What is biosecurity?

Biosecurity on a poultry farm includes all measures taken to minimize the risk of introduction and spread of pathogens, and thus includes all actions to maintain the health of the poultry and the farm. By adopting these biosecurity measures and implementing effective management, farm animals are protected from both endemic and epidemic diseases.
A distinction is made between external and internal biosecurity.
External biosecurity focuses on the poultry farm’s points of contact with the outside world and aims to prevent pathogens from entering facilities. This applies to both exotic diseases that are rarely seen in the country and endemic diseases that are common in the country but are not found on every farm. All measures taken to counter the spread of pathogens within a poultry farm are covered by internal biosecurity.

Why biosecurity?

The poultry sector has evolved over the years from small scale to industrial animal production. The goal is to have close control of production by optimizing components such as genetics, nutrition and rearing conditions. However, due to the high production rate, an outbreak can have a serious impact not only at the farm level but also on the poultry sector as a whole. The most effective and economical way to control poultry diseases is to implement biosecurity measures.
The main objective of biosecurity is to keep the infection pressure in the poultry farm as low as possible. In this way, the immune system of a particular animal will be less stressed, resulting in a reduced risk of disease outbreak and therefore improved animal health and welfare.
By reducing the potential risk of a disease outbreak with the use of biosecurity measures, other beneficial effects on the farm may be established. For example, the use of antibiotics can be significantly reduced. In addition, reducing the use of antibiotics in livestock production will reduce the development of antibiotic resistance, and this is beneficial to both animal and human health.

Pathways of disease transmission

Regarding disease transmission, not all routes of transmission are of equal importance. Therefore, it is not easy to rank the different routes according to their relevance. This is mainly because of the large differences between infectious agents in their ability to infect a living being, such as their chances of survival in the environment. Thus, it is clear that not all biosecurity measures will contribute equally to the prevention of different infectious diseases in poultry.
Direct contact between animals is considered the main route of transmission of infectious agents. Therefore, more emphasis should be placed on biosecurity measures that avoid direct contact between animals than on measures taken to prevent indirect transmission, such as through work materials or humans.
An additional but still important factor is the frequency with which a pathogen can infect an animal population via a particular pathway. A less important transmission pathway can become very important the moment it creates an entrance for pathogens on the farm multiple times.
Therefore, separate consideration and awareness must be given to the fact that any transmission pathway, including the less important one, can pose a risk for the introduction and spread of infectious diseases. Thus, vigilance at all levels of biosecurity will always be very important for the poultry farm.

The figure below shows the relative importance and specific probability weight of different pathogen transmission routes in poultry production.

Planting of chickens

Animal-to-animal transmission of the disease

Direct contact between infected and susceptible animals is the most effective means of pathogen transmission. Infected animals spread many pathogens through all sorts of secretions, including saliva or manure. When susceptible animals come into contact with this infected animal or any of these secretions/secretions, pathogens can be easily transmitted from one animal to another. Thus, disease can spread rapidly through a given poultry house. For example, the number of Campylobacter spp. bacteria will expand very rapidly within a poultry population through manure contamination of drinking lines and through coprophagy (eating feces). The pathogen can also be transmitted through eggs. This transmission route includes both vertical transmission from hen to egg and transmission through contaminated eggshells in the hatchery.

Transportation and disease transmission

Poultry transport trucks move poultry from hatchery to feedlot and increase the risk of disease transmission. Various studies show that transportation can play an important role in the entry of certain infectious agents into poultry farm facilities. Therefore, poultry should only be transported in thoroughly cleaned and disinfected vehicles. All dead animals, all contaminated debris and all manure should be removed from the vehicle before transporting new live animals. It is also mandatory to clean and disinfect vehicle tires before entering the farm.
Crucial to the spread of infectious diseases through poultry transportation is cleaning and disinfecting between different shipments of poultry coming from other farms and after the animals have been unloaded at the slaughter plant. If this is not done carefully, there is a high risk of disease transmission as different poultry populations come in indirect contact with each other. A higher biosecurity status on a poultry farm can be guaranteed if vehicles do not visit more than one farm per day and if these vehicles are only used for the same purpose.

Source herds with high health status

New animals should always come from a farm with equal or higher sanitary status. Since each poultry farm uses its own management and thus focuses on different biosecurity measures, this sanitary status can vary considerably from one farm to another. Day-old chicks can be infected with pathogens both during their time in the hatchery and by vertical transmission through their development in the egg (chicken to chicken). Hence, higher or equal sanitary status in the source flock or hatchery is very important to prevent disease transmission within the broiler population.

Multi-age farms

In some poultry farms, flocks of chicks of different ages are kept on sites. The goal should be one age and one parent flock. Older birds may be asymptomatic carriers of pathogens such as Salmonella, Gumboro, Mycoplasma, Newcastle and infectious bronchitis virus, which can affect young birds that have not yet developed resistance to these pathogens. The introduction of offspring from new stock, such as in the case of spaying, is associated with a high risk of biosecurity

Catching and preparation of poultry houses

Disease transmission between humans and animals

It is widely known that infectious agents can be transmitted from human to animal and vice versa, or that humans can transmit infectious pathogens from animal to animal. It is for this reason that the number of visitors to a poultry farm should be limited and the goal should be to keep people as far away from animals as possible. Every time a truck driver or a person from the catching team enters the fattening site, it creates a real risk of introducing infectious agents. Humans can serve as both mechanical vectors and biological vectors for the transmission of infectious diseases on a poultry farm. For example, visitors played an important role in the spread of avian influenza in 2003, among other things.
Humans can act as mechanical vectors (e.g., carrying feces on their shoes) if they have been in contact with infected animals and then switch to susceptible animals. Without action, transmission occurs primarily through fecal residues of infected animals on shoes and clothing. Biological transmission may exist in pathogens that can affect both humans and poultry, such as avian influenza virus and Salmonella spp.

It is very important that contact with persons who come into contact with non-free-range poultry is avoided as much as possible. Studies show that there is frequent contact between professional poultry farms and private farms. All this leads to serious risks of disease transmission, as the level of biosecurity of private farms is often much lower than that of poultry farms.


Since humans can be mechanical vectors of infectious diseases, it is recommended that special biosecurity measures be taken the moment a person enters a poultry farm.


There is a significant risk of introducing infectious diseases into the poultry farm due to the entry of trapping crews and the importation of their equipment. Containers in which poultry are transported have been repeatedly associated with pathogen transmission. For this reason, it is recommended that poultry houses be depopulated as soon as possible and that the entire capture team be provided with protective clothing. In addition, it is also important that transport containers are thoroughly cleaned and disinfected before introduction to the fattening site. In a study on the transmission of Salmonellae and Campylobacter through transportation, it was found that many shipping containers are regularly reused between different sites without proper cleaning or disinfection.

Multi-age farms

In some poultry farms, the sites contain broods of chickens of different ages. The goal should be one age and one parent flock. Older birds may be asymptomatic carriers of pathogens such as Salmonella, Gumboro, Mycoplasma, Newcastle and infectious bronchitis virus, which can affect young birds that have not yet developed resistance to these pathogens. The introduction of offspring from new stock, such as in the case of spaying, is associated with a high risk of biosecurity

Feed and water

Separation between clean and dirty areas

The principle of clean and dirty road in a poultry farm means that there is a clear separation between clean and dirty (risky) areas of the premises. Poultry transport vehicles are constantly in contact with other areas. This creates a rather high risk of disease transmission. All inbound and outbound traffic is always driven on a dirty road. The clean road is kept for poultry supply and clean product transport (internal movements) and only in fully cleaned and disinfected trucks.
Only the dirty road is relatively easily accessible to visitors, suppliers and consumers. Carcass collection is understandably part of the dirty section. Containers and other tools used for this purpose can only be returned to the clean section after they have been thoroughly cleaned and sanitized. Manure removal is always carried out along the dirty road.

Feed and disease transmission

Feed can be a potential source of contamination on a poultry farm. Microorganisms such as Salmonella spp., Aspergillus spp. or E. coli can contaminate feed and pose a real risk to the poultry population. Feed contamination can occur during production, transportation or storage.
To avoid the spread of pathogens through feed conveyors, it is recommended that feed be fed through proprietary piping from the contaminated part of the premises. This prevents the feed carriers and associated foreign pathogens from entering the poultry farm. In addition, it is also important to ensure that rats or other wild animals do not have access to feed silos to prevent parasite contamination of the feed.

Water and disease transmission

Pathogens can easily spread through contaminated drinking water to the poultry population. Water can come from a variety of sources (surface water, borehole…), after which it is stored in a storage tank most of the time and fed to the poultry. Water storage tanks and pipelines should be completely and properly covered to keep out dust, pests or wild birds. In this way, pests and dust will not be able to be a source of contamination of the animals’ drinking water. Studies show that the type of drinking water system in a poultry house has an effect on the colonization of certain bacteria. Therefore, drinking cup systems will pose a greater risk compared to drinking nipple systems. However, drinking cup systems are unlikely to avoid drinking water contamination because water is often left in the cup.
Drinking water quality is affected by the presence or absence of biofilms in water supplies. Biofilms form a protected environment for bacteria. For this reason, bacteria can survive longer and pose a risk to the poultry population. Therefore, regular (preferably quarterly) inspection of drinking water quality, both at the inlet and at the nipples/cups, is certainly advisable, as is systematic cleaning of pipes.

Removal of manure and grazing

Separation between clean and dirty areas

The principle of clean and dirty road in a poultry farm means that there is a clear separation between clean and dirty (risky) areas of the premises. Poultry transport vehicles are constantly in contact with other areas. This creates a rather high risk of disease transmission. All inbound and outbound traffic is always driven on a dirty road. The clean road is kept for poultry supply and clean product transport (internal movements) and only in fully cleaned and disinfected trucks.
Only the dirty road is relatively easily accessible to visitors, suppliers and consumers. Carcass collection is understandably part of the dirty section. Containers and other tools used for this purpose can only be returned to the clean section after they have been thoroughly cleaned and sanitized. Manure removal is always carried out along the dirty road.

Carcasses and disease transmission

Carcasses or carcasses are always a major source of infectious material. Animals often die due to infection and potentially spread a lot of infectious material. Therefore, it is strongly recommended that carcasses be removed from livestock buildings as soon as possible and stored in a well-isolated location. Dead animals should be removed at least twice a day, and this frequency should be increased if there are many cases of acute mortality.
The cadaver storage area should be located as far away as possible from the rearing buildings, at best outside the fattening area where the carcasses can be picked up without entering the site.
The storage area should be sealed so that no parasites can reach the carrion (through a well sealed, cooled storage area). It is recommended to thoroughly clean and disinfect the storage area after collection of the carrion. The person handling the carrion should always wear disposable gloves for their own safety and to avoid further spread of pathogens.

Refrigerated fallow storage

Refrigerated fallow storage has several advantages over non-refrigerated storage. First, a fully enclosed system prevents the spread of pathogens and effectively prevents contact with parasites. In addition, these refrigerated systems reduce the rotting process, ensuring less odor development and less frequent visits by fallow removal staff.

Access control

To maintain a high level of biosecurity on a poultry farm, it is important to provide access to as few people as possible. Visitors can carry many pathogens with them and these pathogens will contaminate the poultry population. Therefore, it is recommended to prevent unauthorized persons from entering livestock facilities and to ensure that outside personnel spend as little time as possible in and around the facilities.
It is strongly recommended that proper access control be provided so that there is sufficient supervision of persons who wish to enter the poultry houses. Every visitor must register before entering the farm and livestock buildings. The installation of a farm fence creates an effective entry barrier.

Poultry “exposure”Often visitors and staff require exposure from poultry production for 24 to 72 hours before they can gain access to the poultry facility.
This assumption is based on the fact that pathogens excreted by poultry can survive in humans for a period of time. During this period, humans can also passively excrete these infectious agents and transmit the pathogens to susceptible animals through direct contact. However, when all other preventive biosecurity measures (such as the use of special clothing and footwear, hand hygiene, or showering) are properly applied, the “exposure” period has only limited additional protective value.

Special clothing

Since humans can serve as mechanical vectors of infectious diseases, it is recommended that special biosecurity measures be taken the moment a person enters a poultry farm.

When visitors and staff enter the houses, they should shower and wash their hands. The latter is a simple but very useful measure that is often forgotten. The hands of poultry handlers are undoubtedly an effective way of transmitting pathogens through direct contact with animals. Thus, when changing clothes and shoes in a sanitary skip, it is also necessary to have hands washed both on arrival and departure.Sanitary passThe sanitary pass, where visitors must wear overalls and shoes, is particularly designed to reduce the risk of mechanical transmission of diseases through people.
The location of the sanitary passageway within the feedlot is extremely important. The sanitary bunkhouse should have one entrance and one exit, and the room is divided into clean and dirty areas.
An example of the layout of a sanitary unit:

Supply of commodities

Material and disease transmission

Pathogens can find entry to the fattening site through the supply of commodities. This occurs especially when materials have had previous contact with poultry or when they have been manufactured or packaged at other poultry farms.
To prevent the transfer of pathogens from one company to another, it is recommended to use proprietary, tested TMCs. However, if generic material has to be introduced, this can be done through special gateways with disinfecting UV light.

Infrastructure and biological vectors

Litter and disease transmission

The litter from the poultry house is highly contaminated at the end of the production cycle with all kinds of infectious agents such as avian influenza, E. coli, infectious bronchitis virus and many others. Also in many places contaminated garbage is scattered in the surrounding agricultural fields. This will greatly increase the risk of disease transmission for poultry farms located near these fields. Therefore, contaminated litter should not be left out of the poultry farm itself.
The risk of infection if litter is spread to surrounding fields will additionally depend on wind direction, the presence of vermin or wild birds and the spread of infection through personnel or equipment.

Rodents and disease transmission

Rodents play a significant role in both mechanical and biological transmission of some infectious agents. These species will be important for the spread of certain pathogens within the poultry farm, but also for the introduction of pathogens from neighboring production facilities. Parasites, like rats, often serve as reservoirs for specific pathogens, and they spread these pathogens in the environment. It has been repeatedly demonstrated in experiments that rodents are active vectors of many microorganisms, such as Salmonella spp. and Campylobacter spp.
It is also important to note that rodents are sources of damage to on-farm equipment (electrics, communications) as well as sources of contamination of feed and water if they have direct access to the latter.

Rodent control measures

An effective control program is necessary to control parasites. This is often developed in cooperation with specialized companies.
It is important to prevent rodents from establishing themselves in the neighborhood of fattening sites. This can be achieved by avoiding the presence of all types of specific shelters nearby in the neighborhood (e.g. plants, heaps of dirt…). In addition, feed should be stored in closed tanks that limit access of rodents or birds.
To minimize contact with rodents and other wildlife, a proper fence or other type of barrier should be installed around poultry houses.

Birds and disease transmission

Wild, free-living birds can directly or indirectly transmit pathogens to the poultry population. In addition, these birds may also damage farm facilities or equipment. Examples of infectious diseases in which wild birds can play an important role include avian influenza, Newcastle Disease, Mycoplasma spp., Campylobacter spp., and Salmonella spp.
To keep birds (and rodents) outdoors and avoid direct or indirect contact with the avian population, it is wise to cover all air intakes with netting). Ponds or other sources of standing water should also be covered with nets to keep migratory birds away and prevent them from using the water as a resting place. In addition, surface water from the environment should not be used as drinking water as it is likely to be contaminated by wild birds. The presence of trees or other shrubs in the vicinity of bird houses should be avoided as they may provide protection for wild birds from sun or rain.It is strongly discouraged that farm personnel keep poultry at home. By coming into contact with their poultry, they can very easily introduce infectious agents into the feedlots.Pets and disease transmission

Pets (dogs and cats) can act as indirect vectors of infectious agents when they have the opportunity to enter poultry houses. Thus, they can carry infectious material to the poultry population. Thus, control of rats or mice by pets is not an ideal method and is therefore absolutely not recommended. In addition, dogs and cats can also be carriers of some infectious diseases such as avian influenza. These pathogens can be transmitted to poultry populations through direct contact between animals or indirectly through food (if pets have access to food storage areas).

Other farm animals and disease transmission

Various infectious agents can be transmitted between different animal species. For example, the presence of other farm animals on a poultry farm (pigs, cattle, etc.) may represent a potential source of infection to an existing poultry population.
It has been repeatedly shown in experiments that Campylobacter jejuni can be transmitted between poultry and pigs or between poultry and cattle. Avian influenza has also been associated with pigs kept near poultry houses.
In addition, it is strongly discouraged to keep different poultry species on the same farm because some pathogens are more or less pathogenic to different poultry species. For example, a specific infectious agent may be less pathogenic to chicken, while it is highly pathogenic and dangerous to turkey. This is the case with Histomonas meleagridis, also called eel disease. Another example is the different sensitivity to avian influenza – chickens or turkeys are much more susceptible to this virus than ducks or pigeons.


Vaccination and health status

Vaccination of the poultry population is an important part of good disease management, along with proper euthanasia policies, removal of carrion from livestock buildings and control of boarding densities. When poultry are properly vaccinated, losses from disease and mortality will be less. In addition, vaccination has a positive effect on animal welfare and can lead, in combination with other measures, to the eradication of an infectious disease.
The risk of disease outbreak is generally lower in areas where poultry populations are vaccinated against a particular infectious disease (e.g. avian influenza) compared to areas where vaccination is not carried out. This can be explained by the fact that proper vaccination reduces the number of animals that excrete the virus and reduces the overall infectious pressure for that disease in the vaccinated area.

It is critical to have data on the maternal immune level of animals when a poultry population is vaccinated. In the case of strong maternal immunity, the effect of the vaccine may be buffered by the maternal antibodies present (causing a significant reduction in vaccine function). In cases of weak maternal immunity, administration of the vaccine may provoke a severe reaction. Protective antibody titers are usually not formed until 12 days after vaccination. Therefore, animals with weak maternal immunity may be susceptible to certain pathogens for up to 12 days after vaccination.
In addition to vaccination, it is also valuable to know the disease status of the poultry farm. In this way, the good health of the flock can be ensured and it enables timely intervention where necessary – possibly by (re)introducing a specific vaccination protocol.

Planting density

Stocking density has a significant impact on the extent of an outbreak. When birds are housed close together, they become stressed. As a result, their susceptibility to various infectious diseases increases and the poultry population will excrete more pathogens. For this reason, the overall on-farm infection pressure will eventually increase dramatically. Thus, a reasonable reduction in flock density is an important measure to control infectious diseases.
When stock density is too high, it will have an impact on the transmission of certain infectious diseases, but it will also affect the production performance of the poultry farm. It has been shown that a population with high stock density has more bone and muscle production problems, resulting in more fractures and cases of leg injuries. In addition, there will be more problems with foot pad dermatitis and the daily weight gain of the animals will be less good compared to a lower density poultry farm.

Poultry of different ages have different levels of sensitivity to certain pathogens. On the one hand, this is due to the fact that certain receptors are only present during certain periods of the chick’s life. On the other hand, maternal immunity (protection of the chick by maternal antibodies in the egg) will disappear over time. Therefore, it is crucial to separate different age groups to avoid the transmission of pathogens to each other. In addition, work at the feedlot should be done from the youngest poultry population to the oldest poultry population. The most ideal situation for a poultry farm is to have only one age at a time in the same animal house or, even better, one age in the entire poultry farm.

Cleaning and disinfection of animal houses

To control infectious diseases on the poultry farm and to break through the pathogen infection cycle, these separate stages of cleaning the animal houses are very important: thorough cleaning (dry and wet), thorough disinfection and allowing sufficient time for the enclosures to dry (exposure).
Having a free period between two production cycles is a good measure to reduce the number of pathogens present. However, the effectiveness of the exposure period depends on the type of pathogen. For pathogens such as Coryza and Mycoplasma spp. this exposure period can be very important because these pathogens do not survive for long periods of time in the environment. For infectious microbes that can remain in the environment for long periods of time, cleaning and disinfection are indeed critical to control these microbes (e.g., Gumboro, coccidiosis). It is recommended to maintain a vacancy period of at least one week after cleaning and disinfection.
However, in European studies on risk factors for Campylobacter infection in poultry houses, it has been shown that a vacancy period of more than 10 days has a negative effect on the colonization of this infectious microbe. This could be explained, for example, by the fact that companies with longer exposure periods (> 10 days) often clean and disinfect their enclosures less thoroughly.
If cleaning and disinfection are not done thoroughly, infectious germs can persist in the houses. This can cause many problems for the poultry population in the next production cycle (through contact with residual manure, dust or feathers). However, some infectious microbes can survive for long periods of time in the environment without the presence of animals. Drinking water nipples, drainage holes and cracks in the floor of enclosures are the most critical places where bacteria can be found after cleaning and disinfection. As follows, special attention should be paid to cleaning and disinfection at these locations.
The optimal cleaning and disinfection protocol consists of seven steps:
1. dry cleaning to remove all organic material,
2. soaking all surfaces with a special detergent,
3. high pressure cleaning with water to remove all contaminants. This step will go much easier, faster and more efficiently if a long soaking step is performed beforehand,
4. drying the enclosure to avoid dilution of the disinfectant used in the next step,
5. disinfection to achieve a further reduction in microbial concentration,
6. drying to ensure that animals do not subsequently come into contact with puddles of residual disinfectant,
7. verifying the effectiveness of the procedure by taking surface samples (hygienogram). If all previous steps have been performed correctly, there is no need to provide an additional exposure period.
Cleaning and disinfection should be treated as two separate steps. Each step requires a specific chemical product and they should not be in contact with each other. Considerable care should be taken to remove all organic material during the cleaning process, as organic material can deactivate the detergent used. In addition, the presence of grease provides a good defense for bacteria and other microorganisms.
Not only should the interior of the houses (including drinking water piping, feed silos and the external feed system) be thoroughly cleaned and decontaminated, but also the environment around the houses (paved areas, loading areas, etc.) should be properly taken care of.


Good cleaning and disinfection is not always easy on a poultry farm. A hygienogram can be used to evaluate the effectiveness of the cleaning protocol. To make a hygieneogram, samples are taken using pressure plates (RODAC) from control points and areas inside the enclosure. These plates measure and quantify the presence of bacterial contamination (total aerobic flora) present after cleaning and disinfection of agricultural buildings. The results obtained are expressed in colony forming units (CFU)n per plate.
Contact agar plates (such as RODAC plates) are often used as a standard assessment for cleaning and disinfection, but in fact contamination levels can be better determined by counting bacteria using swabs.
This is a hygienogram assessment system for poultry farms (Anonymous, 2017):

Shoe washes and disinfection baths

To prevent the spread of pathogens through shoes, shoe washers and disinfection baths should be placed at the entrance to each house. If disinfection tubs are not properly used and maintained, it is really a waste of money because these tubs can even be a possible pathway for transmission of infectious germs.
Effective disinfection can only be achieved if the dirt and fecal matter is removed from the boots beforehand. This can be done by washing the boots and water with detergent added. The boots should then be placed in a visually clean solution with disinfectant. This protocol requires that the concentration of disinfectant and cleaning duration be followed according to the instructions in the disinfectant manual. The disinfectant in disinfection baths should be refreshed regularly, especially when the liquid has become visibly dirty, as direct contact with organic material inactivates the disinfectant effect.