Prevalence of and Risk Factors for Campylobacter spp. Colonization of Broiler Chicken Flocks in Greece

Abstract

The prevalence and risk factors for Campylobacter spp. colonization of broiler flocks and broiler carcass contamination in Greek slaughterhouses were investigated. Over a 14-month period, a pool of 10 ceca and 5 neck skin samples from chicken carcasses were collected from each of 142 batches of broiler flocks slaughtered in 3 different slaughterhouses. Information on potential risk factors for Campylobacter infection in broilers was collected by an on-farm interview and linked according to the Campylobacter contamination status of broiler flocks and differences in farm characteristics and management practices identified from questionnaires. Campylobacter spp. was isolated from 73.94% and 70.42% of ceca (95% CI 65.92–80.94) and carcasses (95% CI 62.19–77.78), respectively. A significant correlation (p < 0.001) between the presence of Campylobacter spp. in broiler ceca and contamination of carcasses was found, suggesting the spread of the microorganism on the skin of carcasses during the slaughtering procedure. A multiple logistic regression showed the disinfection of the poultry house being conducted by unskilled personnel (odds ratio [OR] ¼ = 3.983) as a significant risk factor (p < 0.05) and the use of straw litter as bedding material (OR ¼ = 0.170) and closure of windows during the intervals of production cycles (OR ¼ = 0.396) as significant protective factors (p < 0.05) for broiler flock contamination. These results are important and help further the understanding of the epidemiology of Campylobacter spp. derived from poultry in Greece.

Introduction

C ampylobacter spp. are of high importance to food safety and public health since they are identified as the most common cause of foodborne bacterial diarrhea in humans worldwide (Silva et al., 2011).

The prevalence of human campylobacteriosis has been progressively rising worldwide since the 1990s (WHO, 2011). In the European Union (EU), campylobacteriosis has been reported as the most common cause of human foodborne zoonoses since 2005 (EFSA, 2006; EFSA and ECDC, 2018). Campylobacter jejuni is the predominant species isolated from poultry samples, followed by Campylobacter coli, with other Campylobacter species such as Campylobacter lari being less detected (EFSA, 2010a). Moreover, C. jejuni is considered responsible for the majority of human campylobacteriosis, while C. coli and C. lari are less frequently implicated in human infections (Zhang and Sahin, 2013). In Greece, there has been a lack of information on Campylobacter prevalence and species distribution in broiler flocks (Natsos et al., 2016), as well as on human campylobacteriosis cases, and sufficient data on the epidemiology of the pathogen are not available since cases of campylobacteriosis are not monitored by the Mandatory Notification System in the European Union (EFSA and ECDC, 2018).

Different risk factors for Campylobacter infections are related to outbreak or sporadic cases (Hue et al., 2011). Untreated raw milk (Heuvelink et al., 2009) and contaminated water (Abe et al., 2008; Karagiannis et al., 2010) are mainly related to outbreaks, while the main risk factor for sporadic infection in humans is the consumption of poultry meat or exposure to food cross-contaminated by contact with raw poultry (Doorduyn et al., 2010; EFSA and ECDC, 2018). Thus, reduction of Campylobacter in broiler meat is the main focus of controlling campylobacteriosis (Hue et al., 2010). Until recently, broiler meat be tested for Campylobacter was not required by law; however, in 2017, the European Commission made an amendment to the standing regulation regarding Campylobacter in broiler carcasses (EU, 2017/1495), introducing the mandatory sampling of poultry carcasses for Campylobacter analysis at slaughterhouses on a regular basis.

Risk assessment of Campylobacter in poultry slaughterhouses is applied as a means to prevent human zoonotic diseases (Nauta et al., 2009) and therefore it is essential to ascertain the degree of contamination of raw poultry (Hue et al., 2011). Romero-Barrios et al. (2013) reported that a reduction of Campylobacter colonization in cecal contents of flocks by 2 log₁₀ or 3 log₁₀ CFU (colony-forming units) would decrease human campylobacteriosis cases attributable to broiler meat by at least 76% or 90%, respectively. Therefore, the most common approach to Campylobacter control is the decrease of prevalence and bacterial load within the flock and during the slaughterhouse process (Prachantasena et al., 2016). Extensive research efforts have been made to look for appropriate intervention methods, which can be broadly segregated into preharvest and postharvest interventions (Umaraw et al., 2017). Campylobacter control measures at the farm level may include biosecurity, vaccination, complete exclusion, bacteriophage therapy, food additives, probiotics, or novel antibacterial treatment of flocks (Newell et al., 2011; Zhang and Sahin, 2013), most of which are under development and not yet commercially available. Thus, the reduction of Campylobacter levels on carcasses after evisceration is the most effective intervention measure to control Campylobacter in broiler meat, rather than reducing the prevalence of positive broiler flocks (Nauta et al., 2009; Hermans et al., 2011).

Several risk factors can lead to introduction of Campylobacter into flocks, and once introduced into the flock, Campylobacter quickly spreads to all birds and large numbers are shed, leading to heavy contamination of the broiler house environment and equipment (Battersby et al., 2016). The possible sources and transmission routes of Campylobacter in poultry flocks have been well investigated, focusing on different parts of the production processes and practices. The main potential risk factors suggested include season (summer and/or autumn) (Ellis-Iversen et al., 2009), higher age of broilers at slaughter (Ansari-Lari et al., 2011), use of partial depopulation practice (Ellis-Iversen et al., 2009; EFSA, 2010b; Hansson et al., 2010; Lawes et al., 2012), distribution of drinking water (Nather et al., 2009) and its quality (Ellis-Iversen et al., 2009), presence of other animals in the surrounding area of the farm (Hansson et al., 2010) or in the same farm (Ellis-Iversen et al., 2009), and presence of rodents (McDowell et al., 2008; Sommer et al., 2013) and flies (Royden et al., 2016). In contrast, Campylobacter infection can be reduced by good hygiene practices by farmers or seldom or never thinning (Hansson et al., 2010). The most frequently reported risk factors associated with horizontal transmission of Campylobacter spp. to broiler flocks and broiler carcass contamination during the slaughtering process have been reviewed by Natsos et al. (2016).

In this article, we describe the study undertaken to (i) assess Campylobacter prevalence in broiler flocks and on broiler carcasses, along with the level of contamination by Campylobacter on broiler carcasses collected during the slaughtering process; and (ii) identify risk factors associated with the presence of Campylobacter spp. in broiler flocks and on chicken carcasses.

Materials and Methods

Experimental design

The study was performed in 3 european commission (EC)-approved Greek poultry slaughterhouses located in central Greece, each of which processes more than 5,000,000 chickens per year. Flocks were derived from 4 different Greek regional units (Arta, Attica, Boeotia, and Euboea) producing in total 50,000,000 chickens per year (45% of the total Greek chicken production). In total, 142 samples were collected, originating from 60 different poultry farms, of which 8 are situated in the regional unit of Arta, 9 in Attica, 20 in Boeotia, and 23 in Euboea. The sample size was set on the basis of an expected prevalence of 50% and a confidence interval of 95%, and the unit for statistical analysis was the slaughter batch defined as a group of chickens from the same flock, delivered at the same time to the same slaughterhouse.

Ten birds per batch were randomly selected during evisceration and their ceca were pooled into a sterile bag. Neck skin samples of five birds from the processing line after chilling were also taken using a clean pair of latex gloves and put into a sterile bag. Samples were sent in an insulated box containing ice packs to maintain a low temperature within 2–4 h to the Veterinary Laboratory of Chalkida where bacteriological analyses were performed the same day of sampling.

Sample analysis

Campylobacter spp. were recovered from cecal contents by direct isolation following the procedure described by Hue et al. (2011). For each positive plate, if present, up to five typical Campylobacter colonies were then subcultured onto plates of Columbia Blood Agar (Oxoid, Dardilly, France) for further characterization in accordance with the standard procedure of International Organization for Standardization (ISO) 10272-1 (ISO, 2006a). Speciation of Campylobacter strains was carried out following the protocol for polymerase chain reaction (PCR) amplification of C. jejuni and C. coli recommended by the EURL-AR (2nd version, November 2013). The flock was considered Campylobacter positive when at least one colony typical for Campylobacter yielded a positive result by the PCR procedure.

For recovery and detection of Campylobacter from the skin of carcasses, the procedures described in parts 1 and 2 of ISO 10272 (ISO, 2006a, b) and by Hue et al. (2011) were followed. For each positive plate, up to two colonies typical of Campylobacter were subcultured onto Columbia Blood Agar plates for further characterization and enumeration, according to the standard method of ISO 10272-1:2006.

Statistical analysis

Epi Info™ 7 software (CDC, Atlanta, GA) was used to calculate the prevalence of Campylobacter-positive batches of ceca and carcasses. If Campylobacter was detected and/or enumerated, a batch was considered positive, and for enumeration purposes, bacterial counts were log₁₀-transformed to obtain approximately normally distributed data.

Information on potential risk factors for Campylobacter infection in broilers was collected by an on-farm interview, with questions concerning the farm and house characteristics such as the environment around the farm and broiler houses, sanitary practice, control of wild birds and rodents, in-house environment (humidity, air quality, and temperature), design of the broiler houses, and on-farm management practices (Supplementary Data). Data concerning the structural and functional characteristics of slaughterhouses such as hygiene level along with data derived from the microbiology analysis were also statistically analyzed using the appropriate statistical methodology.

Univariate statistical analysis was carried out to identify the main trend, variability, and distribution of each individual variable, and bivariate analysis was performed to study relationships between independent variables and Campylobacter contamination of ceca and neck skin samples. Variables with more than 20% of missing data and those for which there was no variability were excluded from the analysis. Finally, a multiple logistic regression, including all the previously selected explanatory variables, was performed. A downward selection, using Epi Info 7 software, was performed, with variables introduced if p < 0.20 and excluded if p > 0.05.

Results

Prevalence

Overall prevalence of cecum-based Campylobacter-positive batches was 73.94% (number of infected/total examined samples). In the case of carcasses, 100 of 142 (70.42%) batches were positive for Campylobacter (Table 1). The presence of Campylobacter in broiler ceca was strongly correlated (p < 0.001) with contamination of carcasses of the same batch. In 20 batches (14.08%), Campylobacter was detected in ceca, but not on carcasses, while 17 batches (11.97%) were found to be Campylobacter positive based on carcasses, but negative based on ceca. Finally in 20 batches (14.08%), Campylobacter spp. were not detected either in ceca or in neck skin samples. The number of Campylobacter isolates recovered from carcasses ranged from 3.22 up to 5.96 log₁₀ CFU/g with a mean value of 4.639 ± 0.11 log₁₀ CFU/g (Table 2).

Table 1.

Prevalence of Campylobacter in Ceca and on Carcasses of Broiler Flocks (n = 142, Greece, 2015)

Samples	Positive batches/investigated batches	Prevalence (%)	± Standard deviation	95% Confidence interval
Ceca	105/142	73.94	44.05	65.92–80.94
Carcasses	100/142	70.42	45.80	62.19–77.78

Table 2.

Numbers of Campylobacter on Carcasses of Positive Batches of Broiler Flocks (n = 142, Greece, 2015)

Positive batches/investigated batches	Percentage of samples with positive results for enumeration purposes	Mean ^a (log₁₀ CFU/g)	Median (log₁₀ CFU/g)	± Standard deviation	95% Confidence interval
100/142 (70.42%)	99/100 (99%)	4.639	4.613	0.559	4.528–4.749

Italic values represent the prevalence of Campylobacter in the samples.

Includes only samples with positive results for enumeration purposes.

Selection of variables

Fifty-eight variables were selected by univariate analysis, which were further processed by bivariate analysis. Variables related to common management practices and characteristics of poultry farms were eliminated from further analysis (Table 3).

Table 3.

Common Management Practices and Characteristics of Poultry Farms Excluded from Statistical Analysis

Presence of quality assurance system	0%
Presence of watercourses close to the farm	4%
Use of different boots for each house	6%
Farms with houses of different age	8%
Presence of house divider	8%
One disinfection per production cycle	8.5%
Presence of communal anteroom	9%
Disposal of droppings performed by special agency	91%
Presence of effluent collection system	96.5%

Bivariate analysis of explanatory variables allowed the selection of variables most related to the presence of Campylobacter in broiler ceca (Table 4). Multivariate logistic regression was used to analyze further 15 variables significantly related to the presence of Campylobacter in ceca. None of the parameters related to slaughterhouse characteristics and slaughtering procedure, for example, type of chilling, time of slaughter, and temperature in the evisceration room, were found to be statistically significant.

Table 4.

Selected Variables (Threshold of 20%) Entered in the Multiple Logistic Model Used to Explain Campylobacter spp.-Positive Batches (n = 142)

Variable^a	Variable modality	Size	% Positive	p (χ² test)
Age of poultry house	<15 years	18	55.56	0.082
Age of poultry house	>15 years	124	76.61	0.082
Antibiotic treatment during life	Yes	47	65.96	0.156
Antibiotic treatment during life	No	95	77.89	0.156
Bathroom	Presence	89	79.78	0.049
Bathroom	Absence	53	64.15	0.049
Bedding material	Straw	109	68.81	0.012
Bedding material	Other^b	33	90.91	0.012
Closure of windows during the interruption of production cycles	Yes	60	81.67	0.084
	Maybe/no	82	68.29	0.084
Detergent	Presence	104	70.19	0.130
Detergent	Absence	38	84.21	0.130
Disinfectant	Presence	60	80.00	0.179
Disinfectant	Absence	82	69.51	0.179
Faucet	Presence	84	67.86	0.053
Faucet	Absence	58	82.76	0.053
Hygiene level	Very good	66	68.18	0.180
Hygiene level	Poor	76	78.95	0.180
Keeping of bedding material	In a protected and clean room	82	82.93	0.006
Keeping of bedding material	In an unprotected room	60	61.67	0.006
Number of disinfection treatments	Only one	12	100	0.036
Number of disinfection treatments	Two	130	71.54	0.036
Person who disinfects	Breeder/personnel	129	77.52	0.005
Person who disinfects	Special agency	13	38.46	0.005
Responsible for thinning	Breeder/personnel	105	70.48	0.131
Responsible for thinning	Specialists	37	83.78	0.131
Sink	Presence	86	67.44	0.032
Sink	Absence	56	83.93	0.032
Watering System	Bell drinkers	98	79.59	0.037
Watering System	Nipple drinkers	44	61.36	0.037

Values in bold are significantly different.

All variables are significantly related to the presence of Campylobacter in cecal samples (p < 0.20).

Sawdust, rice husk, or mixed up with straw litter.

The multivariate logistic regression analysis produced a model, which showed two parameters as protective factors and one parameter as a risk factor for contamination of broiler flocks (Table 5).

Table 5.

Risk and Protective Factors for Contamination of Broiler Flocks by Campylobacter spp. (n = 142)

Variable	Estimated parameters	Standard deviation	OR ¼	95% CI	p
Closure of windows during the interruption of production cycles
Yes	−0.925	0.444	0.396	0.166–0.947	0.067
No	—	—	—		—
Person who disinfects
Breeder/personnel	1.382	0.681	3.983	1.048–15.134	0.042
Special agency	—	—	—		—
Bedding material
Straw	−1.772	0.660	0.170	0.047–0.619	0.007
Other	—	—	—		—

OR, odds ratio.

Risk and protective factors

The risk of Campylobacter contamination decreased (odds ratio [OR] ¼ = 0.396) when windows were kept closed during the interruption of production cycles. In 82 batches derived from farms that follow closure of windows as a common practice, the contamination rate was 60%, whereas it was 82% in the 60 batches derived from farms where windows are kept open during the sanitary waiting period.

Batches derived from houses that had been disinfected by untrained farm staff seemed to have more chances to be positive for Campylobacter (OR ¼ = 3.983) in comparison with those coming from farms where disinfection was carried out by a special agency. Ceca from batches derived from farms where unskilled workers perform the disinfection had a relatively greater contamination rate (77.5%) than those coming from farms that hire skilled specialists to perform the programmed disinfection (38.4%).

The percentage of Campylobacter-positive batches was found to be lower (OR ¼ = 0.170) when straw was solely used as the bedding material. Ceca of broilers from farms that use only straw as the bedding material showed a lower contamination rate (68.8%) compared with those derived from farms where sawdust or rice husk was used as the bedding material (90.9%).

Discussion

The current cross-sectional study carried out in Greece generated representative data on broiler ceca (73.94%) and carcass skin samples (70.42%), indicating the high prevalence of Campylobacter at the national level. These results are in agreement with several studies both for ceca and carcasses (Allen et al., 2008; Hue et al., 2010, 2011; Lawes et al., 2012) and the EFSA scientific report for Campylobacter-positive batches (71.2%) and Campylobacter-contaminated carcasses (75.8%) in the EU member states (EFSA, 2010a).

A significant proportion of carcasses (12%) were positive for Campylobacter contamination, while ceca of the same batches were found to be Campylobacter negative. Rosenquist et al. (2006) and Figueroa et al. (2009) demonstrated that during the evisceration step, cross-contamination might be possible. Rupture of viscera from infected chickens may release high numbers of Campylobacter isolates that contaminate the surfaces of the slaughterhouse, explaining these results. A cross-contamination may also occur between batches from different flocks during the slaughterhouse process (Rivoal et al., 1999; Johannessen et al., 2007), and the level of contamination of noninfected chicken batches can be influenced by several factors such as the Campylobacter status of previously slaughtered batches, the amount of cross-contamination taking place, and the position of carcasses in subsequent negative batches (Hue et al., 2011). Therefore, the use of a logistic slaughtering schedule could help preserve Campylobacter-free batches, considering that the later in the day the batch is slaughtered, the higher the probability that it will be contaminated (Hue et al., 2010).

In recent years, quantitative risk assessment modeling is supported by a growing demand for quantitative data to describe the occurrence and dynamics of Campylobacter in the broiler meat chain (Uyttendaele et al., 2006; Nauta et al., 2009; Prachantasena et al., 2016). Researchers previously concluded that for enumeration of thermotolerant Campylobacter in chicken meat, direct spread plating on Modified Charcoal Cefoperazone Deoxycholate Agar (mCCDA) is an acceptable protocol and a reliable alternative to the most probable number method (Scherer et al., 2006; Rosenquist et al., 2007). Currently, mCCDA is the recommended medium by the ISO for enumeration of thermophilic Campylobacter in foods (ISO, 2006b), although alternative enrichment and plating combinations have been evaluated (Habib et al., 2011). In our study, the average concentration of Campylobacter recovered from carcasses was 4.639 ± 0.11 log₁₀ CFU/g, while the normal distribution of positive values leads to an average close to the median, clearly separating values into two halves. The result of our study has shown a much higher colonization rate of Campylobacter than the respective results of previously published data (Scherer et al., 2006; Hue et al., 2011). This finding could be attributed to a high degree of cecal contamination, to visceral rupture and subsequent release of large numbers of Campylobacter isolates on the carcass skin, or even to short processing times or inadequate slaughterhouse hygiene and cleaning conditions, which possibly promote the survival and spread of Campylobacter spp. during the slaughtering process.

Of the 206 identifications performed, two different species of Campylobacter were identified (C. jejuni and C. coli) and C. coli was found to be the predominant species. This result is in line with a previous study from Greece (Marinou et al., 2012), but contradictory to other studies showing C. jejuni as being much more frequently associated with poultry meat than C. coli (Pepe et al., 2009; Hue et al., 2011). However, according to the results of a baseline survey conducted by EFSA in 2008, seven EU member states reported C. coli as the predominant species isolated from ceca and carcasses (EFSA, 2010a). Moreover, the same survey showed that in southern member states, C. coli was more abundant, whereas C. jejuni was the only species identified in northern member states. Climatic conditions, environmental reservoirs, housing systems of broiler chickens, and age of slaughter differ significantly between northern and southern Europe and could partially explain the observed variance of species distribution (EFSA, 2010b).

The contamination of slaughtered batches by these species fluctuated according to the sample, with C. jejuni being more frequently identified on carcasses than in ceca (43% and 35.24%, respectively). Therefore, it is possible that C. jejuni is more resistant than C. coli to stress encountered during slaughtering (Hue et al., 2011). It has been shown that C. jejuni adheres more to inert surfaces than C. coli (Sulaeman et al., 2010), which may allow C. jejuni to have better biofilm formation capacity, especially under stressful environmental conditions (Reuter et al., 2010; Teh et al., 2014). Swelling of the skin during slaughter and processing allows the survival of Campylobacter on poultry carcasses (Chantarapanont et al., 2003).

Moreover, since only one well-isolated colony from a pure culture underwent PCR for species identification, any cocontamination with both Campylobacter species could not be detected. The simultaneous presence of the two species both in ceca and on carcass skin is common (Hue et al., 2011) and could explain the observed disagreement in 22 batches between the identified species in cecal content and neck skin samples. Biofilm formation might also be attributed to a short processing time or inadequate cleaning procedures in the slaughterhouse and should be further investigated.

In line with previous studies, the current results suggest that Campylobacter infection is a multifactorial problem and is caused by several potential sources. The closure of windows between production cycles seemed to decrease the chance of the poultry batch being infected by Campylobacter. This result could be probably attributed to prevention of the access of flies or other vectors into the house (Hald et al., 2008; Choo et al., 2011). Royden et al. (2016) demonstrated that flies may play a role in the transmission of Campylobacter to broilers, and due to the large number of flies around broiler house ventilation inlets, the risk of transmission is high. It seems that keeping windows firmly closed during the downtime prevents the introduction of Campylobacter into the farm by not letting the potential vectors enter the farm.

The results of our study suggest that disinfection of the house plays an important role on the Campylobacter status of the poultry batch as when it was performed by unskilled personnel the chances for the batch to be positive were substantially higher compared with when it was undertaken by a special agency. These findings suggest that insufficient disinfection of the farm leads to increased contamination rates. It is clear that effective cleaning and disinfection of broiler houses and their surroundings can decrease the risk of Campylobacter transmission between subsequent flocks (Battersby et al., 2017). Overall, the absence of sanitizing procedures can be considered an important risk factor for Campylobacter spp. contamination (Bouwknegt et al., 2004; McDowell et al., 2008; Newell et al., 2011), and even with the use of most efficient biosecurity programs, this pathogen may enter the facilities and colonize the birds (van de Giessen et al., 1998). Several disinfection programs have been tested and evaluated for their effects on the environmental Campylobacter contamination (Battersby et al., 2017; Castro Burbarelli et al., 2017) and it is suggested that these cleaning practices should be routinely tested on all broiler farms to determine their effectiveness in reducing exposure of poultry and humans to the pathogen.

The material used as bedding material seemed to affect the contamination status of the flock. In particular, the sole use of straw as a bedding material reduced Campylobacter contamination, compared with the use of other materials, such as sawdust, rice husk, or mixtures of these bedding materials. Different bedding materials (straw and wood shavings) have been compared on how they affect the total aerobic bacterial counts and it was found that less contamination was detected in wood shavings than straw (Fries et al., 2005). Wood can exhibit strong antibacterial characteristics due to a combination of hygroscopic properties of wood and the effects of wood extracts (Milling et al., 2005). Other studies have found that such essential oils have antioxidant activity by scavenging free radicals and have shown antimicrobial activity against a range of foodborne organisms (Zeng et al., 2012), including Campylobacter (Kurekci et al., 2013). However, the findings of our study suggest that straw litter protects from Campylobacter contamination and maybe this is due to the fact that wheat straw contains less moisture than rice husk and wood shavings (Monira et al., 2003). The higher water content in the bedding material may protect Campylobacter from the effects of desiccation, thus enhancing its survival (Smith et al., 2016). Although, environmental challenges linked to the disposal of bedding material impose the litter reuse in some countries, a practice that may have an impact on key food safety pathogens such as Campylobacter, a survey conducted by Chinivasagam et al. (2016) found no direct influence between reuse of litter and either the timing of emergence or the levels of Campylobacter concentration across sequential farming cycles.

In conclusion, the cross-sectional study carried out in Greece produced valuable results concerning the prevalence of Campylobacter spp. in poultry production countrywide. A high prevalence of Campylobacter spp. in broiler flocks and on carcasses was found, along with a remarkably high load on broiler chicken carcasses, while the predominance of C. coli was noted both in ceca and on carcasses. The analysis of potential risk factors proposed that closure of windows during the downtime and the use of straw as the bedding material act as protective factors, whereas disinfection of the poultry house performed by unskilled personnel acts as a risk factor for contamination of the flock with Campylobacter. The results help in understanding the epidemiology of Campylobacter spp. derived from poultry in Greece and indicate the need for further investigation.

Footnotes

Acknowledgment

The authors would like to thank the Ministry of Rural Development and Foods, National Reference Laboratory of Salmonella and Antimicrobial Resistance of Chalkida, for its contribution in isolation, detection, enumeration, and PCR speciation of Campylobacter spp. in ceca and poultry carcasses.

Disclosure Statement

No competing financial interests exist.

Funding Information

The project “Campylobacter spp. in the broiler food chain: Measuring and monitoring the risk for public health” is granted by the “General Secretariat of Research and Technology”—Ministry of Education and Religious Affairs—under the “Bilateral Cooperation R&T Program between Greece and France.”

Supplementary Material

Supplementary Data

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