High-Resolution Monitoring of Antimicrobial Consumption in Vietnamese Small-Scale Chicken Farms Highlights Discrepancies Between Study Metrics

Abstract

Chicken is, among farmed species, the target of the highest levels of antimicrobial use (AMU). There are considerable knowledge gaps on how and when antimicrobials are used in commercial small-scale chicken farms. These shortcomings arise from cross-sectional study designs and poor record keeping practiced by many such farmers. Furthermore, there is a large diversity of AMU metrics, and it is not clear how these metrics relate to each other. We performed a longitudinal study on a cohort of small-scale chicken farms ( n = 102) in the Mekong Delta (Vietnam), an area regarded as a hotspot of AMU, from October 2016 to May 2018. We collected data on all medicine products administered to 203 flocks with the following aims: (1) to describe types and quantities of antimicrobial active ingredients (AAIs) used; (2) to describe critical time points of AMU; and (3) to compare AMU using three quantitative metrics: (a) weight of AAIs related to bird weight at the time of treatment (mg/kg at treatment); (b) weight of AAIs related to weight of birds sold (mg/kg sold); and (c) “treatment incidence” (TI), or the number of daily doses per kilogram of live chicken [Vietnamese animal daily dose (ADDvetVN)] per 1,000 days. Antimicrobials contained in commercial feed, administered by injection ( n = N = 6), or antimicrobials for human medicine ( n = N = 16) were excluded. A total of 236 products were identified, containing 42 different AAIs. A total of 76.2% products contained AAIs of “critical importance” according to the World Health Organization (WHO). On average, chickens consumed 791.8 (SEM ±16.7) mg/kg at treatment, 323.4 (SEM ±11.3) mg/kg sold, and the TI was 382.6 (SEM ±5.5) per 1,000 days. AMU was more common early in the production cycle and was highly skewed, with the upper 25% quantile of flocks accounting for 60.7% of total AMU. The observed discrepancies between weight- and dose-based metrics were explained by differences in the strength of AAIs, mortality levels, and the timing of administration. Results suggest that in small-scale chicken production, AMU reduction efforts should preferentially target the early (brooding) period, which is when birds are most likely to be exposed to antimicrobials, whilst restricting access to antimicrobials of critical importance for human medicine.

An estimation of total antimicrobial usage in humans and animals in Vietnam

“…For pigs, chickens, and aquaculture (all aquatic species combined) data on AMU were obtained from quantitative published surveys [13][14][15][16]. Data on on AMU through consumption of commercial feed (i.e.…”

Veterinary Drug Shops as Main Sources of Supply and Advice on Antimicrobials for Animal Use in the Mekong Delta of Vietnam

“…It has been shown that antimicrobials intended for veterinary use are extremely affordable in the region (average of 0.56 cents of a USD per kilogram treated) and represent only a small fraction of overall chicken production costs [12]. We found that, despite high levels of AMU by chicken flocks in the area [15], antimicrobial sales represented a relatively small fraction of the total income of veterinary drug shops. There were, however, the large difference across establishments.…”

“…High levels of AMU have been reported both in chicken and pig production in the Mekong Delta of Vietnam [13][14][15]. This behaviour is partly driven by the prevailing farming conditions that lead to a high incidence of disease and mortality [8].…”

Labelling and quality of antimicrobial products used in chicken flocks in the Mekong Delta of Vietnam

“…Globally, the quantity of antimicrobials used in chicken production is estimated at 138.0 doses/1,000 animal‐days [inter quartile range (IQR) 91.1–438.3], a higher amount than AMU in the two other major terrestrial food animal species (pig and cattle) (Cuong, Padungtod, Thwaites, & Carrique‐Mas, ). Previous studies have reported exceptionally high levels of antimicrobial use (AMU) in chicken farms in the Mekong Delta region of Vietnam (Carrique‐Mas et al., ; Carrique‐Mas et al., ; Cuong et al., ; Nguyen et al., ). However, there are currently no published data on the quality of antimicrobial products used in these farming systems.…”

“…TA B L E 1 Characteristics of 20 antimicrobial products investigated, sorted by the number of flocks where they were used 91.1-438.3], a higher amount than AMU in the two other major terrestrial food animal species (pig and cattle) (Cuong, Padungtod, Thwaites, & Carrique-Mas, 2019). Previous studies have reported exceptionally high levels of antimicrobial use (AMU) in chicken farms in the Mekong Delta region of Vietnam (Carrique-Mas et al, 2015;Carrique-Mas et al, 2019;Cuong et al, 2019;Nguyen et al, 2016).…”