Background

EAE (experimental allergic encephalomyelitis) is an animal model for Central Nervous System autoimmune disease and is widely used to study Multiple Sclerosis and other demyelinating diseases.[1] Although clinical signs of EAE vary according to species and strain, they include visual, sensory, and motor deficits. Such deficits generally manifest as an ascending paralysis, and for research purposes are graded on a five-point scale from loss of tail tone (1) to moribund (5). The course of EAE progression may vary from one or more episodes with short periods of remission of clinical signs to a progressive chronic state.

For animal care, the critical aspects of this model center around the animal’s paralysis, as it affects many aspects of its life, such as the ability to reach food and water, and the prospect of being trampled on or attacked by healthy, robust animals within the same cage. EAE animals may show self-mutilating behavior, which must be monitored for and promptly addressed. They may also develop skin lesions, either from injection of EAE-inducing compounds or due to urine scald after paralysis; careful daily examination of animals is vital to detect these complications and to begin rapid treatment, or to perform euthanasia if cases are severe. The ARC protocol under which the experiment is conducted should describe these possible complications and provide a treatment plan and humane end-points for each. Research labs are encouraged to consult with DLAM veterinary staff when planning their studies.

Policy

This Policy establishes the minimum welfare requirements for EAE mice in order that they may receive appropriate care to minimize pain or discomfort. The assessment, care, and recordkeeping of EAE mice are the responsibility of the Principal Investigator and their research staff.

A. Care

  1. Every animal to be injected with any substance to elicit EAE will be identified on its cage card with the letters "EAE." A pink "Study related" card will also be initiated and placed on the cage (refer to the DLAM Worksafe training module "DLAM Cage Side Communication Cards"). All subsequent observations and treatments by the lab must be recorded on this card.
  2. At the time of inoculation, a baseline weight of each animal will be obtained and recorded on the pink "Study related" card, as well as all subsequent weights or body condition scores (BCSs).
  3. Animals will be monitored at least daily, including weekends and holidays. As soon as an animal begins showing signs of rear limb paralysis or paresis, the following must occur:
    1. Separate paralyzed animals from non-affected animals. No animal in a paralyzed state will be maintained in the same cage with non-paralyzed animals because the following problems may occur:
      1. Non-paralyzed animals may walk on paralyzed animals causing discomfort or even injuries, and
      2. Non-paralyzed animals may eat the apples or HydroGel intended for paralyzed animals.
    2. Supply regular pelleted rodent chow on the floor of the cage so all paralyzed mice have full and easy access. This chow should be moistened with water and replaced daily.
    3. Supply water in the form of an elongated sipper tube that is accessible without the animal having to rear up on the hind limbs, or provide an alternative such as apple slices or HydroGel[2] on the cage floor. If apples are used, they must be replenished daily.
    4. All mice with clinical paralysis must be monitored twice per day, as close to twelve (12) hours apart as possible, for the following, with monitoring and treatments recorded on the pink "Study related" card:
      5. Problem/Task Diagnosis/Treatment
      Dehydration Lightly pinch the skin over the neck to determine skin turgor. If skin remains in "tented" position, administer 1 ml USP-grade Normal Saline or Lactated Ringer’s solution subcutaneously twice per day, as close to twelve (12) hours apart as possible.
      Urination At least 2-3 times per day (morning and afternoon) and additionally as needed, roll the mouse on its back and lightly palpate the abdomen to assist with voiding. If male, monitor for penile irritation secondary to flaccid paralysis. Refer to the ARC protocol for treatment or euthanasia options.
      Weight or BCS Record daily once animals reach the paralyzed state.
      Skin Integrity Check the animal’s skin over its entire body (including all four feet) for any signs of skin irritation, lesions (sores), chewing, etc. Refer to the ARC protocol for treatment or euthanasia options.
  1. Animals must be continuously monitored to assess their stage of paralysis. As EAE progresses or resolves, regroup animals as needed:
    1. Individual housing: place animals in a cage by themselves if their mobility is significantly reduced.
    2. Group housing: Alternatively, house animals together only if they share a similar level of mobility.

For all animals–whether housed individually or in groups–follow the care procedures outlined in sections 3b and 3c above.

B. Endpoint

Any deviation from those described in the ARC Policy Humane Treatment and Endpoints must be described and justified in the approved ARC protocol. In addition, any of the following criteria are endpoints prompting immediate premature euthanasia:

  1. The mouse is paralyzed in all four (4) limbs and is not mentally alert.
  2. The mouse is alert but exhibits paralysis in all four (4) limbs for more than 24 hours.
  3. The mouse exhibits dermatitis or posthitis (penile inflammation) with skin ulceration from excessive urinary moisture.
  4. The animal has self-mutilated to the point that any digit on a limb has been lost.
  5. The animal is in a moribund state.

Communication between the lab and DLAM is critical for animal welfare and the achievement of scientific goals. The DLAM veterinary staff may require  euthanasia at timepoints earlier than the lab’s experimental points based on animal welfare concerns; such orders must be promptly followed. If a research lab has questions on a health condition or humane end-points that are not addressed in the ARC protocol, they are to contact the DLAM veterinary staff for consultation.

References

  1. Rhonda R Voskuhl  and Allan MacKenzie-Graham. Chronic experimental autoimmune encephalomyelitis is an excellent model to study neuroaxonal degeneration in multiple sclerosis. Front Mol Neurosci. 2022 Oct 19:15:1024058. doi: 10.3389/fnmol.2022.1024058. eCollection 2022.
  2. HydroGel by Clear H2O: Available from the DLAM Pharmacy.

Approved 2/12/01; Revised 4/28/03, 2/25/08, 11/10/25