Evaluation of effectiveness and efficiency of wild bird surveillance for avian influenza

Abstract

This study aimed to assess which method of wild waterbird surveillance had the greatest probability of detecting highly pathogenic avian influenza (HPAI) H5N1 during a period of surveillance activity, the cost of each method was also considered. Lake Constance is a major wintering centre for migratory waterbirds and in 2006 it was the site of an HPAI H5N1 epidemic in wild birds. Avian influenza surveillance was conducted using harmonised approaches in the three countries around the lake, Austria, Germany and Switzerland, from 2006-2009. The surveillance consisted of testing birds sampled by the following methods: live birds caught in traps, birds killed by hunters, birds caught in fishing nets, dead birds found by the public and catching live Mute Swans (Cygnus olor); sentinel flocks of Mallards (Anas platyrhynchos) were also used. Scenario tree analysis was performed including sensitivity analysis, followed by assessment of cost-effectiveness. Results indicated that if HPAI H5N1 was present at 1% prevalence and assuming HPAI resulted in bird mortality, sampling dead birds found by the public and sentinel surveillance were the most sensitive approaches despite residual uncertainty over some parameters. The uncertainty over the mortality of infected birds was an influential factor. Sampling birds found dead was most cost-effective, but strongly dependent on mortality and awareness of the public. Trapping live birds was least cost-effective. Based on our results, we recommend that future HPAI H5N1 surveillance around Lake Constance should prioritise sentinel surveillance and, if high mortality is expected, the testing of birds found dead.

Figure 1.

Scenario tree for the surveillance of HPAI H5N1 in wild waterbirds on Lake Constance by sampling birds Found dead. Branch for D/G/M is not completed but would have the same structure as the branch for Swan.

Figure 2.

Scenario tree for the surveillance of HPAI H5N1 in wild waterbirds on Lake Constance by sampling live birds i.e. sampling birds by Bycatch, Trap, Swan Catch or Hunt. Branch for D/G/M is not completed but would have the same structure as the branch for Swan.

Figure 3.

Scenario tree for the surveillance of HPAI H5N1 in wild waterbirds on Lake Constance using sentinel flocks of Mallard ducks (Anas platyrhynchos). Branch for D/G/M is not completed but would have the same structure as the branch for Swan.