Abstract
Avian influenza outbreaks have been occurring on smallholder poultry farms in Asia for two decades. Farmer responses to these outbreaks can slow down or accelerate virus transmission. We used a longitudinal survey of 53 small-scale chicken farms in southern Vietnam to investigate the impact of outbreaks with disease-induced mortality on harvest rate, vaccination, and disinfection behaviors. We found that in small broiler flocks (≤16 birds/flock) the estimated probability of harvest was 56% higher when an outbreak occurred, and 214% higher if an outbreak with sudden deaths occurred in the same month. Vaccination and disinfection were strongly and positively correlated with the number of birds. Small-scale farmers - the overwhelming majority of poultry producers in low-income countries - tend to rely on rapid sale of birds to mitigate losses from diseases. As depopulated birds are sent to markets or trading networks, this reactive behavior has the potential to enhance onward transmission.
Highlights
Livestock production systems have been a major driver of novel pathogen emergence events over the past two decades (Gao et al, 2013; Guan et al, 2002; Rohr et al, 2019)
We present a longitudinal study of small-scale poultry farms where we aimed to characterize the effect of disease outbreaks on livestock harvest rate and on two prevention practices, vaccination and farm disinfection
The main poultry species kept on these farms was chicken, with ducks and Muscovy ducks as the other two primary relevant species held
Summary
Livestock production systems have been a major driver of novel pathogen emergence events over the past two decades (Gao et al, 2013; Guan et al, 2002; Rohr et al, 2019). The same observation applies to disease emergence and spread in livestock populations as farmers adapt their farm management to maximize animal production and welfare while limiting cost in a constantly changing ecological and economic environment (Chilonda and Van Huylenbroeck, 2001). Poultry farming generates substantial risk for emergence of novel infectious diseases. It is the most important source of animal protein for the human population and the industry is changing rapidly (FAOSTAT, 2019). Pathogenic Avian Influenza (HPAI) causes severe symptoms in the most vulnerable bird species (including chicken, turkey, and quail), with mortality rates as high as Delabouglise et al eLife 2020;9:e59212.
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