Current epidemiological issues in human campylobacteriosis

Campylobacter has been the most commonly reported bacterial cause of human gastroenteric infection in England and Wales since 1981 and yet the epidemiology of this pathogen remains poorly understood. Indeed, the prevalence of Campylobacter infection is underestimated since the study of Infectious Intestinal Disease in England calculated that the true annual incidence was nearer 420 000 than the 55 000 reported in 1999. The epidemiology of Campylobacter infection is complex since the organism is widely distributed in the environment and throughout the food chain. Sources of human infection are likely to be contaminated with more than one strain of Campylobacter and cross contamination in domestic or commercial food preparation means that the source and vehicle of infection may not be the same food item. The vast majority of Campylobacter infections are reported as sporadic and the lack of outbreak data makes identification of sources and vehicles of infection difficult. Studies are further hampered by the lack of widely used, standard subtyping methods. A wide variety of phenotypic and genotypic typing methods have been applied to this organism although rarely on a sufficient scale to address the broader epidemiological issues. Furthermore the wide range of variation detected makes correlation of data from human infection with water and food sources difficult. The present paper describes a number of the more widely used typing methods together with examples of their impact on our understanding of the epidemiology of this important pathogen.