Analysis of Swine Movements in a Province in Northern Vietnam and Application in the Design of Surveillance Strategies for Infectious Diseases

Abstract

Summary While swine production is rapidly growing in South-East Asia, the structure of the swine industry and the dynamic of pig movements have not been well-studied. However, this knowledge is a pre-requisite for understanding the dynamic of disease transmission in swine populations and designing cost-effective surveillance strategies for infectious diseases. In this study, we assessed the farming and trading practices in the Vietnamese swine familial farming sector, which accounts for most pigs in Vietnam, and for which disease surveillance is a major challenge. Farmers from two communes of a Red River Delta province (Northern Vietnam) were interviewed, along with traders involved in pig transactions. Major differences in the trade structure were observed between the two communes. One commune had mainly transversal trades, i.e. between farms of equivalent sizes, whereas the other had pyramidal trades, i.e. from larger to smaller farms. Companies and large familial farrow-to-finish farms were likely to act as major sources of disease spread through pig sales, demonstrating their importance for disease control. Familial fattening farms with high pig purchases were at greater risk of disease introduction and should be targeted for disease detection as part of a risk-based surveillance. In contrast, many other familial farms were isolated or weakly connected to the swine trade network limiting their relevance for surveillance activities. However, some of these farms used boar hiring for breeding, increasing the risk of disease spread. Most familial farms were slaughtering pigs at the farm or in small local slaughterhouses, making the surveillance at the slaughterhouse inefficient. In terms of spatial distribution of the trades, the results suggested that Northern provinces were highly connected and showed some connection with Central and Southern provinces. These results are useful to develop risk-based surveillance protocols for disease detection in the swine familial sector, and to make recommendations for disease control.

Surveillance of swine influenza viruses in sentinel familial farms in Hung Yen province in Northern Vietnam in 2013–2014

“…Similar findings on the impact of farm typology and trading practices on swine infection in Dinh Du and Me So has been observed in our previous study of swine value chains and trade dynamics (Baudon et al, ). We found that large farrow‐to‐finish farms in Me So had a non‐negligible risk of disease introduction through purchase of breeders and a high risk of disease spreading to other farms, especially fattening farms (not included in the sentinel farm study) through sale of weaners.…”

“…On the contrary, our surveillance in the large slaughterhouse in Hanoi, still ongoing as of February 2019, allowed us to isolate many SIV and appeared to be an efficient means of surveillance of SIV. The large slaughterhouse in Hanoi mainly sources pigs from the very large farm sector (eg company farms) (Baudon et al, ). Therefore, an outstanding question was whether such large abattoir based SIV surveillance may miss SIV subtypes circulating in the small farm sector.…”

Swine influenza viruses in Northern Vietnam in 2013–2014

“…The large company sector provided 42% of the sampled pigs, 20% arose from the familial husbandry sector and 38% had no data recorded. From the previous network analysis, it is likely that the familial farms were predominantly large farms 25 .…”

Competing biosecurity and risk rationalities in the Chittagong poultry commodity chain, Bangladesh

“…A 'hot spot' originally meant "a location with high biodiversity and wildlife density that was under significant threat of degradation or destruction as a consequence of human activities" (Paige et al 2015, p. 79). Later, a 'hot spot' meant a virus 'dissemination point' or a 'high risk area' (Ahmed et al 2012a;Gilbert et al 2010), or a geographical area prone to the emergence of zoonotic infectious diseases (Baudon et al 2017). In anthropology, a hot spot refers to a convergence of circumstances that create the conditions for disease communicability, ethnographically focused on intimate interactions between humans, animals and viruses (Brown and Kelly 2014).…”