Care in Use and disposal of sheep dips
Sheep dips contain three main classes of chemical:
- Organophosphate sheep dips (diazinon)
- Pyrethroid sheep dips (cypermethrin)
- Formamidine sheep dips (amitraz)
All sheep dips authorised by HPRA are presented as chemical concentrates that must be diluted with water in the sheep bath before use. Handling product concentrate often presents a significant hazard for farmers and operators, but care is also needed during and following dipping and in the disposal of spent dipwash.
Dipping sheep is often a strenuous task. It involves charging the dip with the appropriate volume of concentrate for the volume of the dip bath, handling the individual animals to ensure they get a thorough plunge into the bath and are immersed for an appropriate length of time. It also involves ensuring that the dip is re-charged with concentrate at appropriate intervals, handling freshly-dipped sheep to ensure that any run-off is channelled back into the bath, cleaning the bath if it becomes fouled, and disposing of the spent dip wash at the end of the procedure.
Use of sheep dips in plunge dipping baths
This is the recommended and only authorised way of using sheep dips in this country. The goal of treatment is to kill or remove parasites that may be on the sheep and to protect them from re-infestation for a period of time.
Baths vary greatly in size, the primary requirement being that they permit total immersion of the animal. Knowing the capacity of the bath is critical to be able to ‘charge’ the bath with the product to be used. Baths should be carefully calibrated either by permanent side markings or with a graduated stick which is always used at the same position in the bath. This enables the operator to know the correct quantity of dip concentrate to use and also indicates the level at which replenishment or ‘topping-up’ is needed.
When a sheep leaves the bath after being dipped, it will take with it a considerable volume of dip wash, a large proportion of which will drain back into the bath. The wool of the sheep selectively absorbs the chemical from the dip wash, meaning that the run-off is more dilute than the original wash. This is the reason why dips need to be replenished or charged regularly.
Use of sheep dips through showers or jetting equipment
All sheep dip concentrate products for the treatment or prevention of external parasites in sheep that are authorised by HPRA are for use in dip baths only. No data has been provided to us to provide evidence of safety or efficacy of the products when used through sheep showers or similar equipment. The products concerned should not be therefore be used by means other than those authorised and stated on the product labelling/package leaflet. While is no evidence that the products will achieve their intended effects if used other than in accordance with the authorised conditions of use, they could prove to be harmful if used incorrectly. Moreover, in accordance with national legislation (SI No. 786 of 2007) it is an offence for a farmer to administer a veterinary medicine to an animal other than in accordance with marketing authorisation.
Care in the use of sheep dips
Irrespective of the nature of the product being used, operator exposure to sheep dips can be minimised by proper planning of the work, good dipping facility design and the use of suitable protective clothing (typically consisting of non-lined synthetic rubber gloves [heavy duty gauntlet style PVC or nitrile at least 0.5mm thick], wellington boots, waterproof trousers or leggings and waterproof coat or bib-apron (made of nitrile or PVC). When handling the concentrate use a face shield. Protective clothing should be in good condition and should be washed after use.
Whichever chemical is to be used, it is essential to wear suitable protective clothing when:
- Handing the concentrate,
- Working with diluted dip,
- Handling freshly dipped sheep, and
- Washing concentrate containers or delivery systems (where applicable).
It is also recommended to use protective clothing when disposing of the spent dipwash.
In the event of accidental spillage, wash all concentrate or splashes off the skin immediately.
The following additional precautions relate to the handling of sheep dips containing organophosphates (diazinon/diamplyate):
Concentrate may be added to water in the dip bath only by using a closed dispensing transfer system and should not be poured directly from the product container, due to the risks of human contact.
We note that the Health & Safety Authority has issued advice that when dipping sheep or handling animals afterwards, handlers are most at risk from absorption through the skin. They also advise on risk management measures that may be taken to reduce the risk of exposure.
Cases of heavy contamination should be treated as an emergency and the patient taken straight to hospital after removing contaminated clothing and rinsing with water areas of skin that came in contact with sheep dip. The symptoms of mild poisoning are a feeling of exhaustion and weakness that may be accompanied by cramp-like abdominal pains, diarrhoea, excessive sweating, constricted pupils and salivation to up to 24 hours after exposure. Severe poisoning can cause general muscle twitching and convulsions.
Doctors can obtain advice on clinical management of organophosphate exposure from the Poisons Information Centre, Beaumont Hospital, Dublin. All cases of organophosphorus poisoning must be treated in hospital.
The following precautions relate to the handling of sheep dips containing pyrethroids (cypermethrin):
Doctors should note that cypermethrin is not an organophosphate. Cypermethrin is a potential skin sensitiser and may cause tingling effects on exposed areas of human skin.
The following precautions relate to the handling of sheep dips containing amitraz:
Doctors should note that amitraz is not an organophosphate. If poisoning is suspected, treatment should be symptomatic and supportive, paying particular attention to monitoring of cardiac and respiratory function. Do not use atropine. Do not induce vomiting.
Care should also be taken in handling and managing freshly dipped sheep. Dip that drains from the sheep should not be allowed to enter watercourses. Freshly dipped sheep should not be allowed into streams or waterways, as some of the chemical may be released into the environment.
Care in the disposal of spent sheep dips
Once sheep have been dipped, the waste dip water that remains in the bath as well as the run-off from treated animals is known as spent dip. Advice for safe disposal of spent dip is particular to individual products – please consult the label/package leaflet.
The Department of Agriculture, Food and the Marine has issued general advice on the disposal of spent sheep dip. Spent dip is regulated by legislation for the protection of groundwater. Their advice is that it must never be disposed of to a soakpit, or dumped on sacrifice land. It must be landspread - diluted 1 part dip to 3 parts slurry or water at a rate not exceeding 5,000 litres/ha (440 gallons per acre) of spent dip, equivalent to 20,000 litres/ha (1760 gallons per acre) of diluted dip. Therefore if you had a 1,000 litres of spent sheep dip you would have to dilute it with at least 3,000 litres of water or slurry before spreading. Spent sheep dip must be land spread as soon as practicable after use. All precautions pertaining to the spreading of animal manures are also applicable. Farm livestock should be excluded from the disposal area for at least 28 days. Empty dip concentrate containers must be rinsed when dip is being prepared so that rinsing liquid may be added to form part of the diluted dip. Where there is an outlet at the bottom of an existing tank, controlled by a stopper, the outlet must be permanently sealed.
The Environmental Protection Agency has also drawn attention to the need to protect high status water bodies from pollutants causing ecological damage, including the need to control the release of sheep dip pesticides into the environment.