SPATIO-TEMPORAL EPIDEMIOLOGY of HPAI in LAMPUNG PROVINCE, INDONESIA, 2010-2014

Gunawan SetiajiDisease Investigation Centre Lampung, Directorate of Animal Health, Ministry of Agriculture of Republic

IndonesiaCorresponding author; Email: gnwnsetiaji@gmail.com

Abstract

Since 2004, H5N1 has been endemic in Indonesia, the outbreak circullated extensively in several provinces, including Lampung. We describe spatial and temporal pattern, and identify risk factors of HPAI during 2010 and 2014 in Lampung Province and to provide recommendation to improve HPAI surveillance. The retrospective analyses purely spatial revealed two high risk clusters, first cluster in Metro district, the second cluster in Bandar Lampung and Lampung Selatan district, during 2010 and 2010 to 2011, respectively. Epidemic wave was occurring almost in every year during December to April. The epidemiology of HPAI is changing over the time, HPAI outbreak during 2012 due to clade 2.3.2.1 viruses, indicating the introducing of an exotic H5N1 which duck appears as the most affected species. Based on exact logistic result, human population density had statistic significant with p-value 0.01 and confidence interval 1.2 to 2.9. It’s recommended to study in duck movement pattern and conduct surveillance in wild bird and live bird markets.

Keyword: HPAI, Lampung, Spatial Temporal Cluster.

Introduction

On January 2004, Indonesia declared the first outbreak of HPAI (1), to date the outbreak still circulated extensively in several Provinces, including Lampung, although HPAI local outbreak response activities has been conducted by local government through the Local Disease Control Centre (LDCC) and Participatory Disease Surveillance and Response (PDSR), surveillance routine by Disease Investigation Centres (DIC) Lampung, Directorate General Livestock and Animal Health Service (DGLAHS), animal movement between Island is controlled under the National Animal Quarantine Service. HPAI vaccination, biosecurity and compartmentalization has been conducted in sector 1 in Lampung Province, however the information in sector 2 and 3 is still insufficient, HPAI vaccination is applied in many flock layer chickens, broiler and duck flock usually do not vaccine their poultry flock. Previous study carried out to investigate risk factors of HPAI spread and persistence in Indonesia, the associates and significant factors are human population density, elevation, rice cropping ( 2) , poultry density, road density (3). Spatial and temporal cluster studies have been studied in other countries Vietnam (4), Thailand (5), Nigeria (6). This study describes spatial and temporal pattern at the Subdistrict level during 2010 to 2014, we also investigate risk factor during 2013-2014 in Lampung Province. Result from this study could improve methods of HPAI surveillance.

Material and MethodData CollectionData from HPAI event cases from 2010 to 2014 were gathered from a DIC laboratory database (INFOLAB), this database contains an active sample from DIC Lampung surveillance activity and passive sample submission from PDSR or farmer. Poultry population and human population were obtained from BPS Statistic of Lampung Province (7), poultry movement from Java Island through Bakauheni seaport was collected from Quarantine Agriculture. Data analysisAffected speciesThe number affected species were calculated by the number of an outbreak at village level and distinguish by the type of a poultry positive PCR, with exact 95 % confidence interval.

TemporalWe plotted the number of source sample submission at the subdistrict level as surveillance coverage and subdistrict with one or more HPAI event by month during 2010 to 2014 as infected subdistricts.Spatial and temporalThe choropleth maps were used to describe HPAI situation in Lampung Province, the data were presented outbreak HPAI by subdistrict level during 2010 to 2014 and the proportion of subdistricts outbreak within each district. A spatial scan analysis was used to perform space-time cluster analysis using SatScan, we used a poisson method to observed yearly infection status of subdistrict, a subdistrict with one or more HPAI event in a village was classified as case, number of villages in each district were a population, a purely spatial were used by carried out using a maximum cluster size 30 % of the population at risk. P-value detected by Satscan program uses computer simulation to generate a number of random replications of the data set under the null hypothesis, if the maximum likelihood ratio of the identified cluster among 5 % highest, then the test is significant at the 0.05 level, the number replication was computed using 999 Monte Carlo permutations (8).Risk FactorsData analysis was performed by using R program version 3.1.2 (9), the predictors variables of interest include poultry movement from Java Island into Lampung Province, poultry density (heads/km2), and human density (people/km2) and the binary outcome is subdistrict with one or more HPAI event or not (1/0) during 2013 to 2014, this technique was appropriate because the sample size is small, imbalance and outcome was binary (10).

Result

Affected Species

During 2010 to 2014, majority species infected was chickens, however in 2011 there was one outbreak in duck species and then in the end of the year 2012 increase to 8 outbreaks, one swallow and turkey also reported during this study, during 2013 and 2014, respectively (Table. 1)

Table 1. Affected species by HPAI during 2010 and 2014Type of poultry 2010 2011 2012 2013 2014Chicken 88 (81-94) 25 (9-41) 1(-5-7) 42 (29-54) 36 (22-50Duck 0 1 (-2-5) 8(-8,24) 4(-1-9) 3 (-2-8)Muscovy duck 1 (-1-3) 0 1 (-5-7) 9 (2-16) 4 (-1-10)Quail 0 1(-2-5) 0 2 (-2-6) 3(-2-10)Swallow 0 0 0 1(-1-4) 0Turkey 1(-1-3) 0 0 0 0Total 90 27 10 58 46

Temporal and spatialFrom 2010 to 2014, HPAI were reported in 71 out of sub districts. The temporal pattern in figure 1 show epidemic wave was occurring almost in every year, from January to April 2010, the outbreak occurred in 45 subdistricts, the second wave happened in 20 subdistrict, between December 2010 to April 2011, 17 subdistricts in December 2012 to April 2013 and 20 subdistricts from January to April 2014. Two subdistrict had outbreak in every year, 4 subdistricts in 4 years, except 2012 and 8 subdistricts in 3 years.

The choropleth map in figure 3 shows that the outbreaks in 2010 affecting the large of outbreaks in 45 subdistrict, 5 new infected subdistricts occurred in 2011 and 2012, 1 subdistrict in 2013 and 7 in 2014. Figure 2 (right) presents the proportion of subdistricts outbreak during 2010 to 2014, within each district shows that all subdistricts in Metro districts had outbreaks, 80 % subdistricts in Bandar Lampung and Pesawaran, 60 % subdistricts in Pringsewu and Lampung Selatan, below 40 % in 8 districts, Pesisir Barat districts had no outbreak through all periods

Figure1.Bar chart of number of infected and coverage subdistricts.

Figure 2. Choropleth map presenting year of report subdistricts outbreak (left) and the proportion of subdistricts outbreak within each district (right).

Figure 3. Map of Lampung province showing result of spatial scan statistics (p<0.01), most likely cluster (red dot) and secondary cluster (green dot).

The retrospective analyses purely spatial indicate the primary cluster was located in Metro districts, with relative risk ratio 6.68, radius 6.37 km and a p-value of 0.00000095, the time period was in 2010, all five subditricts in the Metro district were infected, a secondary outbreak was detected in Bandar Lampung and Lampung Selatan district, 9 and 1 subdistricts, respectively, the radius of the cluster was 10.44 km, p-value of 0.017 and relative risk 2.68. The distance between these clusters was 12 km.

Table 2. Location of high risk cluster using the discrete poisson model.

Cluster Latitude Longitude Radius Relative Risk P-Value Time Period No.of Subdistricts

Primary 105.30676 5.094861 6.37 km 5.82 0.00000095 2010 5

Secondar

y

105.219916 5.351839 10.44 km 2.68 0.017 2010-2011 10

Risk factorsDuring 2013 to 2014, out of 71 sub districts were coverage by surveillance activity, 41 were infected sub districts, of these, 18 (44%) having a history of poultry movement from Java Island and high of poultry population, 27 (65 %) high density of human population. Based on exact logistic result, poultry movement and poultry population had no statistic significant with HPAI events in sub-districts, however, human population density had statistic significant with p-value 0.01 with confident interval 1.2 to 2.9 (see Table 1 for detail result).

Table 3. Result of exact logistic regression for the joint effect of poultry movement, poultry population and human density

Variable Estimate P-value 95 % CIJoint NA 0.018

Poultry movement -0.53 0.31 -1.18-0-61Poultry population -0.61 0.29 -1.9-0.52

Human density 1.46 0.01 1.2-2.9Affected speciesThe first affected duck was detected on March 2011 at Bandar Lampung districts and the number affected duck increasing progressively in 2012. In Indonesia, up to 2011 the outbreak infected by clade 2.1.3 viruses, this virus typically caused high mortality among gallinaceous birds, especially broiler, layer and native chicken, these viruses less pathogenic in aquatic birds. After report unusual mortality (10 to 90 %) among duck in Java Island in 2012, this HPAI outbreak due to clade 2.3.2.1 viruses, indicating the introducing of an exotic H5N1 clade into Indonesia (11, 12). Study with analysis of phylogeny tree in Lampung area revealed AI isolates from 2012 to 2013 that infect waterfowl had approximately 98.5 to 99.1% homology compared with AI isolates that infect waterfowl of Javanese origin and belonged to the clade 2.3.2.1.(13). The source of new introduction of the new clade to Java Island is still unknown(12). At Indonesia longitudinal study risk factors and sero-prevalence in the moving duck flock have been conducted in Java Island and the result showed the crude bird-level prevalence was 5,3 % and the characteristic of the moving duck production system appear to be conducive to spreading and transmitting the HPAI virus to the other birds (14), however the duck sero-prevalence and producing system after the new introduction clade 2.3.2.1 in 2012 and improvement of outbreak response and control by government may influence different results therefore further study in the production system and movement pattern of duck in Lampung Province is needed. Spatial and temporal clusterThe result of spatial analysis showed that two clusters were detected in Metro districts and Bandar Lampung, these two districts is the biggest city and highest human density in Lampung province, several factor my influence in the location of biggest city, In this study Bandar Lampung is the highest density of human population and have the biggest poultry trade market in Lampung Province, therefore the market and poultry trade activities may increase chance HPAI event, however some issues may influenced in this study, HPAI reporting and sample submission to laboratory were higher in Bandar Lampung district due to location of laboratory is within this district, during 2010, number of sample submission from PDSR officer at Metro and Bandar Lampung is the highest, 32 and 23, respectively. The occurrence of epidemic wave seen almost every year during December to April, possibly related rainy season with an average temperature between 24°-28°C (15) or migratory waterfowl during December to March (16). Risk factorsThe result of this study showed that the risk factor human density were significant with infected subdistricts, the factor may influence has been described in above, poultry population was not significant in this study, the reason may be highest poultry populations in sub district level are found in the area with highest broiler commercial farm, which have a good management and hygiene

practice than backyard farm. Yupiana et al (3) found poultry density negatively associated with HPAI outbreak in poultry in West Java Province. Poultry movement from Java to Lampung Province was no significant with HPAI event in subdistricts level, this movement data contains of legal poultry which have been inspected by quarantine officer at origin and destination seaport, the sender majority are a big company of commercial farm, therefore the probability of sick poultry move by seaport is less likely occurred, however the trade pattern is dynamic and can change according to production/demand and price difference between two geographic regions (4).

Conclusion This study highlighted the epidemiology of HPAI is changing over the time, HPAI outbreak during 2012 due to clade 2.3.2.1 viruses, indicating the introducing of an exotic H5N1 clade into Indonesia, however the source of introduction is unknown, it’s recommended to strengthen quality of outbreak investigation. Wild bird may influence in disease introduction, therefore surveillance in wild birds is needed. Our analyst spatial-temporal and risk factors show that outbreak were clustered in the high density human area, based on this finding it’s recommended to study in duck movement pattern and enhance surveillance in live bird markets.

Acknowledgment The author acknowledges to the head of Lampung DIC (Disease Investigation Centers) and laboratory staff, Dinas Peternakan dan Kesehatan Hewan Provinsi Lampung, Dinas Peternakan se-Kabupaten/Kota Lampung, Indonesia.

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