Cancer and Other Diseases

Cancer in amphibians is considered to be an extremely rare event. However, four cases were found by CSIRO during their chytrid testing of hundreds of frogs from eastern Australia. Not intending to outdo the rest of the country, Cairns has the dubious distinction of already having confirmed seven cases of squamous cell carcinoma (skin cancer) in local frogs (these are in addition to what CSIRO has found) and, most recently, at least one case of sebaceous adenocarcinoma.

Unfortunately, other tumours have also turned up. A biopsy of a growth on a rainforest frog's back was found to contain melanin but no futher determination was made as to if and what type of cancer it might be. From 2000 to 2002, four frogs were turned in with growths which have been identified as "epidermal papillomas" or benign tumours (see photos at left and below). However, just in the period from April to June 2003, we received another five cases of this type of growth. Two of these had both the inverted papilloma type growth and another which was different again and definitely not nasopharyngeal squamous cell. We missed the opportunity to test the first frog sporting this new unobtrusive growth type but the second from (from Trinity Beach) was biopsied and the results have just come back (January 5th, 2004) as sebaceous adenocarcinoma - a highly malignant cancer. This confirmed case appeared to be exactly the same tumour type as the previous case which was untested so it is possible we have received two cases of sebaceous adenocarcinoma.

The number of cancer cases we are getting is extremely disconcerting. First impressions might be that the skin cancer cases are the result of the powerful sun exposure here in the tropics but this is not the 'best guess'. Chronic infections can also lead eventually to cancer but this is still not the 'best guess'.

The squamous cell tumours we have seen on six of these frogs are called nasopharyngeal squamous cell carcinoma and this particular type of tumour is very common in people in China. In that country, that cancer is caused by a virus! Two different viruses have been implicated there: Epstein Barr Virus (which is common around the world) and one of the Papilloma (herpes) group of viruses. We have provided the tissues of this type to a virus researcher but the tissues became damaged in a power outage. Another lab had a look at the fifth case of this type (from Gordonvale) and reported that the tumour tissues were entirely consistent with papilloma induced growths.

Adenocarcinoma has been found in the Leopard frog (Rana pipiens) in the USA and Dr. Debra Carlson has been researching the virus that causes this particular cancer known as Lucke rhenal adenocarcinoma. She discovered a herpes virus as the cause. The cancer cases here in Cairns are likely to be viral as well. Most of the cancer cases we have received are from a very specific part of Cairns, that being the northern beaches. An odd case arrived from Gordonvale, clear across the other end of Cairns and one papilloma case was from Port Douglas. We don't know what cases there might have been prior to our start up in August 1998.

Another possible coincidence to these cases stems from the reference above to a particular type of squamous cell carcinoma being common in China. It is worth pointing out that, on March 12th, 1999, a boatload of illegal immigrants from China grounded and disembarked right on the northern beaches of Cairns at Holloways. They dispersed throughout the immediate area, taking two weeks to all be caught. One month later, our first two cases of squamous cell turned up within two days of each other - one from the suburb next to Holloways and the other from three suburbs away. All the subsequent squamous cell cases except one have been from the northern beaches.

We contacted the immigration department to ask about what sort of medical procedures would have been invoked before the immigrants were returned to China and if any viral tests were done or tumours seen. However, they said that their medical examinations did not include any virus tests and no visible tumours were noted amongst the arrivals. Perhaps there is no connection at all but it remains an interesting coincidence.

Another anomaly in the neoplasia cases is the interruption of incoming cases coming in during 2004/05 when an increasing trend was so apparent in 2003. After a long gap of no arriving neoplasia cases at all, an epidermal papilloma case arrived on our doorstep in May 2006. A report of another epidermal papilloma case from Machans came in during early October and the same property dropped off a squamous cell carcinoma case to us on October 6th.

There are two possible reasons for this gap in cases being found: one is economic and the other is an indication of how different disease problems in the same area can interact, making investigation that much more difficult. On the economic front, the public support base for our small organisation was washed away with the Dec 2004 tsunami debris and we rapidly ran out of money in early 2005 for our frog rescue/rehab activity. For the rest of 2005, we were only able to receive very limited numbers of animals (we are still struggling) and so, any tumour cases that might have been found during this period were not directed to us.

The second possible explanation for a sudden disappearance of neoplasia cases might be explained by the arrival of the new "respiratory"/nervous system disease in July 2002. When this outbreak began, it wiped out SO many frogs that many residents watched every frog in their backyard die one after the other, or they simply disappeared and no frogs replaced them. This new disease problem attacked frogs at all ages (including metamorphs) so there would have been a break in the normal flow of frogs reaching mature age. Now that the "respiratory"/nervous system disease has been estabished in the area for four years, some frogs appear to have some limited tolerance to the pathogen and we're starting to see very mature frogs again. On April 28th, 2006, it was one of these mature frogs that arrived with epidermal papillomas. We may see more of these cases now that the "respiratory" disease has settled into the ecology and is no longer at an initial outbreak stage (in this area, at least!).

The table below lists the cases we have received of neoplasias (tumours). The species involved in ALL cases is Litoria infrafrenata except for record number 334 from Bayview Heights which was Litoria leseueri. (If you are referring to our information in your own reports or work, please provide a credit for our information and a copy of the resulting publication to us.)

A point about the identification methods we use: although our academic readers would be more confident if we always sent growths for an official biopsy result, each of these biopsies costs us $200. Considering how distinctive some of these tumour types are and how many of them are arriving, we can't afford to pay $200 to verify something that is certain. We use biopsies for the first couple cases or when a tumour is different. We are a small organisation which is grossly undersupported for the kind of work that we do - when our financial situation improves, we will be happy to send every case to a lab for formal verification!

We would like to know urgently of any frogs you find with lumps on the face or body so that we can verify if it is a neoplasia or another problem which can be treated. Always use gloves (or a plastic bag over your hand if nothing else is available) to handle a sick or injured frog and carry a couple clean, plastic containers with secure lids (air holes too please!) in your car, ready for anything you might find.

last edited: October 6th, 2006