Prevention & Control

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Swedish program for control of Salmonella in broilers

reported by Wierup-Metal, (1995)

A Voluntary program to control Salmonellosis in poultry was initiated in 1961 following a number of food-borne S. typhimurium in the mid-1950s. In 1982, a law dealing with administrative provisions to control Salmonella in animals was promulgated and detailed procedures to suppress Salmonella infection in all domestic animals.

In 1983, a law on the control of Salmonella in animals was passed, which placed the obligation of control on owners of flocks and denied compensation in the event of outbreaks of Salmonella infection in broilers. In 1992, specific ordinances were passed to control Salmonella in poultry flocks. Regarded as the core of the voluntary preventive program, this legislation lays down standards of hygiene for hatcheries, breeding farms and feed mills. Complementary legislation passed in 1992 represents the mandatory components of the Salmonella control program, stipulating sampling for Salmonella before slaughter of broilers and requires records to be maintained by breeding farms and hatcheries to facilitate flock trace back in the event of outbreaks.

The objective of the Swedish program is to prevent Salmonella contamination of any food product at any stage in the production chain. The principles of hazard analysis critical control point (HACCP) management are employed, requiring monitoring of specific products in the integrated broiler production cycle.

The program requires that all veterinary laboratories report isolations of Salmonella sp. to relevant authorities. Local isolates are submitted to a reference laboratory and the diagnosis is confirmed by the National Veterinary Institute. The Swedish Board of Agriculture undertakes field investigations of all outbreaks and supervises depletion of farms that are involved. Infected poultry flocks are subjected to restrictions in movement and, in the case of broilers, mandatory destruction is required. Antibiotics are not used in Sweden to control Salmonella infection. Any food product contaminated with Salmonella sp. is regarded as unwholesome and is destroyed as being unfit for consumption.

The overriding principle of the Swedish program is that Salmonella infection is not tolerated at any stage in production, as infection invariably results in contaminated broilers and food products.
The program requires all grandparent-level broiler breeders to be thoroughly tested to confirm freedom from Salmonella infection. Samples are obtained during the initial 15 week quarantine period according to a mandatory schedule. Parent stock is subjected to voluntary sampling during the rearing and laying periods, and there is compulsory testing of all broilers two weeks before the intended date of slaughter. Between 1982 and 1988, approximately 30% of improved grandparent flocks were shown to be infected with salmonella spp. During the period 1989 to 1992, Salmonella was obtained from only 6% of consignments, reflecting more stringent preventive measures imposed by the world’s leading broiler breeders.

Detailed procedures relating to hygiene and biosecurity are mandated by regulations enforced by veterinary officers appointed by the Board of Agriculture. Intensive decontamination is carried out if Salmonella spp. is isolated from a flock.

Parent flocks are subjected to regular monitoring for the presence of Salmonella infection, including autopsies and fecal examinations. Regulations lay down procedures for the collection, selection, and fumigation of hatching eggs. Hatcheries are also subject to regulations which limit the possibility of introduction of Salmonella infection by applying hygienic measures and routine monitoring.

Since 1984, all broiler flocks have been subjected to salmonella monitoring two weeks before intended slaughter. This comprises 30 fecal droppings pooled in one sample and three replicates of liver and caecum pooled from ten birds. This protocol is designed Salmonella in a flock at a threshold prevalence rate of 5%. If Salmonella is detected, the flock is destroyed without compensation. During the decade 1981-1991, controlled slaughter of contaminated flocks was possible, but this provision has now been eliminated.

Prevalence Of Salmonella In Broilers In Sweden

During late 1990, a survey was conducted to determine the prevalence of Salmonella in broilers processed in the nation’s major plants. Each of these facilities processed more than 80,000 birds per week and collectively represented 97% of all broilers slaughtered in Sweden. Sampling has performed on a 9 cm square area of neck skin taken from birds at the point of release from the evisceration line.

At this point, carcasses would have passed through a chlorinated (10ppm) spin chiller and postchill washer. Sampling was carried out three times per day on two designated days each week to establish possible patterns of in-plant contamination relating to length of operation. Approximately 2,500 broilers derived from 140 farms were examined during the sampling period. Salmonella was isolated from 1.3% of pooled samples, contributing to a mean prevalence rate of 0.7%. Only six farms produced contaminated carcasses with four serotypes of Salmonella was independent of time of day or day of week, suggesting that in-plant cross contamination is not a factor in Sweden, contrary to the situation in western Europe and the United states.

This may relate to the extremely low prevalence of contamination in incoming broilers compared to other countries. The low prevalence of Salmonella contamination in carcasses is consistent with the infrequency of detection of Salmonella in flocks. During the period 1988-92, six cases were reported annually, reflecting the success of the control program.

Control Of Salmonella In Feed

Previous studies on paratyphoid Salmonellosis in many countries have demonstrated the role of contaminated feed in disseminating Salmonella to broiler flocks. Currently, 90% of all livestock feed is monitored for Salmonella in terms of a voluntary control program.
The HACCP approach has been used to detect and control Salmonella infection, including:

• Microbiological assay. Samples of all raw material are routinely screened by the producer. Presumptive Salmonella isolates are referred to the National Veterinary Institute for confirmation and serotyping. Reference samples are stored for three months after delivery.
• Reduced dust contamination. In-place vacuum cleaning systems have been installed in mills to facilitate cleaning. Dry cleaning is mandated on a weekly basis in all processing areas and is carried out each day in the unloading area for raw materials. Regulations require monthly and quarterly cleaning of the plant and its surroundings, silos, vehicles and aspiration system. Air for the pellet cooler must be ducted from the exterior. This avoids contamination with mill air carrying potentially infected duct. This air is mixed with feed after heat treatment.
• Hygienic storage. Ingredients must be stored in clean and dry silos and be subjected to regular inspection. Pelleted feed should be stored at a temperature not exceeding 5C above room temperature to minimize condensation after cooling.
• Partitioning of plants. Clear distinctions should be made between raw, unprocessed ingredients and finished, pelleted feed to avoid cross contamination by dust, personnel and rodents.
• Effective pelleting. Pelleting of broiler feed to obtain a temperature above 75 C has been mandated since 1986. Special provisions are required to prevent contamination of pellet coolers, including rejection of material initially exiting the die.

The implementation of the HACCP approach to the management of mills has effectively reduced recovery of Salmonella from broiler feed, in 1992, only 1% of 5,000 samples yielded Salmonella.
Regulations designate a specified company employee to be responsible for management of hygiene in a feed mill. Authorized veterinary officers conduct routine inspections and supervise sampling protocols.

Economics Of Salmonella Control in Sweden

Sweden documents only one-quarter of the cases of Salmonellosis in the human population compared to other countries in Europe. It is also noteworthy that only 10-15% of cases are acquired within the country, reflecting the low prevalence rates in domestic poultry, swine and cattle.
Detailed costs of treatment of cases and indirect costs, including sick leave, childcare and decreased work output, have been calculated. A beneficial return is obtained on the cost of control in feed mills, breeding farms, hatcheries and broiler units. Additional costs associated with the Salmonella prevention program in the broiler industry are equivalent to the cost of irradiating poultry as projected by the World Health Organization.

Conclusion

It is evident that the program adopted by Sweden to reduce food-borne Salmonella infection is effective, measured by prevalence rates in poultry and diagnoses in the human population. The Swedish model requires analysis and evaluation by public health authorities in other countries. Not all aspects can be transferred to other situations due to logistic and economic restraints. Provisions relating to improved control of disease in grandparent and parent breeders, and suppressions of Salmonella in hatcheries and feed plants, are universal in application.

The relatively small size of the Swedish industry (approximately one million birds per week)and concentration among a few processing units has favored the remarkable achievements in suppression of salmonellae in the human population. Data represented in the WHO report attests to the application of epidemiologic principles in the control of a serious disease affecting both humans and livestock. It is obvious that politicians and public health authorities will examine the Swedish model and pressure poultry industries in other countries to achieve similar advances.

Salmonella Control in New Zealand

A working example

Reported by, Bates-C and Granshaw (1996).

In an effort to achieve freedom from Salmonella infection a comprehensive program was implemented. Staff were informed of the situation and consulted about changes which were to be made. They were assigned responsibility to protect their sites and made aware of management support to carry out their duties effectively. Each property was divided into single-age sites with staff assigned to one site only. Previously there were no physical barriers between sites and staff movement was not actively controlled. To demonstrate management commitment and to encourage staff input the general manager became more involved in the daily routines, and insecurity was emphasized.

Key points required to control Salmonella:

• To prevent grazing sheep from becoming a reservoir of infection, stock was removed, houses were fenced off and weeds and grass maintained with herbicides and mowers. Rodent infestation was high with sites providing breeding areas in stockpiles of rubbish and unused equipment. Clearing around the houses allowed proper rodent bait stations to be installed.
• Houses design was of a raised slat type which made rodent control and make removal difficult. A contractor was previously employed to scrape and clean the slats after depopulation, and the equipment was moved across all sites with little regard for decontamination. Manure was often dumped on the farm property.
• As each house was depopulated it was converted to deep litter unit to alleviate these problems. Manure is now moved completely off site and the rodent control program is monitored weekly. Walls of houses harbored a large population of darkling beetles. Insecticides were used to suppress black beetles (Alphitobius).
• The main entry to the house was through annex but side entrances were available and were used without a change of footwear. Side entrances were blocked so that only one controlled entry remained. Shower facilities were built, and were made as comfortable as possible to ensure staff acceptance. Showering is a pre-requisite for everyone, including contractors, visitors, government officials and the general manager. The company provides all protective clothing which is laundered on site.
• Each site gradually became more self-sufficient and equipment including catching frames and scales were purchased to avoid transfer between sites. All other equipment is sanitized before entry and items that have been in contact with other livestock, such as, catching crates, are swabbed and confirmed free of salmonella by the laboratory before reuse. Movement of vehicles onto sites is restricted and staff vehicles are not permitted. Essential vehicles are visibly inspected for cleanliness before entry and the undersides and wheels are sprayed with disinfectant.
• The feed supplier is contractually required to ensure trucks are clean and have not been in contact with any other production sites for 48 hours prior to delivery.
• To ensure that all feed reaches the correct pelleting temperature product from the 10 minutes of the run is recycled from the pellet press to the preconditioner.
• Chambers were installed on every site to fumigate eggs immediately after the 4 daily collections. Only clean nest eggs were set for hatching. During the period of growing out the contaminated flocks it was found that nest and egg hygiene helped minimize the risk of transmitting Salmonella to the next generation. Monitoring nest hygiene by examination of egg membrane contamination was a useful procedure to maintain standards.
• Dead bird disposal using a concrete tank above the ground previously allowed leakage into the surrounding soil. Dead birds are now transported from the site in plastic bags and are destroyed by incineration.
• The laying stock was separated from the broiler parent flocks which are housed on different properties.
• Catching procedures are strictly controlled to minimize the risk from processing facilities. The company has its own catching crates and only company personnel can enter the site to catch the birds. The crated birds are taken by a company vehicle to a “holding area”. From here they are transferred to the processors’ crates. The processor’s truck must be clean and have had a 48 hour stand down time even though they do not actually come onto the site. After use the crates are cleaned and sanitized using a product comprising a blend of organic acids, this is followed by formaldehyde fumigation.
• Cleaning of houses is routinely monitored for total viable Salmonella and count units must be physically clean and free of Salmonella before clean shavings are placed. The shavings store was secured and bird-proofed.
• Insect control is an important part of the clean down and vermin control process. Immediately after depopulation insecticide is applied while the shed is still warm. This is critical to destroy darkling beetles before they can migrate into wall linings. When the cleandown, house assembly and final fumigation are completed, a synthetic pyrethroid cypermethrin is applied. Just prior to lay (about 24 weeks) a similar insecticide is sprayed onto walls, nest boxes and other surfaces. The site managers report good control of northern fowl mite and do not have problems with either cockroaches or flies.
• Soil around the shed perimeters (2.5m) was scraped away and removed from the site. The soil underneath was sprayed with 20% commercial formalin using a tractor spray unit. Formalin has been shown to be very effective in eliminating Salmonella from the environment. Formalin spray was also utilized on all house surfaces and equipment and roadways on site.
• Hygiene procedures are audited by the laboratory and a scoring system has been established to provide a measurable objective that can monitor progress. Company specifications for hygiene scores include a minimum of 80% in the houses and 90% in the hatcheries. Results above standard must result in remedial action and results are circulated to all staff to maintain their interest. Comparisons between sites are also made available to stimulate competition and peer pressure as well as encouraging site managers to consult each other on how to make continual improvements.
• The laboratory and technical staff play an important role in helping the company to achieve its objectives. All sanitation chemicals are evaluated by the laboratory which provides training on their correct use. All disinfectants must pass an “in-house” laboratory test before being approved for use.
• The PIANZ Code of Practice became the minimum standard and critical control points were monitored to ensure compliance. Anything that comes onto the site is a potential carrier of Salmonella in addition to other pathogens. Visitors are not encouraged and must conform to company entry requirements and all visits are documented.
• Staff involvement was initiated, through an “ in-house” biosecurity manual covering essential aspects of disease monitoring and control. An “in-house” training program involves staff at all levels. This ensures that everyone understands company procedures. The course covers poultry anatomy and farm and hatchery management. Initially recruits participate for one day a month per year. It is intended to have regular ``refresher’’ sessions.

Discussion:

• There were some setbacks with positive salmonella isolations from the environment. Infected soil at the grandparent farm was treated with formalin by spray and subsequent samples were negative.
• One of three sites was repopulated in 1992 with 12 week old birds from the quarantine site after a 10 week period of cleaning and disinfection. It became positive for S. infantis one month later, possibly due to contaminated feed. The supplier was subsequently changed and the site was kept under isolation and culled out early.
• The hygiene procedures applied at grandparent level and to broiler parents has resulted in these flocks being clear of salmonella since March 1994. A policy of depletion has been introduced for any flock now found to carry Salmonella.
• The control program has taken 2 years at an estimated cost of NZ $ 500,000, excluding the revenue lost through a drop in sales.
• The benefits gained include improved credibility of the company, and increased market share. The subsequent rise in volume has permitted reduced operating costs and this combined with genetic improvements and better heath status has enhanced improvements overall in bird performance. This factor is greatly appreciated by customers.
• Workers have gained a sense of achievement and pride which in turn has contributed to the effectiveness of the program.

Looking Ahead

• Cooperation from the feed supplier is essential. In the future we will build larger silos close to the road frontage which will allow feed to be sampled before delivery and also reduce traffic onto the farm site.
• We believe that the external environment will always be a potential source of salmonella infection. Vigilance must be maintained through biosecurity and sampling programs.
• 1.3.3."AMERICANS FOCUS ON SALMONELLA"
  Reported by McCapes-D et al. (1998)

Unique Features Of Poultry

They highlighted several unique features of poultry production; which favoured Salmonella.
These were:

• The majority of the birds are relatively young and therefore relatively susceptible to infection.
• Poultry production is characterized by large numbers of birds in small areas which favors the spread of infection.
• The young age at slaughter favors a rapid turnover of birds. Thus, there is often insufficient time for birds to fully recover from infection and stop the shedding of their Salmonella organisms.
• The feathers provide a large surface area for Salmonella organisms to contaminate.
• Breeding birds and those in table egg production produce eggs which is an ideal way to transfer Salmonella to the next generation or the consumer.

In addition, poultry feed and its ingredients favor Salmonella because:

• They provide a favorable environment for the Salmonella organism to survive in.
• They are produced in large quantities.
• They can be easily contaminated by vermin and their droppings.
• They come from different parts of the world.
• They go into feed which gets inside every bird in the flock and thereby provide Salmonella with a direct route into the bird.

Managment Pratices :

Management practices on farms and hatcheries favor the survival and spread of salmonella.
These include:

• The hatchery sourcing its eggs from a multitude of breeder laying farms.
• Multi-age farms.
• Floor rearing.
• Recycling of (broiler) litter over several cycles which is a common North American practice.
• Dirt floors that cannot be properly cleaned and sanitized.
• Bell drinkers that collect faecal contamination.
• Fans that are almost impossible to clean.
• Litter ‘wet spot’ that favor salmonella survival and growth.
• Transportation in great numbers in large vehicles to the poultry processing plant for slaughter.
• The skin is left on the carcass at processing.

But and very rightly so, they also highlighted several consumer practices that favored salmonella.
Consumer factors that favor salmonella:

• The product is purchased raw.
• Cross contamination in the kitchen.
• Shell eggs preferred and purchased.
• Consumers like runny yolks in the eggs that eat.

Two Key Strategies

They saw the future of salmonella control being centered on two key strategies:

• Excluding salmonella from flocks (insecurity) and then
• Managing the flocks, minimize or avoid the risks associated with salmonella.

These strategies were addressed later on by other speakers at the symposium. They highlighted the fact that some 70% of cases of human food poisoning in Great Britain were caused by S enteritidis (60% being S. enteritidis PT4) and that S. typhimutium DT104 was rapidly increasing in importance.

Reasons For Dominance

So why do S. enteritidis PT4 and S. typhimurium DT104 dominate the scene? He felt there were several reasons and these are :

• They are associated with common foods.
• They are highly invasive of the food animal and get into its tissues (meat, milk, eggs).
• They contaminate the interior of food.
• They are more tolerant of acid (stomach contents).
• They probably have a higher incidence in man.
• The concept of more tolerant strains is highlighted. Interestingly these strains also appear to survive better in the environment which could well be a very important factor in their epidemiology.

It also appears to be the case that these more tolerant, more resistant strains kill more of the chicks than they infect than do the ‘normal’ strains. In addition to the reasons given above, the fact that S. enteritidis PT4 is a very successful colonizer of the birds reproductive tract should not be overlooked.

Quickly Into Reproductive Tract

Research has shown that S. enteritidis PT4 can be in a hen’s reproductive tract within one hour of the hen’s exposure to an aerosol infection of S. enteritidis.
Because of this characteristic S. enteritidis will be found in eggs. Currently the indications are that one in 6000 table eggs in Britain contains S. enteritidis. The tolerant strains of Salmonella also survive better in aerosols. This airborne infection is probably more important than many think because one infected bird in a flock could quickly infect others as shown in the following table:

• Route Effectivenes (%)
• Respiratory (aerosol) 80-90
• Muscle 30-40
• Egg 25-40

Other studies have suggested that more virulent organisms such as S. enteritidis PT 4, S. typhimurium DT 104 and even E. coli 0157 are able to survive and persist in more adverse environments, for example temperatures of 4 degree C.

Benefits Of Refrigeration

However, at this temperature, which is the temperature of a well managed domestic refrigerator, the organism will not multiply, it will multiply on the removal of a contaminated product from the refrigerator. The reasons for the success of S.enteritidis PT4 :

• Eggs are its vehicle.
• It persists on certain farms.
• Infected replacement flocks.
• It can persist in vermin.
• The consumer likes to eat raw eggs, for example, mayonnaises.

They also reported that a correlation could be seen between the Salmonella serotypes seen in feed and those subsequently seen in the flocks that consumed that feed. It should be noted that S. enteritidis is rarely found in feeds. When it comes to controlling Salmonella in poultry feed the following points are critical:

• Knowledge of the status of the source of ingredients.
• A monitoring program for raw materials.
• The use of HACCP in the mill.
• Risk analysis and for this purpose coliform counts give a good indication of Salmonella risk.
• Recontamination can easily occur by airborne dust particles.

The importance of control was emphasized with the following:

• Enhanced acid products work better than straight organic acid or their salts.
• Heat treatment will kill salmonella but it leaves no residual effect and the feed can easily be recontaminated.
• Air filters of 5u will stop airborne spread.
• The mill for producing Salmonella free feed must have dedicated vehicles and staff and the latter musts be fully briefed

Competitive Exclusion

Spring-P (1998) stated the following report on Understanding the development of the avian gastrointestinal microflora In ZOOTECNICA International:

Indigenous intestinal microflora inhibit colonization of invading pathogens. Many complex bacterial mechanisms are involved in regulating the composition of the gastrointestinal (GI) microflora and to exclude intestinal pathogens. Imbalances in the GI ecosystem can reduce the protective effect of the indigenous microflora that provide enteric pathogens with an opportunity to colonize the gut. Imbalances in the ecosystem occur in the young animal, during periods of stress or digestive dysfunction, following changes in the diet or due to antibiotic administration. The young chicken is prone to colonization with enteric pathogens such as Salmonella and Campylobacter. An understanding of the development and composition of the avian microflora and regulatory action is essential to understand failures of the innate microflora to exclude pathogens.

Competitive exclusion (CE) describes the process by which beneficial bacteria exclude pathogens. Competitive exclusion involves the prevention of entry or establishment of a specific bacterial population in a niche colonized by a competitive bacterial population. To be able to colonize the GI tract, the species must be better suited to establish in that environment or must produce compounds which inhibit competition. The complexity of microbial interactions make it extremely difficult to study the effects of isolated factors. Comparisons between the microflora of newly hatched and adult chickens reveals some of the elements in the GI microflora. These concepts can therefore guide the development of CE products in young birds.

Development Of The Gastrointestinal Microflora

The alimentary tract of the newly hatched, healthy chicken is usually sterile. The most striking difference between the early and climax microflora in commercial poultry is the lack of complexity of the microflora, especially the absence of obligate anaerobes in the lower GI tract during the first weeks of life. In addition, Lactobacilli become the dominant organism in the upper part of the GI tract within days of hatching. Natural CE mechanisms to exclude pathogens are prone to fail in the entire GI tract during the first days of life and in the ceca during the first month. Strategies to improve CE in the gut should emphasize compensation of the two deficiencies relating to immature microflora.

Bacterial Cultures

Competitive exclusion cultures must create a diverse intestinal microflora, especially in the cecum. Complex defined mixture provide better protection than cultures with only a few species. The ability to adhere is also an important characteristic of CE microorganisms in poultry.

There are important conclusions can be drawn from research on the requirements of an effective CE-culture:

• There should be only few bacterial generations between the harvest of intestinal contents from the adult chicken and the final CE-product.
• Anaerobic conditions should be maintained during production to sustain the viability of obligate anaerobic bacteria.
• Production must maintain appropriate proportions among the major organisms in the culture similar to those found in the gut.

Mannanoligosaccharide and Other Inhibitors Of Bacterial Attachment

Mannose-sensitive type-1 fimbriae are involved in attachment of pathogens. In laboratory trials mannanoligosaccharide (MOS) has been shown to reduce the prevalence and concentration of Salmonella expressing type-1-fimbriae in the cecum of 10-day-old chicks. The ability of MOS to bind type-1 fimbriae and therefore block bacterial attachment is considered to be the major mode of action of CE. MOS has been shown to be effective in reducing Salmonella enteritidis colonization in challenge trials during the growing period. Chicks treated with MOS were free of Salmonella before controls.

INTERACTIONS OF MANNANOLIGOSACCHARIDE WITH INTESTINAL MUCOSA.

Interactions among the intestinal microflora affects both development of the immune system and the intestine. Pigs with post-weaning diarrhea have shorter intestinal villi and deeper crypts indicating faster cell turnover compared to healthy pigs. Rapid cell turnover will reduce the age and maturity of the absorptive cells and increase the energy requirement for gut maintenance. Since the metabolic activity of GI tissue is high, improving energy utilization in the digestive system may have a profound influence on overall efficiency.

Administration of antibiotics in the diet has been shown to reduce intestinal tissue weight and to decreases the turnover of mucosal cells. Slow cell turnover is associated with a low rate of energy expenditure in the GI tract. This could explain some of the improvements in performance observed following subtherapeutic dietary levels of antibiotics. Yeast culture reduces the crypt depth and decreases the numbers of goblet cells in poults. The energy conserved by reduced production of epithelial cells (decreased crypt depth) may be diverted to synthesize lean tissue mass.

This may explain improvement in body weight gain following dietary supplementation with Saccharomyces cerevisiae var boulardii. Two trials have examined intestinal morphology with dietary; MOS supplementation in broilers, and increase in both villus length and crypt depth has been documented. An increase in villus length indicates a greater absorptive surface. An increase in crypt depth is attributed to greater expenditure of energy to develop the absorptive surface. Addition of 0.1% of dietary MOS to turkey diets decreased crypt depth and increased width of villi without affecting villus length. Dietary MOS might alleviate the undesirable effects of enteric pathogens by adsorption and might result in increased villus to crypt depth is accepted as indicating savings in energy to maintain the integrity of the intestinal tract, and might explain the performance response to MOS in turkeys.

(Adapted from a paper presented at the 1997 Alltech Symposium on Biotechnology for the Feed Industry).

Hakkinen-ENM and Nuotio-L, from National Veterinary and Food Research Institute Helsinki, Finland stated the following report on Competitive exclusion in ZOOTECNICA International (1998):

Introduction

The idea that indigenous intestinal microorganisms are involved in protection of the host animals against disease was recognized during the 1950s. It was reported that the development of intestinal flora increased resistance to Salmonella infections in young chicks. It was until the early 1970s that the CE concept originated from studies in Finland which showed that early establishment of normal adult flora in the intestines of newly hatched chicks inhibited intestinal colonization with Salmonella sp.

Development Of Competitive Exclusion

A severe epidemic of salmonella infantis affecting 80% of Finnish broiler flocks occurred in 1971. The origin was a contaminated consignment of a feed ingredient. There was a simultaneous increase in incidence of human cases caused by the serotype. Poultry and other domestic animals had been relatively free from infectious diseases up to that time and the situation was unique. Failure to overcome the problem with antibiotic treatment suggested a different approach. Investigations were initiated at the National Veterinary Institute in 1972 to identify key differences between production of broilers and other domestic livestock. It was shown that: intensive broiler production requires a high standard of hygiene at every level.

Broiler production based on the all in, all out system could effectively prevent transfer of intestinal microorganisms from one flock of birds to the subsequent placement of chicks.
The level of Salmonella challenge from feed, hatcheries, or the environment was usually low.
To ensure rapid and effective transfer of adult intestinal flora to newly hatched chicks, a preparation from the intestine of chickens was developed and tested in 1973. This approach to suppressing Salmonella sp. became known as the Competitive Exclusion (CE) concept. The validity of this method for different serotypes of salmonella has been confirmed by several research groups in different countries.

Methods Of Administration

CE preparations can be administered to birds either directly into the crop, in drinking water or by droplet application. These methods are suitable to dose birds under commercial conditions.
Droplet application offers the advantage that treatment can be given at the earliest possible opportunity after hatching. It is crucial to exclude Salmonella when birds are infected at an early age. Protective microflora is spread evenly among the chicks, in comparison to drinking water application.

Mechanisms Of CE

Knowledge concerning the mechanisms of CE is still incomplete. Available evidence suggests that viable anaerobes are essential to prevent Salmonella colonization in the intestine of chickens.
Consistent protection against Salmonella has been achieved only with undefined mixtures of intestinal bacteria. Attempts to produce effective defined mixtures of isolated microorganisms have met with limited success.

The possible means of the protection by intestinal flora against pathogens include:

• Competition for attachment sites on the mucosa,
• Competition for nutrients,
• Production of inhibitory substances including volatile fatty acids and bacteriocins.

Commercial Application Of CE

The CE method has been used routinely in Finland since 1976 and on a commercial basis worldwide since 1987 (Broilact, Orion Corporation, Farmos, Finland).
The product was launched in the United Kingdom in 1989. The Finnish preparation is available in Ireland, Sweden, Denmark, the Netherlands, Norway, France, and Spain. In the U.K., it is used mainly to treat breeders. A new CE product was launched in the U.K. in 1993. Although the Finnish preparation is more strictly selected, both commercial products are similar undefined mixtures of anaerobic intestinal bacteria.

Safety Requirements For Undefined CE Preparataions

Both commercial CE products are marketed in several countries. Reluctance of authorities to grant licenses to undefined products is the major reason for slow penetration of the market. The requirements depend essentially on the licensing category which may vary among countries. A WHO Workshop (WHO/CDS/VPH/94.134) has recommended that a new product category “Normal Gut Flora” should be created for CE preparations these products should be distinguished from live probiotics, which usually consist of only one or a few strains to enhance performance.

The official requirements for current undefined preparations include:

• Disease free donor bird from a health-monitored specific pathogen-free flocks.
• Good laboratory and manufacturing practices (GLP and GMP) used throughout the production process.
• Meticulous examination of primary inocula for human and poultry pathogens by laboratories certified by licensing authorities.

Additional requirements contributing to the safety of an undefined CE product:

• Low prevalence of contagious diseases in the country where the CE preparation is produced.
• Consecutive stages of propagation in manufacture which contribute to a total dilution of at least 1:10.
• Media used for propagation should not support the proliferation of Mycoplasma sp. Or viruses.
• Careful quality control of the composition of the final product batches using indicator organisms.

The safety of the current CE preparations is also reflected by prolonged field experience applying treatment to hundreds of millions of birds without any reported adverse effects. There are also no substantiated claims for inhalation allergy or other occupational risks or hazards to workers administering the treatment.

Results Obtained Using CE:

The effect of consistent and widely applied CE treatment can be assessed from the data obtained in Finland, Sweden, and the U.K. From Finland, two monitoring and treatment programs are cited. A broiler integration used Broilact® to treat 400 flocks. A total of 192 untreated flocks served as controls during a three year period from 1986 to 1988. Only 6.5% of the treated flocks compared to 21% of the untreated flocks were positive for Salmonella at the time of slaughter. In a second integration, 49% of 55 flocks were infected with Salmonella in 1987. Introduction of hygiene control measures and CE treatment reduced the incidence to 11% within a year.

The long term use of CE preparations contributed significantly to the favorable salmonella situation in Finland. At present, more than 90% of broiler flocks are treated with Broilact®.
The percentage of Salmonella contaminated broiler flocks has averaged 2.2% this decade, and 0.5% in January-May 1996. The level of Salmonella contamination in retail poultry meat has also been very low; and only one of the 101 portioned broiler meat samples examined for salmonella was positive in 1995.
It must be remembered , that CE treatment is no panacea or substitute for satisfactory production hygiene. The problem of salmonella can only be solved by a coordinated program..

Future Development and Applications Of CE:

The concept was originally devised to control salmonella infections. It has been shown experimentally that the adult intestinal populations contains bacteria which can protect chicks against pathogenic E .coli, yersinia, and campylobacter spp.

Implicit in the CE concept is the early establishment of a normal adult flora. This also applies to situations where the flora has been destroyed or seriously disturbed by antibiotic treatment or stress.
Combined antibiotic therapy and CE treatment is recommended, especially when breeding or laying flocks are infected with invasive species including S. entertidis or S. typhimurium. Bailey-JS et al., (2000) conducted a series of four paired-house studies in Arkansas, Alabama and Georgia (two farms) to determine the efficacy of Mucosal Starter Culture (MSC) in eliminating or reducing Salmonellae in broiler chickens. Randomly designated chicks were treated twice with MSC. First they were sprayed with an MSC solution using a spray vaccination cabinet in the hatchery, and then they received MSC in the first drinking water at the growing house.

Chicks were grown in identically constructed and equipped paired houses managed by the same grower. At the end of grow-out, broilers were tested for the presence of Salmonellae on the farm and during processing. The results confirmed that when Salmonellae levels were controlled in the hatchery, a significant reduction in the salmonellae was found on processed broiler carcasses treated with MSC and that this reduction in Salmonellae was carried through processing to the final processed carcass, thus potentially reducing consumer exposure to Salmonellae.

In the International Health review in International Poultry production (1997). Under the title of New challenges-new approaches The following report was recorded on Competitive Exclusion:

Competitive exclusion or the nurmi Concept as it was previously known, is an effective way of controlling Salmonella infection in poultry.
Competitive exclusion (CE) is basically the early establishment of an adult intestinal micro flora in the bird’s digestive tract that will help prevent the colonization.
Of that digestive tract by undesirable micro organisms or enteropathogens such as salmonella.
Even 1997 the exact mechanisms by which CE works is not fully understood.
Bacteria have one or more of several mechanisms that enable them to inhibit or reduce the number of other species in the chicken's digestive tract.

These includes:

• The removal of essential nutrients (substrates) by either consuming them or competing for them.
• Production of antibiotic substances.
• Creating a physiological environment in the digestive tract that restricts their growth.
• Competing for bacterial receptor or sited on the intestinal wall.
• Volatile fatty acids such as acetic, propionic and butyric acids are produced by anaerobic bacteria in the birds caeca and these are known to have an inhibitory effect on salmonella.

This action is thought to be an important aspect of the CE mechanism, However , other actions such as a purely physical one of bacterial types and their respective numbers is also important.
The ability of a bacterium to adhere to the wall of the digestive tract and thereby colonize its mucosal surface is important.
Thus, if bacteria in a product can colonize the wall of the digestive tract, undesirable organisms such as Salmonella are not able to adhere to the mucosal lining of the digestive tract. Thus, if they cannot colonize the digestive tract they cannot assume importance or create infection.
In practice CE is usually involved in one of two situations.

Firstly, it can be given to the day old to ensure that it has a comprehensive gut flora established at the earliest possible age. This then places the day old in the best possible position to ward off a subsequent salmonella challenge. If the normal gut flora was deficit, the salmonella would have a better chance of becoming established in the chick’s digestive tract and causing problems.
Secondly, the CE problems can be administered after a period of medication. This is because the medication will have reduced the beneficial bacterial flora in the bird’s gut and in this instance the CE product is being used to top up or re-establish the beneficial microflora.

This approach can be used in salmonella control programs
In such a program:

• The salmonella in the bird’s tissues and digestive tract are treated by medicating with a suitable antibiotic.
• CE is then used to quickly re-establish the intestinal tract flora so as to remove any potential window of opportunity that the presence of a depressed intestinal micro-flora presents to any opportunist Salmonella organisms.
• If this can be combined with moving the birds into a clean environment, then all the better.
  The benefits of this are compounded if the procedure is used over several production cycles.
• In 1994 and 1995 the Dutch Poultry Health Ministry at Doorn treated 32 known Salmonella enteritidis positive flocks with a procedure based on medication with enrofloxacin followed by the use of competitive exclusion.

Movement of birds into clean houses was not practical. After one treatment a success rate of 72% had been achieved and after two treatments this rose to 93%.
In this study Salmonella status was confirmed by bacteriological testing of the breeder flock and its progeny. Experience in many countries now indicates that the most effective Salmonella control programs are those based on several strategies and not those that place all their reliance on one method.

An excellent Salmonella control strategy is summarized as follow:

Control strategy should include;

Biosecurity + First class hygiene + Competitive Exclusion + Vaccination + Feed Acidification + Coperhensive Monitoring and when necessary, Treatment.
The importance of a balanced program can not be over emphasized and the program will only work if everyone-staff, management and suppliers- give the program 100% support.
In recent times evidence has begun to surface that CE has some hidden benefits in terms of growth rate, body rate and FCR improvements.
There are also indications that this technology has effects similar to those seen with Salmonella against organisms such as campylobacter and enterepathogenic E. Coli.
Combine this observation with the current consumer led trend against in-feed use of chemicals and the importance of CE in poultry production may assume new dimensions in the year ahead.

Selective enrichment of Salmonella using a combination of 0.3% Selenite, 0.5% cholate and Static incubation was examined for five common serotypes in the presence of Salmonella-free chicken faeces. Enrichment cultures were then assayed by the polymexin-cloth enzyme immunoassay (polymexin CEIA). This selective enrichment method was effective in suppressing large excesses of chicken faecal microflora, while permitting the growth of small numbers of Salmonella. When the medium contained no selective agents, the ability of the polymexin CEIA to detect Salmonella was markedly reduced in the presence of large excesses of chicken faecal microflora. The advantages of using static incubation and a dot-blot format for the polymexin CEIA are discussed for application in the hazard analysis critical control point program. (Chen-H et. al, 1995)

The effect of treatment with a newly developed characterized continuous flow (CCF) culture composed of 29 strains of caecal bacteria on Salmonella colonization was evaluated in commercially reared broiler chickens. The results indicated that the CCF culture served to enhance Salmonella colonization resistance and it is suggestesd that it may serve as a useful component of an integrated control program. (Corrier-DE, et al., 1995). Two experiments were conducted to determine the role of the microbiotic preparations, Lactiferm L-400 and L-50, in protecting ducks against Salmonella infection. Any form of Lactiferm application resulted in an increase in Live weight and decrease in mortality. Feed conversion was slightly, better in trial groups than in the control. (Weis-J et al., 1997).

Control by competitive exclusion of intestinal colonization by salmonella infantis was studied in domestic chicks and turkey poults given a commercial product developed for use with chicks, compared with two similar preparations containing intestinal microorganisms from turkeys. Each type of material protected both avian species when given orally before challenge; the degree of protection depends at least as much on the type of protection as its host origin (Schneitz-C and Nuotio-L, 1992).

A review considers the concept of competitive exclusion ( CE), mechanism of (CE), Lactobacillus and growth in domestic fowl, Lactobacillus interaction with enteric pathogens, L. reuteri in the normal intestinal microflora, the L- reuteri-reuterin system, site (S) of action of Lactobacillus in the process of CE, Lactobacillus involvement in reduced pathogenicity of Salmonella, current in ovo technology, and L-reuteri in ovo studies with chicken and turkey embryos (Edens-FW et al., 1997).