Evaluation of strategies using simulation model to control a potential outbreak of highly pathogenic avian influenza among poultry farms in Central Luzon, Philippines

Abstract

The Philippines confirmed its first epidemic of Highly Pathogenic Avian Influenza (HPAI) on August 11, 2017. It ended in November of 2017. Despite the successful management of the epidemic, reemergence is a continuous threat. The aim of this study was to conduct a mathematical model to assess the spatial transmission of HPAI among poultry farms in Central Luzon. Different control strategies and the current government protocol of 1 km radius preemptive culling (PEC) from infected farms were evaluated. The alternative strategies include 0.5km PEC, 1.5km PEC, 2 km PEC, 2.5 km PEC, and 3 km PEC, no pre-emptive culling (NPEC). The NPEC scenario was further modeled with a time of government notification set at 24hours, 48 hours, and 72 hours after the detection. Disease spread scenarios under each strategy were generated using an SEIR (susceptible-exposed-infectious-removed) stochastic model. A spatial transmission kernel was calculated and used to represent all potential routes of infection between farms. We assumed that the latent period occurs between 1-2 days, disease detection at 5-7 days post-infection, notification of authorities at 5-7 days post-detection and start of culling at 1-3 days post notification. The epidemic scenarios were compared based on the number of infected farms, the total number of culled farms, and the duration of the epidemic. Our results revealed that the current protocol is the most appropriate option compared with the other alternative interventions considered among farms with reproductive ratio (R i) > 1. Shortening the culling radius to 0.5 km increased the duration of the epidemic. Further increase in the PEC zone decreased the duration of the epidemic but may not justify the increased number of farms to be culled. Nonetheless, the no-pre-emptive culling (NPEC) strategy can be an effective alternative to

Elucidating the Local Transmission Dynamics of Highly Pathogenic Avian Influenza H5N6 in the Republic of Korea by Integrating Phylogenetic Information

“…The number of cases only decrease by one, whereas an additional 31 farms were depopulated. Another simulation study based on the transmission kernel function suggested a non-depopulation strategy for low-risk regions [22]. It appears that a standard culling radius is not optimal for poultry premises across the whole country because of variation in the transmission rate and vulnerability to infection.…”

“…We hypothesized that local spatial transmission would occur between poultry farms within a spatiotemporal cluster with a high rate of HPAI infections. To test this hypothesis, we derived the force of infection based on a transmission kernel function, in accordance with previous research [8,10,22], as follows:…”

“…Thus, we assumed that the infectious period lasts 7 days, which correspond to the duration between the start date of the infectious status and the reporting or sampling date [20]. An HPAI-infected farm is supposed to be infectious at 1 day after the infection [8,10,22]. An IP was also classified as having a "removed" status if culling started.…”

A systematic review of mechanistic models used to study avian influenza virus transmission and control

“…Most IBMs (16/19; Table 2 ) investigated the transmission process between farms [ 42 , 46 , 47 , 50 , 54 – 56 , 59 , 61 , 63 , 67 , 70 , 71 , 75 ] or between administrative areas [ 36 , 40 , 50 , 55 ], with two articles evaluating both in the same study [ 50 , 55 ]. The remaining three articles considered transmission at two different scales (e.g., within-farm and between-farms) [ 38 , 60 , 74 ].…”

Influenza virus strategies to regulate S1P-metabolizing enzymes and evade host innate immunity for robust viral replication

“…IAV exhibits remarkable genetic and genomic diversity that allows IAV to be both a pandemic and zoonotic threat (Brooke, 2017). Recurrent outbreaks of avian influenza add to mounting concerns of the next potential influenza pandemic (Cowling et al, 2013;Fraser et al, 2009;Salvador et al, 2020;Wang and Palese, 2009). Vaccines targeting influenza viruses must be reformulated annually (Krammer et al, 2018).…”