A ‘what-if’ scenario: Nipah virus attacks pig trade chains in Thailand

Abstract

Background: Nipah virus (NiV) is a fatal zoonotic agent that was first identified amongst pig farmers in Malaysia in 1998, in an outbreak that resulted in 105 fatal human cases. That epidemic arose from a chain of infection, initiating from bats to pigs, and which then spilled over from pigs to humans. In Thailand, bat-pig-human communities can be observed across the country, particularly in the central plain. The present study therefore aimed to identify highrisk areas for potential NiV outbreaks and to model how the virus is likely to spread. Multi-criteria decision analysis (MCDA) and weighted linear combination (WLC) were employed to produce the NiV risk map. The map was then overlaid with the nationwide pig movement network to identify the index subdistricts in which NiV may emerge. Subsequently, susceptible-exposed-infectious-removed (SEIR) modeling was used to simulate NiV spread within each subdistrict, and network modeling was used to illustrate how the virus disperses across subdistricts. Results: Based on the MCDA and pig movement data, 14 index subdistricts with a high-risk of NiV emergence were identified. We found in our infectious network modeling that the infected subdistricts clustered in, or close to the central plain, within a range of 171 km from the source subdistricts. However, the virus may travel as far as 528.5 km (R 0 = 5). Conclusions: In conclusion, 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.

Henipaviruses—A constant threat to livestock and humans

“…Importing infected pigs from a contaminated area in Malaysia infected 11 slaughterhouse workers and caused one death [15,23,25]. Based on these outbreaks, a study aimed to identify the potential threat of pig trading in the transmission of NiV and examined how long-distance transportations of living pigs may facilitate disease dissemination in Thailand [55]. Findings showed that, although the risk of NiV dissemination through pig trade is low, it is not negligible and may cause local outbreaks that requires preventive strategies concerning international trading [55].…”

Understanding the relationship between environment, agriculture and health: An interdisciplinary challenge

“…In many cases, livestock production creates an important conduit between diseases in wildlife and humans. For instance, Nipah virus in Southeast Asia, a disease of bats, entered humans via pig production in peri-urban areas where bats roosted in trees over pig pens, and so the pigs ingested bat feces containing the virus, which was then passed on to humans (Wongnak et al, 2020).…”