Other Bacterial and Fungal Problems

Amphibians, especially ground dwelling species, can come into direct contact with various bacteria and fungi constantly which will be living in the soil or water or present on the insects they eat. If the frog or toad is healthy, these "environmental" pathogens will not cause any problems. But when the animal is stressed or these pathogens build up in an enclosed environment (such as a keeper's tank in captivity), these bacteria and fungi can overwhelm the animal and cause infection.

Frogs have a habit of shedding the outer cuticle layer of their skin, rubbing it forward on the body, then consuming it. This is probably some form of recycling energy but in a disease filled environment, it is probably something which is more detrimental than it is useful.

The skin of an amphibian is protective to the body and keeps out many of these environmental pathogens, but when that skin is breached by injury, a scratch, or an ulcer, this allows bacteria and fungi to enter the body and cause infection and death if not treated.

There are a variety of symptoms which can point to a bacterial infection but all amphibians are slightly different and a symptom seen in one species is not necessarily the same symptom that will appear in another species. But there are some things to look for, especially in the green coloured tree frog species.

• Fluid retention throughout the body is sometimes seen in a bacterial infection.
• The lower ventral surface (near the vent and thighs) can have a pinkish flush and a very close look might reveal tiny red blood vessels becoming visible at the surface of the skin. The bacteria that causes "red leg" (Aeormonas hydrophilla) can cause extensive redness on the ventral surface as well as numerous ulcers and sliming on the body.
• Pale speckles against an other wise darker body colour is also an indication of a bacterial infection that is systemic and will need antibiotic to clear. On the White-lipped tree frog (Litoria infrafrenata), the speckles are very small (see photo at right) and numerous while they are much larger and have very fuzzy edges to them on the Common Green (White's).
• Ulcers caused by bacteria have a wet, mucous-y surface to them with a slightly raised edge; other bacterial ulcers can be small and even in size and scattered all over the ventral surface.
• Fungal ulcers can very clean edged, very large and very numerous on the body (look carefully and you will see plenty of them in the photo at top), mostly on the feet, legs and ventral surface. The muscle tissue visible through the ulcer is red and irritated but the aquarium product Multicure will clean them up in a few days (contact us for dosage if you have a frog with these ulcers at right).

We have seen an unidentified problem on frogs which we are calling "skin rot" until better identified. Some limited lab work resulted in a diagnosis of "Aeromonas and pseudomonas" but the rest of the testing we requested was not done. This problem resembles leprosy in that it starts out attacking the skin but rapidly becomes systemic. We can only treat this in the very early stages - once advanced, as in the photo below, the same antibiotic seems to cause anaphylactic shock instead of working against the pathogen!

The problem starts out as an army green, rounded discolouration in the skin, usually on the back of the thighs but sometimes other places on the back, and then turns blueish. As it progresses, the patches get darker until they are black and new greenish/blue ones appear elsewhere on the back. By the time the skin is blackened (necrotic), the bacteria has eaten through the skin and some bleeding could be present.

There are some other flesh-eating bacteria and fungi which are extremely rapid and can eat away skin by a cm per hour - there will be inflamation and bleeding at the edge of the skin (these need veterinary attention immediately!). Thankfully these cases are very rare. The last one we received has been sent to a lab but we are still waiting on results. Some Mycobacteria are known to cause this kind of massive skin deterioration so we will not be surprised if the lab result indicates a mycobacterium.

Bacterial and fungal problems on frogs need to be treated quickly before they become systemic. If the affected frogs are in captivity, their enclosures need to be dismantled and thorougly disinfected and rinsed before being setup again with new plants, substrate, etc. A tip for reducing the problems caused by environmental pathogens are to use leaves from your shrubs and trees as your substrate for tree frogs instead of fancy mosses and soils. River sand that has been thorougly rinsed and soaked for several days can be used for burrowing species as this can be easily rinsed out to keep clean whereas soils can't.

last edited: May 14th, 2006