USDA/APHIS PRELIMINARY REPORT: Epidemiologic Analysis of HPAI-Affected Turkey Flocks May 1, 2015

[Emily]

http://minnesotaturkey.com/wp-conte...iminary-Epidemiologic-Analysis-May-1-2015.pdf

Preliminary findings for questionnaires analyzed to date are given in Table 1. All three control farms had fewer than five barns compared to half of case farms. All three control farms (versus half of case farms) had three or more employees. Although all farms used footbaths, two of three control farms used a dry type. This was rarely used on case farms. All three control farms (and only 39% of case farms) used fly control. All three case farms disposed of dead birds via burial pit. None had an uncovered rendering bin. Wild birds were generally seen less often on and around control farms.

Based on this comparison, the two do not match and suggest a simple wind movement of infection based on predominant wind direction during this time window does not explain the spread of Avian Influenza in this cluster of positive cases in Minnesota.

Results suggest that geography is playing a role in disease risk. This analysis identified broad categories of risk factors using readily available data, which may be used to help guide future analysis. Consistent with the outbreak dynamics seen so far in Minnesota, being a turkey operation was the most significant risk factor identified. The risk of infection also increased within a distinct band of latitude in southern Minnesota, where the majority of cases have appeared. Since highway 12 runs east to west across this band, farms located close to this highway may be at increased risk. The effect of being near a highway decreases outside of the high risk latitude band.

Influenza virus genetic material could be detected in air samples collected inside and outside of poultry facilities with birds acutely infected with HPAI. Viral genetic material was found in samples collected with the three air samplers. The quantity of virus present in the air could only be semi-quantified and it was not considered very high (only Ct values above 30 were obtained). Samples positive or suspect were obtained inside and outside at the exhaust point, and only suspect results were obtained at 150 yards.
In conclusion, we showed that HPAI can be aerosolized from infected facilities. However, the implications of these findings in terms of understanding the transmission of HPAI between flocks needs further investigation. Future work needs to include sampling of more flocks, detection at various distances from infected premises and the assessment of environmental contamination outside infected facilities.

See full report for more, including study limitations.