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Ear Problems In A Mouse And A Short-Tailed Opossum

A mouse with a mass by its ear and a short-tailed opossum with extremely dry ears receive treatment.

By Jerry Murray, DVM
Posted: May 4, 2011, 5 a.m. EDT

mouse with mass by ear
© Courtesy Jerry Murray, DVM
Surgery revealed that the mass on the ear of this mouse was not a tumor.

Ear infections are very common in dogs and cats, but exotic pets seem to have exotic ear problems. The first case was a mouse with a large mass by its ear. By just looking at it, I initially thought it was a tumor. Surgery was scheduled to remove the mass from the mouse. During the surgery, it became clear that the mass was actually swollen and infected lymph nodes of the mouse. In addition to having surgery, the mouse also received an antibiotic to treat the infected lymph nodes.

The second case was really different. The owner brought in a short-tailed opossum. Short-tailed opossums are sometimes called Brazilian opossums, Rainforest opossums or South American opossums. Short-tailed opossums are friendly marsupials that are roughly the size of a hamster. Short-tailed opossums originated from Brazil, Bolivia and Paraguay.

short-tailed opossum
© Courtesy Rebecca Stout
GusGus is a healthy short-tailed opossum. Common ailments for STOs include dehydration, respiratory infections, ear problems and tail problems.

Despite being marsupials, short-tailed opossums do not actually have a pouch. Young are born after a short gestation period of only 14 days. The typical litter has seven to nine babies, but litter size can range from one to 16.

In the wild, short-tailed opossums usually eat insects, small rodents, small frogs, small lizards and worms. This is a high-protein diet, so dry cat food, farm-raised insects and a small amount of fruit can be fed to short-tailed opossums in captivity.

Common medical problems of short-tailed opossums include dehydration, diarrhea, respiratory infections like pneumonia, and ear and tail problems.

This case did, indeed, have an ear problem. On one ear the top third of the ear flap had sloughed off. On the other ear the top third of the ear flap was dry and starting to slough off also. Ear flaps can be damaged by fighting with other opossums. This short-tailed opossum was housed alone, so trauma from fighting wasn’t the cause of the ear problem. Mites can also cause damage to the ear flaps, but no mites could be found on a skin scraping of the ear flap. Low humidity can also cause damage to the ear flap and to the tail.

Short-tailed opossums do better in a warm cage (75 to 85 degrees Fahrenheit) and with a high humidity (40 to 50 percent). In a low humidity setting, the ear flaps and distal tail can become too dry. This case was treated for mites (with Revolution) as a precaution, and the humidity level was raised in his enclosure.

See all of Dr. Murray's columns>>

Posted: May 4, 2011, 5 a.m. EDT

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