Classical swine fever: challenges for the emerging swine sector in Bhutan.

Given the importance of pork in the Bhutanese diet and to enhance food security, the Government of Bhutan has generated policies to promote development of the swine sector in the country. One of the main threats to swine farming is classical swine fever (CSF), a transboundary disease of wild and domestic swine thought to be enzootic in the country. In 2018, three outbreaks of CSF were notified in Bhutan. The type of animals, their vaccine status, and the aftermath of these outbreaks highlight the interplay of epidemiological and context-specific factors that may result in CSF undermining the emerging Bhutanese swine sector. This communication reports on the CSF outbreaks of 2018, discusses some of the challenges posed by these events, and proposes some research priorities.

Turnover of Village Chickens Undermines Vaccine Coverage to Control HPAI H5N1.

Highly pathogenic avian influenza (HPAI) subtype H5N1 remains an enzootic disease of village chickens in Indonesia, posing ongoing risk at the animal-human interface. Previous modelling showed that the fast natural turnover of chicken populations might undermine herd immunity after vaccination, although actual details of how this effect applies to Indonesia's village chicken population have not been determined. We explored the turnover effect in Indonesia's scavenging and mixed populations of village chickens using an extended Leslie matrix model parameterized with data collected from village chicken flocks in Java region, Indonesia. Population dynamics were simulated for 208 weeks; the turnover effect was simulated for 16 weeks after vaccination in two 'best case' scenarios, where the whole population (scenario 1), or birds aged over 14 days (scenario 2), were vaccinated. We found that the scavenging and mixed populations have different productive traits. When steady-state dynamics are reached, both populations are dominated by females (54.5%), and 'growers' and 'chicks' represent the most abundant age stages with 39% and 38% in the scavenging, and 60% and 25% in the mixed population, respectively. Simulations showed that the population turnover might reduce the herd immunity below the critical threshold that prevents the re-emergence of HPAI H5N1 4-8 weeks (scavenging) and 6-9 weeks (mixed population) after vaccination in scenario 1, and 2-6 weeks (scavenging) and 4-7 weeks (mixed population) after vaccination in scenario 2. In conclusion, we found that Indonesia's village chicken population does not have a unique underlying population dynamic and therefore, different turnover effects on herd immunity may be expected after vaccination; nonetheless, our simulations carried out in best case scenarios highlight the limitations of current vaccine technologies to control HPAI H5N1. This suggests that the improvements and complementary strategies are necessary and must be explored.