CONSIDERACIONES PARA LA APLICACIÓN DE LA EUTANASIA EN PROCEDIMIENTOS. PUNTO FINAL

Transcription

1 CONSIDERACIONES PARA LA APLICACIÓN DE LA EUTANASIA EN PROCEDIMIENTOS. PUNTO FINAL 1. Euthanasia of mice with severe clinical signs such as hunching or labored breathing irrespective of weight loss. 2. Euthanasia of mice where weight loss of 25% of their pre-experimental body weight is detected or absolute weight has dropped to 15 gram (for those mice that weighed less to begin with). 3. Euthanasia of mice where weight loss of 20% or more of their pre-experimental body weight is detected over a 2 day period and is accompanied by other clinical signs comprising isolation, inactivity, hunched posture, very greasy and ruffled fur. Mice should be monitored twice daily around the time of expected endpoint "Body weight loss is robust and is useful as an early predictor of the level of morbidity or mortality that may occur if animals are allowed to progress" * Weight loss allowance for most institutions is dependent upon the study objectives eg. lower percentage weight loss (10%) allowed for studies of virus infection vs higher percentage weight loss (20%) allowed to compare effects of different treatments on the course of infection. * The range of weight loss allowed tends to fall between 10-20% * One group has also seen the "bounce-back" in mouse weights (seen by our investigators) and is currently amending a protocol to give the mice more time at 25% weight loss if there are no other clinical signs to see if the mouse regains weight. * One person responded that they have approved weight loss of 30% which is certainly significant weight loss but that the group had provided papers demonstrating that particular weight loss and subsequent recovery. The group also had to do a pilot study to demonstrate a similar response in their own mice prior to approval. The group provides supportive care. * Most people agreed that animals should not be euthanized based on weight loss alone and that it should be accompanied by other signs of a sick mouse (eg. lethargy, hunched, scruffy coat, social isolation, inactivity, absence of grooming etc). This is of course true to an extent- if weight loss is as drastic as 30% or below 15g then weight loss alone is a good enough reason to cull. People also noted, though, that weight loss may be the only indicator of an animal feeling sick since mice mask their illness so it's a tough call to make!! * Most people advocated the use of a score sheet/scoring system * Many people suggested temperature (as measured by microchip or thermal imaging)was a good predictor of impending death. * People suggested the implementation of supportive care such as moistened feed on the floor, wet mash, high-calorie feed, treats eg. peanut butter, grapes etc, warmed subcutaneous

2 fluids, providing additional nesting materials, cage mates to help them maintain normal body temperature if they are inappetent. * It was pointed out that the provision of nutritional support may also depend on the study because if studying lethality, for example, this would affect that and therefore it might be warranted to do a pilot study to assess to what degree nutritional support impacts "lethal dose" * One group uses low spo2 as an endpoint (measured using a "mouse-ox"- pulse oximetry for rodents) * Useful article sent by one responder: Trammel RA, Toth LA Markers for predicting death as an outcome for mice used in infectious disease research. Comp Med 61(6): * "We work with a range of influenza viruses, and in a range of animal species. Our experience is that in influenza infection studies in mice, bodyweight loss is robust and is useful as an early predictor (humane endpoint) of the level of morbidity or mortality that may occur if animals are allowed to progress. The actual percentage of bodyweight loss (intervention point) is dependent on the objectives of the study. For example in mice infected with H1N1 the endpoint is sometimes it is 10%, sometimes 20%, depending on the study objectives. For example if we just want to know if the virus has caused infection, 10% will suffice as we know we can recover virus from tissues at this point, demonstrating infection. However, if we want to compare effects of different treatments on the course of infection, then we may need to take the animals to 20% to allow a greater range of clinical signs to manifest and allow the virus to have chance to establish in various tissues. Here is an example of a justification taken from an animal ethics application (to go to 20%): We would like to be able to compare the level of protection from the various vaccines over as much of the time course of the infection as possible. As we expect even the most strongly protected groups of mice will become infected, there is great value in generating as much information as possible about the relative severity of any disease that develops. This is best assessed by monitoring the animals through the infection "lows" into recovery, but necessitates allowing the disease to fully express itself in each animal We would euthanase upon reaching 20% or sometimes euthanase early if we think the animal is close and will reach 20% by the next check. Justification for sustaining it over two readings would be required in the AEC application. Sometimes we do use multiple readings (2 readings) as endpoints, or bodyweight plus an additional indicator such as clinical signs consistent with the infection of interest." * "I agree that you should not euthanise animals for weight loss alone, it should always be accompanied by some other signs (note plural depending on the sign) e.g. Reduced temperature (microchip implants, body imaging?), lethargy, hunched posture, starey coat, as then it becomes significant.

3 This is especially true in animals with a large proportion of weight in the gut. In my experience, mice can fluctuate in BW by 5-10% during 24 hours, and a serious feed restriction (not water) for 3-4 days it can lead to a loss of 20-25%. Supportive care, e.g. Feed one the floor, wet mash, some treats e.g. Grapes, peanut butter, maize cobs, fruit, veggies (they can all be washed and made safe) etc. Are you giving any drug therapies/interventions? Nesting materials, box, transparent cage so they can be observed. Another mouse perhaps? Weight loss varies in its significance according to the species. I would be more worried about a 10-20% weight loss in carnivores than herbivores, fermentation chambers are good ballasts!" * "10% weight loss that is typically used in combination with other factors (inappetance or not drinking water for X amount of time, hunched posture, hair fluffed up, isolation from litter mates, lack of grooming behaviors, etc.) is an arbitrary number. I would not make any decision on intervention without being able to interpret it within the realm of the study. What is the endpoint of the study and will intervention potentially alter the outcome? How long does the weight loss last? Is it different between control & treatment groups that could allow you to predict which animals will recover? Any literature references that may help you predict expected duration? If it takes 20% weight loss AND recovery time to have a valid model then that's what it takes for the scientific question under study and the question from an animal welfare standpoint then becomes is the projected benefit worth expected degree of suffering?" * "We are dealing with objections to the 20% cut-off as well. Our IACUC decided to let it stand as a baseline, and that investigators are free to make exceptions for their protocols; there is data that they can drop to as low as 30% loss and recover. While we are still in the initial implementations, I highly recommend a morbid/moribund scale of at least 10 points with a couple categories, depending on what clinical signs you expect to see. I agree with David's as a good place to start. Temperature drops and weight <15g seem to be great indicators. And for mice, there is always the 'last resort' sign of laying the mouse on its side. I think that if it allows you to do so, that is enough of a sign, but the official 'righting reflex' is 5 seconds. Bottom line- best to work with the investigator. They are the expert and should know the signs when they know they are at the point of no return (and if they don't, ask their techs). If they won't say, then go with your best guess and then edit based on feedback from them later. It is hard to have one definitive criterion for this kind of study. As for nutritional support etc, it depends on what is being studied. That will definitely affect lethality, so you may have to do a pilot to see to what degree, and whether the 'lethal dose' would then need to be recalculated."

4 * "A cluster of signs was what we used for influenza studies at my previous institution. The mice (housed 3-4 per cage, which helps with heat loss) could look quite crappy but come back so it's weight loss, dehydration, hunching, piloerection, activity level, and temperature that can be taken in context. In addition to the supportive care already mentioned by other compmed writers, warmed SC fluids can help some." * "Here is what our most prominent influenza research group uses as the criteria in their protocol. In speaking with this lab they too have experienced the bounce-back effect in mouse weights, and are looking to ammend the protocol to give them more time even at the 25% wt. loss if there are no other clinical signs to see if the mice will regain wt. All animals are observed daily for signs of illness, rapid breathing, ruffled fur or feather, rapid weight loss, inappetence, and impaired ambulation. If any of the animals are judged to be moribund by the following criteria, they will be anesthetized and euthanized. Animals (mice, ferrets, ducks, chickens, or hamsters) will be judged as having reached the predetermined endpoint by the criteria listed below: 1. Rapid breathin 2. Breathing rate very slow, shallow and labore 3. Ruffled fur or feather 4. Hunched posture 5. Rapid weight loss (10-25%) 6. Shivering 7. Inappetence 8. Diarrhea or constipation 9. Evidence of muscle atrophy or other signs, e.g., lethargy 10. Any obvious illnesses such as twitching of limbs, superficial skin injury 11. Inability to remain upright 12. Hemorrhage from any body orifice Criteria 1, 2, 3, 4, 5, 6, 7, 8, 9, and 10: Animals exhibiting these criteria singly or in combination with any of the above listed criteria (except 11, 12, see below) will be monitored with increased frequency (2-4 times daily) for any change in status. If the symptoms do not improve within 48 hours and resolution is determined to be improbable, the animals will be euthanized after consultation with veterinary staff. Baseline weights will be done prior to challenge, animals will be weighed daily.

5 Criteria 5 (at 25% loss), 11, and 12: Animals exhibiting these criteria singly or in combination with any of the above listed criteria will be considered to have reached the predetermined endpoint and the animal will be immediately euthanized." * "I would agree with the other poster that said weight loss alone is not a reason to euthanize. Generally true, albeit if the weight loss was 30% or more then euthanasia is probably the best option. We give nutritional supplements to the animals and chart them with a score sheet that I attached as a pdf. I would combine the weight loss with other clinical signs (lethargy, laboured breathing, unkempt coat, etc) and keep close track of the weight with twice daily measurements and track them day to day to make sure no one is slipping through the cracks and losing in excess of 25-30%. Again, weight loss alone is hard to be the reason for euthanasia, although the weight loss is indicative of the animal feeling systemically ill, so it is a tough call sometimes." * "We have use LD50s to determine temps & weight loss endpoints if needed - the attached document is a summary from some 2011 work - for weight loss maximums the more virulent the virus/greater pfus the faster the onset of death & hence the lower the weight loss (they die faster); for treated vs. untreated animals there is an added 5% loss allowed as the PIs need to determine that the animals are sick enough & won't imp[rove on their own; in the past our baseline has been 20% untreated & 25% treated -> this all increased by 5% for a while & now seems to be dialing back again to 20/25...committee fashion. For body temps we usually get a sustained temp loss for >24hrs of from 33-35C. Good luck with getting fast collection once they reach endpoint - it's the only humane treatment." * "We have several groups using flu that have approved a weight loss of 30%. quite significant but groups provided papers demonstrating the weight loss and subsequent recovery of these mice. Initially they had to do a pilot study to demonstrate similar repsonse in their own mice and also provide supportive care; eg; extra tissues and high calorie wet food." * "why not add some additional parameters, such as dehydration, hunched posture, hypothermia (shivering), lack of movement, etc. If you can combine endpoints and come up with a 'endpoint score' that is indicative of impending demise, animals can be euthanized before they get to a suffering point and still provide good scientific data on 'survival'. We used the attached worksheet to get data in other studies where animals would have eventually died a painful death but we could determine before they got to that point that they were headed that way. Gave us very good treatment response data in an ovarian cancer model with ascites. Takes a couple pilot studies to determine the parameters to follow and to set scores for euthanasia. The parameters

6 change with each model and the precise scores will be different, but I've seen it work in many different studies. " * "Have they considered including pulseoximetry? We have an investigator here that uses a mouse-ox and use low saturation as an endpoint."