMDV infection or circulation. It is surveillance intensity rather than waiting periods that establishes the risk of residual FMDV. EU Directive 2003/85/EC implicitly recognizes this, permitting derogation of the OIE waiting periods.

A multi-species indirect ELISA for detection of non-structural protein 3ABC specific antibodies to foot-and-mouth disease virus

“…This observation underscores the utility of NSP diagnostics as the basis of the 'vaccinate to live policy' [11], a proposal for avoiding the pre-emptive slaughter of animals at risk in the face of an outbreak in disease-free regions, as has been followed in Korea [12]. However, demonstrating the absence of FMDV infection as required in the OIE terrestrial code is impossible in a vaccinated population, as tests are not sensitive enough to detect infection in some animals [3,12], and there is wide variability in the ability of these tests to identify infected animals [13,14]. The ability of a given test to detect an NSP antibody response in the vaccinated and subsequently infected animals depends on the potency and protective efficacy of the vaccine in question.…”

A Review of OIE Country Status Recovery Using Vaccinate-to-Live Versus Vaccinate-to-Die Foot-and-Mouth Disease Response Policies II: Waiting Periods After Emergency Vaccination in FMD Free Countries

“…Yet until the EU ceased vaccinating in 1992, the Code approved equivalent movement of animals and animal products irrespective of countries that were free with or without vaccination with no outbreaks. Modern epidemiological, diagnostic and vaccine technologies allow for an updated risk management approach to FMD. Surveillance objectives for a threshold of evidence to statistically substantiate absence of FMDV infection for a FMD free country where vaccination is not practised, and FMDV circulation for a FMD free country where vaccination is practised should replace time‐specified waiting periods (Barnett et al., ). The ad hoc FMD Working Group has long recognized the need for a target substantiation of statistical certainty (OIE, ).…”

“…The factors impacting the number of animals in a vaccinated population that develop the carrier status in the field have been discussed in the first article of this two‐part review (Barnett et al., ). In summary, these are as follows: (i) The number of animals already infected at the time of vaccination; (ii) The proximity of vaccination to time of exposure to FMDV; and (iii) The magnitude of the viral challenge (Schley et al., ; Garland and de Clercq, ).…”

Development of vaccines against Crimean-Congo haemorrhagic fever virus

“…Classically, vaccines which have DIVA antigens are useful when special restrictions are in place for infected animals which may be relaxed when those animals can be proven to be vaccinated and not infected. Whilst this is applicable for animal pathogens such as bovine tuberculosis [81], avian influenza [82] and foot-and-mouth virus [83], CCHFV is not addressed by the same regulations as it is specifically a human and not an animal pathogen. However, the benefits of distinguishing vaccinated animals from those infected with the wild type CCHFV would be useful to track vaccination and study vaccine efficacy in the field.…”