Non-harmful / below threshold / severity degree 0 Mild / severity degree 1 Moderate / severity degree 2 Severe / severity degree 3
Home Office (2014 a)

    Pain of any significant intensity is of no more than a few hours duration and is not considered of a severe nature, as judged by species specific criteria (for example, repeated vocalisation/persistent self trauma in rodents). Animals that undergo procedures that produce chronic low-level pain or discomfort or dysfunction such as altered gait will usually be classified as moderate. A higher level of pain that persists, such as non-weight bearing lameness without improvement, even in the absence of other signs of severe pain, would be considered severe unless a diagnosis can be made that indicates the condition is associated with pain of a lower intensity.
Home Office (2014 a)     Many chronic pain models, including those involving minor surgical procedures such as nerve ligation and including when this is carried out without post-operative analgesia, tend to cause allodynia rather than permanent pain. When pain detection methods are necessary to distinguish these animals from normal they are not considered to be suffering long-term pain and are classed as of moderate severity. The animals show overt signs of pain for a prolonged period without improvement, for example, by persistently licking the affected part for more than three hours in a model such as formalin injection into the footpad, they should be classed as severe.
Home Office (2014 a)       Acute pain models, such as the writhing test or assessment of visceral pain using balloon inflation, may involve more severe pain. Where the pain is not sufficient to lead to distress and where the entire painful technique lasts no more than three hours these procedures will be classed as moderate.
Federal Food Safety and Veterinary Office FSVO (2018)   Experiments causing mild short-term pain at the pain detection threshold with slight tissue swelling. Examples:Plantar test. Von Frey filament test or Randall-Selitto test without inflammation or neuropathy (Hargreaves method).Hot plate test or cold plate test. Tail flick test. Tail immersion test.

Experiments causing short-term moderate pain or medium to long-term mild pain.

Examples: Formalin test inducing nocifensive reactions lasting not longer than 60 minutes. Local subcutaneous capsaicin injection. Paclitaxel and toxin-induced neuropathy. Writhing test with < 0.2 ml 2% acetic acid or 0.4 ml 1% aqueous acetic acid. All models with acute paw oedema (e.g. subcutaneous zymosan A) with withdrawal as measurement criterion. Chemically induced sub-acute pain model. Writhing test with 0.25 ml aqueous suspension of phenyl-p-benzoquinone 0.02%

Experiments causing severe pain with severe impairment of mobility, with dehydration and weight loss or automutilation and autotomy behaviour.

Examples: Bone cancer pain. Chronic constriction injury (CCI) of the sciatic nerve, spinal nerve ligation and spared nerve injury (SNI) without autotomy.
Working Group of Berlin Animal Welfare Officers (2010)   Experiments that cause shortterm mild pain: Hot plate test. Tail flick test without restrainer. Tail immersion test. Writhing test with 0,25ml diluted suspension of phenylp-benzoquinone 0,02% in tragacanth 0,4%.

Experiments that cause shortterm moderate pain, or chronic mild pain, without considerable restrictions on motion: All models with acute paw oedema with parameter “withdrawal”. All models with acute paw oedema with parameter “paw volume”, duration of experiment < 6 hours. Tail flick test with restrainer. Writhing test with < 0,2ml of 2% acetic acid, or with 0,4ml of 1% diluted acetic acid. Writhing test with alcoholic solution of phenyl-pbenzoquinone 0,02% in tragacanth 0,4%.

Experiments that cause shortterm severe pain, or chronic moderate to severe pain, with or without considerable restrictions on motion: All models with acute paw oedema with paramater “vocalization”. All models with acute paw oedema, duration of experiment > 6 hours. Application of noxious stimuli, without means of escape or avoidance behaviour. Writhing test with > 0,2ml and > 2% of diluted acetic acid. Causing of anatomical and physiological damage, combined with stress or distress.


This page was updated on 01 January 2021

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