The Distribution of Bovine Tuberculosis in Cattle Farms Is Linked to Cattle Trade and Badger-Mediated Contact Networks in South-Western France, 2007–2015

Abstract

Bovine tuberculosis (bTB), mainly caused by Mycobacterium bovis, can affect domestic and wild animals as well as humans. Identifying the major transmission mechanisms in an area is necessary for disease control and management. In this study, we aimed to evaluate the involvement of different types of contact in M. bovis transmission between cattle farms of south-western France between 2007 and 2015. We analyzed an empirical contact network of cattle farms as nodes, with known infection status and molecular types (16 circulated during the study period of which 14 affected only cattle and two both badgers and cattle). Edges were based on cattle trade data (T-edges) and on spatial neighborhood relationships between farms, either direct (P-edges) or badger-mediated, when two farms neighbored the same badger home range (B-edges), or two distinct but neighboring badger home ranges (D-edges). Edge types were aggregated so that the contact network contained only unique edges labeled by one or several edge types. The association between the contact network structure and bTB infection status was assessed using a non-parametric test, each molecular type being considered a marker of an independent epidemic. Using a logistic regression model, we estimated the contribution of each edge type to the probability for an edge originating from an infected farm to end at another infected farm. A total number of 1946 cattle farms were included in the study and were linked by 54,243 edges. Within this contact network, infected farms (whatever the molecular type) always belonged to the same component, suggesting the contact network may have supported bTB spread among those farms. A significant association between the pattern of bTB-infected farms and the structure of the contact network was observed when all the molecular types were simultaneously considered. The logistic regression model showed a significant association between M. bovis infection in direct neighbors of infected farms and the connection by T-, B- and D-edges, with odds-ratios of 7.4, 1.9, and 10.4, respectively. These results indicate a multifactorial M. bovis transmission between cattle farms of the studied area, with varying implication levels of the trade, pasture and badger networks according to the molecular type.

Role of Live-Duck Movement Networks in Transmission of Avian Influenza, France, 2016–2017

“…A new aspect of this study is the inclusion of a permutation-based approach based on the dates of holding infection to evaluate whether the acquisition of holding infection was consistent with virus transmission through the network. This approach has been limitedly applied in the epidemiology of infectious diseases (23)(24)(25), although it outperforms other degreebased statistical methods, such as logistic regression and nonparametric tests. Outcomes about the relative contribution of movement and proximity networks represent a required basis on which predictive models of HPAI spread could be developed.…”

“…Next, we assessed the likely contribution of liveduck movements in the distribution of H5N8 outbreaks in the network using a permutation-based approach (23)(24)(25). The rationale behind this approach was that if the outbreaks resulted from disease spread through the movement networks, the mean number of infected holdings in contact with an infected holding in the network would be significantly greater than expected if infected holdings were randomly distributed in the network.…”

Animal tuberculosis: impact of disease heterogeneity in transmission, diagnosis, and control

“…The commercial trade of domestic animals, namely cattle, seems to also play a significant role in TB spreading between long‐distance locations (Bouchez‐Zacria, Courcoul, & Durand, 2018). One such example is the wide spreading of M. bovis lineage Eu1 promoted by animal trading (Smith et al, 2011).…”

“…Furthermore, infected badgers are socially isolated from their own groups but have more interactions with other groups, an extremely important component in TB transmission dynamics between neighbouring social groups (Pope et al, 2007). Also, terrain features and food availability may influence animal TB spread between badger and cattle populations, leading to concomitant infection (Bouchez‐Zacria et al, 2018).…”

Influence of pathogenic and atypical mycobacteria on immune status of guinea pigs

“…Despite the achieved success in the control of animals' infection diseases today the danger is represented by infectious diseases of bacterial etiology, which are characterized by high contagiousness. Tuberculosis -it is the main economically significant bacterial disease (LoBue et al, 2010;Paliy et al, 2015;Bouchez-Zacria et al, 2018;Borja et al, 2018).…”