Unusual Crow (Corpus splendens) and Indian flying fox (Pteropus medius), fruit bats death in Dhaka, Bangladesh: a One Health approach to outbreak investigation

Le résumé fourni par la source

Highly pathogenic avian influenza (H5N1) has caused ≥500 reported outbreaks in poultry and wild birds in Bangladesh since 2007. In early 2011 and 2016 H5N1 spread among wild crows in several Bangladesh districts, including, Dhaka. Responding to reports of a crow mortality event in Mohakhali, Dhaka, a multidisciplinary One Health team investigated crow mortalities between January 15th and February 20th, 2017. The aim was to identify the etiologic agent, source of the infection, and characterize the extent of the outbreak. The One Health team collected swabs from moribund and dead crows (N=171) and environmental samples from 19 neighboring LBMs (N=149) where crows were observed feeding from within a 7km radius surrounding the crow roosts of the reported outbreak and LBMs in Dhaka. Swabs and tissue samples were collected from two dead Indian flying foxes (Pteropus medius). All samples were tested by specific q-PCR for influenza A (M gene) H5/H7/H9/N1. The wildlife investigation identified 3 crow roosts had evidence of crow morbidity and mortality approximately 7km from the reported outbreak site and an additional 7 apparently healthy crow roosts where there was no evidence of crow mortality or unusual illness. The team observed crows feeding on poultry offal in neighboring LBMs and sharing the roosts with other wild birds and fruit bats. Eighty-seven percent of the sampled crows (n=149; 95%CI:81-92) were positive for A/H5 and 3% for A/untypable (n=5; 95%CI:1-7). Among LBMs samples, 41% were positive to A/H5 (n=61; 95%CI:33-49), 6% for A/H9 (n=9; 95%CI: 3-11), 5% had a co-infection with both A/H5 and H9 (n=7; 95%CI:2-9), and 19% for A/untypable (n=28; 95%CI:13-26). None of the crow samples were positive for H7 or H9. A subset of H5 positive crows and LBM samples were tested for N1; results revealed that 49% H5 crows (n=45) and 21% H5 LBMs (n=19) samples were positive for N1 and the remaining were negative which indicates that other N types might be co-circulating in both crows and LBMs. Both fruit bats swab and tissue samples were positive for influenza A/H5N1.Phylogenetic analysis based on partial sequence of the HA gene suggests that strain is similar to the Bangladeshi 2.3.2.1a clade that circulated in 2011.Data findings suggest that highly pathogenic AIV is present in the LBMs, and may have been transmitted to crows while they were feeding on poultry waste in the LBM; bats may have acquired infection while roosting with the infected crows. These findings improve our understanding of avian influenza viral diversity in a key wild species. The unusual finding of bat mortality potentially linked to HPAI infection. Improved LBMs biosecurity measures are needed to reduce the risk of influenza virus spillover to wild birds or people in Bangladesh

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