DISEASE ▶▶▶
Backyard producers transmit bird flu
Researchers believe that small-scale poultry farmers could be increasing the risk of avian influenza transmission during outbreaks. They found that backyard producers in Vietnam tended to respond to viral outbreaks by rapidly selling their birds to avoid financial loss.
BY TONY MCDOUGAL L
ead author Alexis Delabouglise, animal health econo- mist at CIRAD-Agricultural Research for Development, France, explained that millions of households in southeast Asia run small-scale poultry operations,
mostly with fewer than 100 birds. He said the farmers made decisions on a daily basis – often in response to economic in- centives – about when and where to sell their flocks. And their decisions could influence the spread of disease. “If the price of poultry goes up, farmers might expand their farming activities which could create more outbreak risk. If there is an outbreak on a neighbouring farm, they might choose to sell their poultry early to avoid their own birds from being infect- ed and to avoid lower prices. And if there is an outbreak on their own farm, the evidence from our study shows that they would be likely to sell their birds early to avoid both monetary loss and epidemiological risk.”
Study Working with Maciej Boni at Penn State University, USA, and researchers at the Oxford University Clinical Research Unit in Ho Chi Minh City, Vietnam, the team conducted a longitudi- nal study of small-scale poultry farms in the Mekong river delta region of southern Vietnam with the aim of determining the effects of disease outbreaks on poultry harvest rates, as well as on two prevention practices: vaccination and farm dis- infection. The team followed 53 farmers managing more than 1,000 poultry flocks for two years (2015-2017). Delabouglise said that the team found that farmers did send their chickens to market early when there were outbreaks oc- curring on their farms. “Specifically, small-scale farmers in- creased their harvest of broiler chickens by 56% during out- breaks with no sudden deaths and by 241% during outbreaks
with sudden deaths. This has the potential to exacerbate and spread the virus even further,” he added.
Vaccination The team noted that sudden deaths – the deaths of chickens less than one day after the onset of clinical symptoms – are considered to be indicative of HPAI infection. Interestingly, they found that the probability of disinfection was not affect- ed by the occurrence of the outbreaks. Finally, the team dis- covered that the likelihood of vaccination against avian influ- enza strongly increased with flock size. The probability of vaccination was almost zero for flocks of 16 birds or fewer and nearly 100% for flocks of more than 200 birds. Two rea- sons for smaller producers not vaccinating could be their de- sire to avoid the transactional costs associated with declaring flocks to government vets, or simply due to the small number of birds involved, Delabouglise commented. “Crucially, it is these smaller flocks that are more likely to be sold into trading networks during outbreaks. The rapid sale of sick birds can contaminate other birds at traders’ storage places and those at live bird markets. It also exposes consum- ers and traders, slaughterhouses and retailers to an increased risk of infection.” Delabouglise noted that, on the flip side, the massive arrival of underage birds at a live bird market or a price decrease due to a temporary oversupply of poultry, might provide a signal to government agencies that an outbreak is occurring. “This is an interesting area for the surveillance of livestock diseases,” he added.
▶ POULTRY WORLD | No. 8, 2020
Small-scale farmers selling off birds during disease episodes may increase the likelihood of widespread disease transmission.
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PHOTO: ANP/EVELYNE JACQ
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