Thermophilic Campylobacter spp. in Danish broiler

Avian Pathology (2000) 29, 123–131

Thermophilic Campylobacter spp. in Danish broiler production: a cross-sectional survey and a retrospective analysis of risk factors for occurrence in broiler flocks B. Hald*, A. Wedderkopp & M. Madsen Danish Veterinary Laboratory, 2 Hangøvej, DK-8200 Aarhus N, Denmark

In order to elucidate the rate of thermophilic Campylobacter spp. carriage in Danish broiler production and to identify risk factors for occurrence of campylobacter in broiler flocks, a total of 88 randomly selected broiler flocks were tested for campylobacter infection, and a subsequent study of risk factors based on a questionnaire was conducted. The sample material comprised cloacal swabs from live birds before slaughter, and neck skin samples from carcasses at the end of the processing line. A total of 52% of the flocks were found Campylobacter spp.-positive before slaughter. At the end of processing, 24% of the flocks were positive. The species distribution was 87% Campylobacter jejuni, 8% Campylobacter coli and 5% Campylobacter lari. The following parameters were identified as significant risk factors: lack of a hygiene barrier (odds ratio (OR) = 3.1, 1.1 < OR < 9.3), presence of animals in the vicinity of the broiler house on farms with a missing hygiene barrier (OR = 7.0, 1.6 < OR < 33.9), livestock other than chickens on farms with a missing hygiene barrier (OR = 7.6, 1.4 < OR < 44.9), dividing the flock into batches for staggered slaughter (OR = 6.8, 1.2 < OR < 49.3), a down period of less than 14 days (OR = 5.0, 1.2 < OR < 22.6), and feeding purchased wheat rather than home-grown wheat (OR = 3.1, 1.0 2 weeks) between successive flocks. A similar finding has been published previously (Berndtson et al., 1996). We believe that the empty period after clearing out the litter and sanitation should be at least long enough to allow the broiler house to dry thoroughly in order to secure death of all remaining campylobacters. In a study on campylobacter survival, the bacteria were found to survive on floors until the floor was visibly dry (Oosterom et al., 1983a). Furthermore, a recent investigation (Hazeleger et al., 1998) indicated that campylobacters are able to survive for some time in the environment due to chemotactic and aerotactic properties, i.e. they move to more favourable locations. It might be possible to find such niches in broiler houses. Water has been identified as an important source for campylobacter infection, both for broiler flocks (Kapperud et al., 1993; Pearson et al., 1993) and among humans (Hopkins et al., 1984; Kapperud et al., 1992; Adak et al., 1995). In contrast, we found no correlation between the risk for campylobacter infection and the water supply. This may be due to the nature of the water supply to the Danish farms; every poultry house in this study was supplied with groundwater for both drinking and cleaning purposes. In 62/72 (86%) farms, this supply was from a municipal waterworks and in 10/72 (14%) farms it was from a private well. We found no risk for campylobacter colonization associated with the use of a private well (OR = 0.6, 0.1 < OR < 2.9).

Campylobacter colonization of broiler flocks 129

We recorded significant differences in carriage rates between abattoirs in both live birds and processed broilers at the flock level. The highest carriage rate, 85% of the flocks, was noted among live birds on arrival at abattoir B (Table 2). This was ascribed to the fact that these flocks originated from an area where all flocks had been thinned by slaughter of a primary batch 1 week earlier, potentially introducing campylobacter in the flock before slaughter of the remaining birds. We also noted that the processing conditions in the abattoirs exerted a reductive effect on campylobacter carriage rates, although caution should be exercised when comparing results of different sample materials and sample size (15 cloacal swabs versus 10 neck skins). However, we found 46 flocks to be campylobacter-positive on arrival at the abattoir compared with only 21 flocks following processing. In particular, two abattoirs, A and C, were successful in reducing the carriage rates during processing. For example, abattoir A recorded 8% and abattoir C only 4% positive flocks after processing, compared with 44 and 36% positive flocks, respectively, on arrival at the abattoir. This indicates that the abattoir may play a significant role in reducing the contamination of broiler meat and broiler products. Similar observations have been reported by Oosterom (1983b), who found that spin-chilling and air cooling were effective in reducing campylobacter contamination of carcasses. The elucidation of the epidemiology of a microorganism with a ubiquitous ecology like Campylobacter spp. is intriguing, but extremely complicated. However, the number of routes of introduction into the broiler houses are limited, and biosecurity measures must focus on blocking these routes. The results from this study showed that hygiene barriers at the entrances were the single most important currently used biosecurity measure fairly effective in protecting broiler flocks from campylobacter infection. The results suggest that expanding hygiene barriers to include the gates and probably also enhancing the hygiene practices could further decrease the campylobacter carriage rate in broiler flocks. However, the results question the possibility of preventing Campylobacter spp. infection in freerange or organic broiler production by hygiene practices alone, due to the access to outdoor areas in these production systems. Acknowledgements We thank the staff at DANPO A/S abattoirs, the broiler farmers, and the AM-veterinarians for their courteous cooperation. Our staff, Annie Brandstrup, Lis Nielsen and Gitte Lauridsen, are also thanked for excellent technical assistance. We are grateful to Dr Flemming Bager of the Danish Zoonosis Centre for his dedicated and constructive criticism of the manuscript.

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´ RESUM E´ Campilobacter spp. thermophile dans la production de poulet de chair danois : Enquˆete et analyse r´etrospective des facteurs de risque relatifs a` leur apparition dans les troupeaux de poulets de chair Dans le but d’´etudier le taux de poulets danois porteurs de Campilobacter spp. thermophile dans la production du poulet de chair

et d’identifier les facteurs de risque relatifs a` l’apparition de campilobacter dans les troupeaux, 88 d’entre eux s´electionn´es au hasard ont e´ t´e test´es pour la d´etection de l’infection par des campilobacters et une e´ tude ult´erieure de l’analyse des facteurs de risque a e´ t´e entreprise et a e´ t´e bas´ee sur un questionnaire. Les e´ chantillons ont e´ t´e repr´esent´es par des e´ couvillons du cloaque a` partir d’oiseaux vivants avant l’abattage et par la peau du cou a` partir des carcasses en fin de chaˆõ ne. Avant l’abattage, Campilobacter spp. a e´ t´e trouv´e chez 52% des troupeaux. A la fin de la chaˆõ ne d’abattage 24% des troupeaux ont e´ t´e trouv´es positifs. La distribution des esp`eces a e´ t´e la suivante : Campilobacter jejuni 87%, C. coli 8% et C. lari 5%. Les param`etres suivants ont e´ t´e identifi´es comme des facteurs de risque significatifs : manque de barri`ere d’hygi`ene (OR = 3,1; 1,1 < OR < 9,3), pr´esence d’animaux dans l’´elevage et autour du bˆatiment h´ebergeant les poulets avec absence de barri`ere d’hygi`ene (OR = 7,0; 1,6 < OR < 33,9), pr´esence sur la ferme d’´elevage d’animaux de rente autres que les poulets avec absence de barri`ere hygi´enique (OR = 7,6; 1,4 < OR < 44,9), abattage des troupeaux en lots e´ chelonn´es (OR = 6,8; 1,2 < OR < 49,3), un vide sanitaire de moins de 14 jours (OR = 5,0; 1,2 < OR < 22,6), et en ce qui concerne l’aliment, achat de bl´e a` l’ext´erieur plutˆot que l’utilisation du bl´e de la ferme (OR = 3,1; 1,0 < OR < 9,9). La pr´esence d’une barri`ere hygi´enique a e´ t´e la mesure de bios´ecurit´e la plus importante pour la production de poulets de chair non porteurs de campilobacter.

ZUSAMMENFASSUNG Thermophile Campylobacter spp. in der da¨ nischen Broilerproduktion: eine Querschnittsubersicht ¨ und eine retrospektive Analyse von Risikofaktoren fur ¨ das Vorkommen in Broilerbesta¨ nden. ¨ Um die Ubertragungsrate von thermophilen Campylobacter spp. in der d¨anischen Broiler-Produktion aufzukl¨aren und Risikofaktoren f¨u r das Auftreten von Campylobacter in Broilerbest¨anden zu identifizieren, wurden 88 zuf¨allig ausgew¨ahlte Broiler-Herden auf CampylobacterInfektionen untersucht. Anschließend wurde eine Untersuchung der Risikofaktoren auf der Grundlage eines Fragebogens durchgef¨uhrt. Das Probenmaterial umfasste Kloakenabstriche von Tieren vor der Schlachtung und Halshautproben von Schlachtk¨orpern am Ende des Verarbeitungsbandes. Insgesamt 52% der Herden erwiesen sich vor der Schlachtung als Campylobacter spp.-positiv. Am Ende der Verarbeitung waren 24% der Herden positiv. Die Spezies-Verteilung war: Campylobacter jejuni 87%, C. coli 8% und C. lari 5%. Folgende Parameter wurden als wesentliche Risikofaktoren erkannt: Fehlen einer Hygiene-Barriere (OR=3,1, 1,1