Metabolic Bone Disease
(MBD)
in
Opossums

What is it?

MBD is a life-threatening complex of diseases that cause outward signs of crippling of the bones, similar to rickets. The physiology of calcium and phosphorus metabolism is complicated; to understand it better see the full text of Dr. Henness's article, along with the suggested reading. The most important thing to know is that the body strives to maintain a narrow range of calcium in the bloodstream. If the diet does not provide enough calcium, or if other nutrients interfere with its uptake, or if too much is lost through the kidneys, then the body will leach calcium from the bones to maintain adequate levels in the blood.

What causes it?

Various mistakes in the diet provided to opossums are the cause of MBD. The most common errors are too much meat protein, too much fruit, and too much Vitamin A (either from foods or vitamin supplements).

What are the signs of it?

Often the care-giver does not notice the first signs of MBD, which are loss of grip, decrease in climbing ability, and decrease in general activity. Many times the opossum will be completely "down", that is, crawling instead of walking, before the care-giver realizes there is an urgent problem.

The following list of signs are exerpted from Dr. Henness's article NUTRITIONAL METABOLIC BONE DISEASE: Its Causes . . . Its Cure. Follow the link to read the article.

Sequence from earliest (mild NMBD) to advanced (severe and/or chronic NMBD):

  1. Slight to significant depressed grip in hands/feet and in strength of limbs or tail; reluctant to climb.
  2. Depressed activity level. Tends to sleep more; cranky when awake; will not run when active. (Pain begins here.)
  3. Appetite may begin to change; grip markedly reduced.
  4. Stands with restricted stance; walks with short mincing steps, variously described as "walking on egg shells." Can't climb. (Pain increases.)
  5. Early signs of systemic changes (e.g. urinary output may rise, dilute urine, sometimes increased water intake).
  6. Limbs appear to have become stocky or chubby; palpation (examining by touching) of the long bones causes signifcant pain. Changes are due to thinning of the cortex (outer portion of the bone) while the diameter of the limb widens.
  7. If blood calcium is fluctuating, may see tremors and jerky movements. Or blood level may be normal and phosphorus may be elevated.
  8. Fractures are possibility at any time from 5 or 6 above - digits first, then long bones, spine, etc.
  9. Walks in crouched posture with creeping movements of limbs; down on elbows and/or knees and ankles; hands and feet have abnormal postures with little use.
  10. Distortion of limbs, loss of appetite, further changes in urine and bowel habits.
  11. Skull changes, including, but not limited to, inability to effectively use mouth/jaw parts; bulging of eyes, etc.
  12. Depending on the severity of the diet, site of fractures (e.g. thoracic (chest) area has potential for extremely grave prognosis), age of animal, and other problems (e.g. parasites, infection, etc.), the animal is ill enough to die at any point if intervention is not immediate and aggresive.

What fixes it?

The ONLY way to correct MBD in the opossum is to correct the diet. CALCIUM SUPPLEMENTS SHOULD ALMOST NEVER BE USED, as a dietary supplement, although this is an appropriate prescription for other species. The opossum processes dietary nutrients very quickly and efficiently, and supplementing with calcium can cause hypercalcemia and complicate the disease. However, an opossum that has a poor diet history and that has developed tremors or other neurological symptoms may need immediate veterinary intervention to prevent death.

A "safe" way to BEGIN correction of the diet is to start feeding the following mixture as soon as any symptom is noticed:


This is a STARTING POINT ONLY, and for opossums over 1 pound. You must make contact with someone experienced in correcting MBD in opossums!! Other items must be added into the diet, and it should be customized to each individual's particular situation. Medications may also be needed. Call us!

MBD is life-threatening, and must be treated approriately. The opossum can recover much of its mobility and life span, but ONLY with the correct treatment.

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