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

For countries with OIE status, FMD free country where vaccination is not practised, vaccinate‐to‐live policies have a significant economic disincentive as the trade restriction waiting period is double that of vaccinate‐to‐die policies. The disposal of healthy vaccinated animals strictly for the purpose of regaining markets with debatable scientific justification is a global concern. The feasibility of aligning the waiting periods to facilitate vaccinate‐to‐live is explored. The first article of this two‐part review (Barnett et al., 2015) explored the qualities of higher potency Foot‐and‐Mouth Disease (FMD) vaccines, performance of differentiating infected from vaccinated animals (DIVA) diagnostic assays particularly in vaccinates and carriers, as well as aspects of current limitations of post‐outbreak surveillance. Here, the history behind the OIE waiting periods for FMD free status is reviewed as well as whether the risk of vaccinated animals and their subsequent products differ appreciably at 3 versus 6 months. It is concluded that alignment is feasible for vaccinate‐to‐live using higher potency FMD vaccines within the current OIE waiting period framework of 3 and 6 months blocks of time. These waiting periods reflect precedence, historical practicalities and considered expert opinion rather than a specific scientific rationale. The future lies in updated epidemiological and diagnostic technology to establish an acceptable level of statistical certainty for surveillance or target probability of freedom of FMDV (infection or circulation) not time restricted waiting periods. The OIE Terrestrial Code limits trade from a FMD free country where vaccination is not practiced to animal products and live non‐vaccinated animals. The risk of FMDV in products derived from higher potency vaccinated animals is appreciably less than for countries with infected FMD status or even from a FMD free country where vaccination is practised for which the Code has Articles with guidelines for safe trade with time restrictions of 3 months or less. All these presume that key requirements in the implementation of emergency vaccination including appropriate vaccine match, vaccine application, susceptible population coverage, etc. are addressed.     

Assessment of the Safety of Aquatic Animal Commodities for International Trade: The OIE Aquatic Animal Health Code

Trading of aquatic animals and aquatic animal products has become increasingly globalized during the last couple of decades. This commodity trade has increased the risk for the spread of aquatic animal pathogens. The World Organisation for Animal Health (OIE) is recognized as the international standard‐setting organization for measures relating to international trade in animals and animal products. In this role, OIE has developed the Aquatic Animal Health Code, which provides health measures to be used by competent authorities of importing and exporting countries to avoid the transfer of agents pathogenic for animals or humans, whilst avoiding unjustified sanitary barriers. An OIE ad hoc group developed criteria for assessing the safety of aquatic animals or aquatic animal products for any purpose from a country, zone or compartment not declared free from a given disease ‘X’. The criteria were based on the absence of the pathogenic agent in the traded commodity or inactivation of the pathogenic agent by the commercial processing used to produce the commodity. The group also developed criteria to assess the safety of aquatic animals or aquatic animal products for retail trade for human consumption from potentially infected areas. Such commodities were assessed considering the form and presentation of the product, the expected volume of waste tissues generated by the consumer and the likely presence of viable pathogenic agent in the waste. The ad hoc group applied the criteria to commodities listed in the individual disease chapters of the Aquatic Animal Health Code (2008 edition). Revised lists of commodities for which no additional measures should be required by the importing countries regardless of the status for disease X of the exporting country were developed and adopted by the OIE World Assembly of Delegates in May 2011. The rationale of the criteria and their application will be explained and demonstrated using examples.     

Indicators of emerging hazards and risks to food safety

There is a widely felt need to develop methods for the early identification of emerging hazards to food safety with the aim of preventing these hazards from becoming real risks and causing incidents. This paper reviews various activities and previous reports that describe methods to select indicators that can be used for the purpose of early identification of hazards. These indicators have been divided over three different environments, including (i) the environment surrounding food production, (ii) the food production chain from farm to fork, and (iii) consumers. Changes in these indicators are signals that may require follow-up action. Besides indicators that are linked to specific kinds of hazards, the indicators used for vulnerability assessment can help identifying weak spots in the food production system that are sensitive to a broader range of hazards. Based on the various indicators for emerging hazards that have thus been identified in literature, a set of generic indicators is provided that can be useful for the early identification of hazards.     

Multiple dose vaccination with heterologous H5N2 vaccine: immune response and protection against variant clade 2.2.1 highly pathogenic avian influenza H5N1 in broiler breeder chickens

Circulation of an antigenically variant lineage of highly pathogenic avian influenza (HPAI) H5N1 virus in chicken breeder flocks in Egypt is a continuing problem. The protective efficacy of multiple repeated vaccinations using the currently available H5N2 vaccines is unclear. Here, broiler breeder chickens were vaccinated at weeks 6, 12 and 18 with an inactivated H5N2 commercial vaccine. HI-titer against an Egyptian H5N1 field isolate of classic clade 2.2.1 (EGYcls/H5N1) were significantly lower after the first immunization but increased after booster vaccinations. In contrast, no HI titers were induced against an antigenically distinct field virus of the variant lineage of clade 2.2.1 (EGYvar/H5N1). Upon challenge at week 50 mild, if any, clinical signs were observed in the group infected with EGYcls/H5N1 although one of eight (12.5%) birds died. Mortality reached 6/8 (75%) in the EGYvar/H5N1 challenge group. Virus excretion in all vaccinated groups was reduced in amplitude, but in vaccinated surviving birds, time of virus excretion was extended to up to ten days. Strikingly, challenged vaccinated birds kept laying eggs almost throughout the observation period. Virus was detected on the outer egg-shell of 17 of 40 eggs. The majority of the infected eggs were derived from the EGYcls/H5N1 challenged animals; here the virus was detected also in the yolk and albumin. Repeated vaccination using a commercial H5N2-based vaccine broadened the antigen profile of induced antibodies but did not provide adequate protection against heterologous virus variant. In addition, the observation of AIV contaminated eggs from infected flocks highlights the risk of silent virus spread by vaccinated animals and point to eggs as a possible vector.     

Protective efficacy of a single immunization with capripoxvirus-vectored recombinant peste des petits ruminants vaccines in presence of pre-existing immunity

Sheeppox, goatpox and peste des petits ruminants (PPR) are highly contagious ruminant diseases widely distributed in Africa, the Middle East and Asia. Capripoxvirus (CPV)-vectored recombinant PPR vaccines (rCPV-PPR vaccines), which have been developed and shown to protect against both Capripox (CP) and PPR, would be critical tools in the control of these important diseases. In most parts of the world, these disease distributions overlap each other leaving concerns about the potential impact that pre-existing immunity against either disease may have on the protective efficacy of these bivalent rCPV-PPR vaccines. Currently, this question has not been indisputably addressed. Therefore, we undertook this study, under experimental conditions designed for the context of mass vaccination campaigns of small ruminants, using the two CPV recombinants (Kenya sheep-1 (KS-1) strain-based constructs) developed previously in our laboratory. Pre-existing immunity was first induced by immunization either with an attenuated CPV vaccine strain (KS-1) or the attenuated PPRV vaccine strain (Nigeria 75/1) and animals were thereafter inoculated once subcutaneously with a mixture of CPV recombinants expressing either the hemagglutinin (H) or the fusion (F) protein gene of PPRV (10³ TCID₅₀/animal of each). Finally, these animals were challenged with a virulent CPV strain followed by a virulent PPRV strain 3 weeks later. Our study demonstrated full protection against CP for vaccinated animals with prior exposure to PPRV and a partial protection against PPR for vaccinated animals with prior exposure to CPV. The latter animals exhibited a mild clinical form of PPR and did not show any post-challenge anamnestic neutralizing antibody response against PPRV. The implications of these results are discussed herein and suggestions made for future research regarding the development of CPV-vectored vaccines.     

Global Avian Influenza Surveillance in Wild Birds: A Strategy to Capture Viral Diversity

Wild birds play a major role in the evolution, maintenance, and spread of avian influenza viruses. However, surveillance for these viruses in wild birds is sporadic, geographically biased, and often limited to the last outbreak virus. To identify opportunities to optimize wild bird surveillance for understanding viral diversity, we reviewed responses to a World Organisation for Animal Health–administered survey, government reports to this organization, articles on Web of Knowledge, and the Influenza Research Database. At least 119 countries conducted avian influenza virus surveillance in wild birds during 2008–2013, but coordination and standardization was lacking among surveillance efforts, and most focused on limited subsets of influenza viruses. Given high financial and public health burdens of recent avian influenza outbreaks, we call for sustained, cost-effective investments in locations with high avian influenza diversity in wild birds and efforts to promote standardized sampling, testing, and reporting methods, including full-genome sequencing and sharing of isolates with the scientific community.     

Early identification systems for emerging foodborne hazards

This paper provides a non-exhausting overview of early warning systems for emerging foodborne hazards that are operating in the various places in the world. Special attention is given to endpoint-focussed early warning systems (i.e. ECDC, ISIS and GPHIN) and hazard-focussed early warning systems (i.e. FVO, RASFF and OIE) and their merit to successfully identify a food safety problem in an early stage is discussed.     

Immune responses in mice vaccinated with a suicidal DNA vaccine expressing the hemagglutinin glycoprotein from the peste des petits ruminants virus

Peste des petits ruminants (PPR), an acute and highly contagious disease, affects sheep, goats, and some small ruminants. The hemagglutinin (H) glycoprotein of the PPR virus (PPRV) is considered important for inducing protective immune responses. In this study, a suicidal DNA vaccine based on the Semliki Forest virus (SFV) replicon was constructed and tested for its ability to induce immunogenicity in a mouse model. For this, the H gene of PPRV was cloned and inserted into pSCA1, an SFV replicon vector. The resultant plasmid named pSCA1-H was then transfected into BHK-21 cells following which the antigenicity of the expressed protein was confirmed by Western blotting and immunofluorescence. The pSCA1-H plasmid was then injected intramuscularly into BALB/c mice thrice at 2-week intervals. To evaluate the immunogenicity of pSCA1-H, specific antibodies and neutralizing antibodies against PPRV-H were measured using an indirect enzyme-linked immunosorbent assay and a microneutralization test, respectively. Cell-mediated immune responses were also examined using a lymphocyte proliferation assay. The results showed that pSCA1-H could express the H protein in BHK-21 cells. Specific antibodies, neutralizing antibodies, and lymphocyte proliferation responses were all induced in mice. Thus, this suicidal DNA vaccine could be a promising new approach for vaccine development against PPR.     

世界卫生组织和世界动物卫生组织禽流感检测流程的比较

目的了解世界卫生组织（World Health Organization,WHO）和世界动物卫生组织（Office International DesEpizooties,OIE）的禽流感检测流程的差异,旨在相互借鉴,以建立更加完善的检测流程。方法重点比较WHO和OIE推荐的禽流感RT-PCR检测流程中对于初步阳性、可疑和阴性的样本处理程序,以及发出报告的确证程序,来探讨和完善科学的检测模式。结果 WHO的禽流感检测流程中为防止假阴性结果,还需要进行人流感病毒的进一步检测,为防止假阳性,需要进行测序确证;OIE的禽流感检测流程中为防止假阴性结果,还需要再次采样进行确证,为防止假阳性,还需要与病毒分离培养结果综合定论。结论 WHO和OIE的检测流程都能有效的防止假阴性和假阳性的结果产生,但仍需要补充和完善禽流感其他亚型检测流程。