To the editor:

I read with interest the “What's your diagnosis? Limb discoloration on a depressed tree frog (Hyla cinerea)” in Lab Animal, Vol. 34, No. 3. As a superintendent of herpetology at the Bronx Zoo in New York, and later as curator of animals at the Central Park Zoo, I often had occasion to observe somewhat mysterious and acute onslaughts of remarkable diseases. Thus, I was eager to apply my past expertise to the challenge at hand.

There are some obvious precursors to a diagnosis. First, the frog is missing at least one of its five toes. Second, it is deep green and the view lacks either white spots on the face under the eye, or a white stripe along the jaws that usually extends well onto the side of the body, suggesting that the frog depicted is not a Hyla cinerea, which is commonly called the green tree frog. Also, the American tree frog is the name usually applied to Hyla avivoca, the bird-voiced tree frog, or Osteopilus septentrionalis, the Cuban tree frog.

Regarding the diagnosis, one can clearly see that the animal has a red swollen leg. Moreover, having a single red swollen leg, that incidentally lacks some of its toes, suggests to me a case originating by what us old supervisors would call 'keeperitis'. Redleg bacterial infections are usually visible as small capillary hemorrhages and inflammation that shows on the inside of both hind legs, resulting from a systemic infection. Most often, small frogs are dead long before any localized necrosis sets in. A single badly affected leg does not ring true. Rather, upon seeing such a presentation, I would first ask the keeper of the frog if he or she might have inadvertently crushed the leg as the frog attempted to leap from the tank, or secondly, if the frog had been marked for identification by clipping off one or more toes on the front foot in a numerical order. In either case, the trauma could have led to a localized infection, swelling, reddening, and necrosis of that one foot. Further, systemic redleg, regardless of the actual bacteria involved, is almost always fatal if not treated systemically. That the frog was treated locally and survived for weeks takes me back to the localized trauma and subsequent infection scenario.