Vaccination of poultry against highly pathogenic avian influenza - Part 2. Surveillance and mitigation measures

Selecting appropriate diagnostic methods that take account of the type of vaccine used is important when implementing a vaccination programme against highly pathogenic avian influenza (HPAI). If vaccination is effective, a decreased viral load is expected in the samples used for diagnosis, making molecular methods with high sensitivity the best choice. Although serological methods can be reasonably sensitive, they may produce results that are difficult to interpret. In addition to routine molecular monitoring, it is recommended to conduct viral isolation, genetic sequencing and phenotypic characterisation of any HPAI virus detected in vaccinated flocks to detect escape mutants early. Following emergency vaccination, various surveillance options based on virological testing of dead birds ('bucket sampling') at defined intervals were assessed to be effective for early detection of HPAIV and prove disease freedom in vaccinated populations. For ducks, virological or serological testing of live birds was assessed as an effective strategy. This surveillance could be also applied in the peri-vaccination zone on vaccinated establishments, while maintaining passive surveillance in unvaccinated chicken layers and turkeys, and weekly bucket sampling in unvaccinated ducks. To demonstrate disease freedom with > 99% confidence and to detect HPAI virus sufficiently early following preventive vaccination, monthly virological testing of all dead birds up to 15 per flock, coupled with passive surveillance in both vaccinated and unvaccinated flocks, is recommended. Reducing the sampling intervals increases the sensitivity of early detection up to 100%. To enable the safe movement of vaccinated poultry during emergency vaccination, laboratory examinations in the 72 h prior to the movement can be considered as a risk mitigation measure, in addition to clinical inspection; sampling results from existing surveillance activities carried out in these 72 h could be used. In this Opinion, several schemes are recommended to enable the safe movement of vaccinated poultry following preventive vaccination.

Struggling to improve farm biosecurity: Do free advice and subsidies hit the target?

Biosafety measures (BSMs) often aim at reducing the likelihood of cross-species interactions at the wildlife-livestock interface. Examples include means to segregate wild ungulates from cattle at waterholes or at feeders. Subsidies or incentives for BSM implementation are expected to contribute to improved BSM acceptance. However, several recent experiences led us to write a cautionary commentary on the variable success of incentives in farm biosafety promotion. We list examples where, after offering farm-specific biosecurity action plans for free or subsidizing 100% of the cost of a given BSM, 25-40% of the farmers remained unwilling to invest efforts in farm biosafety and BSM maintenance. We suggest seeking a better understanding of farmers' motivations through social science research, to train farm veterinarians on biosecurity and on how to tailor biosafety communication, and to set up formal regional risk mitigation programs including financial, logistical, and educational assistance, as well as monitoring plans, through public-private collaboration.