Campylobacter Infections

Definition

Campylobacter jejuni is one of the most commonly recognized bacterial causes of diarrhea in developed and underresourced nations. More than 95% of campylobacter isolated in developed countries are C. jejuni or C. coli . However, other Campylobacter species are also associated with human disease.

Epidemiology

C. jejuni infections are endemic in young children in underresourced nations, where it is among the three leading causes of childhood diarrhea, along with norovirus and rotavirus ( Chapter 350 ). In industrialized nations such as the United States, Campylobacter infections are the most common bacterial causes of diarrhea in children and adults, and the incidence of diagnosed Campylobacter infections has increased recently, likely due to the more widespread use of culture-independent diagnostic tests. Nonetheless, the actual burden of disease caused by Campylobacter is probably much higher than suggested in surveillance reports as even active surveillance systems substantially underreport the true incidence of infection. Epidemiologic studies have estimated that more than 2 million people in the United States are infected with C. jejuni each year. For reasons that are not clear, the incidence is highest in western states, such as California and Hawaii. Similarly high rates of infection are observed in Europe. In the United States, Europe, and Australia, C. jejuni infections show a substantial peak in warmer months, but such seasonality is not observed in tropical underresourced countries, perhaps because of the absence of extreme temperature variations. Polymerase chain reaction (PCR) testing and other culture-independent diagnostic tests can now identify bacterial pathogens in most individuals with traveler’s diarrhea ( Chapter 265 ), which is commonly associated with C. jejuni , particularly in Southeast Asia.

The incidence of Campylobacter infections is highest in early childhood, an epidemiologic feature common to many food-borne bacterial pathogens. However, in the United States and other industrialized countries, the incidence of infections peaks again in early adulthood. The incidence of infection is also higher in men, a sex difference most pronounced in young adults.

Most human C. jejuni infections occur sporadically, with only a tiny fraction occurring as part of outbreaks. The dominant source of sporadic infections in both developed and underresourced countries is consumption or handling of poultry, although cattle and pigs also can be sources of infection. Other sources of transmission in developed nations include foreign travel, contact with pets and other animals, contaminated drinking water, and consumption of unpasteurized milk. Cross-contamination within a kitchen (e.g., use of the same utensils or cutting boards to prepare uncooked chicken and to chop fruit) has led to a variety of foods being implicated as sources of human C. jejuni infection. In contrast to sporadic infections, the most common source of C. jejuni outbreaks is unpasteurized milk; large waterborne outbreaks occasionally occur. Transmission of C. jejuni infection from ill food handlers is uncommon. Even in households in which an individual has culture-proven C. jejuni gastroenteritis, secondary transmission to other family members is unusual.