The purpose of disinfection is to decrease pathogen numbers and prevent disease transmission.
But as we know, different areas across the farm are prone to different pathogens, and not all disinfectants are effective in all situations or across all surfaces.
As such, it’s important to make the right disinfectant choice for each situation to ensure you maximise your chance of preventing the spread of pathogens across your farm and further.
Firstly, it’s important to think about what needs disinfecting.
Common things requiring disinfection include livestock housing, milking equipment, feeding equipment, stock handling equipment, animal care equipment (including hoof knives and calving kit), people (hands and clothing), and sometimes the animals themselves (teats and navels).
Many disinfectants are used for varying purposes on dairy farms. Some are more suitable for housing facilities and others for feeding equipment.
It is important to know which disinfectant is suitable for what purpose and which mixing rates are safe to use and when.
Alcohols
Such as methylated spirits, Glen20.
Effective against bacteria and fungi. Fast-acting, rapid evaporation, leaves no residues but can swell or harden rubber and plastics, and is flammable. Inactivated by organic matter. Ideal as part of teat cleaning protocols prior to administering treatment.
Alkalis
Such as caustic soda.
Alters pH, corrosive to metals, environmental hazard and can cause severe burns to skin and mucous membranes. Variable efficacy depending on temperature and surrounding pH. Effective against bacteria, viruses and fungi (including spores).
Lime has a positive drying effect and raises surface pH, which helps inhibit bacterial growth. However, there is little evidence to suggest that lime reduces the number of pathogens and it should still be used in conjunction with a suitable disinfectant.
Aldehydes
Such as formaldehyde.
Slow-acting but effective against bacteria, some viruses and fungi. Non-corrosive, but inactivated by organic material, hard water, soap and detergents. An irritant, with carcinogenic potential and is an environmental hazard.
Oxidising agents
Such as Virkon-S.
Effective against many bacteria, a broad range of viruses, fungi and bacterial spores. Relatively stable in the presence of organic material and are commonly and effectively used to disinfect surfaces. Can cause moderate skin irritation and damage some metals.
Iodophors (iodine-based compounds)
Such as navel and teat dips.
Traditionally used as antiseptics and disinfectants but are less effective in the presence of organic debris, limiting their use as a disinfectant for surfaces but making them ideal as teat and navel dips when mixed to the appropriate concentration. Generally less toxic than other disinfectants but can stain clothes and some surfaces.
Chlorine-based compounds
Such as household bleach.
Eliminate most viruses, bacteria, moulds and algae but not bacterial spores. Good disinfectants on clean surfaces and are more active in warm water. Can irritate the skin and damage clothing, rubber goods and some metals.
Chlorine-based disinfectants are generally compatible with soaps but should never be mixed with acids. They are ideal for disinfecting feeding equipment which has already been cleaned with soapy water.
In calf sheds, a disinfectant needs to be effective against pathogenic viruses, bacteria and protozoa such as Cryptosporidium parvum. Many disinfectants are effective against viruses and bacteria but the oocysts (eggs) from Cryptosporidium parvum are very stable and relatively resistant to chlorine-based disinfectants. This results in crypto often recurring year after year. Speak with your veterinarian to discuss holistic options for the control of crypto.
Phenols
Such as Dettol.
Generally active against bacteria, some viruses and fungi but not bacterial spores. Good activity in the presence of some organic material but are ineffective against rotavirus, which can limit their use in calf sheds.
Quaternary ammonium compounds
Such as Pine O Cleen.
Effective against many bacteria and some viruses, but not moulds or bacterial spores. Older quaternary ammonium compounds are effective on clean surfaces but newer quaternary ammonium compounds can retain activity in the presence of some organic material. They are generally used for the disinfection of milking machine equipment.
Safety always comes first
Regardless of the type of disinfectant used, always read the label carefully, store correctly, and wear appropriate personal protective equipment when handling and applying.
Similarly, protect livestock where possible from harmful exposure such as inhalation or ingestion.
Take a holistic approach
Disinfectants do not replace cleaning, and will not ‘clean dirt’.
All organic material including soil and dried manure must be removed prior to disinfection. This means all equipment should be washed thoroughly with detergent and water, and allowed to dry prior to disinfectant application.
If faced with an outbreak situation, disinfectants alone are unlikely to control the pathogen. Seeking veterinary advice is recommended.
How can I find out more?
The Australian Pesticides and Veterinary Medicines Authority (APVMA) issues permits to allow minor use of registered and unregistered agvet chemical products for use as disinfectants for treatment of equipment, fabric and surfaces in certain situations, such as this permit for use in case of an outbreak of foot and mouth disease: https://permits.apvma.gov.au/PER83649.PDF
Before registering a disinfectant product, APVMA evaluates relevant efficacy studies to ensure label claims are accurate. For more information, visit https://apvma.gov.au/node/1026
Lucy Collins is completing her Dairy Residency with The University of Melbourne. She works as an on-farm veterinarian for Apiam Animal Health, and dairy farms with her husband in south-west Victoria. She is a 2021 Nuffield Scholar supported by Gardiner Dairy Foundation. Comments, feedback and suggestions can be sent to: lucy.collins@apiam.com.au
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