Fusarium Outbreak

The "Respiratory/Nervous System" Disease

Fungi Can be Elusive Although Their Effects Aren't!

In July 2002, something new and highly contagious arrived in the Cairns Frog Hospital. We suspected chytrid but it wasn't. We then obtained some positive results for Mucor amphibiorum but several hundred frogs came in with respiratory symptoms and M. amphibiorum does not have a respiratory component. Since it first arrived, we have received well over 1,500 frogs with the new disease (we bought a very expensive biological air filter to handle it!) and these have come from an area stretching from Gladstone to Thursday Island in the Torres Strait. We have had reports from other areas such as northern NSW and we've seen TV footage of Northern Territory frogs that looked suspicious but the animals have not yet been sent to Cairns for confirmation.

The collection of symptoms we are seeing with the new condition are consistent with a fungal disease and there are other species in the Mucor genus that match the symptom profile as well as some species in the Fusarium, Rhizomucor,and Rhizopus fungal genus'. However, we have had difficulty getting this widespread pathogen identified - the disease is attacking the nervous system so standard histology does not detect that anything is wrong. The disease also appears to be a mycotoxin and special equipment is used to find and identify toxins in the body (such as a gas chromatograph) but those few labs who have such equipment don't want to do the testing for us.

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Examples of nervous system irritation: leopard spots to the far left and bottom; and a shift in normal pigmentation from emerald green to a greyish-brown. We have even collected individuals who have become entirely greyish-white! The normal colour of this species is emerald green.

We have ordered cultures on the tanks themselves hoping that the pathogen might be easier to find outside the body.

So far, the experimental cultures (done by DPI's diagnostic lab in Townsville) have revealed the presence of several fungal species which fit the profile.

When we have the funding, work will continue to isolate which of these might be the cause of the outbreak that has been causing frog and toads deaths here since July 2002. 

The fungal species most consistently cultured from frog tanks and cane toad skin were:

- Trichosporon cutaneum

- An unidentified species of Mucor

- An unidentified species of Curvularia

- An unidentified species of Fusarium

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We have been told that ID to species level will require molecular methods and we have received a quote of $2,000 to pinpoint the three species above (we don't have that kind of money). However, we have shortlisted a species of Fusarium as the prime target as Fusarium has been positive in all the specimens we have sent to the lab in recent years that also had the clinical symptoms of this disease.

Until such time as we can get a toxicology lab to confirm the ID of this pathogen, we would like to present the "new" collection of symptoms in the species we have seen them in so far. If you live in a part of Australia or elswhere that has experienced severe drought, you should be on the lookout for these symptoms as they MIGHT indicate this new fungal problem!

All species of frogs and toads seen exhibit lethargy, sitting out in open during day and increased greyish-white skin sloughing on the feet and legs. All lose weight rapidly. The frogs demonstrate breathing changes in that rapid, shallow panting can be seen when looking at the sides of the abdomen (in other words, don't judge the breathing by the chin area - look at the abdomen behind the elbow from the sides or top). If a frog dies and is opened for examination or preservation, at least one lung will be observed to be have expanded to more than double its normal size (distended). In cane toads, both lungs are grossly inflated and occupy the entire body cavity.

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Additional symptoms by species are:

Common Green (White's) tree frog (Litoria caerulea):

  • frog might spend more time in the water bowl than normal
  • rear toes can take on a yellowish tinge and experience increased sloughing (note: in some regions like Mt. Isa, there is a regional variation for this species which means that yellowish toes are normal)
  • eyes might look darkish and cloudy
  • frog does NOT go ballistic when touched or vocalise pain

Roth's tree frog (Litoria rothii):

  • eyes are darkish and cloudy, crimson upper iris is almost obscured in comparison
  • increased sloughing on toes
  • toes might have a dull brownish discolouration

Graceful/Dainty tree frog (Litoria gracilenta):

  • very little indication other than sitting out in the open sun during the day when this species is normally not even seen day or night in the absence of rainfall
  • can be an 'off' colour and thin
  • toes are discoloured to a brownish tint
  • ventral surface of frog is very pale compared to its normal banana yellow

White-lipped tree frog (Litoria infrafrenata):

In the early stages:

1
Body colour is excellent but very subtle signs start to appear with lethargy, rapid panting and some minimal damage occuring to the pigmented layer of skin on the toes and webbing (such as pock-marks, flaking off - a general look of the skin being a bit "beat up" looking)
2
Frog sits in same spot for days but bolts wildly when touched
3
When picked up, frog inflates the abdomen, emits a grunting noise and tries desperately to get away including flipping itself upside down
4
When held, the rear legs often tangle up so that they are almost locked into an X formation
5
Where the skin has been touched and stroked, a tiny amount of foam appears on the skin when the finger is lifted
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As the condition advances:

1
The eyes take on a 'drugged look' with the pupils not responding properly to light and being slightly 'shifted up'; the bottom of the eyes sometimes look 'saggy' which is an illusion created by the presence of the nictitating membrane remaining visible at the bottom of the eyeball instead of being fully retracted under the skin
2
The colour of the iris might also go a speckled brown
3
The frog doesn't eat and loses weight rapidly
4
Body colour might start to change to shades of khaki, brown or streaked between the two; radical colour shifts of grey and greyish-white are also being seen; some frogs are exhibiting a brown freckling or leopard spot pattern on their backs
5
Sloughing on the feet increases and 'pock marks' appear on the skin anywhere on the body where the pigmented layer of skin has flaked off leaving the inner white layer visible; instead of seeing white marks in the skin, sometimes grey or black marks can be seen where hydatid parasites or bacteria have invaded these injured patches of skin
6
The rear feet and toes start to go crimson red and tiny pores of blood can be seen on some frogs; white streaks are visible in the webbing (see photo above)
7
The frog becomes very aggitated by the skin irritation and over-stimulation in the nervous system and might repeatedly bash itself on the sides of an enclosure
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In very advanced cases:

1
The frog has lost all its body weight and goes very dark or khaki in colour and can have fine watercolour blotches in the skin
2
The underside of the body and the thighs often will go pink or red
3
It might also have pale speckles scattered over the back and legs (this indicates systemic baterial infection brought on by open ulcers in the skin)
4
The body becomes covered in heavy slime and anywhere the frog sits or climbs, it leaves a pasty, oil slick behind
5
Some frogs will have extensive lesions and may include large areas of skin that have dissolved off the body and holes in the tympanums or tympanums missing entirely; the underside of the body may be riddled with holes
6
The rapid panting symptom slows right down to very slow panting (this might be because the nervous system is beginning to shut down after being overstimulated for so long)
7
The frog will often be found in weird positions or fully stretched out upon death

Cane Toads (Bufo marinus):

1
Toads will lose weight, becoming very thin but not very dark (which is a symptom of another condition)
2
Toads will become lethargic and not hop away when approached; instead they might flatten themselves to the ground as you approach
3
Patches of dark skin might be seen flaking off the legs and toes and may be dragging along instead of falling off completely
4
In advanced cases, holes might appear on the underside of the body and belly skin might appear to be 'crumbling' off and the toad might 'slime' in the same way as described for the White-lipped above but it will not be as copious as the frog (it will look like a fine oily sheen on the skin)
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If you live in an area that is drought affected, be on the lookout for frogs and toads with the symptoms above.

If you find something, please bring it to your nearest frog group, museum or university so that it can be tested for Fusarium and other drought tolerant fungi which might exist in your area.

Use disposable gloves or a plastic bag on your hand and don't touch anything else until you have disinfected your hands with betadine solution or Microshield 4.

Mucor and the mystery fungus described above are highly contagious to other frogs and toads. If you are near an airport in Queensland which has flights to Cairns, you can contact us about sending the frog/toad up to us for confirmation of its condition.

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