impact of climate on avian influenza spread in minnesota turkeys
TRANSCRIPT
The influence of climate on influenza A virus (IAV) introductions in Minnesota turkeys: Spring 2007 - 2015
Xi Guo1, Nitipong Homwong2, Jeanette Munoz-Aguayo3, Cristian Flores3,
Carol J. Cardona1
Introduction
• Climate affects the transmission cycle of infectious diseases• The landscape that gives rise to the transmission of influenza A virus
(IAV) between wild and domesticated avian species is greatly impacted by the climate.
• The behavior of the wild waterfowl, the natural host of IAV, is also affected by the climate condition.
• In the spring of 2015, highly pathogenic avian influenza (HPAI) H5N2 was introduced to turkeys in Minnesota (MN). Prior to 2015, there were seven low pathogenic avian influenza (LPAI) introductions occurred in the same area and the same season in the turkey flocks.
List of Spring introductions of IAV
*The dates were based on an estimation of the date of infection from positive serological and virological findings
Case ID Year Date Subtype County
1 2007 03/22* H7N9 Brown
2 2009 05/06* H7N9 Redwood
3 2011 05/13* H7N9 Wright
4 2012 04/26* H8N4 Kandiyohi
5 2013 05/08* H3N2/H9N2 Kandiyohi
6 2014 05/09 H4N2 Kandiyohi
7 2015 02/27 H5N2 Pope
8 2015 03/22 H5N2 Lac Qui Parle
9 2015 04/08 H5N2 Kandiyohi
10 2016 03/14 H1N1 Kandiyohi
Objective
To characterize the climate conditions associated with the Spring introductions of IAV in MN turkeys.
Data source
Daily climatic variables including maximum temperature, minimum temperature and snow depths during 1960-2015 were retrieved from the National Climatic Data Center (NCDC) archives. The weather stations selected for data analysis were within 20 miles of the case sites, which were clustered into five regions.
Weather data analysis • Spearman correlation was performed between the week of the
introduction cases and the weather indicators including temperature 7 to 9°C, heading degree days (HDD) 18 to 20 days, and the yearly average temperature.
• Wilcoxon Ranked-sum tests were performed to compare the sum of introduction years and non-introduction years.
• Permutation tests were performed to validate the significance between the mean difference of temperature and snow depth between introduction years and non-introduction years.
Result - Temporal pattern of temperature
Result - Temporal pattern of temperature
• The relationship between Case 7 and the lowest point resembles the temporal pattern illustrated by Liu et al (Plos one, 2007), recapitulating the same climate condition for HPAI introductions.
• The temperature pattern of other LPAI cases is different from Case 7, suggesting different mechanism of HPAI and LPAI introductions.
Result - Weather indicator correlation
Weather indicator Spearman correlation p value
Spearman correlation coefficient
The week when weekly average temperature was the closest to 7 °C 0.2005 0.5062
The week when weekly average temperature was the closest to 8 °C 0.0083* 0.8447
The week when weekly average temperature was the closest to 9 °C 0.0532 0.7000
The week when weekly average temperature was the closest to the
yearly average 0.1344 0.5768
The week in which weekly average HDD was the closest to 18 0.0083* 0.8447
The week in which weekly average HDD was the closest to 19 0.0137* 0.8149
The week in which weekly average HDD was the closest to 20 0.2005 0.5062
Result - Weather indicator correlation
• The relationship between Case 7 and the lowest point resembles the temporal pattern illustrated by Liu et al (Plos one, 2007), recapitulating the same climate condition for HPAI introductions.
• The temperature pattern of other LPAI cases is different from Case 7, suggesting different mechanism of HPAI and LPAI introductions.
Result - Snow depth analysis
Result - Snow depth analysis
Case Rank (From low to high) Wilcoxon P value 1 26 out of 56 0.90
2 21 out of 56 0.66
3 40 out of 56 0.50
4 27 out of 54 1.00
5 54 out of 56 0.12
6 49 out of 56 0.21
7 11 out of 56 0.29
8 4 out of 55 0.14
Case 7 and 8 have lower snow depths than non-introduction years. Other cases have average level of snow depths among all the year.
Conclusion and future direction • The similar temporal patterns of Case 7 and the HPAI cases
from other locations suggest a universal climatic condition that drives the occurrence of HPAI outbreak.
• Several weather indicators correlate with the timing of the introductions. These indicators could help to predict the timing of the next IAV introduction in turkey flocks.