Due to the corona virus pandemic, biosecurity for humans has made continuous headlines for three months. Jim Bigmore, managing director of hygiene specialists, Hysolv, takes a timely and critical look at the comparisons with salmonella control in the layer industry. 

As the UK slowly returns to some sort of normality and the “lockdown” becomes less severe – well, at least for some privileged individuals! – there is still a group of people for whom wariness about the disease status of strangers and avoidance of contact with the outside world will continue.  

These are the egg producers!  

Just like the lockdown, social distancing and mask-wearing caused by the Covid-19 pandemic, the reason for this continuing high security, seen on every layer and pullet farm, is to protect members of the public from the on-going ubiquitous and still-serious disease – salmonella. 

How many of us have watched the coronavirus pandemic unfold and noticed certain similarities to the normal working day on a farm?  

Internationally, we’ve seen the different control measures used, with fairly predictable outcomes. However, whichever approach was used to control the pandemic, four clear messages emerged: 

1. There must be early recognition that there is a problem and control measures must be developed and disseminated clearly and quickly to those involved. 

2. The spread of the disease must be controlled. 

3. “Herd immunity” must be established to effect long-term control. 

4. Scientific methods and advice should be followed, and misinformation avoided. 

So how do these four points compare with salmonella control on pullet and layer farms? 

1. Early problem recognition, control measures development and implementation: The salmonella situation sprang to prominence on the 3^rd December 1988. In 1993 breeders were vaccinated to reduce Salmonella Enteritidis (SE) prevalence.  Later the improved use of biosecurity and hygiene coupled with SE vaccination in layers brought down the prevalence of SE. The introduction of the Lion Code by the British Egg Industry Council (BEIC) setting out strict testing and reporting systems for both the pullet rearer and layer farms, similar to the rules since adopted by the EU, has driven the further decline of salmonella in the egg industry. Each flock from day old, to point-of-transfer to the laying house has their environment tested four times. Thereafter, each laying flock has its environment tested twice.  Not only are the tests compulsory, the consequences of having a salmonella positive farm are also clearly defined and enforced.  

2. The spread of the disease must be controlled: At the end of every poultry rearing, or production period, the houses are emptied, cleaned and disinfected. Before the houses are restocked with the new flock, boot-dips and hand-sanitisers are put in place to help stop the transmission of salmonella and other diseases to the flock. This “lockdown” is aimed at preventing diseases entering buildings through vectors such as: 
    2.1 Human. Access to housing must be limited, poultry house-specific clothing to be used, hands should be sanitised and boots disinfected/changed going into and leaving the house. It must be made sure that that all employees are not ill when working with the birds. 
    2.2 Vermin. Control methods have to be instigated through using strategically-placed bait-stations/traps together with landscaping the environment outside the housing to discourage vermin
    2.3 Wild birds. Disease control in free-range farms is extremely difficult as wild birds are attracted to poultry feed and obviously carry avian diseases and parasites. However, closed-housing should be bird-proof. 
    2.4 Vehicles. Supply and waste management vehicles will travel from farm-to-farm. So vehicle washes/disinfectant points and wheel dips with appropriate disinfectants must be used to prevent disease spread from other farms. 
    2.5 Red mite. Red mite are not only a major bird welfare issue within the layer sector, but they also have the added problem of being a vector for salmonella. Red mite can be controlled, but there are no shortcuts, or tricks for red mite management.  Control always involves knowledge of the red mite’s lifecycle and habits, and the strategic use of available products and resources. There are many methods of red mite control including conventional biocides, diatomaceous earths and silicon-based products that dehydrate the mite, glue to prevent their movement and heating poultry houses until the mites and eggs have been destroyed. The author also has experience of a chlorocresol-based disinfectant killing red mite eggs and adults if left to work for 24 hours rather than the usual 2-3 hours.    

3. Establishing herd immunity. Vaccination has been a key factor in the success of salmonella control in the egg industry. Unlike Covid-19 control, the bird’s natural immunity is not allowed to develop. They are either vaccinated or slaughtered if positive for salmonella  
    

4.  Following science and avoiding misinformation. In the previous three points, the egg industry has really been guided by a good scientific approach to disease control. However, before we become too smug, it is fair to say that some companies supplying the egg industry may have made some over-ambitious claims for their products, based upon unrealistic testing criteria. 

Along with vaccination, disinfectants have a key role. The BEIC publishes a list of disinfectants that can be used in farms adhering to the Lion Code. This, in turn, is based upon the Department of Food and Rural Affairs (Defra) list of approved disinfectants and the concentration at which the products passed the General Orders and Poultry Orders. This is certainly science-based, but does this really give the industry a clear comparison of the available products in terms of their ability to kill salmonella in on-farm conditions? The answer is probably NO! 
 
In 2011 Defra carried out further tests that mimicked conditions under which disinfectants would be expected to control salmonella on real-life poultry farms. These involved the use of disinfectants in boot dips (Wet Model) and on housing surfaces at end-of-cycle cleaning and disinfecting (Dry Model). 

 
Wet Model – simulating boot-dip disinfection. Objective – disinfection of a solution Salmonella Enteritidis mixed with chicken faecal matter. 

Results of disinfectants used at General Orders concentration and two hours contact time.  

• Glutaraldehyde + Formaldehyde (2 products) – Passed 
• Chlorocresol#1 – Passed 
• Chlorocresol#2 – Passed 
• Glutaral – Passed 
• Peroxymonosulphate – Passed 
• Amphoteric surfactant – Passed 
• Formalin – Passed 
• Substituted phenol blend – Failed 
• Glutaral + Quaternary Ammonium Compound (QAC)- Failed 
• Iodophor – Failed 
• Alkylamine + QAC – Failed 
• Peroxy/Peracetic (2 products) – Failed 

Dry Test – simulating surface disinfection within a poultry house. Objective – disinfection of Salmonella Enteritidis on porous surfaces covered with chicken faecal matter. 

Results of disinfectants used at General Orders concentration and the elimination of viable salmonella from the disinfected surfaces. 

• Glutaraldehyde + Formaldehyde (2 products ) – Passed 
• Chlorocresol#1 – Passed 
• Glutaral – Passed 
• Formalin – Passed 
• Chlorocresol#2 – Failed 
• Substituted phenol blend – Failed 
• Peroxymonosulphate – Failed 
• Amphoteric surfactant – Failed 
• Glutaral + Quaternary Ammonium Compound (QAC)- Failed 
• Iodophor – Failed 
• Alkylamine + QAC – Failed 
• Peroxy/Peracetic (2 products) – Failed 

All these disinfectants had passed General Orders.  However only 57 per cent passed the Boot Dip simulation and only 36 per cent passed the Defra simulation of a poultry house disinfection. The tests also showed that just because products share some active ingredients – such as chlorocresol – doesn’t mean that they perform similarly. It is the product’s non-active or “helper” ingredients that make the difference. Some good news for the Lion Code farms, the successful chlorocresol disinfectant, Interkokask, is on the list! The full report is available on-line and makes interesting reading.  
The results are plain to see, but the number of pullet-rearers and egg producers who don’t investigate the science behind disinfection and just buy on price is still surprising. 

 
However, in comparison with the Covid-19 control, the egg industry is still a very long way ahead!