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Table 1 Timeline of NiV-related activities as part of the triangulated surveillance in the past two decades in Thailand

From: Two decades of one health surveillance of Nipah virus in Thailand

Year Activity & Findings Reference
HOST: BATS
2000–2018 An assessment of the niche centroid hypothesis: P. lylei (Chiroptera)
• We were unable to identify relationships between patterns of abundance using coarse-scale environmental variables but were able to identify relationships at a finer scale.
[29]
2002–2004 Surveillance of NiV in bats in 9 provinces of Thailand, 1304 bats (12 species) were tested for PCR and serology.
• IgG Antibody seropositive: 7.8% (9.3% for P. lylei)
• PCR positive:
- Pooled saliva: 2/142
- Pooled urine: 6/142
[2]
2005–2007 Surveillance of NiV in pooled urine collected under roosts of P. lylei bats in 7 provinces in central plains of Thailand
• NiV PCR positive from bat urine collected from all 7 provinces.
• Seasonal prevalence transmission was found in April and May
[24]
2008–2012 Annually collected bat pooled urine specimens from Chonburi
• NiV PCR positive was found in pooled urine ever year
• % positive varied between 0 and 26% depending on number of samples collected, month. Note: there was possibility of duplicate positive from the same plastic sheet (urine from same bat could have been collected)
This study
2010–2011 Surveillance of NiV in pooled urine of P. hypomelanus bats in southern Thailand
• NiV-MY strain was found in P. hypomelanus (PCR and sequencing).
[16]
2012 Monthly capture of P. lylei bats at 2 pig farms and bat roost (Fig. 1c). NiV-PCR and serology conducted
• PCR positive bat saliva samples found in samples collected during Mar to Jul, highest number of positives in April.
• NiV IgG antibody was found from bat throughout the year, except Jan (low number of tested bats)
This study
2012 High-Resolution GPS Tracking of Lyle’s Flying Fox Between Temples and Orchards in Central Thailand
• Maximum linear distances between day roosts and foraging areas varied greatly between individuals (2.2–23.6 km) but were similar between seasons.
[26]
2014 Genetic diversity and relationships among Lyle’s flying fox colonies in Thailand
• The sequence data suggested that the overall P. lylei population has high levels of haplotype diversity, which may reflect genetic exchange during P. lylei movement. These results will help manage populations and assess the risk of outbreaks of NiV carried by Lyle’s flying fox.
[25]
2015 Spatial characterization of colonies of the flying fox bat, a carrier of NiV in Thailand
• Passive and active surveillance programs should be prioritized around Bangkok, particularly on farms with low biosecurity, close to water, and/or on which orchards are concomitantly grown.
• Integration of human and animal health surveillance should be pursued in these same areas.
• Such proactive planning would help conserve Lyle’s flying fox colonies and should help prevent zoonotic transmission of NiV and other pathogens.
[27]
2015–2016 Assessing the distribution, roosting site characteristics, and population of P. lylei in Thailand
• The field survey validated the results of the questionnaire, with 67.65% of respondents correctly identifying P. lylei in their area
• There were 30 roosting sites (8 new roosts), a total population of 75,016 bats, and a total roosting area of 1,328,720 m2
• Our results confirm that close proximity between P. lylei and human populations is common.
[28]
2015–2016 Patch metrics of roosting site selection by Lyle’s flying fox (P. lylei) in a human-dominated landscape in Thailand
• The most suitable habitat areas for Lyle’s flying fox were associated with low patch contiguity, which was the most important spatial parameter affecting roosting site location
[30]
2016–2020 Annually collected bat pooled urine specimens from Chonburi
• Whole genome of NiV was successfully sequenced from urine specimens collected from Chonburi in 2017.
• NiV PCR positive was found in pooled urine ever year
• % positive varied between 0 and 11.32% depending on number of samples collected, month. Note: there was possibility of duplicate positive from the same plastic sheet (urine from same bat could have been collected)
This study
HOST: PIGS
2001 - present Annual NiV serosurveillance in pigs (4000–5000 pigs sampled each year)
• All pigs seronegative to date
National surveillance; DLD database
2011–2012 A total of 246 pigs were sampled (246 nasal swabs, 233 serum samples) from 9 pig farms in Chonburi and Prachin Buri provinces where pig farms located close to (within 30 km radius) bat colonies where previously NiV-positive bats were found
• All nasal swabs tested negative for NiV RNA using PCR
• All pig sera tested negative for NiV antibody using ELISA
This study
2016–2017 A total of 1348 pigs were sampled from 36 pig farms on 3 sampling trips, in May 2016 (434 pigs), November 2016 (439 pigs), and February 2017 (475 pigs) in Chonburi and Chachoengsao provinces.
• All pig nasal swabs tested negative for NiV by PCR at the National Institute of Animal Health (NIAH) laboratory under the Department of Livestock and Development, Ministry of Agriculture and Cooperatives, Thailand.
• NiV IgG antibodies were not tested in specimens from these sampling trips
This study
2019 A spatial assessment of Nipah virus transmission in Thailand pig farms using multi-criteria decision analysis
• We believe that risk-based surveillance in the identified priority areas may increase the chances of finding NiV and other bat-borne pathogens and thereby optimize the allocation of financial resources for disease surveillance.
• In the long run, improvements of biosecurity in those priority areas may also contribute to preventing the spread of potential emergence of NiV and other bat-borne pathogens.
[31]
2020 A ‘what-if’ scenario: Nipah virus attacks pig trade chains in Thailand
• The risk of NiV dissemination through pig movement networks in Thailand is low but not negligible.
• The risk areas identified in our study can help the veterinary authority to allocate financial and human resources to where preventive strategies, such as pig farm regionalization, are required and to contain outbreaks in a timely fashion once they occur.
[32]
HOST: HUMAN - Patient
2001–2012 Archived CSF specimens from encephalitis patients admitted at the King Chulalongkorn Memorial Hospital were tested for NiV PCR
• CSF from 232 encephalitis patients tested negative for NiV PCR
This study
HOST: HUMAN – Healthy Volunteers from high-risk community
Nov-Dec 2010 A total of 418 serum of local residents (voluntary participation; informed consent was sought) in Wat Luang village, Chonburi province, were collected where NiV-positive bats were previously found in the bat colonies
• Blood samples were assayed for IgG antibodies using indirect ELISA against NiV-infected cell lysate.
• No NiV-specific IgG antibodies were found.
This study
May 2017 &
May 2018
Samples (oral swabs, urine, and serum) were tested for NiV and NiV antibodies in May 2017 and May 2018 (115 and 128 subjects were enrolled respectively)
• All oral swabs and urine specimens tested negative for NiV using PCR.
• All serum specimens tested negative for NiV antibodies using Luminex serology assay.
This study