Ringtail
?Tail Necrosis?         
Definition
A lesion or annular constriction of the tail resulting from the lack of hydration in the skin of the tail.
Clinical Signs
May see the following:
  A circular ring at the base of the tail if an infant rat, or an oozing sore at the base of the tail in adult rats.
  Swelling, inflammation, or necrosis of the portion of the tail below the annular constriction.
Etiology
Tail necrosis or ringtail, as it is more commonly called because of the annular lesions or constrictive rings that are seen, can occur in all ages of rats, but primarily occurs in infant or suckling rats.
The condition may first appear with inflammation, edema, and lesions. Necrosis may then develop causing sloughing of the tail distal to the lesion or constriction. If predisposing factors aren?t corrected early on, amputation may be required if healing does not occur.
In cases where the condition is mild and the predisposing factors are corrected, few or no annular constrictions may be seen.
Factors which predispose, or contribute to this condition, are a low humidity enviroment of less that 20%; poor temperature regulation in the vessels of the tails in infant/suckling rats in response to the surrounding environmental temperature changes; overly absorbent bedding or litter, such as corn cob type litter; blood lab draws from tail veins, or dietary deficiencies of essential fatty acids.
Prevention plays a key role in correcting some of these before the condition develops. Such as maintaining humidity of 50% in the rats environment, using humidifiers not only in the drier parts of the country, but in winter months when homes are being heated, paying attention to the type of diet being given, and using recommended litters such as Aspen, Yesterdays News or CareFresh just to name a few.
Photo examples showing annular rings in the following figures.
Fig. 1: Ringtail in adult rat
Fig. 2: Ringtail in a baby rat
Diagnostics
Recognition of presenting signs.
Obtain history of husbandry practices, including type of cage, temperature of the environment, type of litter used, type of diet.
Treatment
Correction of predisposing factors:
Increase humidity in rat room to at least 50% or higher with the aid of a humidifier.
Change to less absorbent litter. For recommendations and listings see Litter.
Change to a more nutritious diet. For recommendations and listings see Diet.
Application of topical moisture such as olive oil.
If severe infection or necrosis develops, amputation of the area proximal to the constriction may be required. However, in uncomplicated cases and when at all possible, it is preferred to let the tail slough of its own , in order to permit the remaining tissue to heal covering the exposed bone.
Nursing Care
  Assess condition of tail daily.
  Maintain treatment until resolved.
  Maintain clean cage environment. Use bedding and litters as recommended. For more information on types   
  of litter and bedding, see the Care section of the Rat Guide.
  Evaluate and maintain adequate temperature and humidity in rat room.
  Maintain healthy diet to include fresh water daily. Include juicy types of fruits to encourage adequate hydration.
  Seek the attention of a veterinarian if condition becomes worse.
Outcomes
  Condition reversed if mild.
  Necrosis of tail prevented.
  Infection prevented.
Prevention
  Use cages where there are solid bottoms.
  Avoidance of hygroscopic (overly absorbent) litters.
  Addition of a humidifier in dry climates or during winter months when homes are being heated.
  Maintenance of a healthy diet, that includes essential fatty acids for weaned rats and in does that are still suckling young.
Figure 1: Ringtail in adult rat
Case history and photos
Clinical Signs
The rat shown below is a 1 1/2 year old female that presented with a dark circular ring around the distal portion of the tail. She was part of a colony of approx 60. Interestingly only this rat presented with this condition.
Diagnosis
Diagnosed with ringtail.
Treatment
A dehumidifier that was already present in the room with the colony had been kept in the range of 50-60%. When the classic sign of ringtail was observed, it was raised up to to 60-70 % humidity. Olive oil was then applied to the tail twice daily for several weeks.
Outcome
The outcome following treatment was resolution of the ringtail.
Fig 1
Photo 1: Note the dark concentric ring or constriction seen around the tail
Photo 2: Additional view
Figure 2: Ringtail in baby rat
Case history, photos and diagnosis
Ringtail was noticed on two baby rats at the age of 12 days and treatment started (photo of one of the babies shown below).
Treatment
The tails were rubbed twice a day with mineral oil for two weeks and then once a day until weaned.
Outcome
The ringtail was completely resolved.
The Rat and Mouse Association Victoria Incorporated is at this time unble to verify the Author/s of the above aarticle
If anyone should know the Author passing on of this information would be greatly appreciated so that proper acknowledgement can be made
However at this time the Association passes on its thanks to the Author
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Photo 3: Baby ringtail