Amplification of avian influenza viruses along poultry marketing chains in Bangladesh: a controlled field experiment

Abstract

The prevalence of avian influenza viruses (AIVs) is commonly found to increase dramatically from farms to live bird markets (LBMs). Viral transmission dynamics along marketing chains is, however, poorly understood. To address this gap, we implemented a field experiment altering chicken supply to an LBM in Chattogram, Bangladesh. Chickens traded along altered (intervention) and conventional (control) marketing chains were tested for AIVs. Upon arrival at the LBM, the odds of detecting AIVs did not differ between control and intervention groups. However, 12 hours later, intervention group odds were lower, particularly for broiler chickens, indicating that viral shedding in LBM resulted partly from infections during transport and trade. Curtailing AIV prevalence in LBMs requires mitigating risk in marketing chain nodes preceding chickens’ delivery at LBMs.Article Summary LineThe high prevalence of avian influenza viruses in marketed chickens cannot be solely attributed to viral transmission within live bird markets but is also influenced by infections occurring prior to the chickens’ supply to these markets.

Modelling the transmission dynamics of H9N2 avian influenza viruses in a live bird market

“…S1A) drew together a steady supply of susceptible animals and unsold chickens offered for sale in previous days, thus creating opportunities for amplification of AIVs. Following our experimental design, explained in detail in 33 , we focused on exotic broiler (BR) and local, backyard-raised (BY) chicken types, which represent a large share of chickens traded daily in the LBM (Fig. S1B).…”

“…We fitted our model to H9N2 Polymerase chain reaction (PCR) positivity data 33 . We considered samples with a cycle threshold (Ct) < 40 as positive, in accordance with the laboratory protocols of the Australian Animal Health Laboratory (Geelong, Australia, http://www.csiro.au/places/AAHL).…”

“…In this work we removed 80 broiler chickens corresponding to 8 experimental replicates where there was a suspect of cross-contamination of samples. More details about the experimental design can be found in 33 .…”

“…Our work is instead grounded on a longitudinal dataset of H9N2 AIV acquisition in exotic and indigenous chickens in an LBM in Chattogram, Bangladesh 33 .…”