David Hodson, Rosehill Agricultural Trading Company
Richard Turner MA VetMB MRCVS, St David’s Poultry Team
Biosecurity is not a phrase that hit the mainstream press as of late, however many other words which are commonplace in the poultry industry have been, such as duration of immunity, coronavirus, T-cell immunity, PCR testing and our personal favourite, 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 poultry site, or indeed a country.
Open Borders –The United Kingdom would be a good example with a population of 66 million, with a death rate of 86,015 so far putting our fatality rate at 1.3 deaths per 1000 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 0.005 deaths per 1000 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 and Avian Influenza, as well as whole host of other bacteria and viruses. Now, while we cannot have a closed border due to the nature of deliveries of essentials and field support, we can work to the above 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 confirmed 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. Dr Nicholas Christakis, Professor of Social and 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 each layer are covered by the next layer, 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 provides 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 one of the worst decisions that can be made, from a cost perspective and from a bird welfare perspective.
a. Prior to entering the site, we should ensure that any vehicles that must enter have undergone disinfection of the wheels, wheel arches and underside of the vehicle. The chemical should be applied via a coarse spray and these areas should be well coated. Ideally the vehicles should have left whatever depot they originate from clean, but with winter weather there is also the requirement to clean wheels on entry. The most important vehicle to have clean is the one that goes into the poultry house and that might need further disinfection on site.
b. 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. Whilst not the cheapest, probably one of the best foot dip products is Interkokask as it will last longer than some other products.
c. A signing in book may be present here which require details of who the visitors 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.
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, viruses and other pathogens. In addition, any standing water or spilt 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.
a. On exiting the vehicle, the visitor should ensure that disposable overalls
and boot covers are worn on entering the building,
b. Boot covers should be dipped into the footbath,
c. Hands should be washed, and gloves worn if possible on entering the
d. Where possible, ensure that site specific footwear is used within the
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 is whether they have any form of organic matter (mud, dirt, overalls used elsewhere etc) that could 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. Whilst nobody wants to waste money, it is all too common to see disposable overalls being used many times, sometimes with zips that are broken. The risk is not worth the money saved.
- Prior to entering, change footwear to area specific wellies and ensure the physical barrier is used to prevent shared floor space with dirty footwear. Alternatively, 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.
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 is 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, 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 both AI and Salmonella makes control a must.
Many clients 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.
Many farmers also partake in shooting and this does mean that anyone involved in shooting has a responsibility to make sure the vehicle or protective clothing worn out of the shoot is separate from that worn or used on the farm.
An often-overlooked agent of disease is the humble red mite. 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. As mites feed primarily at night and reside in the roosting areas, an environment is created where the birds do not 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 host’s 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 of transferring disease 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, this can mean 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. It works via entering the bloodstream via the gut and 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 present in faeces and remove encrusted muck
- Disinfection –
A Defra approved disinfectant used at the approved rate. Special attention should be paid to ensuring the appropriate dose rate is used and always ensure that the product used is suitable for use when temperatures are low.
- Secondary Disinfection –
The use of Halamid fogging as a 10% solution as the final stage.
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 very powerful. Its unique formula containing chlorocresol and has shown excellent effectiveness used at an approximate rate of 11 litres in 350L of stock solution.
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 ensures 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 consider the DEFRA trial work as this work is completely independent of the manufacturers. Looking at this work, the two standout products 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.