Topical tips on salmonella control


By Jim Bigmore, managing director of hygiene specialists, Hysolv

Hysolv’s Jim Bigmore, who points out that salmonella has been causing problems for over 2,000 years!

It is a very odd thing to say, particularly to a farming readership, but I may be unique having benefited, since the early 1990s, from poultry having salmonella! At that time, I worked for Hoechst Animal Health where we were offered a strain of Salmonella Enteritidis PT4 by the UK Government.

The strain was very interesting to us, particularly since a certain junior health minister had wreaked havoc on the UK poultry industry.  This made the introduction of strict control measures for salmonella in layers essential to build back the lost trust of the consumer. Since then, I have been involved with two other salmonella vaccines, so my career has been inextricably linked to this scourge of poultry farmers!

For the UK’s layer farmer, the introduction of the British Egg Industry Council’s (BEIC) “Lion Eggs” has been a crucial factor in the control of salmonella, as it coordinated the measures necessary to manage salmonella under the Lion Code of Practice. This defines all the processes required to produce salmonella-free eggs and has resulted in the tremendous improvement in salmonella control throughout the industry.  It has been so successful it has been used as a model for salmonella control in other countries.

Why then, do we still have a problem with salmonella?

The answer, like the problem is multifactorial. Salmonella is ubiquitous. It has been successfully causing problems to mankind for at least 2,000 years.  It was even thought to be the cause of the Great Plague of Athens in 430 BCE.

It can be found on many of the things we eat and touch and can enter poultry units via many different vectors. For the poultry industry, the most important of these are feedstuffs, poultry, eggs, people, mice, beetles, red mite, other insects and, of course, vehicles.

Red mites are a major vector of salmonella.

Simply put, there should always be a three-way approach to salmonella control:

  • Good management
  • Vaccination
  • Effective biosecurity

These three aspects are interrelated, so good management for example would involve the use of effective biosecurity and vaccination. Having only one of these aspects working well isn’t enough.

Almost every farm I’ve ever visited has perfect management – or so they told me! So, firstly, let’s concentrate on vaccination of the birds and biosecurity. In particular, let’s look at the less well-known bits of advice.

Without adequate control red mites can rapidly form large colonies and perpetuate infection.


Birds should be “well” when vaccinated. In particular, they should not have salmonella when the vaccine is administered. Vaccinating a salmonella infected bird, will not remove the infection.  Even if an infected bird is treated with antibiotics, it may simply become an asymptomatic carrier, posing a risk to other birds.

Most modern salmonella vaccines are ‘live’ preparations. This means that they contain, in effect, bacteria, almost the same as a ‘field’ salmonella. Therefore, the same practices that kill and prevent field salmonella will kill and prevent the vaccine-strain of salmonella from working when administered through the water system. So, don’t give vaccines directly after, or at the same time as, probiotics, antibiotics, or water sanitisers as they will kill the vaccine. The general rule is to leave a three-day break between such activities and vaccination.


 Biosecurity is the front line of defence against salmonella.  So, make sure that boot dips are used and changed on a regular basis. A general guide for renewing boot dips is:

  • Oxidising disinfectants may need to be changed on a daily basis.
  • Glutaraldehyde twice a week
  • Phenolics weekly

Therefore, if an oxidising disinfectant is a one-third of the cost per litre of a phenolic disinfectant, it may be still be costing the same on a weekly basis! And that is ignoring the chore of the daily change – which can be easily overlooked in times of stress, staff changes, etc.  Another bonus of using the phenolic boot dip disinfectant is that it should also prevent live coccidial oocysts and campylobacter being walked back into the clean poultry house.

Another point often overlooked is the need to apply disinfectants to dry surfaces! A damp surface may contain 50ml-100ml per m2 water.

If a disinfectant is applied at either 200ml per m2 or 300ml per m2 with a concentration of 1% the following drop in concentrations will occur:

Original spray concentration and application rate (ml/m2)New concentration with 50ml surface water/m2New concentration with 100ml surface water/m2
1% (300ml/m2)0.88%0.75%
1% (200ml/m2)0.8%0.67%

Some disinfectants stop working if the concentration is too low. It’s not just a case of “leave it a bit longer it will be OK!” It won’t!

Please don’t forget hand sanitisers! Farms have been in a permanent state of “lock-down” for decades. People, and particularly hands, can transmit salmonella and campylobacter. So, put an alcohol hand sanitiser next to each door and use them. We should all be well aware of this in the current situation!

British eggs are among the safest in the world now, but farmers still need to keep a sharp eye on salmonella control, says Jim Bigmore.

There is one last fact to bear in mind when choosing a hand sanitiser. Remember the famous slogan “Removes 99 per cent of all known household germs?” This means that if a surface has 1 million bacteria before treatment, it will still have 10,000 after treatment. Since salmonella can double in number every 20-35 minutes, the number of bacteria can be back to 1 million in two to four hours!

Some hand sanitisers kill 99.999 per cent of bacteria, meaning hands with 1 million bacteria before treatment, will have 10 bacteria left, which would require 6-10 hours to grow back to 1 million. Therefore, 99.999 per cent reduction is 1,000 times more effective than the 99 per cent reduction!

Food for thought – or should I say thought for food if you’ve just sanitised your hands before eating a sandwich!