Campylobacter is a bacterium that can be present in the gastro-intestine of both animal and man. Pathogenic Campylobacter has a long history and was first noted in 1886 in diarrhoeal feces of children and kittens as a non-culturable, spiral-shaped micro-organism named Vibrio felinus (Kist, 1985). Campylobacter eluded culture until 1973 because of its fastidious nature and requirement for a microaerophilic environment (Butzler et al., 1973). A simpler isolation technique was reported in 1977 based on antimicrobials contained in blood agar enabling routine isolation of Campylobacter from fecal samples (Skirrow, 1977). The ability of the scientific community to culture Campylobacter spp. has enabled us to recognise the importance of this zoonotic agent.
Campylobacter Human infectionThere are 19 species, subspecies and biovars that comprise the genus Campylobacter. In the 1970s Campylobacter was first cultured from patients with diarrhoea (Butzler et al., 1973). In the past 30 years Campylobacter has emerged as an important public health zoonotic agent, in particular C. jejuni and C. coli.
The infectious dose for Campylobacter is potentially relatively low, with as few as 500 to 10,000 organisms infectious (Mentzing, 1981; Anon., 2002a). Experimental infection of volunteers has used higher doses (up to 109 colony forming units) to achieve high attack rates (Black et al., 1988). However, the infectious dose can vary with strain virulence and host susceptibility. The incubation period can vary from one to seven days (Wassenaar and Blaser, 1999). Following infection with Campylobacter the patient may experience symptoms ranging from a mild self limiting enterocolitis lasting 24 hours to a severe illness including diarrhoea, bloody diarrhoea, abdominal cramps and vomiting (Anon., 2002a; Lucey, 2002; Anon., 2003a). The patient may also experience malaise, headache, dizziness, anorexia, myalgia, arthralgia or fever before the onset of diarrhoea (Skirrow and Blaser, 1992; Anon., 2002a). The majority of infected patients recover without any specific treatment. However, Campylobacteriosis tends to be more severe in immunosuppressed patients e.g. HIV-infected patients (Altekruse et al., 1999). Also, in the developing world Campylobacteriosis has been associated with severe life threatening disease (Crushell et al., 2004).
There are a number of potential sequelae from Campylobacteriosis: appendicular syndrome; cholecystitis; peritonitis; arthritis; erythema nodosus; bacteraemia; meningitis; Guillain-Barré syndrome (GBS); HUS and death (Anon, 2004; Lucey, 2002; Endtz et al., 2003). The CDC reported an incidence of four deaths in 100,000 of population related to Campylobacter in 2003 for the 10 States that FoodNet surveys (Anon, 2004).
GBS affects the peripheral nervous system resulting in symmetrical limb weakness, loss of tendon reflexes, absent or mild sensory signs and variable autonomic dysfunction (Hahn, 1998; Yuki, 2001). GBS is an important sequel of Campylobacteriosis because of the prolonged debilitating consequences of this syndrome. It is estimated that a person is 100 times more likely to develop GBS for the two month period after having a symptomatic episode of Campylobacteriosis compared to the normal population (McCarthy and Giesecke, 2001). Furthermore, in England during the year 2000 C. jejuni was identified as responsible for 157 cases of GBS (Tam et al., 2003). This was equivalent to 15% of all GBS cases reported during the same period. Another report estimated that Campylobacter enteritis precedes approximately 30% of all GBS cases in humans (Bersudsky et al., 2000).
Distribution of human infection
Campylobacter spp. is the second most frequent causes of Food-borne disease in the US. In 2006 the CDC's FoodNet reported that total number of cases of Campylobacter infection in 10 states was 5,712 (Anon, 2007). In 2003, Campylobacter infection was linked to the death of 9 people out of the 10 States surveyed (Anon, 2004). It has been hypothesised that approximately 1% of a population become infected with Campylobacter each year (Skirrow and Blaser, 1992).
Campylobacter is now recognised as the single most frequent cause of bacterial gastroenteritis infection in Ireland (almost three times higher than the number of salmonellosis cases reported in 2001) (Foley and McKeown, 2002b). Similarly, Campylobacter has surpassed Salmonella as a cause of bacterial gastroenteritis in Denmark, Finland, Sweden and the UK (Lior, 1996; Anon., 1999b). The CIR recorded by the National Disease Surveillance Centre in Ireland was 35.5 cases / 100,000, 44.5 cases / 100,000 and 57.5 cases / 100,000 in 2001, 2000 and 1999, respectively (Foley and McKeown, 2001; Foley and McKeown, 2002b). These rates are based on laboratory-confirmed cases and the true rate of infection has been estimated to be 10 to 100 times higher (Skirrow, 1991; Kapperud et al., 1992). In Ireland during 2001 children under five years of age accounted for 26.6% of the reported cases of Campylobacteriosis (Figure 2-1) (Foley and McKeown, 2002b). This trend was consistent with most other EU countries in 2002 (Anon., 2003b). Factors contributing to this observed trend might be susceptibility on first exposure or a lower threshold for seeking medical care. Young adults (25 to 34 years) are also associated with an incidence peak (Figure 2-1). This may be linked to low standards in food preparation (Foley and McKeown, 2002b).
Sources of human Campylobacter infection
Campylobacter is an environmental and foodborne zoonotic pathogen. Unlike VTEC Campylobacter spp. are not frequently associated with conspicuous outbreaks of disease in man. The majority of cases of Campylobacteriosis present as sporadic cases and person-to-person transmission is uncommon (Pebody et al., 1997; Alterkruse et al., 1998). Handling raw poultry and eating undercooked poultry have been identified as significant risk factors for sporadic Campylobacteriosis (Kapperud et al., 1992; Lior, 1996; Vellinga and Loock, 2002). However, cattle products (milk and beef) and contaminated drinking water have also been identified as important sources of the pathogen in outbreaks of Campylobacter infection in the US between 1978 and 1996 (Table 2.3) (Anon., 2002a). Cattle have also been identified as a risk factor and a source of Campylobacter spp. through the consumption of meat and raw milk along with direct contact with cattle or their environment (Butzler and Oosterom, 1991; Skirrow, 1991; Pearson and Healing, 1992; Troutt and Osburn, 1997; Fitzgerald et al., 2001; Anon., 2003a; Neimann et al., 2003). Further evidence suggesting a possible link between cattle as a source of Campylobacter spp. and infection in man is the isolation of indistinguishable Campylobacter isolates and serotypes common to both cattle and human patients (Munroe et al., 1983; Nielsen et al., 2000). Pets, in particular dogs and cats are another important potential source of Campylobacter for the public. It has been estimated that approximately 5% of human cases originate from domestic dogs (Lior, 1996; Anon., 2003a). However, dogs and cats are associated more with the carriage of C. upsaliensis than either C. jejuni or C. coli (Burnens et al., 1992; Baker et al., 1999).
Prevalence of Campylobacter contamination of Beef It is accepted that cattle shed Campylobacter spp. in their feces and as a result must be regarded as a potential source of the pathogen for humans. Campylobacter spp. have been isolated from beef carcasses in a number of previously reported studies. The prevalence ranged from 0.16 to 2%, with C. jejuni and C. coli accounting for the speciated Campylobacter isolates in these studies (Kwiatek et al., 1990; Vanderlinde et al., 1998; Beach et al., 2002). Campylobacter has also been isolated from beef products. In 2002, a surveillance study detected Campylobacter spp. in 0.1% of 3046 samples of minced beef in Denmark, in four out 60 (6.7%) samples of minced beef in Spain and in one out of seven (14.3%) samples of minced beef in Portugal. In Italy two out of 53 (3.8%) beef product samples were Campylobacter spp. positive. Also, a UK study on cold cooked- beef samples detected Campylobacter spp. in 0.03% of 2894 samples (Anon., 2003b). A US study reported the prevalence of contamination of minced beef and beef flank with C. jejuni and C. coli as 3.6% and 4.7%, respectively (Stern et al., 1985). All Campylobacters isolated were confirmed as C. jejuni. A Greek study investigating beef from butchers’ shops isolated Campylobacter from 8.2% of the samples (Grigoriadis et al., 1992). All Campylobacters were C. jejuni and C. coli. In 2001 a limited Irish study reported the detection of Campylobacter from four of 20 (20%) minced beef samples tested (Cloak et al., 2001). The results of a recent Irish study demonstrated Campylobacter in raw beef samples at retail level in seven of 221 (3.2%) samples tested (Whyte et al., 2004). Samples were purchased in retail outlets and small-throughput butchers’ shops in both Ireland and Northern Ireland.
Prevalence of C. jejuni and C. coli in cattle Previous studies have reported the prevalence of Campylobacter spp. in cattle ranging from 0-80% (Munroe et al., 1983; Rosef et al., 1983; Giacoboni et al., 1993; Minihan et al., 2004; Minihan et al., 2004a). Diagnostic investigations usually report lower levels of infection compared to targeted surveillance studies (Anon., 2003b). Authors of targeted surveillance studies of cattle have reported that intestinal infection prevalence with C. jejuni and C. coli ranging from 12 to 37% and from 1 to 16.5%, respectively (Myers et al., 1984; Garcia et al., 1985; Frederick, 1988; Giacoboni et al., 1993; Ono et al., 1995; Wesley et al., 2000; Minihan et al., 2004). Meaningful comparisons of the prevalence of infection of Campylobacter spp. between different studies is complicated by variations in sample size, animal type and age, sampling method, recovery methodology, and local husbandry practices.
Factors affecting Campylobacter shedding by cattle
A number of studies have investigated potential factors that could affect cattle’s Campylobacter fecal shedding. Seasonal periodicity in fecal shedding rates of Campylobacter within dairy herds has been reported (Robinson, 1982; Meanger and Marshall, 1989). Stanley et al., (1998) reported two peaks of fecal shedding per year, in approximately spring and autumn. However, no evidence of a seasonal peak of Campylobacter fecal shedding was observed in beef cattle at slaughter (Stanley et al., 1998). The lack of an observed seasonal periodicity with beef cattle may have been a result of the husbandry systems under which these animals were kept. It has been consistently reported that young animals have a higher prevalence of fecal shedding of Campylobacter compared to adult cattle (Grau, 1988; Giacoboni et al., 1993; Stanley et al., 1998). Furthermore, young animals were reported to shed higher numbers of Campylobacter and a wider range of species of Campylobacter (Giacoboni et al., 1993; Stanley et al., 1998).
Farm management and husbandry practices have been associated with an increased prevalence of Campylobacter. Higher prevalences of C. jejuni have been reported in cattle raised on feedlots compared to cattle raised on pasture (Garcia et al., 1985; Grau, 1988; Stanley et al., 1998). A US study’s results indicated that a higher proportion of cattle positive for fecal Campylobacter was associated with larger herd size (Hoar et al., 2001). The authors of a UK study, which investigated 12 herds for fecal shedding of Campylobacter, reported that animals from the 10 positive herds drank from either rivers or streams while grazing (Humphreys and Beckett, 1987). A study investigating management factors associated with fecal shedding of C. jejuni in cattle identified four factors: application of manure with broadcast spreaders; feeding of whole cottonseed or hulls; feeding of alfalfa; and accessibility of feed to birds (Wesley et al., 2000). However, a recent study reported no significant difference between the prevalence of Campylobacter on conventional farms (29.1%) compared to organic dairy farms (26.7%) (Sato et al., 2004). A longitudinal study identified that prevalence of Campylobacter spp. fecal shedding within pens was positively correlated to the pen, the month of sampling and the Campylobacter spp. contamination status of the pen dividing bars and the water trough surface(Minihan et al., 2004). The farm managements differed significantly between production systems in a number of areas including housing, grazing style and use of antimicrobials.
Few studies have investigated the effect of transport on the prevalence of Campylobacter. The results two studies indicated that Campylobacter fecal shedding remained relatively constant before and after transport of feedlot cattle to the abattoir and during lairage (Beach et al., 2002; Minihan et al. 2004a).