Campylobacter spp. remain one of the most frequent bacterial causes of foodborne gastroenteritis around the world .
Poultry, and specifically consumption of undercooked poultry and
mishandling raw poultry, is thought to be an important source of Campylobacter to humans [2-7]. The prevalence of broiler flocks colonized with Campylobacter spp. varies among countries, ranging from 5% of flocks to more than 90% .
Once a flock is exposed, the bacteria spread rapidly through the flock,
and most of the birds become colonized and remain so until slaughter [9-14].
In Iceland, the incidence of domestically-acquired human
campylobacteriosis peaked in 1999 at 117.6 cases per 100,000 persons , and sampling of broiler carcasses and domestic human cases from August to October 1999 showed that 85% of Campylobacter isolates in humans had identical genetic sequences (flaA SVR) to isolates from broilers . Due to the difficulties in eliminating contamination of carcasses in slaughter plants, the control of Campylobacter in
broiler flocks and subsequent production of birds free from
colonization at slaughter is essential for preventing human cases [5,14,17-19].
Several epidemiological studies have examined risk factors for the colonization of broiler flocks with Campylobacter. Farm-level factors associated with an increased risk of colonization include: the presence of other animals on the farm [13,20-23]; the presence of other poultry nearby ; manure disposal inside the farm ; greater than 200 m between the broiler house and the nearest manure heap (versus ≤200 m) ; farm water supply ; providing broilers with non-disinfected drinking water ;
increasing number of birds raised per year on the farm (which was
highly correlated with the number of broiler houses on the farm)  and increasing flock size .
These factors were identified using univariable and multivariable
statistical methods to examine a large number of risk factors that
potentially act at the flock, house or farm level. To our knowledge,
there are no farm-level studies that have attempted to delineate risk
factors that specifically influence the proportion of positive flocks
on a farm.
The strong association between the increased incidence of human
campylobacteriosis and increased consumption of fresh chicken meat in
Iceland, prompted a longitudinal study of the poultry industry . The ultimate goal of the full project was to identify the means to decrease the frequency of broiler flock colonization with Campylobacter,
thereby reducing the burden of foodborne illness associated with
poultry consumption. Our objective in this study was to identify risk
factors for flock colonization acting at the broiler farm level.