RTFM – a good start for salmonella control 


In the past year, everyone has become much more conscious of the need for strict biosecurity. For egg producers, salmonella is still a disease against which they just cannot afford to drop their guard. In giving some topical tips, Jim Bigmore, managing director of hygiene specialists, Hysolv, says 

RTFM – a good start for salmonella control 

“RTFM” first entered my life in 1983 when the company for which I worked bought its first computer. The mighty IBM XT computer boasted a mindboggling 10MB hard drive, a small screen with green lettering and almost limitless opportunities for making mistakes when incorrect commands were entered after the c:\ appeared on the screen. Our computer guru would usually respond to our mistakes with his own command – “RTFM”, or “Read The Flaming Manual” although “flaming” wasn’t the actual word he used! 

This notion of reading and following instructions may seem obvious but, in my experience, in the animal health world, products are regularly used in ways that defy logic – or at least the logic envisaged by the manufacturer. The usual reasons for not following instructions are: 

  • We’ve always done it this way with the other products! 
  • It’s too expensive to do to the way they suggest! 
  • I haven’t vaccinated my birds against xxxxxx and I’ve never had a problem. 

And so on… 

Quite often the result of being adventurous with products is that unexpected consequences occur, most of which are costly! 

Salmonella control, as we all know, is one of the most vital health procedures on any layer farm. Any mishap can be extremely damaging. 

Getting value from vaccines 

Vaccines have been very much in the news lately and I am sure we are all aware just how crucial it is to follow correct recommendations. When a manufacturer is called to a farm to investigate a vaccine complaint, or a ministry vet arrives to investigate a salmonella-positive farm, they will have in mind that if the product is being blamed for not functioning, it is probably the only part of the vaccination process that has been quality controlled and has been tested to prove it works!  

The manufacturer’s representative, or veterinary surgeon, will ask the farmer a number of questions to find out what happened. These may include this small, but important, selection: 

  • How was the product stored? 
  • Were the birds healthy before vaccination?
  • At what age were the birds vaccinated? 
  • How many birds were treated and with how many doses?  
  • Were the correct vaccination procedures followed? 

All of these questions will try to ascertain whether the user had RTFM. In this case the label, or pack leaflet, being the “Manual”. If the manufacturer is asking the questions usually the reason will be to avoid liability. 

  • If vaccines are either stored at too high, or too low, a temperature, they might be damaged. The refrigerator, if audited and found to be faulty, may result in the manufacturer refusing to pay for any loses.  
  • If a bird already has a salmonella infection, it’s too late to vaccinate and any positive birds will not be the fault of the vaccine.  
  • Live salmonella vaccines are given at day old. If the birds are vaccinated much later than Day 1, there’s a chance they may already have been exposed to salmonella. This is why a live vaccine is generally accepted to be the best way to prevent salmonellosis in layers. 
  • Some farmers think that “cutting” vaccines and giving 1,000 doses to 2,000 birds will be an okay way to save some money. The manufacturer’s vaccine trials, however, would have been based upon birds receiving full doses and using the correct vaccination schedule. If the number of doses and birds don’t match, there’s not a chance that the farm will be compensated for any losses caused by the vaccine. 

So, the thing about vaccines is that, in order to work correctly, they have to be used exactly in accordance with the instructions on the pack leaflet and bottle label.  

If the manufacturers could have produced a vaccine that could be stored at room temperature, that worked using one half dose and given to birds that were protected by maternal antibodies, or removed salmonella from infected birds. They would have sold it as such. They are bound by rules that insist they give good instructions and proof of efficacy. 

. Keeping birds healthy will depend more upon disease prevention than cure, particularly with the decreasing reliance on antibiotics, points out Jim Bigmore. 

Difficulties with disinfectants 

Disinfectants are another issue altogether and are often the front-line of defence against bringing disease onto a unit or into a poultry house. Most standard disinfectants will eliminate bacteria, viruses and fungi if the correct concentrations and exposure times are used. The trick is to find out exactly what the correct concentration and exposure time should be for the particular disinfectant being used, as not all disinfectants are the same. In this case, the trouble with disinfectants still concerns reading the manual But here the problem is actually finding which manual to read from! 

Farmers should choose their disinfectants very carefully, as not all disinfectants are the same.  DEFRA and VLA websites provide objective information, says Jim Bigmore.

The DEFRA tests for disinfectants1 that apply to poultry are General Orders and Poultry Orders. The tests are conducted at 4°C and over 30 minutes. This is a very low temperature and a very short exposure time. To generalise, these are conditions that would be useful for boot-dip disinfectants in winter.  

Other disinfectant tests according to European standards generally use higher temperatures, either 10°C, or 20°C, and longer exposure times of up to two hours. These are conditions that would more reflect disinfecting animal housing in warmer weather. 

To demonstrate the problem with the disinfectant’s “manual”. 

Low temperatures that would be experienced by boot-dips, favour peroxygen and peracetic disinfectants as they remain active at these levels. Many sales brochures for the peraceric and peroxygen-type disinfectants promote them as being fast-acting. Unfortunately, these types of disinfectants are exactly the sort less able to work in the conditions with high organic matter generally found, for instance, in boot-dips. Low temperatures slow down the activity of glutaraldehyde and chlorocresol disinfectants, but these are better able to handle the high organic matter loading found in boot-dips. 

The usefulness of chlorocresol disinfectants in boot dips was demonstrated in the Animal and Plant Health Agency (APHA) campylobacter boot-dip trial2 . Chlorocresols consistently killed “campy” 30 times faster than other disinfectants, with the peracetic disinfectants failing to kill campy at all. 

This particular piece of work identified which type of disinfectant was effective against campy, but there were no product names against the results. This was of particular importance for iodophor disinfectants, as one was as good as the chlorocresol disinfectants against campy while the other was useless. We found out from personal communications that Interkokask was one of the successful chlorocresols, but the other?  

Campy has become the single most important food borne zoonosis now that salmonella is under control. This experiment could have been a useful guide to farmers wishing to improve campy control, but all the trial has proved is that some chlorocresols are better than other disinfectants in boot-dips to control this problem. 

So this shows that all chlorocresols disinfectants are not the same.  

Another trial conducted by APHA3 focused on salmonella, compared the ability of different disinfectants to break through biofilm, underlined this point. 

This study really demonstrated the difference between various products containing the same active ingredient, and named the products used.  
Such a contrast to the campy trial result which was next to useless to the farmer and veterinary surgeon as it didn’t identify which products are effective.  

The Veterinary Laboratories Agency (VLA) disinfectant comparison trials4 against salmonella, was much more useful as it named disinfectants and showed results “warts and all”. Generally, the most effective boot-dip disinfectant (Wet Model in the DEFRA trial) was our chlorocresol disinfectant Interkokask. With the glutaraldehyde and two glutaraldehyde + formaldehyde disinfectants, performing consistently well as a building surface disinfectant (Dry Model in the DEFRA trial).  

In my opinion, this “Evaluation of commonly-used farm disinfectants in wet and dry models of Salmonella farm contamination” trial still remains the most useful comparison of disinfectants that has ever been conducted by an independent laboratory. The results were clear and the products used in the trials were identified.  

It really is a manual for disinfectants and salmonella control.  

The future of the farming industry depends upon disease prevention, rather than disease cure. As the role of antibiotics dwindles, the reliance upon vaccines and biosecurity will increase. In my opinion, there must be compliance from farmers in the use of vaccines, and there has to be a better manual written for the disinfectant’s market than just the DEFRA approved disinfectants list. 

So, if the farmer should RTFM, then there should be a “M” to “F” well “R”! 


1  “DEFRA approved disinfectants list” http://disinfectants.defra.gov.uk/DisinfectantsExternal/Default.aspx?Module=ApprovalsList_SI 

2 The efficacy of broiler farm boot-dip disinfectants against Campylobacter jejuni J.D. Rodgers, N.H. Kell, R.H. Davies, A.B. Vidal. 

3 “Efficacy of disinfectants and detergents intended for a pig farm environment where Salmonella is present Rebecca J. Gosling, Ian Mawhinney, Kelly Vaughan, Robert H. Davies, Richard P. Smith” 

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