• 5.4.2023
  • Education


Biosecurity is not a phrase that hit the mainstream press as of late, however many others words which are commonplace in the poultry industry have been, such as duration of immunity, coronavirus, T-cell immunity, PCR testing and my personal favourite which is the widespread discussion of vaccines.

Using an analogy of the current situation we have two scenarios when it comes to prevent a disease entering a chicken site, or indeed a country.

Open Borders – in the case of our country, then great Britain would be a good example with a population of 66 million, with a death rate of 83,203 so far putting our fatality rate at 1 per 804 citizens in this case we had the movement of active vectors (humans) moving into and out of the country with minimal quarantine and limited testing initially, prior to recent developments. In this case it allows a novel virus to spread exponentially amongst a population with immune systems that are not in any way primed to mount a defence until infection has passed (similar to the lack of immunity present to Avian Influenza in poultry). This time gap between the pathogen entering a host and the point at which symptoms occur allows for further transmission and the issue of asymptomatic carriers further exacerbates the situation.

Closed Borders – New Zealand with a population of 4.9 million people has had a total of 25 deaths, with a fatality rate of 1 per 196,000 citizens. They enacted a near complete cessation of the movement of people on the outbreak occurring. The pathogen was rendered unable to infect new hosts it was contained and any potential vectors of the disease were put into isolation immediately. This route of action led to a very successful outcome and in turn the challenge to the population was near non existent.

This is a good way of looking at the developments when a pathogen can enter a population without effective control. If we extrapolate this approach to disease onto your poultry site we not only have the challenge of Coronavirus (known as Infectious Bronchitis for the poultry specific virus), but also Salmonella, Avian Influenza as well as whole host of other bacteria’s and viruses. Now while we cannot have closed border due to the nature of deliveries of essentials and field support, we can work to the above mentioned principles of disease control.

The financial burden of a disease outbreak on a site can range from moderate to catastrophic in the case of a confirm case of HPAI or group B and D salmonella strains. Regardless of whether it has a moderate or incredibly serious impact, through careful implementation of biosecurity we lower the chances significantly.

Nicholas Christakis Phd, a professor of natural sciences at Yale University used the example of each layer of biosecurity being like a slice of Swiss cheese. There will always be a hole through which disease can get through. But by having multiple layers of biosecurity layered together, the holes in layer are covered by the next layer which has holes in other places, leading to the outcome of very little day light getting through when enough effective layers are used.

Preventing Disease Ingress

If we break the site down into three key areas for the purpose of looking at preventing disease ingress

  • The Entrance – the gated area that provide primary entrance to the site
  • The Poultry Building Entrance
  • The area immediate to where the birds are held

Entrance to Site

One of the main tools for ensuring we are minimising the risk of disease transmission in the use of DEFRA approved chemicals at the correct dilution rates. Skimping on the step is without doubt one of the worst decisions that can be made, from a cost perspective and from a bird welfare perspective.

  • Prior to entering the site we should ensure that any vehicles that must enter have undergone disinfection of the wheels, wheels arches and underside of the vehicle. The chemical should be applied via a course spray and these areas should be well coated.
  • A sealed boot dip should be present, at a MINIMUM the chemical should be changed every 3 days. People entering the site should remove any debris and submerge their footwear in the disinfectant
  • A signing in book may be present here which require details of who you are, previous sites visited and purpose of visit, this provides key information that can be called upon in the case of managing a notifiable disease outbreak. Much like the track and trace app which has been used to great effect in countries that have controlled coronavirus.

Poultry Building Entrance

This area should be ideally a concrete pad which is kept clean and disinfected frequently. Standing water in this area provides an enormous challenge as it will provide a reservoir for bacteria and disease. Also any standing water or spilled grain will attract both wild birds and rodents. When looking at this issue remember that the faeces of both animals may be infected with Avian Influenzas, Salmonella.. or both which if they enter the bird area could cause a disease outbreak.

  • On exiting the vehicle the visitor should ensure that disposable overalls and boot covers are worn on entering the building.
  • Boot covers should be dipped into the footbath
  • Hands should be washed and gloves worn if possible on entering the poultry building.
  • Where possible ensure that site specific footwear is used within the poultry house.

Immediate Area to Birds

The critical question here for a visitor is do they need to be near the birds? The question for the manager responsible for the birds is whether they have any form of organic matter (mud, dirt, overalls used elsewhere etc) that count transfer a pathogen to the birds in the house. On a mixed species farm it is very important to ensure that dedicated overalls are used for the poultry shed as Salmonella can be easily transferred from other species on clothing and footwear.

  • Prior to entering change footwear to area specific wellies and ensure the physical barrier is used to prevent shared floor space with dirty footwear. Or place another layer of disposable overshoes onto your footwear.
  • Disinfect hands or wear disposable gloves.
  • Clean any equipment that is due to enter the bird area with a suitable disinfectant.

Preventing Internal Vectors of Disease

The great difficulty we face when keeping a flock healthy does not only come from the incoming visitors, it also can start from within.


Speaking with a consultant for one of the UK’s leading pest control companies, Advanced Pest Management, they had a very succinct way of explaining the constant battle with rodents;
“A rodent is attracted to any location that will offer warmth, food, water and a place to procreate”
Not much different to humans in that case. The poultry building has ample supply of all the needs for a mouse or rat population. The primary reason we seek to have a controlled rodent population is due to their ability to incubate and dramatically increase the amount of Salmonella or Avian Influenzas on a site. When this combined with mice being incontinent and traversing the feed trough and water lines the challenge can be so great that it will overwhelm ANY live or inactivated vaccine for Salmonella.

While it is an option to carry out your own rodent control, I believe all sites can benefit from the input of a professional that is up to date with the latest legislation and products.
Work carried out has successfully demonstrated that H5N1 strain Influenza was shed by 100% of the infected rodents in a study. This aggressive propagation of the both AI and Salmonella makes control a must.

Wild Birds

Many of our customers have complained that since the lockdown and the enormous reduction in game shooting they have seen a lot more pheasants and partridge near their sites. Whenever there is contact between migratory birds, game birds and poultry we are in danger of having a positive AI site. While the compulsory housing order which was enacted on 14th December helps to mitigate this, it only takes a morsel of wild bird faeces being walked into the poultry area for housed birds to go positive.

Cleaning the concrete apron of the shed will help prevent the transfer of dirt from outside into the control area of the shed. But it always comes back to vigorously enforcing the biosecurity barriers at every stage.

Red Mite

An often overlook agent of disease is our little friend Dermanyssus Gallinae, the humble red mite. Clive Boase who is one of the leading experts on parasitology explained the life process of the mite to me as;
In nature the mite have evolved to ensure their survival, this includes the ability to go into a dormant state for 6 months or more. In a nest the mite will present out of site, either under the bark of the tree or deep within the nest, they will feed when the birds are not able to kill them during the night. Once the birds have left the nest they will await their return for as long as is required by going deeply into the infrastructure to prevent them being preyed upon and being exposed to the elements”
The key driver to the ruinous effects when a red mite population is out of control, consists of two factors

  • Irritation and increased stress on the host, feeding primarily at night and residing in the roosting areas, this creates an environment where the birds do have any respite when they would usually rest. Night vision cameras demonstrate the increase in activity. It is this increase in stress that can cause immunosuppression.
  • Transfer of virus through two mediums;

Firstly the mite will feed approximately every 24-36 hours, chelicerae will transfer any viral or bacterial diseases present in one hosts blood, to the next host it feeds on. This is not just an issue for a housed flock, the challenge is presented by the red mite surviving the turnaround procedure and terminal disinfection. This raises the possibility from one diseased from to the newly housed flock.

Secondly the birds will seek to groom and peck the irritated areas. The mite primarily feed behind the neck and along the backline of the bird, alongside other birds pecking at the moving object on another flock member. This causes damage to the skin, and as the pecking implement has biological matter on it, the possible ingress of bacteria related diseases.

The answer to this is to ensure there is an effective method of control in place.


Great results have been achieved through spraying with a non toxic product such as Dergall via a coarse spray every two weeks. The approximate cost per 16,000 bird unit is £140.00 per month and requires 4-6 hours spraying time for one operative.


A fluralaner based anti-acaricide which is given via the drinking water in two doses a week apart. The works via entering the bloodstream via the gut, once present in the gut it acts as a GABA inhibitor on the mite rendering them infertile and causing death with 4 hours of feeding. The success of this method is very reliant on a very thorough whole site cleaning procedure alongside the treatment of the birds.


An effective turnaround consists of the following steps

  • Dry clean Removing all organic matter from the shed such litter, feed and muck
  • Wash Down Pressurised spraying down of the system
  • Detergent A foaming detergent is applied and allowed the prescribed active period to break down fat lipids resent in faeces and remove encrusted muck
  • Disinfection A Defra approved disinfection used at the approved rate, special attention should be paid to ensuring the appropriate dose rate is used.
  • Secondary The use of Halamid as a 10% solution as the final stage of the clean down.


On turnaround the temperature of the house will drop as soon as the birds are depopulated, as the mite has evolved to go to ground when the food source is no longer present we need to take a tactical approach to eliminating them. Interkokask used at a rate 3% is lethal, which is a chlorocresol and propionic and phosphoric has shown excellent effectiveness used at an approximate rate of 11 litres in 350L of stock solution. Following disinfection this is applied to the system by the cleanout team.
Several sites have gone to 30 weeks prior to the red mite challenge returning, thus taking the birds through a large part of the most stressful period. Also this ensure the level of stress and challenge is minimal throughout the early weeks.

The use of dry cleaning carries many risks, among them an insecticide which has been fogged will struggle to penetrate a system that has organic matter present. When looking for mites there are key spots which offer the mites safety. The areas under the drinking line clips, in the joints of metal infrastructure and underneath and dried on muck or dust will all be replete with mite in a challenged house on turnaround.

When choosing your product, ensure you take into account DEFRA trial work as this work is completely independent of the manufacturers. Looking at this work the two standout product that are currently available consist of Interkokask and Intercid. Intercid is comprised of Glutaraldehyde and Formaldehyde which are particularly effective against Salmonella when used at the correct rate.

The greater the investment in ensuring your new flock is housed in a clean, sterile, oocyst and worm free environment, the greater the chance the flock will go onto perform well. Performance of a laying flock is reliant on many factors, the stress of disease challenge is a key factor and could be the deciding factor.

Evaluation of commonly-used farm disinfectants in wet and dry models of Salmonella farm contamination
Ian McLaren , Andrew Wales , Mark Breslin & Robert Davies

Foot dips

In 2015 Rob Davies carried out a field study of the effectiveness of Foot dips, the results were mixed to say the least and one of the key areas identified in the paper was the inaccurate measuring of the amount of disinfectant used.

“As a rule, the greater the concentration of the disinfectant, the greater the antimicrobial activity and the shorter contact time needed to exert its effect. However, specific disinfectants are affected in different ways by concentration adjustments (Corcoran et al., 2014; Møretrø et al., 2009; Wong et al., 2010). For instance, QACs and aldehydes have a concentration exponent of 1. This means that halving the concentration will double the time needed for disinfection. Phenols have a concentration exponent of 6, which means that halving the concentration will increase the time needed 64-fold (26; Russell, 1999, 2004). Thus, where the disinfectants were too dilute, a longer contact time would have been required for anti-Salmonella activity to be exerted.”

With this in mind, the management of foot dips is under utilised by our industry as a protective barrier against disease getting onto a site. We see many foot dips on sites and they following issues have been observed.

  • Not replenishing with freshly mixed solution 2 times per week, or when the footbath becomes contaminated, this especially important in the case of peracetic acid and peroxygen based product which are vulnerable to organic matter.
  • Inaccurate measuring of the solution used, there is a strong argument for using a greater rate than the recommendation in light of this study.
  • Not using a covered foot dip, which allows for contimation with leaves etc and also leads to the solution being constantly diluted.
  • The footbath not being filled to the correct level, which in turn only allows the base of the footwear to be cleaned.
  • Not having a brush present to remove organic matter from footwear prior to dipping, as the disinfectant requires an ever increasing amount of time to effectively kill salmonella, should there be large deposits of mud.

In summary, the use of a footdip is only as effective as how well it is managed. By ensuring an effective product is used, at an effective rate and replenished regularly a site is a step closer to being biosecure.

Full Paper: Assessment of anti-Salmonella activity of boot dip samples
André J. Rabie, Ian M. McLaren, Mark F. Breslin, Robin Sayers & Rob H. Davies

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