Five common misconceptions about disinfectants
“All animals are equal, but some animals are more equal than others.” That famous quote from George Orwell’s novel, Animal Farm, is very analogous to the efficacy of disinfectants, says Jim Bigmore, managing director of hygiene company Hysolv.
Similar active ingredients make products behave the same.
This may seem a reasonable statement, but it is simply wrong. Some companies may sell their disinfectants by claiming that theirs contains the same active ingredient and it is therefore equivalent to the market leader. The truth is that the subtle differences in formulation can make a profound difference in efficacy. This was borne out independently when, in 2017, the Animal and Plant Health Agency (APHA) tested different three disinfectants containing chlorocresol against biofilm. The test examined whether the disinfectants could break though biofilm as it built up over a period of 25 days. (Data source: Efficacy of disinfectants and detergents intended for a pig farm environment where Salmonella is present: Rebecca J. Gosling, et al.[i])
Product “K” (Interkokask) was still breaking through biofilm and killing monophasic Salmonella typhimurium after 25 days of biofilm build-up. Products “I” and “J” were ineffective after eight days.
This not nly applies to chlorocresol, but to all other active ingredients as well. Farmers, if you are serious about disinfection and want to compare disinfectants before you buy them, look at an independent source of information. DEFRA and APHA have published some very useful comparisons of disinfectants.
Ask Google about “Evaluation of commonly-used farm disinfectants in wet and dry models of Salmonella farm contamination[ii]”. You may be surprised!
It’s necessary to change disinfectants regularly to prevent resistance build-up.
According to a personal communication from an expert at APHA the usual reason that disinfectants stop working is due to under-dosing, not resistance. The livestock industry has been exposed to some unscrupulous advertising, of disinfectants – promoting products at concentrations that simply aren’t effective in a real-farm setting. The reason for doing this is to reduce the cost of using the product and make it more competitive. A case in point is a product that is promoted for use at 0.25 per cent, whereas in the Defra approvals list it is recorded for General Orders at over three per cent – a 12 times higher concentration! If this product is used on a farm at 0.25 per cent and it doesn’t work, will the disinfectant manufacturer say the farmer was misled, or simply that it could be resistance build-up and sell them another product from their range?
In one Middle Eastern breeder farm the author conducted a biosecurity audit where the farm manager was having the houses disinfected three times, each time with an ineffective concentration of a disinfectants from a different chemical product group. When asked why three times with different types of disinfectant, he quoted resistance build-up as the reason. We finally compromised on using two disinfectants at the correct dose rate.
There are several other misconceptions, one of which being “It smells strong, so it must be good!” or “I like the colour!”. You can’t beat logic like that!
The DEFRA approved disinfectants list will always indicate the best disinfectant.
The DEFRA approval list is a good guide but contains a flaw! The tests are mostly conducted at 4°C for 30 minutes. This type of test favours oxidising and organic acid types of disinfectants, rather than glutaraldehydes and chlorocresols which tend to react more slowly at low temperatures.
In other test methods used by European (EN), and German (DVG) tests, there are varying temperatures and varying lengths of time. This is a better representation of the temperatures that a farmer is likely to see on the farm.
Most UK farmers will rely upon the information shown in the approved DEFRA disinfectants list.
For example: From the DEFRA test results above, the clear product of choice would be the peracetic/peroxy type of disinfectant. However, in DEFRA/APHA disinfectants comparison tests mentioned earlier, the glutaral/formaldehyde-based product was a top performer, while peracetic/peroxy based products used at General Orders, failed the “wet” test simulating a footbath, failed the “dry” test simulating use of surfaces in a poultry house and was the only product group to completely fail Campylobacter footbath tests conducted by the APHA[iii]. So, which one would you chose?
Only oxidising disinfectants work at low temperatures.
It is true to say that oxidising disinfectants are relatively unaffected by low temperatures, but this doesn’t mean that other product groups, such as glutaraldehydes stop working. The DEFRA tests are conducted at 4°C. This is already a low temperature and, looking at average temperatures for the UK from 2015 to 2019, only February 2018 had an average temperature lower than 4°C when it sunk to 3.1°C. On occasions where there is a risk of even lower, sub-zero temperatures, anti-freeze can be added to many glutaraldehyde-based disinfectants and they will continue to work. It will be only be necessary to allow a longer exposure time.
Always trust product approvals!
Disinfectants companies rightly lay great store about EN or DVG test approvals – after all, these tests are very difficult to pass. Unfortunately, in reality, sometimes companies don’t actually have a DVG/EN approval and have just “tested according to the DVG/EN test method”. This normally means that the test varies in some way from the approved method.
An example would be the EN14349:2012 a test “..for the evaluation of bactericidal activity of chemical disinfectants and antiseptics used in the veterinary area..”. The method stipulates using E. hirae, P. vulgaris, P. aeruginosa and S. aureus as mandatory test organisms. One well-known company claims only a P. vulgaris test result for a EN14349 claim. Does this mean that the other bacteria weren’t tested? If so, then it certainly can’t claim an EN14349 approval.
The point is that all the bacteria are important in poultry. Just testing one doesn’t prove anything other than the disinfectant kills that one bacterium. If this is made clear in the company’s advertising then, all is well and good.
Summary: Each of the examples cited have been given to the author as a reason for a farm using a certain disinfectant. It is always difficult to convince a farmer/manager/ stockperson that something is not true, or they have been misled if they have believed it for years. As the disinfectants industry becomes better controlled and policed, we should see some of these pieces of misinformation disappear. Let’s hope so!
[i] Efficacy of disinfectants and detergents intended for a pig farm environment where Salmonella is present
Rebecca J. Goslinga,⁎ , Ian Mawhinneyb , Kelly Vaughana , Robert H. Daviesa , Richard P. Smithc
a Department of Bacteriology, Animal and Plant Health Agency, Addlestone, Surrey, UK
b Surveillance and Laboratory Services, Animal and Plant Health Agency, Bury, St. Edmunds, UK
c Department of Epidemiological Sciences, Animal and Plant Health Agency, Addlestone, Surrey, UK
[ii] Evaluation of commonly-used farm disinfectants in wet and dry models of Salmonella farm contamination
Ian McLaren, Andrew Wales, Mark Breslin & Robert Davies
To cite this article: Ian McLaren, Andrew Wales, Mark Breslin & Robert Davies (2011) Evaluation of commonly-used farm disinfectants in wet and dry models of Salmonella farm contamination, Avian Pathology, 40:1, 33-42, DOI: 10.1080/03079457.2010.537303
[iii] The efficacy of broiler farm boot-dip disinfectants against Campylobacter jejuni J.D. Rodgers, N.H. Kell, R.H. Davies, A.B. Vidal. Dept of Bacteriology, Animal and Plant Health Agency, Addlestone, UK. Contact: firstname.lastname@example.org