Network analysis of poultry movement to assess the transmission potential of novel subtypes of avian influenza in

Farzana Zaman1 , Muhammad Asaduzzaman2,3 1Directorate General of Health Sciences (DGHS), Bangladesh 2International Centre for Diarrheal Disease Research, Bangladesh(icddr,b) 3Institute of Veterinary Animal and Biomedical Sciences, Massey University, New Zealand

Background Bangladesh is at risk of introduction of any emerged subtypes of avian influenza which are circulating in Asia.The movement of live birds is a well-known risk factor for the geographic dissemination of the virus among poultry flocks. Therefore, movement and contact patterns to and from broiler, layer and backyard flocks were investigated in a district of Bangladesh with predominantly commercial flocks, and one with predominantly backyard flocks. Density of poultry in both districts is very high, and they would be severely affected if a novel subtype entered those districts.

Objectives qCharacterise the movement and contact patterns of poultry in Bangladesh that could be associated with transmission of newly-introduced subtypes of avian influenza virus in two q Summarise the patterns arising from the network analysis in a way that can inform the parameterisation of spatially explicit stochastic models of transmission of newly-introduced subtypes of avian influenza virus in the two types of areas.

Method 112 backyard HH and 18 adjoining commercial poultry farms from 2 villages of Kalkini , as well as 270 commercial farms and 267 adjoining backyard HH from 19 villages of Sreepur Upazila , were randomly selected. Then,1-mode and 2-mode social network analysis was carried out to show the farm to farm and farm to agent movements. From each primarily selected farm, details of the last 2 movements of live poultry along with source/destination details was collected with pre-tested questionnaire. Later, data was stored in Epi- Info, analysed with STATA 14 and UCINET. Gazipur Madaripur

315

316 274

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Backyard Commercial

Results Movement patterns differed in a number of aspects between the two districts, and this information has been used to establish the movement parameter settings in a simulation model of avian influenza incursion built in the spatial disease simulation model HandiSpreadTable. 1. Farm to Farm Movement of Live Birds (1-Mode Network Analysis) Network metrics Gazipur Madaripur Network metrics Gazipu Madari A. 1-mode transformed Farm to Farm network r pur Number of nodes (farms) 366 75 Number of links 5102 106 A. Network size Density 0.038 0.019 Number of nodes (farms) 149 291 a1) Degree - number of farm(s) connected 13 (0 – 52) 0 (0 – 8) Number of directed links 100 181 through sharing of one or more agents b1) Degree - number of times the agents shared 39 (0 – 380) 0 (0 – 8) Total number of shipments 119 229 with one or more other farms Network size (all possible 22,052 84,390 B. 1-mode transformed Agent to Agent network links) No. of nodes (agents) 133 68 B. Node level centrality measures - values Number of links 140 28 reported are Median ( Minimum & Maximum) 0.008 0.006 Density Out-degree (using binary 1 (0 – 2) 1 (0 – 2) a1) Degree - number of agent(s) is connected 1 (0 – 6) 0 (0 – 2) to through sharing of one or more farms network) In-degree 1 (0 – 3) 1 (0 – 3) b1) Degree – number of times the agents 1 (0 – 23) 0 (0 – 8) Between ness score 0 (0 – 4) 0 (0-8) shared with one or more other farms c) Number of farms each agent supply or take 1 (1 – 29) 1 (1 – 9) Density 0.005 0.002 birds from Fragmentation 0.994 0.997 Table 1:2-Mode Network Analysis of Farms and Agent Discussion The findings provide guidance on control strategies which would be appropriate in the case of an incursion of a novel subtype of Avian Influenza into each of the types of populations represented by the two study districts. Acknowledgments: