This document was produced by MAFF as a specific response to the FMD outbreak in the UK in 2001 and was made available on their website. Risk Assessments and specific recommendations related to the conditions in the field at the time and should be viewed in this context as they may not be applicable to outbreaks occuring under different circumstances.
Foot and mouth disease
28 April 2001

FMD: Adjusting the pH as a means of disinfection against Foot and Mouth Virus

HEALTH & SAFETY

1. The appearance of a disinfectant on the MAFF approved list means only that it has been shown to be effective for the purpose at the dilution rates listed and HAS NO IMPLICATIONS FOR THE SAFETY OF THE PRODUCT.

2. Manufacturers and suppliers are obliged to provide Information on the hazards and safe use of their products in the form of safety data sheets and on labels, users must take note of this information and use the product accordingly. This information should also give guidance on what to do in the event of accidental spillage or exposure to the product.

3. As a rule of thumb, where there is a choice of products that will do the same job, the least hazardous should be selected.

4. Many disinfectants will be hazardous in one way or another and will require a risk assessment to be made, as required by the CONTROL OF SUBSTANCES HAZARD TO HEALTH (COSHH) Regulations, before they can be used. The assessment, WHICH MUST BE MADE BY THE USER, should be based on manufacturer's/ supplier's safety information and take into account the method of application and the circumstances of use.

5. A common hazard associated with many disinfectants is that they are corrosive, particularly in concentrated form, and can cause burns if they come into contact with eyes and skin. Contact should be avoided and protective clothing in the form of waterproof overalls, rubber gloves, and safety goggles, spectacles or face shields used.

6. Some disinfectants may also be respiratory irritants, again reference should be made to the manufacturer's/ supplier's safety information which will give advice on precautions and, if necessary, specify suitable respiratory protective equipment.

7. A few disinfectants on the list may contain Gluteraldehyde, this is known to be a respiratory sensitiser and it is recommended that alternative products are selected.

Use of Disinfectants

• Only disinfectants, which have been tested and approved by MAFF to kill the foot and mouth disease (FMD) virus, should be used. Even if the disinfectant that you currently use says MAFF approved you must check it has been specifically approved to work against FMD.
• Approved disinfectants must be used at the correct dilution which is effective against the virus. All this information is available on the MAFF website or by ringing the FMD Helpline (Tel No. 0845 0504141).
• The disinfectant must be freshly prepared and you must prevent it becoming fouled with mud or manure. Rain will dilute disinfectant in uncovered containers, footbaths, wheel dips etc and it may no longer be effective. The disinfectant in mats, especially straw will rapidly become dirty and any rain will wash the disinfectant away.
• Apart from the many proprietary disinfectants, the FMD virus is easily destroyed by high pH (alkaline) or low pH (acid). Some disinfectants which work by changing the pH are relatively cheap, commonly available and very effective against the virus and are also approved by MAFF.

Either use an ALKALINE or an ACID disinfectant. Never try to use both together as they will cancel each other out to give a neutral pH and the virus will not be killed.

Before using any disinfectant you must clean off all mud, manure and other matter since most disinfectants will not work if there is manure, mud or any other material present.

ALKALINE DISINFECTANTS. These work by increasing the pH (more than 7)

1. 4% solution of sodium carbonate (also known as washing soda)

To make:
Dissolve 500 grams of washing soda crystals in 10 litres of hot tap water (or 1 lb of crystals in 2 gallons of hot tap water). This is roughly equivalent to two good handfuls of washing soda powder in a gallon of water, or in 4.5 litres of water.

The effectiveness of the solution can be improved by the addition of detergent, such as household washing up liquid. Add 15 ml of detergent to each gallon (or 4.5 litres) of washing soda solution (or one tablespoon to each gallon or 4.5 litres)

This solution can be used for the cleaning and disinfection of all external surfaces (e.g. farmyards, animal accommodation, tractors, trailers, all vehicles, utensils, tools, boots, shoes, waterproof clothing etc). Hands may also be washed and fingernails scrubbed in this solution.

The solution can also be used to reduce infection at places where animals congregate around the farm (e.g. water troughs, feeding troughs, farm gates etc.) In especially muddy places a double strength solution can be used. It is also useful to scatter the dry crystals of washing soda on the surface and mix it into the mud.

The solution can also be used to spray or dip animals. In this case it must be washed off after 30 minutes or so to prevent any possible harmful effect.

Note: Soda solution may corrode metal and damage painted surfaces and for these items citric acid solution (plus a suitable detergent) is preferred. Citric acid or ortho-phosphoric acid may have some slight effect on galvanised metal, but as the virus is destroyed in less than one minute on clean surfaces, these can be quickly rinsed off with clean water. For this reason, galvanised containers are not suitable for use as disinfectant footbaths over long periods.

The killing of FMD virus by sodium carbonate is slower than that of the acid disinfectants, but washing soda itself has a cleaning action, and its residual disinfection capacity is long lasting.

Health Warning

AVOID CONTACT WITH THE EYES, NOSTRILS AND MOUTH OF BOTH THE OPERATOR AND THE ANIMAL. IF THIS SHOULD HAPPEN, THE SOLUTION MUST BE WASHED AWAY WITH COPIOUS AMOUNTS OF RUNNING WATER.

ACIDIC DISINFECTANTS. These work by lowering the pH (less than 7)

Health and safety warning

ALWAYS ADD ACID TO WATER - NEVER ADD WATER TO ACID.

1. 0.2 %CITRIC ACID BP

To make:

Dissolve 30 grams of citric acid crystals in 15 litres of water (or one ounce of crystals in one gallon of water). Alternatively a 10% solution may be prepared by dissolving 500 grams in 5 litres of water (or 1 lb of crystals in 1 gallon of water) and further diluting, as required for use, at the rate of 250ml in 12.5 litres of water (or 1/8 pint in 2 gallons of water). The concentrated (10 %) stock solution should not be kept for more than 2 weeks. Before use the container should be as sterile as possible and should be airtight, otherwise the stock solution may be attacked by moulds and bacteria which reduce its efficiency. Exposure for one minute is sufficient to kill the FMD virus.

2. 0.2 % SULPHAMIC ACID

To make:
Dissolve 30 grams of sulphamic acid crystals in 15 litres of warm water (or one ounce of crystals in three gallons of water). Sulphamic acid has less effect on metals than other mineral acids and may be used safely at the approved dilution for the disinfection of metals, painted surfaces, plastics and rubber. Exposure for 5 minutes to the 0.2% solution is adequate for destruction of the FMD virus, after which the equipment should be flushed with water. This chemical is used by the dairy industry.

3. 0.3 % ORTHO-PHOSPHORIC ACID (Technical Grade)

To make:
Dissolve 15 ml of ortho-phosphoric acid to 4.5 litres of water (or one tablespoon of acid to 1 gallon of water) and stir. This chemical is widely used in the dairy industry.

The effectiveness of all of these acidic solutions can be improved by the addition of detergent, such as household washing up liquid. Add 15 ml of detergent to each gallon (or 4.5 litres) of acid solution (or one tablespoon to each gallon or 4.5 litres).

This solution can be used for the cleaning and disinfection of all external surfaces (e.g. farmyards, animal accommodation, tractors, trailers, all vehicles, utensils, tools, boots, shoes, waterproof clothing etc). Hands may also be washed and fingernails scrubbed in this solution.

The solutions can also be used to spray or dip animals, (e.g. to disinfect the fleece of sheep). In this case the disinfectant should be washed off after 30 minutes or so to prevent any possible harmful effect.