A recent study conducted in Japan confirmed that blowflies (Calliphora) are capable of disseminating H5 virus.  Blowflies feed and females lay eggs on dead animals and birds and can be infected with viruses and toxins in carcasses.  In the reported study, H5 virus was identified applying PCR. The recovery rate ranged from 2 to 15 percent from bowflies contaminated by feeding on carcasses dead wild cranes in outbreaks of H5N1avian influenza during 2022.  In a subsequent 2023 study, only one among 648 Calliphora flies yielded H5N1 virus.

These results are not unexpected given the demonstrated ability of blowflies and their larva to accumulate botulinum toxin and for houseflies (Musca) to transmit Campylobacter jejuni.

The need for fly control on poultry farms is self-evident.  In the case of flock depopulation, appropriate measures should be implemented to transport carcasses under cover to landfills for rapid burial or in the case of on-farm disposal by composting or burial.

Given that houseflies and blowflies will regurgitate their crop contents before feeding on a more acceptable food source, it is considered worthwhile to evaluate their possible role in transmission among poultry farms located in in close proximity.

Fujita, R., et al.  Blowflies are potential vectors for avian influenza virus at enzootic area in Japan (sic) Sci.reports.1410285(2024) Doi.org. /10.1038/s41598-024-61026-1.