Beta-Glucans: A Crucial Weapon to Modulate Poultry Immune System

Introduction
With continuous increase in the economic value of the poultry industry, a deeper understanding of the nature and functioning of the avian immune system is important. The immune system enables the body to mount a defense against foreign organisms and antigens. However, the chicks’ immune system is underdeveloped and immature immediately after hatching, rendering them highly vulnerable to infectious threats present in the environment. The nutritionally balanced feeding program along with antibiotic growth promoters (AGPs’) in poultry diets played a significant role in achieving faster production success. Nevertheless, faster growth is likely to have a negative impact on the immune system due to decreased tolerance towards infectious diseases, thereby increasing the incidence of early chick mortality. In addition, the indiscriminate long-term usage of antibiotic growth promoters created a threat of bacterial resistance with major impacts on the future efficacy of these essential drugs. Consequently, due to the emergence of poultry welfare and environment protection concerns several countries have banned or reduced the prophylactic use of antibiotics as feed additives. This reduced the use of antibiotics in poultry production system, increased the demand for finding of alternate feed compounds along with a nutritious diet that can enhance gut health and immune function.
To address this need, a wide range of products are available in the market today which can help to modulate the innate immune system. One innovative approach that has been thoroughly studied is the use of beta-glucans in poultry diets. Although reports concerning the significance of beta-glucans in poultry are gaining popularity, still there seems to be some confusion in the poultry producers’ mind as to which source is better, how much is needed to improve immunity and what price is fair. The aim of this review was to give guidance on the major types of beta-glucans, their functional properties, and the option in choosing the best source with the potential to modulate the immune response in birds.
Sources and Structure of Beta-glucans
Beta-glucans are naturally occurring polysaccharides found in the cell walls of bacteria, fungi, yeast, algae, and cereals (such as barley, oats, and rye). However, the structure of beta-glucans varies among the different sources and considers the variations in their physiological role as shown in Figure 1. Beta-glucans consist of beta-D-glucose molecules linked by (1,3) or (1,4)-glycosidic bonds. Glucan obtained from bacteria and algae shows a 

linear structure, whereas, beta-glucan extracted from yeast, mushrooms, oats, and barley exhibits branched structure. Fungal beta-glucans have short branches, while they are long in yeast. The beta-glucans are not branched in barley, as with most cereal grains, but linked with twisted linear beta-(1,4) and beta-(1,3) glycosidic bonds.

Mechanism of Action and Functionality of Beta-glucans
The immunomodulatory ability of Beta-glucans has received increasing attention as one of the potential alternatives to AGPs without adversely affecting the bird performance. Beta-glucans belong to a group of physiologically active compounds termed biological response modifiers, because of their ability to stimulate the immune system. Beta-glucans such as algal beta-glucans are not naturally present within animal cells. When animals are supplemented with beta-glucan, it enters the small intestine and pass through the Peyer’s Patches in the gut-associated lymphoid tissue (GALT). Their immune cells (Phagocytes) recognize the beta-glucan molecules as a pathogen-associated molecular patterns (PAMPs) through a specific set of receptors called pathogen recognition receptors (PRRs). The PRRs such as Toll-like receptors (TLRs) and Dectin-1 present on the surface of phagocytes, including macrophages, heterophils, dendritic cells and natural killer cells primarily facilitate the activation of innate immune system through a cascade of signaling pathways resulting in enhanced phagocytosis of foreign pathogens (Figure 2).

Furthermore, beta-glucans have demonstrated the ability to augment the secretion of several cytokines and have antitumor, antibacterial and antiviral effects. A reported significant increase in both Newcastle Disease (ND) and Infectious Bronchitis (IBV) specific antibody titers in birds supplemented with beta-glucan was also observed. An increase in the size of primary and secondary lymphoid organs had shown with dietary beta-glucan supplementation, providing further evidence of their immunomodulating capabilities. As a result, beta-(1,3)-glucan can improve the resistance to infections by enhancing: (i) non-specific immunity that can protect animals from infection, (ii) host defense mechanism, and (iii) growth rate and mortality reduction. Thus, beta-glucan may be used as a replacement for dietary antibiotics in animal feed in combination with one or two other AGP alternatives.
Most Proficient Beta-glucan for Poultry
A wide structural variation in the functional properties of beta-glucans is directly related to their origin/source, which may influence their efficacy in modulating the immune systems. Before the beta-glucans can be incorporated in poultry diets, one must first understand the function and effectiveness of different beta-glucans on the avian immune system and the similarities and differences with the mammalian system. The features and differences between beta-glucans from yeast, oat & barley, and algae were further described below.
It is generally accepted that beta-(1,3)-(1,6)-glucans derived from yeast and fungi are considered the most effective source in terms of stimulating the immune system due to their highly complex branched structure. Numerous investigators have widely studied the effects of yeast cell wall beta-glucans on broiler performance as an immune modulator against infectious agents compared with antibiotic growth promoters. Whereas, the immune-modulating effect of beta-(1,3)-(1,6)-glucan from yeast depends on its native molecular structure, which is immersed in the other cell wall components of yeast beta-glucans and must be released in its intact form by an appropriate isolation technique. However, the extraction techniques developed by various manufacturers are laborious and result in a large amount of variability and inconsistency in the final products. Thus, the beta-glucans isolated from Saccharomyces cerevisiae (baker’s yeast) achieve an optimized yield of only 5–7 % dry weight due to a complicated process of chemical degradation of glucans. In the same way, the low molecular weight (around 190-200 kDa) and degree of polymerization (1500) of beta-(1,3)-(1,6)-glucan from yeast imparts less binding affinity and is responsible for minimal or no biological activity.
Whereas, cereal beta-glucans, such as oat and barley fall short as immune regulators, because they are structurally distinct than those of fungal and yeast beta-glucans and are not recognized as PAMP by the immune system of animals. The researchers also concluded that chicks fed with barley beta-glucans in the corn-based diet result in poor chick performance due to the increase in viscosity of the intestinal contents. This adversely affects the nutrient digestion, absorption, and composition of microflora in the gut by altering the intestinal morphology, decreasing endogenous enzyme production, and increasing susceptibility to disease. Various studies acknowledged mixed performance and immune response discrepancies in the published results with yeast-derived beta-glucans. Similarly, based on the comprehensive analysis of various studies, the content of beta-glucan from different sources, which gave a clear idea of the concentration of this valuable ingredient is shown in Table 1.

The numerous inconsistencies and varying results with fungal and yeast cell wall, and cereals derived beta-glucan opens the way for research expertise to assess the efficacy of alternative beta-glucan sources in achieving consistent results. Recently, another source of beta-glucans that has gained increasing attention by industry manufacturers is paramylon, an algal beta-glucan from the microalgae Euglena gracilis. In contrast to yeast, this algae has a high concentration of beta-(1,3)-glycosidic linkages and does not contain branches of beta-1,6 branches that are typical of yeast beta-glucan products. In contrast to yeast, the algae beta-(1,3)-glucan (Paramylon) has a high molecular weight (larger than 500 kDa) and is responsible for high biological activity along with greater binding affinity. Hence, this linear high molecular weight beta-(1,3)-glucan, when cultivated under optimal conditions, accumulates more than 90% of the cell mass as paramylon, and it does not require any expensive extraction methods like that of yeast beta glucans. Similarly, the linear structure and small particle size (1-3 microns) of algal beta-(1,3)-glucan interact directly with immune cells, while the branched structure and other cell material from yeast cell wall beta-(1,3)-(1,6)-glucan clump together. Another major factor that has traditionally generated more research interest is the higher bioavailability and ease in production of the algal beta-glucans when compared to branched beta-glucans. Since the branched beta-(1,3)-(1,6)-glucan in yeast is bound to other components of the cell wall, such as chitin and mannoprotein, and not available to be taken up by gut-associated lymphoid tissues such as Peyer’s patches. In addition, the beta-glucan product produced from the algae was more consistent and cost effective as it exists as granules within the algal cell and does not require to be extracted due to the lack of a thick cell wall.
Conclusion
It is concluded that all the beta-glucans are built from the same building block of polysaccharides, but the activity of different beta-glucan ingredients depends first and foremost on the source organism from which the compound is isolated, ultimately on the method of isolation and structure of beta-glucans.Though the beta-(1,3)-(1,6)-glucan from baker’s yeast is found to have some immune modulation action, it has its own deficiencies in terms of poor bioavailability, poor recognition by the immune cells, and broader dose range. With the more knowledge on the efficacy of beta-(1,3)-glucan in modulating immunity, the algal beta-glucan is in use these days with high promising results. The algae Euglena gracilis can accumulate extremely at high concentrations of beta-(1,3)-glucan paramylon intracellularly, it offers the function of immune modulation at a more economical cost and represents as one of the efficient AGP alternative products for usage in the poultry industry.

Antibiotics Details with their Withdrawal Time Period

Salt	Description	Mode of Action	Withdrawal Time
Avilamycin	Avilamycin is an orthosomycin antibiotic complex produced by the fermentation of Streptomyces viridochromogenes. Avilamycin is primarily active against gram-positive bacteria.	Avilamycin inhibits protein synthesis. It is thought to bind to 50S ribosomal subunit. It prevents the association of IF2 which inhibits the formation of the mature 70S initiation complex and the correct positioning of the tRNA in the aminoacyl site.	NIL
Bacitracin (ZB, BMD)	Bacitracin is a mixture of related cyclic peptides produced by organisms of the licheniformis group of Bacillus subtilis var Tracy, These peptides disrupt Gram-positive bacteria by interfering with cell wall and peptidoglycan synthesis.	Bacitracin interferes with the dephosphorylation of C55-isoprenyl pyrophosphate, also known as bactoprenol, a membrane carrier molecule that transports the building-blocks of the peptidoglycan bacterial cell wall outside of the inner membrane	It does not absorb in the intestine. So, it has no WHP
Chlortetracycline	Chlortetracycline belong to one of the important classes of broad-spectrum antibiotics. Two of the more common semisynthetic tetracyclines that have been marketed for decades are doxycycline and minocycline. The tetracyclines inhibit bacterial growth by inhibiting bacterial protein synthesis by preventing the association of aminoacyl-tRNA with bacterial ribosomes	Chlortetracycline, like other tetracyclines, competes for the A site of the bacterial ribosome. This binding competes with tRNA carrying amino acids preventing the addition of more amino acids to the peptide chain. This inhibition of protein synthesis ultimately inhibits growth and reproduction of the bacterial cell as necessary proteins cannot be synthesized.	It has withdrawal time of 1-5 days
Colistin Sulphate	Colistin, also known as polymyxin E, is an antibiotic produced by certain strains of the bacteria Paenibacillus polymyxa. Colistin is a mixture of the cyclic polypeptides colistin A and B and belongs to the class of polypeptide antibiotics known as polymyxins. Colistin is effective against most Gram-negative bacilli.	Colistin is a polycationic peptide and has both hydrophilic and lipophilic moieties. These cationic regions interact with the bacterial outer membrane, by displacing magnesium and calcium bacterial counter ions in the lipopolysaccharide. Hydrophobic/hydrophilic regions interact with the cytoplasmic membrane just like a detergent, solubilizing the membrane in an aqueous environment. This effect is bactericidal even in an isosmolar environment.	7 Days
Enramycin	Enramycin or Enduracidin is a polypeptide antibiotic produced by Streptomyces fungicidus. Enramycin is widely used as a feed additive for pigs and chickens to prevent necrotic enteritis induced by Gram-positive gut pathogens. It improves weight gain and feed conversion	Enramycin acts as an inhibitor of the enzyme, MurG, which is essential for cell wall biosynthesis in Gram-positive bacteria. MurG catalyzes the transglycosylation reaction in the last step of peptidoglycan biosynthesis. Inhibiting this step greatly compromises cell wall integrity leading to cell lysis.	7 days
Flavomycin	Bambermycin (flavomycin) is a complex of antibiotics obtained from Streptomyces bambergiensis and Streptomyces ghanaensis used as a food additive for poultry. Bambermycin is predominately effective against Gram-positivepathogenic bacteria	Flavomycin inhibits the transglycosylation step of peptidoglycan biosynthesis, a structural component of the bacterial cell wall. This causes accumulation of cell wall intermediates, and leads to lysis and cell death.	Nil
Lincomycin	Lincomycin is a lincosamide antibiotic that comes from the actinomycete Streptomyces lincolnensis. Lincomycin is a narrow spectrum antibiotic with activity against Gram-positive and cell wall-less bacteria including pathogenic species of Streptococcus, Staphylococcus, and Mycoplasma	Lincomycin inhibits protein synthesis in susceptible bacteria by binding to the 50 S subunits of bacterial ribosomes and preventing peptide bond formation upon transcription.	Nil
Neomycin	A component of neomycin that is produced by Streptomyces fradiae. On hydrolysis it yields neamine and neobiosamine B.	Neomycin is a bactericidal aminoglycoside antibiotic that binds to the 30S ribosome of susceptible organisms. Binding interferes with mRNA binding and acceptor tRNA sites and results in the production of non-functional or toxic peptides.	Nil
Nosiheptide	Nosiheptide is a sulfur-containing cyclic polypeptide, is highly active against Gram-positive bacteria and few Gram-negative bacteria, especially Clostridium Perfringens, Staphylococcus Aureus. Nosiheptide acts bacteriostatically in low dose and bactericidally in high dose.	Nosiheptide inhibits bacterial protein synthesis by inhibiting function of elongation factors Tu and G and greatly reduce the synthesis of guanosine penta- and tetraphosphates in response to stringent factor.	7 Days
Tylosin	Tylosin is an antibiotic and a bacteriostatic feed additive used in veterinary medicine. It has a broad spectrum of activity against Gram-positive organisms and a limited range of Gram-negative organisms.	Tylosin has a bacteriostatic effect on susceptible organisms, caused by inhibition of protein synthesis through binding to the 50S subunit of the bacterial ribosome.	5 Days
Tiamulin Hydrogen Fumarate	Tiamulln is a semi-synthetic derivative of pleuromutilin. It is the only member of the pleuromutili ln class of the diterpenic antibiotics which is approved for use at mts time. It is typically available for oral use as the Tiamulin base or the hydrogen fumarate salt. In some references Tiamulln is considered with the macrolide group of antibiotics.	Tiamulin affects bacterial protein synthesis. It has a strong affinity for the 50S ribosomal sub-unit resulting in breakdown in the peptide chain immediately following initiation.	3 Days
Virginiamycin	Virginiamycin is a streptogramin antibiotic similar to pristinamycin and quinupristin/dalfopristin. It is a combination of pristinamycin IIA(Virginiamycin M1) and Virginiamycin S1.	virginiamycin M blocks the elongation of polypeptide chains by inhibiting both the binding of aminoacyl-tRNA to ribosomes directed by elongation factor Tu (EF-Tu) and the peptidyl transferase reaction.	Nil

Manage somatic cell count and aflatoxins for milk quality

Author: Elliot Block, Ph.D., Research Fellow and Director of Research Arm & Hammer Animal and Food Production

by: CAST PHARMA

Regardless of your milk volume goals, producing high quality milk is your ultimate mission as a dairy producer. Somatic cell count (SCC) and protein content affect dairy product flavour, shelf life and cheese yield. And it’s mandatory to keep contaminants such as aflatoxins out of milk to meet regulatory standards, market expectations and consumer trust.

Many factors affect milk quality, including weather, hygiene, animal genetics and product handling. Diet often plays a critical role as well. Deficiencies in energy or essential nutrients can hamper cows’ resistance to mastitis pathogens. Maintaining the cow’s immune system can help her ward off bacterial challenges that cause high SCC.

RFCs support the immune system

One management solution to consider for bolstering immunity is feeding Celmanax to your lactating cows. The Refined Functional Carbohydrates (RFCs) in Celmanax support the immune system to help cows become more resilient against environmental challenges, including bacteria that impact milk quality. RFCs also optimise digestion and mitigate aflatoxins that can carry over in milk when cows eat contaminated feedstuffs.

Somatic cell count reduction

Research shows how improved immunity translates into higher milk quality. In three separate studies (Study 1, Study 2, Study 3), cows fed RFCs had numerically lower SCCs compared with control groups without the feed additive (Figure 1).

Figure 1 – Celmanax effect on SCC (x 1,000 CELLS/ML).

Preventing aflatoxins in milk

Another milk quality concern is potential carryover of aflatoxin in milk, caused by Aspergillus flavus fungus and related species of moulds in feed. Although many types of mycotoxins occur commonly in feed, a specific concern for dairy feed is aflatoxin B1, which converts to the metabolite aflatoxin M1 during digestion. Aflatoxin M1 can then transfer to the cow’s milk. At high levels, aflatoxin M1 is toxic to humans and animals.

It’s important to know that thresholds limits for aflatoxin M1 in milk vary from country to country. For example, in Europe the maximum aflatoxin M1 content allowed in milk is 50 parts per trillion (ppt), while the US maximum is 500 ppt. Milk with levels exceeding this amount must be discarded. If your lactating cows eat feed containing aflatoxins at 20 parts per billion (ppb) or greater, realise that their milk may exceed the tolerance levels for aflatoxins in milk1.

Mycotoxin contamination

Regardless of the tolerance levels in your region, it’s important to consider the risk of aflatoxin contamination. The levels of feed contamination vary from year to year based on growing conditions, but mycotoxins are almost always present. A 10-year study2 of mycotoxins in feed, involving 72,821 samples from 100 countries, found that mycotoxin contamination is the rule rather than the exception.

In research at 2 dairy production sites affected by alflatoxins, feeding RFCs helped mitigate aflatoxins carried over in milk. Cows in the study consumed feed contaminated with about 10 ppb of alfatoxin B1. As a result, a significant number of them secreted aflatoxin M1 in their milk – more than 40% of the herd at one of the sites.

Figure 2 – Celmanax mitigation of aflatoxin M1 in milk.

The study showed that supplementing rations with RFCs effectively blocked the transfer of aflatoxin M13 to the milk of cows fed the contaminated feed. Within 3 to 7 days of starting on the feed additive, the cows in the study no longer secreted aflatoxin M1 into milk (Figure 2).

RFCs work in synergy to help cows overcome multiple environmental stressors to maintain health and productivity – as well as milk quality.

5 principles to consider when designing biosecurity programmes

Biosecurity is the foundation for all disease prevention programs and all the more important in antibiotic reduction scenarios. It includes the combination of all measures taken to reduce the risk of introduction and spread of diseases and is based on the prevention of and protection against infectious agents. Its fundament is the knowledge of disease transmission processes.

 

Although biosecurity is considered the cheapest and most effective intervention in antibiotic reduction programmes, compliance is often low and difficult. 

The application of consistently high standards of biosecurity can substantially contribute to the reduction of antimicrobial resistance, not only by preventing the introduction of resistance genes into the farm but also by lowering the need to use antimicrobials.

LOWER USE OF ANTIMICROBIALS WITH HIGHER BIOSECURITY

Studies and assessments such as those done by (Laanen, et al., 2013), (Gelaude, et al., 2014), (Postma, et al., 2016), (Collineau, et al., 2017) and (Collineau, et al., 2017a) relate a high farm biosecurity or improvements in biosecurity with lower antimicrobial use. Laanen, Postma, and Collineau studied the profile of swine farmers in different European countries, finding a relation between a high level of internal biosecurity, efficient control of infectious diseases, and a reduced need for antimicrobials.

Others such as Gelaude and Collineau studied the effect of interventions. The former examined Belgian broiler farms, finding a reduction of antimicrobial use by almost 30% when biosecurity and other farm issues were improved within a year. The latter studied swine farms located in Belgium, France, Germany and Sweden, in which antimicrobial use was also reduced in 47% across all farms and observed that farms with the higher biosecurity compliance and who also took a holistic approach, making other changes (e.g. management and nutrition), achieved a higher reduction in antimicrobial use.

BIOSECURITY INTERVENTIONS PAY OFF

Of course, the interventions necessary to achieve an increased level of biosecurity carry some costs. However, the interventions, especially if taken with other measures such as improved management of new-born animals and nutritional improvements, also improve productivity. The same studies which report that biosecurity improvements decrease antimicrobial use also report an improvement in animal performance. In the case of broilers, Laanen (2013) found a reduction of 0.5 percentual points in mortality and one point in FCR; and Collineau (2017) obtained an improvement during both the pre-weaning and the fattening period of 0.7 and 0.9 percentual points, respectively.

IMPLEMENTATION, APPLICATION AND EXECUTION

Although biosecurity is considered the cheapest and most effective intervention in antibiotic reduction programmes, compliance is often low and difficult. The implementation, application, and execution of any biosecurity programme involve adopting a set of attitudes and behaviours to reduce the risk of entrance and spread of disease in all activities involving animal production or animal care. Measures should not be constraints but part of a process aimed at improving the health of animals and people, and a piece of the holistic approach to reduce antibiotics and improve performance.

DESIGNING EFFECTIVE BIOSECURITY PROGRAMMES: CONSIDER THESE 5 PRINCIPLES

When designing or evaluating biosecurity programmes, we can identify 5 principles that need to be applied. These principles set the ground for considering and evaluating biosecurity interventions:

1. Separation: Know your enemy, but don’t keep it close

It is vital to have a good separation between high and low-risk animals or areas on the farm, as well as dirty (general traffic) and clean (internal movements) areas on the farm. This avoids not only the entrance but the spread of disease, as possible sources of infection (e.g. wild birds) cannot reach the sensitive population.

2. Reduction: Weaken your enemy, so it doesn’t spread

The goal of the biosecurity measures is to keep infection pressure beneath the level which allows the natural immunity of the animals to cope with the infections, lowering the pressure of infection e.g. by an effective cleaning and disinfection programme, by the reduction of the stocking density, and by changing footwear when entering a production house.

3. Focus: Hunt the elephant in the room, shoo the butterflies

In each production unit, some pathogens can be identified as of high economic importance. For each of these, it is necessary to understand the likely routes of introduction into a farm and how it can spread within it. Taking into account that not all disease transmission routes are equally important, the design of the biosecurity programme should focus first on high-risk transmission routes, and only subsequently on the lower-risk transmission routes.

4. Repetition: Increasing the probability of infection

In addition to the probability of pathogen transmission via the different transmission routes, the frequency of occurrence of the transmission route is also highly significant when evaluating a risk (Alarcon, et al., 2013). When designing biosecurity programmes, risky actions such as veterinary visits, if repeated regularly must be considered with a higher risk.

5. Scaling: In the multitude, it is easy to disguise

The risks related to disease introduction and spread are much more important in big; more animals may be infected and maintain the infection cycle, also large flocks/herds increase the infection pressure and increase the risk by contact with external elements such as feed, visitors, etc.

CAN WE STILL IMPROVE OUR BIOSECURITY?

Almost 100% of poultry and swine operations already have a nominal biosecurity programme, but not in all cases is it effective or completely effective. BioCheck UGent, a standardised biosecurity questionnaire applied worldwide, shows an average of 65% and 68% of conformity, from more than 1000 broiler and 2000 swine farms between respectively; opportunities to improve can be found in farms globally, and they pay off.

THE BOTTOM LINE

Biosecurity is necessary for disease prevention in any profitable animal production system. To make effective plans, these 5 principles should be applied to choose the right interventions that prevent the entrance and spread of disease. However, maintaining a successful production unit requires a holistic approach in which other aspects of biosecurity need to also be taken seriously, as well as actions to improve in other areas such as management, health and nutrition.

Chicken and Eggs are best for health during COVID19

Foodborne diseases of poultry and related problems

Published on: 9/18/2019

Author/s : Hafez Mohamed Hafez 1 and Hosny El-Adawy 2,3. / 1 Institute of Poultry Diseases, Free University Berlin, Germany; 2 Friedrich-Loeffler-Institut, Institute of Bacterial Infections and Zoonoses, Jena, Germany; 3 Faculty of Veterinary Medicine, Kafrelsheikh University, Kafr El-Sheikh, Egypt.

Summary

In spite of significant improvement in technology and hygienic practices in developed countries at all stages of poultry production accompanied with advanced improvement in public sanitation foodborne diseases remain a persistent threat to human and animal health. Besides the current legislations, the main strategy to control microbial foodborne hazards should include Good Animal Husbandry Practices (GAHPs) at the farm level through sound hygienic measures, which should be applied to poultry houses and environment and the feed. In addition, reducing colonization by using feed additives, competitive exclusion treatment or vaccines is a possibility during transport and slaughtering. In all cases, agent surveillance and monitoring programmes must be adapted and followed strictly in aim to allow early intervention. In addition, the development of antibiotic resistant bacteria will also be a continuous public health hazard

The present paper describes the general the main strategy to control foodborne infections in poultry, with special attention to European legislations toward safe poultry meat.

Introduction

In spite of significant improvements in technology and hygienic practices at all stages of poultry production in developed countries, accompanied by advanced improvement in public sanitation, foodborne diseases remain a persistent threat to human and animal health. Foodborne diseases are still big issues of major concern in those countries. In developing countries, the need to produce sufficient food to meet the requirements of population increases, accompanied by bad economic situations often overshadow the need to ensure safe food products. Regardless of this fact, safe food is a fundamental requirement for all consumers, rich or poor. Food safety is not a discovery of recent times; it is a natural basic instinct of human survival. During human evolution, several approaches were adopted to achieve safety of food. One of the most famous approaches was practiced by several kings which would employ official and well trusted "tasters" that served as food safety sentinels for the kings and royal family members. Food safety and quality of food are currently big issues of major concern.

Many reports during recent years have shown that Salmonella and Campylobacter spp. are the most common causes of human foodborne bacterial diseases linked to poultry. In some areas also verotoxin producing Escherichia coli 0157:H7 (VTEC), Listeria and Yersinia have surfaced as additional foodborne pathogens causing human illness. Several other toxicogenic bacterial pathogens, such as Staphylococcus aureus, Clostridium perfringens, Clostridium botulinum and Bacillus cereus can also enter the human food chain via contaminated poultry carcasses. In addition, the development of antibiotic resistance in bacteria, which are common in both animals and humans, such as Methicillin Resistant Staphylococcus aureus (MRSA) and Extended-spectrum beta-lactamase (ESBL) bacteria, are also an emerging public health hazard.

Salmonella infection

Salmonella infections in poultry are distributed worldwide and result in severe economic losses when no effort is made to control them. In poultry, the genus Salmonella of the family Enterobacteriaceae, which include more than 2500 serovars, can roughly be classified into three categories or groups as follow: Salmonella can also be divided into three groups based on their host specificity and invasiveness [1]. Invasive salmonellas have the capability to “invade” the body from the intestinal lumen and thus infect organs, causing more serious disease. Group 1 contains serovars, which are highly host adapted and invasive. Examples are S. Gallinarum and S. Pullorum in poultry or S. Typhi in humans. Group 2 contains non-host adapted and invasive serovars. Salmonella in this group are of most concern regarding public health, since some of them are capable to infect humans and food producing animals and especially poultry can serve as reservoirs. There are approximately 10 – 20 serovars in this group. Currently, the most relevant serovars of them are S. Typhimurium, S. Enteritidis, S. Heidelberg, S. Hadar as well as S. Arizonae. Group 3 contains non-host adapted and non-invasive serovars, which are harmless for animals and humans. Most serovars of the genus salmonella belong to this group. Some serovars may be predominant for a number of years in a region or country. Then, they disappear and replaced by another serovars [2]. The infection can be transmitted vertically through contaminated eggs laid by infected carriers as well as horizontally spread (lateral). Hatcheries are one of the major sources of early horizontal transmission. Horizontal spread of Salmonella occurring during the hatching was shown in chickens, when contaminated and Salmonella-free eggs were incubated together. Salmonella can also spread through the hatchery by means of contamination of ventilation ducting, belt slots or door seals within hatchers, but may also result from infection and contamination that continuously recycles between hatchers, hatched birds, dust and crate washing equipment. During rearing the infection is transmitted horizontally (laterally) by direct contact between infected and uninfected flocks, and by indirect contact with contaminated environments through ingestion or inhalation of Salmonella organisms. Subsequently, there are many possibilities for lateral spread of the organisms through live and dead vectors. Transmission frequently occurs via faecal contamination of feed, water, equipment, environment and dust in which Salmonella can survive for long periods. Failure to clean and disinfect properly after an infected flock has left the site can result in infection of the next batch of birds. Significant reservoirs for Salmonella are man, farm animals, pigeons, waterfowl and wild birds. Rodents, pet’s insects and litter beetles (Alphitobius diaperinus) are also potential reservoirs and transmit the infection to birds and between houses [3]. Probably one of the most common sources for lateral spread of the organisms is feed. Nearly every ingredient ever used in the manufacture of poultry feedstuffs has been shown at one time or another to contain Salmonella. The organism occurs most frequently in protein from animal products such as meat and bone meal, blood meal, poultry offal, feather meal and fishmeal. Protein of vegetable origin has also been shown to be contaminated with Salmonella [4, 5].

Since November 2003, several regulations from the European Parliament Council Regulation on the control of salmonella and other specified food-borne zoonotic agents were passed. This regulation covers the adoption of targets for the reduction of the prevalence of specified zoonosis in animal populations at the level of primary production, including breeding flocks (Chickens and turkeys), layers, broiler and turkey flocks. Food business operators must have samples taken and testing for the zoonosis and zoonotic agents especially Salmonella (Table 1) as summarized by Hafez (2010) [6].

 

 

Campylobacters

Thermophilic campylobacters are the most common bacterial cause of diarrhoea in humans worldwide. Enteric diseases caused by the thermophilic species C. jejuni, C. coli, C. lari, and C. upsaliensis range from asymptomatic infections to severe inflammatory bloody diarrhoea. The natural habitat of thermophilic Campylobacter is the intestinal tract of healthy birds and raw meat that can be contaminated during the slaughtering process [7]. It is estimated that as many as 90% of broilers and turkeys may harbour Campylobacter while showing little or no clinical signs of illness [8]. Poultry and poultry products remain the most common source of foodborne human campylobacteriosis. The major route for Campylobacter infection in poultry appears to be the horizontal transmission from the environment. Specific flocks that become infected show rapid rate of intra-house transmission and a high isolation rate from caecal swabs, water and litter. Campylobacter spp. are widespread in poultry not only during the growing period, but also on the poultry meat during slaughter and during processing of poultry products. Horizontal transmission is the most important mode of the introduction of Campylobacter into poultry flocks. However, the ability of Campylobacter to spread is limited by their relatively low tenacity, which can vary between strains. Especially dry environments kill Campylobacter within one or two hours [9].

 

Antibiotic resistant

The development of antibiotic resistance in bacteria, which are common in both animals and humans, is an emerging public health hazard. Controlling these foodborne organisms requires a broader understanding of how microbial pathogens enter and move through the food chain, as well as the conditions that promote or inhibit growth for each type of organism.

Multi-resistant bacteria are increasingly posing a hazard to human and animal health worldwide, impeding successful antibacterial treatment [10, 11]. In addition, the development of novel antibiotics does not keep step with the emergence of antimicrobial resistance in bacteria [12].

Among multi-resistant bacteria, vancomycin-resistant enterococci (VRE) have been estimated as one of the most common bacteria causing a rise in cases of nosocomial infections in humans in the last few years [10]. The prevalence of vancomycin-resistant enterococci (VRE) in 20 turkey flocks reared in the southwest of Germany was investigated. Enterococci were tested on the presence of the vancomycin resistance genes vanA, vanB (B1/B2/B3), and vanC (C1/C2/C3). Vancomycin-resistant enterococci were detected in 15 (75%) of the 20 turkey flocks investigated. In a total 68 isolates were isolated from birds and dust samples, enterococci bearing van-genes were detected. Of these, 12 isolates carried the vanA gene (17.6%) and 56 isolates carried the vanC1 gene (82.6%). Neither vanB (B1, B2, B3) genes nor the vanC2 or vanC3 genes could be detected [13].

In addition, Livestock-associated methicillin-resistant Staphylococcus aureus (LA-MRSA) have been isolated from a number of livestock species and persons involved in animal production. Turkey meat was also showed to be contaminated with MRSA [14]. Richter et al. investigated the prevalence of LA-MRSA in fattening turkeys and people living on farms that house fattening turkeys [15]. Eighteen (90%) of 20 investigated flocks were positive for MRSA. All-female flocks were positive, while 8 male flocks were positive. On 12 of the farms 22 (37.3%) of 59 persons sampled were positive for MRSA. None of them showed clinical symptoms indicative of an MRSA infection. People with frequent access to the stables were more likely to be positive for MRSA. In most flock’s MRSA clonal complex (CC) 398 were detected. In five flock’s MRSA of spa-type t002 were identified, which was not related to CC398. Moreover, other methicillin-resistant Staphylococcus spp. were detected on 11 farms and in 8 people working on the farms. Similar results were about MRSA in turkeys were published by El-Adway et al. [16].

Maasjost et al. investigated the antimicrobial susceptibility patterns of Enterococcus faecalis and Enterococcus faecium isolated from poultry flocks in Germany and they found that high resistance rates were identified in both Enterococcus species for lincomycin (72%–99%) and tetracycline (67%–82%) [17]. Half or more than half of Enterococcus isolates were resistant to gentamicin (54%–72%) and the macrolide antibiotics erythromycin (44%–61%) and tylosin-tartate (44%–56%). Enterococcus faecalis isolated from fattening turkeys showed the highest prevalence of antimicrobial resistance compared to other poultry production systems.

El- Adway et al. investigated 76 C. jejuni isolates were recovered from 67 epidemiologically unrelated meat turkey flocks in different regions of Germany in 2010 and 2011 [18]. Only one isolate was sensitive to all tested antibiotics. The numbers of isolates that were sensitive to streptomycin, erythromycin, neomycin, and amoxicillin were 69 (90.8%), 61 (80.2%), 58 (76.4%), and 44 (57.9%), respectively. The emergence of a high resistance rate and multidrug resistance to three or more classes of antimicrobial agents were observed. The resistance against sulphamethoxazole/trimethoprim, metronidazole, ciprofloxacin, naladixic acid, and tetracycline was 58 (76.3%), 58 (76.3%), 53 (69.7%), 51 (67.1%), and 42 (55.3%), respectively. Multidrug resistance to three or more classes of antimicrobial agents was found and ranged from 3.9% to 40.8%. Similar results were also found by examination of isolates collected from different free-range turkey flocks in Germany [19].

General approaches to control foodborne infections

To control the foodborne organisms, information is required to understand more fully, how microbial pathogens enter and move through the food chain, and the conditions, which promote or inhibit growth for each type of organism. In general, the main strategy to control foodborne infections in poultry should include monitoring, cleaning the production chain from the top, especially for vertically transmitted microorganism such as Salmonella by culling infected breeder flocks, hatching egg sanitation and limiting introduction and spread of infections at the farm level through effective hygiene measures [20-22]. An intensive and sustained rodent control is essential and needs to be well planned and routinely performed and its effectiveness should be monitored. In addition, reducing bacterial colonization by using feed additives such as short chain organic acids (formic acid, propionic acid), carbohydrates (lactose, mannose, galactose, saccharose), probiotics, competitive exclusion or use of vaccines are further possibilities [23, 24]. Live and inactivated vaccines are used to control Salmonella in poultry [25]. Generally, vaccination alone is of little value, unless it is accompanied by improvements in all aspects of management and biosecurity. In addition, further attention must be paid to the development of efficient vaccines against campylobacter infections.

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Since the success of any disease control programme depends on the farm and personal sanitation, it is essential to incorporate education programmes about micro-organisms, modes of transmission as well as awareness of the reasons behind such control programmes by people involved in poultry production. In addition, effective education programmes must be implemented to increase public awareness of the necessary measures to be taken for protection against bacteria in food products from poultry.

Furthermore, in spite of significant improvement in technology and hygienic practices at all stages of food production accompanied with advanced improvement in public sanitation foodborne infections remains a persistent threat to human and animal health. The failure of the human population to apply hygienically acceptable food handling and cooking practice, and the fact that the processing plants are not able to reduce the level of pathogenic bacteria in poultry products, mean that every effort must be made to reduce the Salmonella contamination of the live birds before despatch to processing plants. New approaches to the problem of contamination must be adopted and the discussion on the decontamination of the end product must be re-evaluated carefully and without emotion. In addition, research must continue to find additional control and preventive means. Furthermore, the long term, development of poultry lines that are genetically resistant to some pathogens should be progressed.

 

Conclusions

Toward food safety in the EU several legislations are into force and their aims can be summarized according to Mulder (2011) as follows [26]:

1. Safety (consumer health): by new methods to reduce the use of antibiotics/medicines; improve disease resistance; zoonosis control; traceability of animals and products
2. Safety (product safety): stimulate and control hygienic processing, traceability of products and materials intended to come into contact with food
3. Animal welfare: animals kept according to rules/systems
4. Product quality: improved quality and composition; quality and chain control systems; traceability of animals and products.
5. Environment: reducing environmental contamination, Nitrogen and Phosphorous. There is a critical look at the use of by-products of human food production. The re-use of by-products for non-food applications (feathers) should be encouraged.
6. Rural impact, economic effects and biodiversity.