An epidemiological investigation of Campylobacter in pig and poultry farms in the Mekong delta of Vietnam

Abstract

Campylobacter are zoonotic pathogens commonly associated with gastroenteritis. To assess the relevance of Campylobacter in Vietnam, an economically transitioning country in SE Asia, we conducted a survey of 343 pig and poultry farms in the Mekong delta, a region characterized by mixed species farming with limited biosecurity. The animal-level prevalence of Campylobacter was 31·9%, 23·9% and 53·7% for chickens, ducks and pigs, respectively. C. jejuni was predominant in all three host species, with the highest prevalence in pigs in high-density production areas. Campylobacter isolates demonstrated high levels of antimicrobial resistance (21% and 100% resistance against ciprofloxacin and erythromycin, respectively). Multilocus sequence type genotyping showed a high level of genetic diversity within C. jejuni, and predicted C. coli inter-species transmission. We suggest that on-going intensification of animal production systems, limited biosecurity, and increased urbanization in Vietnam is likely to result in Campylobacter becoming an increasingly significant cause of human diarrhoeal infections in coming years.

Fig. 1.

The geographical distribution of chicken, duck and pig farms and human population density in Dong Thap province, Mekong delta, Vietnam. Maps showing Dong Thap province (total area), highlighting the four study districts (Hong Ngu, Thanh Binh, Cao Lanh, Chau Thanh) and communes (smallest shaded areas). (a) The density of chicken farms (per km², as shown by shading in key) and the number of farms sampled per commune (numeral within shaded area). (b) The density of duck farms (per km², as shown by shading in key) and the number of farms sampled per commune (numeral within shaded area). (c) The density of pig farms (per km², as shown by shading in key) and the number of farms sampled per commune (numeral within shaded area). (d) Human population density per km², as shown by shading in key).

Fig. 2.

The prevalence of Campylobacter by district in Dong Thap province, Mekong delta, Vietnam. Bar charts showing the unadjusted (white bars) and adjusted (grey bars) prevalence of (a) Campylobacter spp., (b) C. jejuni and (c) C. coli in chickens, ducks and pigs in Cao Lanh (CL), Chau Thanh (CT), Hong Nhu (HN) and Thanh Binh (TB) districts in Dong Thap province.

Fig. 3.

The antimicrobial susceptibility profiles of Campylobacter isolated from animals in Dong Thap province, Mekong delta, Vietnam. Bar charts showing the antimicrobial susceptibility patterns of C. jejuni (white bars) and C. coli (grey bars) isolated from (a) chickens (68 organisms), (b) pigs (85 organisms), (c) ducks (49 organisms) and (d) all species combined (202 organisms) against 12 antimicrobials: AMP, ampicillin; C, chloramphenicol; CN, gentamycin; SXT, sulfamethoxazole-trimethoprim; NA, nalidixic acid; OFL, oxfloxacin; CIP, ciprofloxacin; CL, clindamycin; and ERY, erythromycin.

Fig. 4.

Multi-locus sequence typing (MLST) of Campylobacter isolated from animals in Dong Thap province, Mekong delta, Vietnam. (a) Minimum spanning tree of 73 C. jejuni isolates from animals in Dong Thap province, calculated by sequencing of the 7-target MLST genes. Each individual sequence type is distinguished by separate circles and linked by lines indicating allelic variation. The colour of each sequence type signifies from which animal species each bacterial strain was isolated: blue, ducks; yellow, chickens; pink, pigs. Background shading highlights clonal complexes. (b) Minimum spanning tree of 70 C. coli isolated from animals in Dong Thap province, calculated by sequencing of the 7-target MLST genes. Each individual sequence type is distinguished by separate circles and linked by lines indicating allelic variation.