Cancers and tumours in Octodon degus

Some photographs in this article may contain sensitive images of disease/injury that may be disturbing to the public. All such images are hidden and can only be seen by clicking on the descriptive spoiler tag. It is possible to read the entire article without being confronted with these images.

Like most animals, it is possible for Octodon degus to develop cancers or tumours. Although these are less common than in rats or mice⁰¹, there are cases of tumors and cancers studied in degus. The Octodon degus is a rodent susceptible to various kinds of pathologies, such as diabetes, cataracts and dental malocclusions. Skin problems are also quite common. However, cancers and non-neoplastic tumours and masses are rather rare, although they may be related to dental problems. Odontoma⁰² is often seen in cases of malocclusion and can lead to cancer, hence the need to feed the degu properly.

Dessin d'octodons — Illustration by Vurologie

Cancer and tumour

Tumours are a deformation of tissue, caused by abnormal reproduction of cells. Tumours can be benign or malignant (cancer). Although benign tumours do not have as widespread consequences as cancer, they can create equally serious complications. Depending on the location and size of the tumour, it can cause serious dysfunction of one or more organs and even lead to death.
Cancer is caused by abnormal behaviour of cells, which multiply excessively and sometimes form tumours. It is when these tumours are malignant (aggressive) that cancer occurs. This pathology causes many health problems and requires extensive treatment in humans.

There are also cases of non-neoplastic masses, i.e. a mass of tissue that has another source than cell proliferation⁰³. It is therefore a non-cancerous mass, which is not a tumour. These masses can have many different causes.

Unfortunately, it is a pathology that is found in almost every living being, as it affects all multicellular beings. The oldest cancer ever diagnosed was found in a dinosaur

⁰⁴ Centrosaurus apertus, which lived… 77 million years ago! In pets, there are now possibilities to treat cancer, but these are limited to dogs and cats⁰⁵ ⁰⁶ and complex to implement⁰⁷. For the degu, the operation to remove the tumour is often the only possible solution, in addition to a treatment to relieve the rodent.

Tumour frequency in Octodon degus

Degus do not get cancer very often, as some studies show. Indeed, out of 300 octodons studied by the team of Dr. V. Jekl’s team, only 6 developed tumours⁰². Other data complement this diagnosis, with signs of tumours and non-neoplastic masses, both benign and non-benign, in 16 per 100 degus studied⁰⁸, but these were older and often consulted for operations. Finally, one study found 7 tumours in a set of 189 rodents⁰⁹.

Cancers and tumours are therefore relatively rare and tend to occur during the old age of the degu¹⁰. In most cases, removal is the only feasible solution, as cancer therapies were not (yet) possible in our pet rodents.

Causes

The risk of cancer can be related to several causes, some of which can be influenced to limit the risk:

Environment: stress, circadian rhythm, pollution, …
Hormones: some breast tumours are linked to hormones,
Genetics: although little studied for degus, in rats, certain linegaes declare more cancers¹¹, because of a genetic factor.
Diet: nutrition is one of the possible causes, on the one hand depending on the quality (treatments, insecticides …) or the analytical components¹² ¹³. In addition, there is evidence that poor tooth growth in octodons can cause lesions in the mouth. It is thus essential to propose to its degu an adapted food, rich in calcium, and low in glucose.
Viruses: in humans, some viruses can cause cancer (16% of cancers¹⁴), such as the papillomavirus. Links have even been found between viruses linked to mammary cancers in mice and breast cancers in humans¹⁵.

Symptoms

The symptoms of the development of a tumour or cancer are very varied. It is necessary to weigh your pet regularly, as well as to handle it to be able to discover potential lumps. In octodons, the manifestations can be varied and depend on the type of cancer. Among these, we mainly find:

Unusual weight loss,
Apathy, lack of interest, excessive fatigue,
Refusal to eat, dehydration,
Dental malocclusion¹⁶,
Skin problems, hair loss,
Formation of lumps, “balls” in various parts of the body (tail, ears, head, stomach, mouth, skin, …),
Respiratory problems (rhinitis),
Lameness, abnormal swelling of the limbs,
Convulsions.

⚠️Cancerous lump in Octodon degus⚠️

A : Fibrosarcoma, B : Chordome

It is important, when a tumour is suspected, to consult a veterinarian as soon as possible to assess the animal’s health. It will then be possible to study the lump, either by taking samples or by medical imaging (X-rays or ultrasound, etc.). Only a veterinary professional will be able to provide an official diagnosis and carry out investigations, as well as treatment.

Treatment

If there are treatments for the hamster¹⁷, the rat or the mouse¹⁸, these are often reserved for a scientific use and are not possible for our degus. Because of the cost, but also the complexity of administering the treatment, as well as the implementation of a decree tending to limit the environmental pollution of these treatments in pets⁰⁷.

In most cases, an operation to remove the tumours is the only option, with treatment to reduce the effects of the operation and/or to improve the degu’s quality of life.

⚠️Cancerous lump related to an odentoma⚠️

Neoplastic mass linked to an odontoma in Octodon degus.

Different types of cancers and tumours

The Octodon degus can deal with various types of cancers, or tumours. While some tumours can be generalised, others are notably very specific and can be linked to certain disorders.

Lung cancer: the Octodon degus can develop a cancer similar to the so-called “smokers’ cancer”, such as bronchioloalveolar carcinoma, diagnosed in an adult male in a zoo ⁰⁹.
Kidney cancer : kidney and liver metastases have been found in the same individual⁰⁹., however, it appears that cancer in degus rarely, or very slowly, spreads.
Lymphoma cancer : a few cases of cancerous masses related to histiocytic lymphoma have been found. In one degu, this caused death, as one of the nodes compressed the trachea.
Liver cancer: two degus developed liver cancer, or hepatocellular carcinoma, unfortunately it seems that this cancer metastasised, as tumours were found in the gallbladder, heart and lungs. One of these degus has contracted cholangiocarcinoma, a cancer of the cells of the bile ducts.
Oral cancer: can result from problems related to non-neoplastic lesions, created by dental malocclusions¹⁶.
Tail cancer: Cancer of the tail: Tail cancer, or chordoma, is seen in the degu¹⁹. The tumour often takes the form of a mass on the tail and can pass for an abscess.

Degus can also have several types of tumours, those reported by research include 8 epithelial tumours, 13 mesenchymal tumours, 4 round cell tumours and 2 chordomas²⁰. Other tumour types include splenic hemangioma, mesenteric lipoma, vaginal leiomyosarcoma (vaginal lesions, which are still very rare), fibrosarcoma (mass in fibrous connective tissue), and a case of transitional cell carcinoma in a kidney.

Conclusion

It can be assumed that cancers and tumours can, as in other rodents, affect all organs in the degu. It is difficult to treat other than by removing the tumour, even if this may lead to removal of a limb. Tumours and cancers being globally very rare, these diseases affect 0.04% of octodons, by making the average of the 3 studies, it is normal that these are still little known. In general, the pathologies and health problems of Chilean degus are not as well described as in other rodent species, although this is improving.

Translation by Matthieu Selles.